I got a local engine shop to rebuild my LT1 engine in my 96 Z28 because a mechanic told me that the best thing to do with a rear main seal leak is to get a rebuilt engine installed in it.
He said he could fix the leak but it would leak again at some point... Not sure if this is true or not, but supposedly the guy is trustworthy.

Anyway, so I dropped of my Camaro and during the engine rebuild I purchased a comp cam 07-304-8 and a Edelbrock 3810 58mm throttle bottle for the engine shop to install with the engine rebuild. They did the rebuild, installed my cam and throttle body, but when we got it home we noticed the car was still leaking oil and we notice a whistling sound coming from somewhere in the air intake system. Forgot, I had previously installed a K&N air filter, which is the one where the air filter mounts underneath the car, so we weren't sure if the engine shop got the filter back on the way it should be.
Also, the engine stalled out on me several times coming home at a stop light and seemed to not be idling correctly.

So I took the car back in to the engine shop, they worked on it for two days, said they had it fixed, so we went to pick it up today. The shop foreman gave me the keys and told me to go out and try starting the car. I did and it started, but then died. Of course from the old days, I pushed the gas pedal all the way to the floor and let go, tried to start it again and it would not start. I smelled gas really bad. The shop foreman came out and cranked and cranked the car and it finally started. He told me it would be ok now, that when I pressed the pedal all the way to the floor it caused the fuel injectors to dump a bunch of fuel into the engine and flooded it out.

One thing, the shop foreman attempted to adjust the idle speed when they were working on it by adjusting the screw that the throttle assembly stop contacts when the gas pedal is not depressed. Before I left to drive the Z28 home he told me that that the adjustment did not help the idle speed but it stopped the whistling sound.

I started thinking that maybe this isn't a good thing, that maybe the adjustment he made decreased the airflow into the throttle body, don't know, maybe someone here does.

I made it home ok, although the car just did seem to run as good as I felt it should. Oh yeah, another thing the engine shop called me during the engine rebuild and told me that the plugs (brand new) were fuel fouled and needed to be replaced and this was cause by bad seals in the fuel injectors, so they had to rebuild the fuel injectors....

What is bad is now we have my Z28 here at home, it looks like it is still leaking oil and now it won't start and smells like it's flooded out every time I try to start it. Any ideas why this is happening?

Could any of the starting problem, idle problem, stalling problem and flooding out be computer related?

I feel they did find the source of one of the oil leaks, although I had never heard of a bad distributor seal causing an oil leak. Help Please!!

Thanks

James

 

The whistle is the BBK TB they do that. A cam swap requires reprogramming the pcm, I don't care what the catalog says. A larger TB with an automatic tranny will blow up the tranny if either the pcm is not tuned for it or a shift kit is not added.

all the aftermarket TBs screwup the idle because they do not keep the factory IAC distribution system sealed and eliminate the bleed hole.

Your mechanic is a flat out thief if he told you a rear main leak made a rebuild a good idea and probably incompetent to boot since actual rear main leaks are rare.

Far as the persistent oil leak the inner lip of the waterpump drive seal was likely folded outward when it was installed ruining the seal.

I have to go out now but will reply with more later.

Post a vague location maybe someone local can help you make it run right.

 

Thanks for the info. I forgot about this, but the engine shop said the water pump was bad and they had to replace it which is interesting because of your comment about the water pump drive seal.
I finally got the car started by pressing the accelerator about halfway down. I hooked up my Actron scanner because the SES light came on and pulled a P0302which shows to be a cylinder 2 misfire.

Man, what do I do now? The engine shop has no way of programming the PCM and I definitely don't want to blow up the transmission. What type of programmer is needed and is the programming hard to do?

Did the engine shop mechanic mess anything up when he adjusted the screw on the Edelbrock TB that the TB stop contacts?

 

Sadly, your mechanics probably know less about your car than the average person on this site, but we probably can't really fix anything for you with that information. You need to provide more information. But here are some things to consider:

If a rear main seal is leaking, it is a pain to get to because the tranny has to come out, but it doesn't imply that t he engine needs to be rebuilt. Did you have a ton of miles on it? The intake manifolds on these cars leak all over if they haven't been sealed up properly - and it will go all over the back of the engine and under the car. The water pump drive can leak oil, too, if it isn't done correctly, and most people don't do it correctly the first time without damaging the orings.

The 58mm throttle body was also not needed and probably didn't help your calibrations if you have an automatic transmission, because the transmission shifts partly from the throttle angle and now you need less throttle angle for the same air flow. Besides that, your stock throttle body is more precise and flows enough air for your engine. Maybe a 52 would be better, but a 58 is a little too big.

You probably need a little tuning of the computer for the cam, not much, but some adjustments are probably needed. Again, this is less important if you have a 6 speed, but if it is an automatic, it will be more picky, especially with a tight stock converter.

You can lift the whole fuel rail/injector assy off the intake and then see if it keeps dripping out if the injectors after it primes when you turn the key to the on position. It is supposed to hold pressure in the fuel system when you turn it off.

You could have a bunch of stuff wrong, though. I can't tell from here...

 

I completely understand. I'm not giving you very good info and not enough. I am definitely no mechanic. I sure didn't think a 58mm throttle body and small cam would cause this many problems. Another thing I forgot to mention.....geez... is I purchased a ported out intake from a guy on ebay that is supposed to be compatible with a 58mm throttle body and it was installed by the engine shop as well.
So are you saying that the 58mm throttle body is definitely a bad idea and that it will not function correctly on my LT1 engine, even with a reprogramming? Man, that is bad news, because it's been on the engine and has about 80 miles on it, so I'm sure I can't return it.
Is 52mm the largest that anyone should go on a LT1 engine?

Sorry I'm not any more intelligent about this stuff. I apparently screwed up bad this time.

 

I read on another forum that as long as you have an intake ported to work with the 58mm TB that the 58mm will work...?

 

A well built high performance engine could benefit from a 52mm throttle body and a blower engine can use a 58, so they do have their applications, but if you just put one on there and twiddle the stop screw, it isn't necessarily adjusted correctly (idle is controlled by the computer and the idle air circuit stepper motor) and like I said, there are references to your transmission pressures based off throttle angle so if you are only opening the throttle 7% degrees to get moving with the 58 instead of 14% or whatever with the 48mm stocker, your transmission might not make enough pressure for the load the engine is under, and aside from that, there are sometimes other differences in the idle circuits and sometimes the springs on those need tweaking so it closes all the way - they aren't without their issues. Basically, most of them aren't built quite as well as the stock throttle body and there are minor problems with them. Your cam shouldn't be much of an issue, but the timing and idle might need to be adjusted a little and that is done in the computer.

 

Thank you,
What type programmer should be used to make the required adjustments?

 

mail-order tune i think you should start with. you can probably keep the 58mm on there its just not gonna benefit you in any way with your mods. you can put the stocker back on if youd like and probably pull a decent amount of money back just selling it on the site. but if you plan to do anything like heads just hold on to it. the mail order tune(if you get one) should be fine with it

secondly those mechanics do not sound bright at all.

also, where are you located? like mentioned if your close someone might help you. I know i would but no one is ever around me lol

 

The fact that your engine shop told you that a leaking rear main seal requires a new engine should tell you to avoid using them again.

When you put the pedal to the floor the injectors actually are forced CLOSED, not open. It's not a carb, it's fuel injection. And there are far better reasons for plugs to be fouled but NOT by bad seals in this case. Red flag.

The idle speed is not set by the throttle stop screw but by the IAC valve located under the throttle body. Setting it correctly requires the use of a scanner to monitor the IAC counts. Personally I'd get rid of the Edelbrock and put the stock one back on; you're not gaining anything (if actually LOSING) at all - just a lighter wallet and idle problems.

Definitely find another mechanic, find the real source of your oil leak, definitely get a tune, remove the Edelbrock throttle body, and definitely find another mechanic.

Did they install new valve springs or reuse the stock ones? The stock ones can only support the stock cam.

 

Sorry, it was another mechanic (at another repair shop, not the engine shop) that said there was a rear main seal leak and he could fix it for $600, but it would probably start leaking again. He recommended we not waste the $600, but put the money toward a rebuilt engine. No, I did not have the engine shop replace valve springs, because it appeared to me by reading up on the Cam that it would work with the stock engine components.
It's my bad, if it is bad, on the throttle body. I decided to do it on the premise that if you get more air into the engine, it performs better. I had no idea I would have this many problems. Like I said, I'm no expert, but I wish I could find one to figure this out here local.
Is there anyone that is using a 58mm TB on a LT1 engine and not having any issues?
I got the car cranked last night but it won't idle and I had to keep the gas pedal pushed down and hold the brake to move it from one side of the driveway to the other. I am smelling gas badly now for the short time it ran.

Man this is frustrating. And to top it all off, I still have an oil leak.

 

Eeek...talk about a waste of money. A properly installed RMS will last plenty long - a remanufactured engine probably won't. That's pretty dumb on his behalf.

The valve springs MUST be replaced - you are undoubtedly running incredibly close to if not definitely coil bind - a very dangerous condition where you can bend valves, pushrods, and do other internal engine damage. Stop driving the car until you can get them changed with the correct springs and hardware (the cam card will recommend a proper spring).

Alot of people use 58mm throttle bodies on stock engines. The trick is to getting it properly programmed for idle characteristics and transmission shift points. You can use it but like I said it's more trouble than it's worth right now. Go ahead and put the stock one back on for sure.

EDIT: Where are you from?

 

Putting your stock TB back on may have the most benefit for now. You have no mods that require a 58mm TB. It seems you made some real uninformed choices and were terribly duped by some local mechanics. That is sad to hear about. A tune for the cam would probably also help. Changing the valve springs is a must. The remaining oil leak will just have to be investigated.

The RMS is easy to change out, but having to remove the transmission and flywheel is the big obstacle (for people without the skills/knowledge/tools).

 

PCM Tutorial - Split BLMs
A little info on why all aftermarkt TBs need extra work to make work correctly.

If you really wanted a larger TB several places can open up stock TBs to 52-54mm and avoid all these issues.

Also really need to drill a bypass hole too.

Grand Sport Tech Tips: Throttle Body Mod

There was a better more comprehensive page at one point but it is down, if anyone has it please share it.

A lot of bad decisions were made and you got involved with a wildly incompetent and crooked mechanic.

I live a little south of Green Bay, if you are in NE WI send me a PM and maybe I can help, if not post where you are so we can find someone to help you make the best of this.

Far as the running rich another simple thing to look at would be if they reconnected the vacuum line to the fuel pressure regulator. I have heard of that being missed on engine reinstall and with max fuel pressure all the time it will run rich.

 

I live in Houston, TX....

I called Edelbrock tech support and they said the 58mm throttle body will work with my LT1 engine. They said the only thing that may occur is a loss of torque at lower RPM's but that the TB would help regain torque at higher RPM's.

Don't shoot me.... I'm just telling y'all what the guy said.

It's funny that their installation instructions say nothing about having to reprogram the LT1 PCM or make any other adjustments.

I had the engine shop come pick up my Z28 this morning since it is smelling of gas terribly, smoking real bad when I rev the engine and it goes from idling at 1000 to idling above 1000, idling below 1000, then stalling out. At this point, this is the only option I have, since I have a 36K mile, 3 year warranty with them.

They rebuilt the fuel injectors when they rebuilt the engine because they said the plugs (which were brand new) were fuel fouled and the injects seals were shot. We had been smelling gas off and on when the engine was completely stock and after we had minor repairs done.

Concerning the cam, the engine shop's "super tech" said it does not require the valve springs to be changed out, so since he told me that, if the engine blows up..... well then they owe me a replacement engine because of the warranty.

Will a Hypertech Programmer for the LT1 engine help this situation any? I know the instructions say when hooked up it asked you questions that you answer and then the programmer sets up the program from the answers you give. Instructions also say shift points can be set with the Hypertech and there was a guy earlier that said the 58mm TB would blow up the tranny if the PCM wasn't programmed correctly.
That seems a little far fetched, but hey, what do I know.

I know as of now I am not removing the 58mm throttle body. I know this engine has other issues that need to be resolved, possibly bad fuel injectors replaced, maybe a bad fuel pump, or something else that is causing the smell of gas and smoke from the exhausts when revved up.

Has there been anyone else here on the forum that has installed a 58mm TB on an LT1 engine with any success? I'd like to know if so.
Thanks