Hauntingly familar secondary failure #3

[GOLDCYLON]

Most are familiar with this post of mine. I present the 3rd documented failure of the secondary screws


http://www.zr1.net/forum/showthread.php?t=15601&highlight=compelling



I present yet once again another secondary screw failure and the result on the number 8 piston. For those doubting Thomas's out there. Background.. a local mechanic and friend of mine is currently working on a local ZR-1 customer (No idea who the customer is) and contacts me for advise, parts finding etc for the ZR-1. Yank the secondary's folks. GC

http://i1120.photobucket.com/albums/l498/goldcylon/Butterfly_zpsc2ba7cde.jpg (http://s1120.photobucket.com/user/goldcylon/media/Butterfly_zpsc2ba7cde.jpg.html)

http://i1120.photobucket.com/albums/l498/goldcylon/Piston_zps6f406163.jpg (http://s1120.photobucket.com/user/goldcylon/media/Piston_zps6f406163.jpg.html)

http://i1120.photobucket.com/albums/l498/goldcylon/Piston2_zps48b4f957.jpg (http://s1120.photobucket.com/user/goldcylon/media/Piston2_zps48b4f957.jpg.html)

http://i1120.photobucket.com/albums/l498/goldcylon/Piston1_zps0984b67a.jpg (http://s1120.photobucket.com/user/goldcylon/media/Piston1_zps0984b67a.jpg.html)

http://i1120.photobucket.com/albums/l498/goldcylon/Chamber_zpsd77d7f90.jpg (http://s1120.photobucket.com/user/goldcylon/media/Chamber_zpsd77d7f90.jpg.html)

[LGAFF]

I think the same happened to 90 #702, the engine I purchased, same damage

[GOLDCYLON]

That makes 4 that I know about then Lee

[John Boothby]

I would yank my secondaries, but I don't know how that would affect the smog check? As it is, if I forget to turn the power key off, I fail the smog check. With the power key off it passes.

[GOLDCYLON]

I would yank my secondaries, but I don't know how that would affect the smog check? As it is, if I forget to turn the power key off, I fail the smog check. With the power key off it passes.

Your right John depends on the State. Sniffer test I would say yes. Treadmill no way in hades.

[Kevin]

That makes 4 that I know about then Lee

4 out of 7,000 aren't we crying wolf a bit early?

[efnfast]

I think I asked before, but what are the down sides of yanking them.
Might be an issue with emitions (sp).
Certainly not OEM, or NCRS.
Needs a chip reprogram.
?

[GOLDCYLON]

4 out of 7,000 aren't we crying wolf a bit early?

Kevin there are no where near 7000 left maybe 5500 after crashed and parts out. regardless its a thing to consider if your are getting head work done and a while your are there type of thing like replacing a headgasket. My argument is not to start taking your car apart. I am simply presenting 4 cases with documentation that we know about. How many that we don't know about? Would you rather be educated about the possibly or not or have the wolf bite you in the full point of contact later? GC

[GOLDCYLON]

I think I asked before, but what are the down sides of yanking them.
Might be an issue with emitions (sp).
Certainly not OEM, or NCRS.
Needs a chip reprogram.
?

None expect emissions as a possibility. Yes maybe a chip reprogram if your doing headwork, you are removing the code 61 (secondary failure) for ever and cleanup a lot of room under the plenum, No more actuators its a total win. Cliffs done a great writeup on the process in his solutions pages. GC

[Dynomite]

Most are familiar with this post of mine. I present the 3rd documented failure of the secondary screws

Daryll......you definitely need one of these Whistler Wireless Inspection Camera 9mm Model IC-3709PX or comparable to put your mind at ease.....that is what I got it for :thumbsup:

I have a Whistler Wireless Inspection Camera 9mm Model IC-3709PX. The camera probe will fit easily into a spark plug port. With the piston at BDC you can actually place a bend in the camera probe cable and by rotating the camera probe cable can look at the side walls of the cylinder. The tops of the pistons can be visually inspected 360 deg.

One can insert the camera probe between the runners and above/below the fuel rail inspecting all sorts of items under the plenum. You can even watch the secondaries function as you like hot wiring Pin C17 with a Pin Probe as described by Marc Haibeck Secondary Operation without removing the Plenum (http://www.zr1specialist.com/HAT%20Web/articles/sec%20throttle%20test.htm)

And :p You can use the inspection camera to look at brake pads, under the dash in places you can only stick a screw driver poking the camera probe between wiring to look beyond wiring, inspection of front cover for leaks, inspection of water pump for leaks, inspection of front seal, inspection for bolts dropped and caught between headers, checking smoothness of secondary operation, inspection of vacuum hoses under plenum, inspection of wiring under plenum, and if you want you can inspect inside your differential case after you have drained the fluid (same with transmission, and oil pan), and especially inspection for those very hard to find oil leaks around the OPRV (Oil Pressure Regulating Valve Cover) :cheers:

Tech Info - Marc Haibeck on LT5 Eliminated Secondaries

Marc Haibeck mentioned to me some time ago....Haibeck Automotive Technology (http://www.zr1specialist.com/)
Removing the secondaries is not a bad idea. Marc dyno tested removing the secondary throttles and found no significant changes.

Marc suggested there are three situations where removing the secondaries are useful.
1. If you are having a problem with them that you can't fix, they can be eliminated.
2. If you can't find a repair part.
3. If you have removed them to port the heads, you can save time and not reinstall them.

Marc also mentioned that removing the secondaries does not effect the idle, fuel economy or torque over 1500 rpm. Having the secondaries in place might be an advantage for an emission test.

Further, with the elimination of the secondary port throttle control the engine idles on the primary injector only. When the main throttle is opened to about 1/2% or more the secondary fuel injector activates. This usually happens while the clutch is being slipped to drive away, typically the engine is running on both fuel injectors before the clutch fully engages. Once the throttle is more than 1/2% open the flow split between the primary and secondary injectors is the same as the OE value of 50%-50% and in sync with each other.

I might also mention eliminating the associated vacuum system and secondary cannisters gets rid of a lot of potential failures later on and makes for a clean looking LT5 installation.

Also keep in mind eliminating the air injection system may have ramifications in regard to a SMOG check depending which State you reside. I have also eliminated the original Exhaust Manifolds and CATS which would be required in some States for SMOG check success.

See LT5 Eliminated Systems (http://forums.corvetteforum.com/c4-zr-1-discussion/2942569-tech-info-lt5-eliminated-systems.html)

[efnfast]

Guess I'm sold when it comes time to do the heads.

[GOLDCYLON]

A lot of us have done it already. I have heard no complaints. I consider it PM for the future.

[Blue Flame Restorations]

For me it was a no brainer on the Turq car. If I ever have to open the plenum on my Purple car, I may do the same thing as well. Not 100% sold on the Purple car yet though.

[GOLDCYLON]

For me it was a no brainer on the Turq car. If I ever have to open the plenum on my Purple car, I may do the same thing as well. Not 100% sold on the Purple car yet though.


The Purple Its uber low mileage Brett I think its for those of us with a lot a miles on the clock to consider. Also its personal preference as I hated pulling the plenum to resolve actuators and other secondary problem issues related to the infamous code 61. Also I drive my car significantly more than the rest of the membership as a DD. GC

[John Boothby]

I just looked up some info on the Nevada DMV site. Classic car plates are available for cars 25 years or older (our 90 will meet this next year) and driven less than 5K per year are eligible for these plates, and are exempt from emissions!! Wall-a!!

[GOLDCYLON]

I just looked up some info on the Nevada DMV site. Classic car plates are available for cars 25 years or older (our 90 will meet this next year) and driven less than 5K per year are eligible for these plates, and are exempt from emissions!! Wall-a!!

Yep one of the many benefits of driving an older car, plates are less, Emissions may no longer need to be required etc etc

[efnfast]

Emissions are easy in NH. If you don't have any trouble lights and exhaust looks intact, you pass.

[Blue Flame Restorations]

The Purple Its uber low mileage Brett I think its for those of us with a lot a miles on the clock to consider. Also its personal preference as I hated pulling the plenum to resolve actuators and other secondary problem issues related to the infamous code 61. Also I drive my car significantly more than the rest of the membership as a DD. GC


For me, I think any ZR-1 that I would drive regularly, I would end up removing them. I just don't like bells and whistles in a system. Simplicity is my preference.

When Pete and I finally do my stroker, it will be a secondary delete for sure.

[GOLDCYLON]

For me, I think any ZR-1 that I would drive regularly, I would end up removing them. I just don't like bells and whistles in a system. Simplicity is my preference.

When Pete and I finally do my stroker, it will be a secondary delete for sure.

Amen

[Dynomite]

Amen

A Man of Few Words ;)

I actually completely reconditioned the secondaries on my 90' because I wanted to experience the Power Key :D

I did eliminate TB and top of Injector Housing Coolant and can now do a Plenum pull in 10 minutes (15 minutes with my eyes closed) :cheers:

Removing Plenum (including the 10 minute Plenum Removal) (http://forums.corvetteforum.com/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-4.html#post1581663365)

[Schrade]

That moth has some pretty nasty fangs! :mrgreen:

[GOLDCYLON]

That moth has some pretty nasty fangs! :mrgreen:

Yes the screw with you moth

[Paul Workman]

Guess I'm sold when it comes time to do the heads.

No need to wait to do the heads. Two ways to go:

If you wanna try it but be able to revert, you can simply zip tie the actuators open and substitute the appropriate calibration (chip).

Or, for optimum performance, or where porting results in expanding the runner size beyond the stock diameter, for instance, the plates and rods can be extracted inside an hour, once you have the plenum removed.

On a 90, as a precaution, you'll want to place a jumper across the POWER switch so that it is always in FULL POWER mode. If you have a 91-95, the chip calibration can be changed to always be in FULL POWER mode.

Aside from you questions regarding what the down sides are, you didn't even touch on what the upsides are, and has anyone ever reverted back to reactivating the SPTs (for other than possibly a new emissions compliance problem). For that there are many UPSIDES to eliminating them:

Both intake valves are constantly washed in fuel, keeping the clean!!
Reliability! Parts that don't exist, don't fail, and don't cost anything.
Throttle response(!) as there no longer is any transition lag.

I've been without 'em for 4 years now, and love the way it runs. I'd go kicking and screaming if I had to reinstall them (assuming that was an option - which it is NOT in my case...)

http://i185.photobucket.com/albums/x220/6PPC_bucket/tech%20files/Headporting1.jpg (http://s185.photobucket.com/user/6PPC_bucket/media/tech%20files/Headporting1.jpg.html)

[GOLDCYLON]

No need to wait to do the heads. Two ways to go:

If you wanna try it but be able to revert, you can simply zip tie the actuators open and substitute the appropriate calibration (chip).

Or, for optimum performance, or where porting results in expanding the runner size beyond the stock diameter, for instance, the plates and rods can be extracted inside an hour, once you have the plenum removed.

On a 90, as a precaution, you'll want to place a jumper across the POWER switch so that it is always in FULL POWER mode. If you have a 91-95, the chip calibration can be changed to always be in FULL POWER mode.

Aside from you questions regarding what the down sides are, you didn't even touch on what the upsides are, and has anyone ever reverted back to reactivating the SPTs (for other than possibly a new emissions compliance problem). For that there are many UPSIDES to eliminating them:

Both intake valves are constantly washed in fuel, keeping the clean!!
Reliability! Parts that don't exist, don't fail, and don't cost anything.
Throttle response(!) as there no longer is any transition lag.

I've been without 'em for 4 years now, and love the way it runs. I'd go kicking and screaming if I had to reinstall them (assuming that was an option - which it is NOT in my case...)

http://i185.photobucket.com/albums/x220/6PPC_bucket/tech%20files/Headporting1.jpg (http://s185.photobucket.com/user/6PPC_bucket/media/tech%20files/Headporting1.jpg.html)

Thanks Paul was hoping you would chime in.

[efnfast]

Better air flow without the plates and rods in the way? I would assume yes, but a measurable difference?

[GOLDCYLON]

Better air flow without the plates and rods in the way? I would assume yes, but a measurable difference?

Mr. Haibeck documented about a second delay from command of a full throttle action to the actuation of the secondary systems for one. With no secondary's to open... no delay.

[chriskinzel]

I'm in the process of removing my secondaries. Just pulled the shafts today with a new tool. It is a vice grip that has a slide hammer attached to it. Slicker than bacon grease! I put a nut on the shaft and with 3 hits from the slide hammer the shaft is out. Under 5 minutes to remove all 8. The shafts are bent, and unsealable, but so what I am throwing them anyway. I have got ant inspection camera and I will be checking all cylinders before reassembly. All of my screws are accounted for. (Maybe not all my marbles though).:)

[PhillipsLT5]

Mine are long gone, great

[mike100]

I have not tested this in any way, but I think if one ran a fairly stock timing and fueling map to about 2400 rpm or so (the speed range of the typical smog check), one could pass running with open secondaries.

Maybe the combustion swirl would be wrong for the original EPA tests they do certifying cars, but for the typical inspection, I think it could do ok.

[Paul Workman]

I have not tested this in any way, but I think if one ran a fairly stock timing and fueling map to about 2400 rpm or so (the speed range of the typical smog check), one could pass running with open secondaries.

Maybe the combustion swirl would be wrong for the original EPA tests they do certifying cars, but for the typical inspection, I think it could do ok.

One way to "test" it and find out once and for all would be to install a special gasket that covered the secondary ports and reinstall the stock chip and then test it again. The results would be quite illuminating.

[GOLDCYLON]

I'm in the process of removing my secondaries. Just pulled the shafts today with a new tool. It is a vice grip that has a slide hammer attached to it. Slicker than bacon grease! I put a nut on the shaft and with 3 hits from the slide hammer the shaft is out. Under 5 minutes to remove all 8. The shafts are bent, and unsealable, but so what I am throwing them anyway. I have got ant inspection camera and I will be checking all cylinders before reassembly. All of my screws are accounted for. (Maybe not all my marbles though).:)


Slick method Chris. Its the simple solutions that work

[Paul Workman]

Better air flow without the plates and rods in the way? I would assume yes, but a measurable difference?

Good question.:)

I asked Marc Haibeck about this some years ago, and if I recall, I believe he said it might be only 5-6 hp range (on an non-ported head)**.

Difficulties in controlling the variables in actual testing (using a actual LT5/dyno) are significant. And, theoretically the harsh** taper immediately following the SPTs may perhaps significantly obscure the effect on performance that removal of the SPTs (alone) might have had.

**Acoustics: Those that know seem to suggest that to practically eliminate reversion in the runner air column, the rate of change in diameter should be 4% or less. The change immediately below the SPTs on my (then stock) 90 heads was approximately 3 times that! However, if the head is ported, then that second restriction would be removed, and the effect of then removing the SPTs would be much more significant.


Either way...Performance wise (on so many levels) removing the plates and rods can't hoit!!:dancing

[zr-1.R1]

excuse my ignorance, I am a neophyte.
if I remove the plenum, and the secondary valves, insert the liquid stop screws, pull the bolt, then the car will give me error 61? and I change gas emissions?

[4-cam]

I removed the secondarys about two years ago while I was porting my top end after reading a thread about the screws and engine damage that can occur. There was no way I was going to let that happen to me. I have corys chip for secondary delete and my 91 passed the IM240 treadmill test here in Colorado with flyin colors. Im not as confident on how its going to do with the SW headers and high flow cats that I am installing now. I did add air tubes and will be ceramic coating headers and cats to keep them nice and hot. I am going to do an emmisions test before we start the tune to see what a difference high flow cats make. Hopefully she will pass without issues.

[Franke]

I removed the secondarys about two years ago while I was porting my top end after reading a thread about the screws and engine damage that can occur. There was no way I was going to let that happen to me. I have corys chip for secondary delete and my 91 passed the IM240 treadmill test here in Colorado with flyin colors. Im not as confident on how its going to do with the SW headers and high flow cats that I am installing now. I did add air tubes and will be ceramic coating headers and cats to keep them nice and hot. I am going to do an emmisions test before we start the tune to see what a difference high flow cats make. Hopefully she will pass without issues.

So you removed the secondary's and still passed the IM240 test here. That's good to hear as I was thinking about doing that very mod but was worried about the emissions. Did you remove the sec throttle bar as well or just the throttle plates? I am curious to see how well your Z will pass with the hi flows and headers.

[4-cam]

I pulled the shafts. After that mod the emmisions test hardly looked any different than with the secondarys. I did install new accel injectors at the same time. I am currenty fabing up the exhaust. Once I get that all welded up and get ceramic coating done, I will give the emmisions a try. Most likley mid Febuary time frame.

[Schrade]

So you removed the secondary's and still passed the IM240 test here. That's good to hear as I was thinking about doing that very mod but was worried about the emissions. Did you remove the sec throttle bar as well or just the throttle plates? I am curious to see how well your Z will pass with the hi flows and headers.

This is something that crossed my mind pertinent to OP.

Did the customer of Darryl's wrench-buddy attempt to do this - plate removal with shafts left in, then change his mind and re-install the screws???

[Paul Workman]

excuse my ignorance, I am a neophyte.
if I remove the plenum, and the secondary valves, insert the liquid stop screws, pull the bolt, then the car will give me error 61? and I change gas emissions?

First, the ECM must be programmed for operating without the secondaries:

The new calibration will allow zero vacuum = OK (so no code 61)

At idle, only 1 injector is signaled "on". Above idle (>1%), the new calibration signals both injectors on but divides the dwell = 1/2 for each injector to provide the proper fuel.

Emissions might change. The tuning must be precise.

On a 1990, the POWER switch must ALWAYS = FULL POWER (VERY important!) For 1991-95 the ECM is programmed for the secondaries to always be "on".

All of the secondary circuitry may be removed (shown in PINK) and the plenum vacuum connection is plugged.

Note: On a 1990 ZR-1 the #11 "switch differential pressure" is located under the ECM. on 1991-95 the switch is under the plenum.

http://i185.photobucket.com/albums/x220/6PPC_bucket/tech%20files/plenumvacuumcircuitsLT5LargeLarge.jpg (http://s185.photobucket.com/user/6PPC_bucket/media/tech%20files/plenumvacuumcircuitsLT5LargeLarge.jpg.html)

Note:...Please forgive me, but I don't understand what you mean by "insert the liquid stop screws, pull the bolt" = ???

Does this help?

[GOLDCYLON]

This is something that crossed my mind pertinent to OP.

Did the customer of Darryl's wrench-buddy attempt to do this - plate removal with shafts left in, then change his mind and re-install the screws???

Nope it just fell out. Mine fell out the same way on the drivers head of the motor then once again when the entire shaft broke screw and all and wedged two valves open on the passenger head. Once again it was not pretty as the pictures showed.

[GOLDCYLON]

I removed the secondarys about two years ago while I was porting my top end after reading a thread about the screws and engine damage that can occur. There was no way I was going to let that happen to me. I have corys chip for secondary delete and my 91 passed the IM240 treadmill test here in Colorado with flyin colors. Im not as confident on how its going to do with the SW headers and high flow cats that I am installing now. I did add air tubes and will be ceramic coating headers and cats to keep them nice and hot. I am going to do an emmisions test before we start the tune to see what a difference high flow cats make. Hopefully she will pass without issues.


It wont pass with the high flow cats on the treadmill. Been there done that with Jeal Headers. Sniffer all day.

[tf95ZR1]

See post #56

http://www.zr1.net/forum/showthread.php?t=19823&highlight=secondarys&page=6

[Schrade]

See post #56

http://www.zr1.net/forum/showthread.php?t=19823&highlight=secondarys&page=6

Looks like one of the more knowledgeable people made a fool of himself on THAT page!

Also looks like a good example of how to handle it too, like I said before:

This is a good point Scott:

Some engines, when you put too much oil in the crankcase, the crankshaft spins IN THE OIL, and makes a foamy, frothy, jammy mess.

It will make the oil light come on, when the system pickup tube starts suckin' up the froth.

I can't imagine WHAT goes through the PCV plumbing when this happens.

And who knows what would go through the cylinders. And the exhaust...

I don't know how LT5 dynamics would handle too much oil...



(good job Admin on editing - some people don't know a tactful way of telling another that they THINK another MIGHT be wrong. Even if they KNOW they're wrong. 'Cause they might NOT be wrong)

[Blownrunner]

There was a TSB on the wifes Nissan which has a similar setup for the air side of the intake, but only has one injector per cylinder. The plates' screws were backing out also and their fix was installing screws that had nylon on the threads like on a nylon lock nut has, then torquing with a calibrated screwdriver. I did her car as a safety precaution even though it wasn't required for the TSB. I removed the screws and reinstalled using red locktite (high strength). I couldn't find what the calibrated screwdriver was set to, so I torqued to 25 in/lbs, the same that Boeing requires for installing inspection panels on the outside of the aircraft (on #10 steel/titanium screws).

I also rebuilt and adjusted the plates on the throttle body of the ZR-1, and could not remove the screws without destroying them. I drilled them out and replaced with new ones and installed again with the red locktite. I think that having screws on the 'air valves' isn't the problem, having them installed without some type of way to keep them from backing out is the problem. After all, isn't this how every throttle body is built today?

[GOLDCYLON]

I think that having screws on the 'air valves' isn't the problem, having them installed without some type of way to keep them from backing out is the problem. After all, isn't this how every throttle body is built today?

Disagree, on my passenger side the shaft failed and fell into the motor along with the screw. The air valves shafts ARE part of the problem. see below the picture where the shaft fatigued. Snipped from my link in post #1


http://i1120.photobucket.com/albums/l498/goldcylon/DSC_0748.jpg

http://i1120.photobucket.com/albums/l498/goldcylon/DSC_0754.jpg

Scope view at point of discovery the awwww Crap moment!!!!!
http://i1120.photobucket.com/albums/l498/goldcylon/scope20view.jpg

[Paul Workman]

See post #56

http://www.zr1.net/forum/showthread.php?t=19823&highlight=secondarys&page=6

I'm not sure if you're asking a question, or making a statement by referring to post #56???:icon_scra

Post #56

http://i185.photobucket.com/albums/x220/6PPC_bucket/Dyno%20graphs/LT5ptopenvsclosed_zps79a8b9ce.jpg (http://s185.photobucket.com/user/6PPC_bucket/media/Dyno%20graphs/LT5ptopenvsclosed_zps79a8b9ce.jpg.html)

Vs. an "FBI 500" motor w/ tuning...

http://i185.photobucket.com/albums/x220/6PPC_bucket/Dyno%20graphs/Dynographs_zps723fdad7.jpg (http://s185.photobucket.com/user/6PPC_bucket/media/Dyno%20graphs/Dynographs_zps723fdad7.jpg.html)

But there's a fly in the ointment (see posts #77 and #78 of that same thread). In short, tuning for both low and high rpm makes a huge difference in overall driveability characteristics with the secondaries deleted.

And, IMO, I think that other thread is slightly out of sync with this one, i.e., an earlier statement (in your referenced thread) was made (in effect) ... pulling the secondaries would make the car only suitable for race applications; ruin(?) it for normal driving. That is just patently wrong, based on experiences of many. Obviously, that statement was devoid of actual experience, as I and dozens of ZR-1 drivers (sans secondaries) can attest!

Note: I invited that poster to come to a BG gathering and test drive mine and some other cars, sans secondaries, and see what he thinks. So far, I haven't heard him accept the offer.

The only "niggling" issue is emissions compliance in your location. Other than that, "no worries mate!"

[bradley]

my callaway 475 supernatural , drives better in every way with the secondaies removed .also since I have had them removed my mileage on the freeway has improved by 2 mpg .example , I go to see bill boudreau 3-4 times a year . before the secondaries were removed I got 21.2-.4 on a round trip now I get 23.5- 24.0 mpg on the trip. my car also has 4.10 gears

[tf95ZR1]

I'm not sure if you're asking a question, or making a statement by referring to post #56???:icon_scra

Just providing info on the subject from a reliable source (Graham Behan) who
says you loose low end HP & torque without the secondaries.
Anybody can take it or leave it. Maybe other factors come in to play.
I would probably do what Marc H. suggested ( if I wasn't in the smog state of CA).
He said keep 'em until they don't work, then delete.

[Paul Workman]

Just providing info on the subject from a reliable source (Graham Behan) who
says you loose low end HP & torque without the secondaries.
Anybody can take it or leave it. Maybe other factors come in to play.
I would probably do what Marc H. suggested ( if I wasn't in the smog state of CA).
He said keep 'em until they don't work, then delete.

Wellllll....practical considerations not withstanding, that graph makes a point -- to a point.

In the first place, the graph was clearly a modified motor by LPE, recorded on a Dynojet. Graham might have provided it, but right off the bat, the data (graphs) are specific to a very unique set of circumstances - and so, the data has to be considered in the context of a modded motor.

"Maybe other factors come in to play"? Oh, yeah - fer certain. For instance:

That LPE was NOT a stock LT5; based on characteristics its probably a 368? Point being, the tuning would be significantly changed, and maybe the cams too. Displacement, tuning, pistons (compression) and probably custom cam profiles - combine to cast considerable suspicion on how it proportionately relates to a stock LT5 (NO reflection on Graham!).

Be that as it may, even in the LPE example, with the power switch in NORMAL the torque "advantage" quickly pinches off at 3900. I dunno 'bout chew, but I don't do much driving at WOT where I'm limited to 3900 rpm. So, really, what's the practical relevance then I wonder?

Modified motors allowed, if Dynojet graphs = "reliable source", then I'd like to point out that Dynojet graphs of my "FBI 500+" modded motor WOT torque is ≈ 25#+ over my stock motor* at WOT from 2000 up and beyond 3900 rpm. (NO pinching off at 3900 rpm either!). So, the net loss/gain as result of opening up both runners and chucking the Secondary Port Throttles (SPTs) is actually a net gain through 3900 rpm compared to what it might have been stock with SPTs closed. (I'm sure Graham might agree).

*with secondaries "open" (i.e., removed, to be precise)

Fuel economy? Virtually the same with vs. w/o SPTs for the same conditions on the same 8 hour round trip destination w/ cruise set at 71 mph in both cases.

So.... I'm suggesting the difference in performance between SPTs open (or deleted) at WOT vs. SPTs closed (power switch = NORMAL) is academic, for any practical purpose. And, the real practical advantages of deleting them, far outweigh reasons to keep them intact, with the possible question of emissions compliance, depending on where you live.

Your mileage may vary.;)

[Dynomite]

http://i1120.photobucket.com/albums/l498/goldcylon/DSC_0748.jpg


Geez......a little carbon there Daryll :eek:
You burning Diesel in AZ?

[GOLDCYLON]

Geez......a little carbon there Daryll :eek:
You burning Diesel in AZ?


pre 380 she was a Dirty Girl

[Paul Workman]

pre 380 she was a Dirty Girl

Yeah... I guess so! But, nuttin like opening a hole in da coolant jacket to clean dem chambers right up, you betcha! (Don't ask!:o)

And kidding aside, that is how my intake valves looked before pulling the SPTs... Just to beat that dead horse a few more licks. LOL!

[HAWAIIZR-1]

Well, now I have another good reason to pull out the secondaries. I will wait until I get back to Hawaii, but I have been reading over the years about the pros and cons. I just figured like Marc said it not giving you problems then one could keep the system. Today while I was doing some final checks I saw the vacuum line snapped that goes past the oil filter to the vacuum pump. Not sure how long it was busted since I don't drive the car much and while not a big issue, I think I do finally want to yank all that garbage out and forgo the issues. It has been one thing or another over the years related to the vacuum system for the secondaries. I really wish I pulled them when I did the heads a few years ago. Oh well, thanks for all the information related to the issue to help me make a decision.

Tomorrow is my quest to find some hard plastic hose here in Japan to replace the broken line until I can get the car shipped back home in a few weeks. So far no luck and will try a large auto parts place and several home improvement on the way home from work.

[LGAFF]

Can you not get a section of rubber tubing to use as a connector and fix it that way?

[HAWAIIZR-1]

Can you not get a section of rubber tubing to use as a connector and fix it that way?

Hello Lee,

Thanks for your thoughts and I do have some rubber tubing that I can use to repair as last resort until I can find the proper hard plastic tubing. It busted about right around the oil filter area near the rubber connected coming out from under the plenum. In fact, it busted before and I was able to take up slack to repair it the first time. I guess the hose is getting very brittle to just snap like that. I would have to imagine they sell that kind of tubing around here and I'll find out today. :cheers: