Speakin of "running rough"...

[Paul Workman]

Regarding my miss/low compression issue, I was pretty certain I was dealing with a mechanical problem on my #8; a bent valve or broken valve spring, or ingested a screw or something?:dontknow: But, I'm just a patient - not a doctor of LT5s. So, since I work only about 10 minutes from Marc H's shop (eat your hearts out!;)) I ran 'er by Dr. Hiabeck's office for a visit.

I was pretty much resigned to an engine pull, and initially intended to inquire about going ahead with a 368 upgrade, as long as I was going to pull the LT5 and be "in there" anyway. But, I was surprised when Marc told me he was not at all sure it was a mechanical problem - could very well be - but(!) possibly the miss and even the low compression symptom could (over time) well have it's roots elswhere: injectors, coil, plug wire, or even the ECM. So! I've got a laundry list of things to eliminate before succumbing to an engine pull.

If it comes to that - an engine pull that is - I'm gonna give the 368 option a hard look-see! So, in the mean time, I'll be shopping for parts; pistons that will work on stock rods (this, according to Marc, has been done successfully at SGC), sleeves, rings, bearings, cam bolts, etc. And, if it comes to that, I'm hoping I can draw on the rich experience and talent that cruises this board. (Wouldn't even think about it, otherwise!).

All comments and suggestions = very welcome.

P.

[ZZZZZR1]

Paul,

368? All I can say is VERY COOL! :cool:


Do it!

Hope you find that issue soon, so you can enjoy that beast!


Cheers

David

[Paul Workman]

Well, so far...

Plug wires: swapped #8 with #5 (same length)

Coil: swapped places w/ the front two (the #7-6 coil now serving 8-5, if memory serves)

Injectors: swapped places; #8's injectors now in the #4 spot.

I shoulda checked resistance of the (Multitech!:jawdrop:) injectors before pulling the plenum (and messing up a gasket:rolleyes:). But! I have a used set of gaskets (some of Jerry's are on order) to slap on there long enough to heat the engine up and then test the injectors, AND swap ECMs too, if need be.

So! The question is, which cylinder is going to miss now? If it is #5, it is a bad plug wire. If it is #4 - the injectors. If either #7 or #6 fails - the coil comes under suspicion (plugs were eliminated earlier).

If it is a combo...:censored:...I don't wanna go there yet. Course if there is no change at all, and the (hot) injector resistance checks out, that leaves the ECM. Then, if nothing comes of all this, I guess an engine pull is on the plate to see what's what with the mechanicals.

Sound like a plan?

P.

[XfireZ51]

How about if you just bring the car up here and let's throw a scantool on it. I really doubt it's an ECM.

[ALZR1]

Well, so far...

Plug wires: swapped #8 with #5 (same length)

Coil: swapped places w/ the front two (the #7-6 coil now serving 8-5, if memory serves)

Injectors: swapped places; #8's injectors now in the #4 spot.

I shoulda checked resistance of the (Multitech!:jawdrop:) injectors before pulling the plenum (and messing up a gasket:rolleyes:). But! I have a used set of gaskets (some of Jerry's are on order) to slap on there long enough to heat the engine up and then test the injectors, AND swap ECMs too, if need be.

So! The question is, which cylinder is going to miss now? If it is #5, it is a bad plug wire. If it is #4 - the injectors. If either #7 or #6 fails - the coil comes under suspicion (plugs were eliminated earlier).

If it is a combo...:censored:...I don't wanna go there yet. Course if there is no change at all, and the (hot) injector resistance checks out, that leaves the ECM. Then, if nothing comes of all this, I guess an engine pull is on the plate to see what's what with the mechanicals.

Sound like a plan?

P.


Forget all questions above,and ask where is all that compression pressure
going.When I checked your compression it was less than 60 PSI and your leak down was at 80% .This is your problem,and it has to do with your pistons,rings,or valves nothing more.



AL.

[A26B]

Forget all questions above,and ask where is all that compression pressure
going.When I checked your compression it was less than 60 PSI and your leak down was at 80% .This is your problem,and it has to do with your pistons,rings,or valves nothing more.

AL.

Might the list also include the head gasket? Was compression rechecked with a squirt of oil in the cylinder? Could help in determining whether or not valve problem.

[ALZR1]

Might the list also include the head gasket?


If it was the head gasket you would either have A cooling issue,or
an adjacent cylinder down on pressure as well or both on an LT5 Motor.
Paul's motor doesn't have any of these problems
Paul also had checked the rest of the cylinders and said that they were about
180 PSI.


AL.

[A26B]

If it was the head gasket you would either have A cooling issue,or
an adjacent cylinder down on pressure as well or both on an LT5 Motor.
Paul's motor doesn't have any of these problems
Paul also had checked the rest of the cylinders and said that they were about
180 PSI.

AL.

Please explain why the LT5 head gasket failure would necessarily affect the adjacent cylinder. Each cylinder has an individual copper seal. LT5's are prone to head gasket failure at about 7:00 position, into the coolant area.

Granted, a head gasket, fully blown, would cause (1)temp issues, and at the very least, (2)areation in the coolant, both of which should be readily detectable.

I'm not saying it IS a head gasket, just that it might also be a possibility since head gaskets have a greater incidence of failure in the LT5 than valves or piston/rings, under normal conditions. The other less frequent possibility is for a secondary butterfly shaft screw gets ingested.

[ALZR1]

Please explain why the LT5 head gasket failure would necessarily affect the adjacent cylinder. Each cylinder has an individual copper seal. LT5's are prone to head gasket failure at about 7:00 position, into the coolant area.

Granted, a head gasket, fully blown, would cause (1)temp issues, and at the very least, (2)areation in the coolant, both of which should be readily detectable.

I'm not saying it IS a head gasket, just that it might also be a possibility since head gaskets have a greater incidence of failure in the LT5 than valves or piston/rings, under normal conditions. The other less frequent possibility is for a secondary butterfly shaft screw gets ingested.

You're not suggesting that copper is indestructible are you?


AL.

[A26B]

You're not suggesting that copper is indestructible are you?

AL.

Of course not.

[Paul Workman]

I'm not saying it IS a head gasket, just that it might also be a possibility since head gaskets have a greater incidence of failure in the LT5 than valves or piston/rings, under normal conditions. The other less frequent possibility is for a secondary butterfly shaft screw gets ingested.

Butterflies...BUTTERFLIES???? WEE DOAN NEEED NO STEEEEKING BUTTERFLIES!!

Parts that don't exist seldom fail, and they don't cost anything. Such is the case with my secondaries. Couldn't be happier in that regard!:thumbsup: But! indigestion is certainly what #8 has.:rolleyes: God willing and the creek don't rise, gonna give the pull a hard charge - or at least get as far as I can go in one weekend - assuming nothing simple (read: non-mechanical) surfaces (but I doubt it!).

P.

[blackjack]

i've been thinking about a 368 too,since i've got the pistons/no sleeve,but nobody around here wants to touch that motor,except a mustang guy,and chicago is soooooo far from here
bj
91/1735

[A26B]

Butterflies...BUTTERFLIES???? WEE DOAN NEEED NO STEEEEKING BUTTERFLIES!!

P.
:worship:


Did you count your screws Paul? Odd numbers are bad news buddy! :sign10:

[XfireZ51]

:worship:


Did you count your screws Paul? Odd numbers are bad news buddy! :sign10:

Jerry,

I thought of that. When I did mine I counted an odd number. PANIC! Found it on the bench. :happy1:

[Paul Workman]

:worship:


Did you count your screws Paul? Odd numbers are bad news buddy! :sign10:

Yeah, I sweated some bullets on the first couple. After that I placed my magnetic "grabber" right on the butterfly as I removed the screws...Just in case. At least no butterfly screws went "south". AND...I drove it for about 600 miles after I put the plenum/IHs back on, and she ran like a scalded dog - no missing.

Thinking back tho, on one of the last times out before putting the headers on I went to down-shift and missed a gear - pegged the tach for just a second:censored::redface:. I wonder...:dontknow: It will be interesting to see what's going on. I'll take some pix. At this point I'm not dreading anything - just itchin' to get in there and see whazzzup!

P.

[LGAFF]

Several companies that rent bore scopes Paul, that might be an option.