Cam and Injection issues.
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Teching In
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From: North Carolina
Cam and Injection issues. So I'm not to well versed with injection systems so I need some help. My brother has a 93 Z28 with the LT1. He recently had the engine rebuilt, had it bored 30 over and put a LT4 cam in the new build other than that the engine is stock for the most part. cold air intake and new injectors and regulator. now that he got the engine back from the builder the engine has and issue with running extremely rich. It is loading the crank case with fuel and it is mixing with the oil. Now he just put new injectors in it cause some one said he may have leaky injectors and he also put a new regulator in along with fuel filter. In the beginning of this issue a few months ago he was told that the stock ECM was not recognizing the LT4 cam specs and that was causing his issue so we bought a JET performance chip and it eliviated the problem for a few miles and it was back. He also had a custom chip built for 500 dollars. The problem seems not to want to go away. I'm beginning to wonder if there is a mechanical problem with the build itself. over honing, rings not seating etc. Any one had this problem after they rebuilt this engine and put a light to mild pretty much stock LT4 corvette cam in there camaro engine? any thoughts would help. he is throwing money at parts and not really mechanically enclined. I'm just not well versed with the technical issues and and trying to get a lead on a diagnosis or where to begin with my checks. thanks.
What injectors? 1993's are equipped with 22lb injectors instead of 24lbs like later years. I also believe the PSI rating is different? Whatever you do, don't run the engine until you figure this out. Could end up washing the cylinders.
Last edited by SS RRR; Mar 21, 2019 at 11:23 AM.
Thread Starter
Teching In
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From: North Carolina
Not sure what injectors he bought, all though he said they looked different. I will have to ask him if he has the specs on the new ones. I get what you mean about washing out the cylinders but what damage would this cause? This engine has run quite a bit but not really been driven. He does change the oil in it when it gets anywhere near saturated so I done think he has washed it out. I'm going to run a leakdown test on the cylinders to see what he may be losing there.
Not sure what injectors he bought, all though he said they looked different. I will have to ask him if he has the specs on the new ones. I get what you mean about washing out the cylinders but what damage would this cause? This engine has run quite a bit but not really been driven. He does change the oil in it when it gets anywhere near saturated so I done think he has washed it out. I'm going to run a leakdown test on the cylinders to see what he may be losing there.
TECH Resident
Joined: Oct 2006
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From: Euless, TX
So I'm not to well versed with injection systems so I need some help. My brother has a 93 Z28 with the LT1. He recently had the engine rebuilt, had it bored 30 over and put a LT4 cam in the new build other than that the engine is stock for the most part. cold air intake and new injectors and regulator. now that he got the engine back from the builder the engine has and issue with running extremely rich. It is loading the crank case with fuel and it is mixing with the oil. Now he just put new injectors in it cause some one said he may have leaky injectors and he also put a new regulator in along with fuel filter. In the beginning of this issue a few months ago he was told that the stock ECM was not recognizing the LT4 cam specs and that was causing his issue so we bought a JET performance chip and it eliviated the problem for a few miles and it was back. He also had a custom chip built for 500 dollars. The problem seems not to want to go away. I'm beginning to wonder if there is a mechanical problem with the build itself. over honing, rings not seating etc. Any one had this problem after they rebuilt this engine and put a light to mild pretty much stock LT4 corvette cam in there camaro engine? any thoughts would help. he is throwing money at parts and not really mechanically enclined. I'm just not well versed with the technical issues and and trying to get a lead on a diagnosis or where to begin with my checks. thanks.
The STOCK LT4 cam should have ZERO issues running on a stock LT1 tune. I had a L98 TPI 350 in my G20 van with the 7730 speed density ECM. I had ported vortec heads, edelbrock base, high flow SLP runners, a stock LT4 cam, 1.6:1 full rockers, headers and LT4 28 lb/hr injectors and it still started up, idled, ran and drove on the stock 350 TPI chip.
Prior to that LT4 cam being in that engine it was in a TBI 350 in the same van. It also ran well on the stock TBI chip. The LT4 cam has great idle vacuum and should not run nearly as richly as you describe.
I also had another LT4 cam in a Vortec 350 running on the stock tune for a while.
If it is the production cam and not the hotcam from my experiences I feel you need to start trouble shooting for other problems.
Thread Starter
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From: North Carolina
it is the hot cam for sure. It was running rich prior to the new injectors being installed. The new injectors are the later 24 pound injectors. he just bought them and installed them the other day but the issue with the car running rich existed prior to that installation. I believe it is due to the cam. I believe the lift and duration are so large that the stock computer is causing the issue. but the custom chip is tuned specifically for the cam that is installed. we are putting it in bow yo see if that makes a difference now with the new injectors. the 24 lb injectors.
Pretty sure with the chip tuning stuff you have to include the flow of injectors used, or you run into exactly what you're facing. Do you know if the 24lb injectors used are at the same PSI as what you're running?
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not sure about the answer to that. I do know the 24 lb injectors he bought are the stock replacement 24lb injectors for the later model LT1. His is the early model so I think he may have created another problem in itself by installing those injectors.
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Teching In
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From: North Carolina
Ok so update. I know for sure it is the LT4 Hot Cam and the injectors he installed are the 24Lb injectors. There are no trouble codes in the ECM and I did a fuel pressure test and it is running right at 38 to 42 LBs of pressure which seems low considering the Chilton manual he has says it should run between 55 and 60 Lbs. whether the manual is correct I don't know. Is the lift and duration of the LT4 Hot Cam to large for a .030 over build with stock fuel injection? I do know we will have to put the stock injectors back in the car if the 24Lb injectors are to large but prior to that it was mixing fuel and oil and running rich. so I'm beginning to think it is the cam and has been all along.
Are you checking this fuel pressure with the vacuum hose off the fuel pressure regulator? If not and you’re checking at idle, the pressure will be low. Taking the vacucum off the FPR simulates wide open throttle.
one thing to make sure with the 24# injectors is that they are rated 24lbs/hr @ 43.5psi and not another fuel pressure.
in regards to is 24# injectors enough for a cam only car? most h/c cars are fine with stock injectors.
in regards to is 24# injectors enough for a cam only car? most h/c cars are fine with stock injectors.
Thread Starter
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From: North Carolina
So problems persist. So as was posted in the earlier thread, my brother has a 93 Camaro LT1. .030 over bore and LT4 Hotcam. The issue was it was flooding the cylinders with so much fuel it was saturating the oil in the crank case. He has replaced all the injectors,MAP, and both temp sensors. After which the car ran fine for about 300 miles then it started again. I found that the wiring connector to the idle air control valve on the throttle body was damaged and was not making a good connection. I disconnected and seen it was broken. Plugged it back in the best I could. (Needs to be replaced). After I did that it seemed to run fine for 300 miles like I stated. This issue also seems to be making the cooling fans run erratic. Sometimes they will run constant as soon as you turn the key on and sometimes the fans won't
run until temp reaches about 200 degrees. I think the issue is in the wiring, whether it is a bad connection or faulty ground etc. He has replaced every thing we can think of. Any ideas would help.
run until temp reaches about 200 degrees. I think the issue is in the wiring, whether it is a bad connection or faulty ground etc. He has replaced every thing we can think of. Any ideas would help.
If there are any codes you can jump the pins on the data port to see what they are. I believe you can find out which pins on www.shbox.com