HOB Re-Read

[LGAFF]

After you have spent some time with the engine, its worth a re-read....there are some subtle notes that you might not have noticed the first time.

-The book notes the crank time to start was shortened by GM against Lotus' wishes....sounds like the long crank might have been done to ensure oiling to the top of the motor prior to firing.

-Some notes under cam failures acknowledging clearance issues, with notes stating that the cams had little to no quality controls in place.

-INA was the original lifter source but it was pulled due to wear issues

Good stuff

[VetteMed]

Couldn't crank time easily be changed in the PROM by increasing the number of revolutions prior to injectors being fired?

[tomtom72]

Couldn't crank time easily be changed in the PROM by increasing the number of revolutions prior to injectors being fired?

Yea, good idea no? I wonder what Marc would say about that one. I'd sure as heck trade "time to fire" for more pressure build up in the oiling system!:mrgreen:

I think I'll go give it another read!:icon_stud

[Hog]

Could you not just hold the throttle at WOT for a few seconds while you crank? This woudl allow oil pressure to build, then when you want to start the car, let off the throttle?.

This is assuming that cranking the engine while at WOT forces the ECM into "Clear Flooded Engine" mode.

The newer OBD2 PCMs shut the injectors off while cranking at WOT.

peace
Hog

[Aurora40]

One thing I don't get... Let's just for convenience pretend it takes 30 revolutions to pump oil all over the engine.

What's the difference in the engine turning over 30 times to pump oil before starting, and it turning over 10 times before starting, then 20 times while running?

It's not like priming the oil pump with the engine not turning. Everything is moving before it's oiled, whether powered by the starter or by combustion.

[LGAFF]

Talked to someone today that made cam regrinds for LT-5s.....he had nothing to do with Mercury or GM but makes one off cams...he stated they were poorly made and agreed that tolerences were not right.

Will be running regrind cams in my 90

[tomtom72]

Talked to someone today that made cam regrinds for LT-5s.....he had nothing to do with Mercury or GM but makes one off cams...he stated they were poorly made and agreed that tolerances were not right.

Will be running regrind cams in my 90

This some what follows what Todd P wrote in his thread when he spoke with his "Cam Guy"....said that the lobe profile is all messed up ( lack of R&D time?) and that the valve spring loads are unnecessarily high for no good reason.

I also remember John Phroggs saying why can't we line bore the caps out so we can use some kind of bearing. That would also withdraw the need for matched cam cover + head.

Okay, obviously I'm out of my depth quite a bit....it's just I think in their haste to get it done before the axe fell the whole LT5 thing was a bit rushed? Dave & et al knew that their BOD cover would not last if they worked out all the small details. I remember that in Dave's book the general tone of the domestic CPC engineers was one of resentment at the Lotus & MM guys for appearing to do the impossible. Heck the domestic CPC guys were having trouble getting the L98 to be OBDI compliant and have power and no gas guzzler tax! I got the idea that Dave was aware that those guys had the long knives out for the LT5 project.

On another note.....I am envious of the resources that all the Brothers out in the Indiana & Illinois area have developed.....you guys don't know how lucky you are, or maybe you do? Out east there isn't a single person that I would trust my LT5 with if it meant going any further into the motor than doing the injectors! Color me green with envy.:mrgreen:

Happy New Year Fellars!
:cheers:
Tom

[LGAFF]

The cam resource I pulled out of my A$$......called a number on a gut feeling.....turns out this guy used to make cams for a well known LT-5 Tuner...hmmmmmmm.

[A26B]

I hate to see an engine that passed incredible durability tests and powered a new speed & endurance record run, get bashed over a hypothetical lube and cam problem. Come on guys, take a look at the actual, empirical data. The LT5 was built with the precision and care of a race engine. It's durability is legendary.

As far as lube goes? I've torn down several engines that have been sitting for 20 years, with no rotation. The last one was a 1990 model, #017. All of the rod bearings/journals still had plenty of oil when I inspected them (like new). I reassembled the engine with the new head gaskets for test purposes, threw in a set of used injectors from my 94 and fired it right up. Ran it for 2 days with no smoke & no problems. Tore it down and found no damage. That's 20 YEARS.

I'm not worried about lube at start-up. When was the last time anyone heard of an engine failing from such?

[LGAFF]

Jerry, Don't think we are really bashing the engine so much as discussing the developement, one issue people bring up is the long crank time on the LT-5.....guess there might be a reason for it...

As far as the cams, guess I always thought the issue was the lady in BG and start technique but sounds like there were clearance issues....and as noted they were corrected. The info I had came first hand from a manager at MM who helped build the first LT-5, even before the assembly line was in place.

The cam issue I am bringing up also due to some problems with regrinds, etc.....looking to have some done for the 90.

If I did not think the LT-5 was great, I would not own 3 motors(2 in car: 1 Spare)...could easily go sell them and get a Z06...

[A26B]

Jerry, Don't think we are really bashing the engine so much as discussing the developement, one issue people bring up is the long crank time on the LT-5.....guess there might be a reason for it...
You're right. So many, non-ZR-1 owners, seem to think it's high maintenance, no parts & a problem child. I get a little defensive. Sorry 'bout that.


As far as the cams, guess I always thought the issue was the lady in BG and start technique but sounds like there were clearance issues....and as noted they were corrected. The info I had came first hand from a manager at MM who helped build the first LT-5, even before the assembly line was in place.

That was very early in the program

The cam issue I am bringing up also due to some problems with regrinds, etc.....looking to have some done for the 90.
The problem with regrinds, in my opinion, are three-fold; (1) the base circle diameter has to be reduced to obtain more lift, (2) when the base circle diameter is reduced for more lift, the ramp angle increases and puts more torque on the camshaft x 8, and (3) the increased torque is ultimately focused at the weakest link in the camshaft, at the nose where the sprocket & vernier fit onto the camshaft. I've seen several cams with broken noses.


If I did not think the LT-5 was great, I would not own 3 motors...could easily go sell them and get a Z06...
LEE, YOU NEED A FEW MORE!:cheers:

[LGAFF]

Jerrys Gaskets: Banned list

Lee Gaffigan=Lifetime ban:eek:

[A26B]

Jerrys Gaskets: Banned list

Lee Gaffigan=Lifetime ban:eek:

OK, OK, stop whining. You can come out of your room now.:)

[LGAFF]

OK, OK, stop whining. You can come out of your room now.:)

:sign10:

[LGAFF]

Speaking of broken noses on cams...anything that can be done with those? I have 1....

[Hog]

It was mentioned by a MM dyno operator that, and I quote

"3)Cam shaft failures....more to it than someone at the plant over revving the motor....there was nearly "0" clearance on the cams, creating an oiling issues...this was fixed....many of the spare motors floating around were the motors with cam clearance issues."

Does this imply that the "crate" LT5's floating around that will have this problem? I ask simply because the MM LT5 program ended so much earlier than the actual Bowling Green ZR-1 program ended. Problems identified by actualy driving the car could not be solved on the LT5 assembly line, simply because that assembly line didnt exist anymore.

I don't own a ZR-1, but I think that the LT5 is an excellent engine.

peace
Hog

[LGAFF]

No not crate engines, it was corrected early.....there were some of the test motors floating around that had the issue......many of them were fixed. I am also guessing that it was a case by case basis.

There was a guy with 10-11 of the motors, and they had the issue, as I understand it they were all corrected by someone. I believe the guy got these for free.

[tomtom72]

I hate to see an engine that passed incredible durability tests and powered a new speed & endurance record run, get bashed over a hypothetical lube and cam problem. Come on guys, take a look at the actual, empirical data. The LT5 was built with the precision and care of a race engine. It's durability is legendary.

As far as lube goes? I've torn down several engines that have been sitting for 20 years, with no rotation. The last one was a 1990 model, #017. All of the rod bearings/journals still had plenty of oil when I inspected them (like new). I reassembled the engine with the new head gaskets for test purposes, threw in a set of used injectors from my 94 and fired it right up. Ran it for 2 days with no smoke & no problems. Tore it down and found no damage. That's 20 YEARS.

I'm not worried about lube at start-up. When was the last time anyone heard of an engine failing from such?

:o okay, may I come out of my room also?

I'm not bashing. I should have put question marks in place of some of the periods. Ignorance breeds fear. When you guys type about the internals of an LT5....I sit up and take notes. This is a steep learning curve for me.

Heck, I'm part of the choir and as far as I'm concerned I take great relish in pointing out that us ZR-1 owners are the only ones with a hand built motor in an American production car :mrgreen:.....contrary to the hand assembled stuff you can get now. I'm not throwing rocks....well maybe small ones! :p ....but nothing about most the parts for an LT5 arrived at MM ready to assemble!
:cheers:
grasshopper

[A26B]

:o okay, may I come out of my room also?


Well...... OK, but only if you promise to play nice.:handshak:;)

[tomtom72]

Well...... OK, but only if you promise to play nice.:handshak:;)

:mrgreen: I promise! :sign10:

Happy New Year guys!:cheers: