Cam Change = Trouble
Thread Starter
Cruising
Joined: May 2004
Posts: 14
Likes: 0
From: Pocasset Ma
Cam Change = Trouble
First of all greetings to all. This is my first post. I have been reading C4 Tech for over a year. There is alot of good info and ideas coming form this site. :cheers: I have a 1990 auto with 2:59 rear. Best run according to G tech was 13.7. Not bad but I wanted better. Thus the Comp Cams 266H-R14,Big Mouth, Large tubes, and roller rocker swap. Cam specs 266-276 with lifts of .500-.510 duration 210-220 lobe seperation of 114. Lt4 hot cam springs also installed. after 34 hours of lots of aggrivation finally fired her up this weekend. Sounded great,no leaks,idles great. The test run was very depressing. No throttle response. 2500 rpm is about the limit. All gears what gives? She wont let me get on it.
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: Cam Change = Trouble (SOUL SKINNER)
First of all check base timing and fuel pressure at WOT. Did you degree the cam or assume the cam card was accurate and install it straight up?
I suspect you may need an AFPR to add more fuel at WOT.
Your might also check idle vacuum; if you lost any manifold vacuum you will need a chip (that may be needed anyway).
I suspect you may need an AFPR to add more fuel at WOT.
Your might also check idle vacuum; if you lost any manifold vacuum you will need a chip (that may be needed anyway).
Thread Starter
Cruising
Joined: May 2004
Posts: 14
Likes: 0
From: Pocasset Ma
Re: Cam Change = Trouble (65Z01)
Afpr is installed I've run between 40-44 lbs. Cam was installed straight up. The chip is hypertech. I have checked for vacum leaks. I'm leaning towards timing or the chip. initial has been set between 6 an 10 with no difference. She idles great and as long as I press the pedal slowly and let it catch up she''ll cruise just fine. No bucking, no surges, no backfire. disgusting problem.
Le Mans Master
Joined: Feb 2000
Posts: 9,715
Likes: 27
From: Kempner Texas
Re: Cam Change = Trouble (SOUL SKINNER)
The cam you installed is very mild so you should have tons of low end and excellent throttle response.
Are you saying the engine will not rev about 2500 rpms? What happens at that point?
Are you getting any error codes?
Jake
Are you saying the engine will not rev about 2500 rpms? What happens at that point?
Are you getting any error codes?
Jake
Burning Brakes
Joined: Jul 2002
Posts: 871
Likes: 0
From: Costa Mesa CA
Re: Cam Change = Trouble (SOUL SKINNER)
Yeah...
Make sure you check your base timing. When my engine was first built, the timing slipped from where my mechanic set it and it fell flat on it's face, like you mentioned. disconnecting the orange wire and setting base timing at 6 degrees did the trick. Be sure and reconnect that wire.
I have had 3, C4's and did most of the work on all of them myself. I can say that the knowledgeable people on this forum has increase my knowledge beyond what I have learned on my own. You have made the best coice you could have made to keeping you car running right by becoming a member here. Great stuff in the archieves.
Welcome to the forum!
BIG JIM
Make sure you check your base timing. When my engine was first built, the timing slipped from where my mechanic set it and it fell flat on it's face, like you mentioned. disconnecting the orange wire and setting base timing at 6 degrees did the trick. Be sure and reconnect that wire.
I have had 3, C4's and did most of the work on all of them myself. I can say that the knowledgeable people on this forum has increase my knowledge beyond what I have learned on my own. You have made the best coice you could have made to keeping you car running right by becoming a member here. Great stuff in the archieves.
Welcome to the forum!
BIG JIM
Drifting
Joined: Oct 2001
Posts: 1,648
Likes: 1
From: Denham Springs Louisiana
Re: Cam Change = Trouble (Dominic Sorresso)
Try out www.pcmforless.com I hear great things about these guys and they are in the process of getting me my new program for my LT4 Hot Cam install. Bryan there at PCMforLess told me thay had great success with the Hot Cam. Great prices and very friendly. :thumbs:
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Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: Cam Change = Trouble (SOUL SKINNER)
Yes, 210/220 at 114 should still have good idle vacuum.
Try 48psi on fuel pressure.
If 2,500rpm is your top it could be either fuel or ignition, assuming valve adjustment is ok.
If upping fuel pressure doesn't do the job, pull a spark plug and check compression.
Try 48psi on fuel pressure.
If 2,500rpm is your top it could be either fuel or ignition, assuming valve adjustment is ok.
If upping fuel pressure doesn't do the job, pull a spark plug and check compression.
Drifting
Joined: Nov 2002
Posts: 1,790
Likes: 0
Re: Cam Change = Trouble (65Z01)
This has nothing to do with your problem, but man, those 2.59s are your weak link, especially with a cam that gives the motor a higher powerband.
There's a lot of arguments that have merit against going with numerically high gears with an LT1, but the fact is, to me, getting off the line with 2.59s feels like pulling a bass boat. When I drove an LT1 w/2.59s for the 1st time, I thought the parking brake was on!
If you lose any torque down low because of your cam, those gears are going to slow you down even more. Cruising the interstate in OD, you could even be chugging along below where the engine makes any power at all, killing your response.
There's a lot of arguments that have merit against going with numerically high gears with an LT1, but the fact is, to me, getting off the line with 2.59s feels like pulling a bass boat. When I drove an LT1 w/2.59s for the 1st time, I thought the parking brake was on!
If you lose any torque down low because of your cam, those gears are going to slow you down even more. Cruising the interstate in OD, you could even be chugging along below where the engine makes any power at all, killing your response.
Melting Slicks
Joined: May 2001
Posts: 3,270
Likes: 26
From: Winchester VA
Cruise-In V Veteran
Re: Cam Change = Trouble (SOUL SKINNER)
I had your exact symptoms with my new motor. I also kept throwing timing at it with no change, I stopped adding timing being nervous about going to far and putting a whole in a piston. Since there was no change at all, I assumed I was barking up the wrong tree. It took a couple guys I work with to sit there with me and keep adding timing, well, it was a whole new motor.
My motor would fall on it's face when the throttle was snapped open. So we sat on the front tires bumped up timing, cracked throttle, and repeated until all of the sudden after adding like 6* with no change an additional 2 woke it up. I thought it was strange that there was no noticeable difference while we worked our way up. This is why I stopped before, I was getting NO change, I assumed it would get progressivley better.
Now I'm not suggesting you go out set it to 15* base and romp on it, BUT, if your not getting detonation at 10*, I don't see the harm in exploring additional timing.
PS. I went from a pathetic (for the motor in the car) 13.9 at 112 to 11.9 at 118, with a little timing.
My motor would fall on it's face when the throttle was snapped open. So we sat on the front tires bumped up timing, cracked throttle, and repeated until all of the sudden after adding like 6* with no change an additional 2 woke it up. I thought it was strange that there was no noticeable difference while we worked our way up. This is why I stopped before, I was getting NO change, I assumed it would get progressivley better.
Now I'm not suggesting you go out set it to 15* base and romp on it, BUT, if your not getting detonation at 10*, I don't see the harm in exploring additional timing.
PS. I went from a pathetic (for the motor in the car) 13.9 at 112 to 11.9 at 118, with a little timing.
Melting Slicks
Joined: May 1999
Posts: 2,037
Likes: 0
From: Sarasota FL
Re: Cam Change = Trouble (SOUL SKINNER)
With your MAP system, a little change in vacuum is going to make a noticable fueling change. At least some of your problems are in there. Learn to burn your own programs to really custom tune your motor.
Thread Starter
Cruising
Joined: May 2004
Posts: 14
Likes: 0
From: Pocasset Ma
Re: Cam Change = Trouble (JAKE)
No there are no error codes. Aftrer 2500 rpm nothing happens. Go from park to drive and roll out the driveway. just touch the pedal a little and everything is still normal she'll even chirp the wheels a little. cruise at 1500 and floor it . :U . I have to let off and press the pedal slowly. All gears are the same. In O.D. at 2500 rpm she going 95.so she is making power. idle vacum meaures 19lb.She can once in a while manage 3000 rpm but no difference in power.
Thread Starter
Cruising
Joined: May 2004
Posts: 14
Likes: 0
From: Pocasset Ma
Re: Cam Change = Trouble (red L98)
Big thanks to all that have replied. I'm gonna try various timing and fuel settings and see what happens. This will take me a few days. I don't have much free time to play. If I get this figured out I'll let you know what fixed it. 0-60 in 15 seconds doesn't cut it. :eek:
Team Owner
Joined: Mar 2000
Posts: 83,383
Likes: 87
From: Boston, MA
Looks like you're about 45 minutes south of me. Let me know if you need someone to come down there with a laptop and scan your ECM while driving around. I can burn chips too, but don't have any spare EEPROMs on hand.
Melting Slicks
Joined: Jul 2003
Posts: 3,413
Likes: 138
From: Texas
Re: Cam Change = Trouble (scorp508)
Has Jesse ever even done a speed density car? :confused:
Safety Car
Joined: Dec 2002
Posts: 3,655
Likes: 24
From: Charleston SC
Re: Cam Change = Trouble (SOUL SKINNER)
Just off hand I don't think it's F/P. I would llok at timing first then valve adjustment. How far past zero lash did you go? If you went one full turn then back them off 1/2 turn and give it a go. My first motor many moons ago I followed the recomended valve adjustment in mt haynes book of 1 full turn past zero lash and it ran just as you describe.
Good luck
Good luck
Thread Starter
Cruising
Joined: May 2004
Posts: 14
Likes: 0
From: Pocasset Ma
Re: Cam Change = Trouble (84LT1)
Yeah, I followed the Haynes book with 1 full turn. This should be fine. Years ago I had a 74 with a 350. that also saw many, many changes Every time I tore into her I've always adjusted with 1 full turn with roller rockers . One time one rocker was incorrect and the roller rocker and pushrod were destroyed. Tooo loose. Lots of clackety clack. unmistakeable sound.