could this be the problem?
Thread Starter
Race Director
Joined: Feb 2000
Posts: 12,431
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From: CT
could this be the problem?
i recently posted about how i think my car is running out of gas on the top end. i may have found the problem, what do you think.
while at my friends shop today i decided to check my timing, with his 200 dollar timing light. at idle i am at 14 deg. that is what i always got with my 50 dollar light. but this light can also tell you the advance of the motor at all rpms. it showed 57 deg. at 5500 rpm!!!!!!! what the f*cK>???? what should i do about this? how can i fix it. shouldnt it be at like 28 deg? my friend says that since i am running a stock 79 Hei distrubutor in a moded vette, the distrubutor may be all wrong for the car.
what should i do? any help much appreciated. i am triing to get this fixed before the covette challenge on saturday. thanks.
ps, im starting to hate cars
while at my friends shop today i decided to check my timing, with his 200 dollar timing light. at idle i am at 14 deg. that is what i always got with my 50 dollar light. but this light can also tell you the advance of the motor at all rpms. it showed 57 deg. at 5500 rpm!!!!!!! what the f*cK>???? what should i do about this? how can i fix it. shouldnt it be at like 28 deg? my friend says that since i am running a stock 79 Hei distrubutor in a moded vette, the distrubutor may be all wrong for the car.
what should i do? any help much appreciated. i am triing to get this fixed before the covette challenge on saturday. thanks.
ps, im starting to hate cars
Race Director
Joined: Dec 1999
Posts: 19,610
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From: Forked River NJ
Re: could this be the problem? (Vetteboy)
You should be about 36 to 38 total without vacuum advance. the bushing that limits advance is worn out and the dist is advancing way to much. Mine went to 60 degrees toatl. I had my dist setup on a machine to get a total of 36 to 38 with 12 initial. You need to have the dist setup properly. Lars is an expert at this and may resond to this also.
Thread Starter
Race Director
Joined: Feb 2000
Posts: 12,431
Likes: 1
From: CT
Re: could this be the problem? (Gordonm)
do you think that this is majorly affecting my performance? how much better is your car running now, compared to before? what should the advance be with the vacume pluged onto the distibutor? i am pretty sure i had the vacume hooked up when we did this. is it still way off?
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Re: could this be the problem? (Vetteboy)
With the vacuum advance hooked up 50 to 52 is not unreasonable. The vacuum advance usually adds another 12 to 16 degrees. This is for better fuel economy while cruising. When your foot is in it the vacuum is out and you should be around 36 to 38. Any more and the car might ping or run poorly. My car would buck at cruising speed. I never ran it hard with the dist in poor shape. I fixed the problem before running it hard.
Race Director
Joined: Dec 1999
Posts: 19,610
Likes: 778
From: Forked River NJ
Re: could this be the problem? (Vetteboy)
I would say no. I still have the original dist. in mine. I had it setup by a pro for about 50 bucks. I was considering a new one and decided to try this. It works great. I run a Crane HI6 triggered by a set of heavy duty points and have run it to 7000 rpm without a miss. Unless the housing is wiped out it can be fixed. I know Lars has done many for people here but a good shop with a distributor machine can set it up for you. Even with a new one it might not be setup for your car. The right weights and advance curve should be setup.
[Modified by Gordonm, 4:59 PM 9/29/2001]
[Modified by Gordonm, 4:59 PM 9/29/2001]
Instructor
Joined: Jul 2001
Posts: 240
Likes: 0
From: kennett square,pa,us
Re: could this be the problem? (Vetteboy)
Vetteboy,
Have you solved your problem yet? I just installed new plugs in my 3.55 and took it for a spin, same problem as you have. At about 5,000 it was like someone turned off the key, let off the fuel it jumped back to life.
What type fuel pump are you using? What size fuel line? I know you have a 750, I am only using a 650 Demon, but with twin squirters. I have 3/8 from the pump to the first outlet tee and the 1/4 from the tee to the secondaries and from the tee to the primeries. I am convinced that we have a fuel problem. I am going to change the fuel size on mine to straight 3/8 and will let you know the results.
Any comments?
Have you solved your problem yet? I just installed new plugs in my 3.55 and took it for a spin, same problem as you have. At about 5,000 it was like someone turned off the key, let off the fuel it jumped back to life.
What type fuel pump are you using? What size fuel line? I know you have a 750, I am only using a 650 Demon, but with twin squirters. I have 3/8 from the pump to the first outlet tee and the 1/4 from the tee to the secondaries and from the tee to the primeries. I am convinced that we have a fuel problem. I am going to change the fuel size on mine to straight 3/8 and will let you know the results.
Any comments?
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Melting Slicks
Joined: Apr 2001
Posts: 3,399
Likes: 278
From: Olmsted Falls, Ohio
Re: could this be the problem? (bud snyder)
Bud, just a thought.... If it was the fuel line size after the "T" then the bowls would have drained. And when you let off the throttle, they would have had to begin to refill. I can't see how it could have "jumped back to life" that fast. I would bet on the distributor. Either module or coil cutting out at that high rpm.
Instructor
Joined: Jul 2001
Posts: 240
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From: kennett square,pa,us
Re: could this be the problem? (KenSny)
Ken,
I have the new MSD Pro Billet in there. I didn't have this problem when I had the car Dynoed! It has only surfaced since the new cam. With this cam I should be using a lot more fuel right? 9 miles to gallon worth! If I could watch the fuel gauge while we are dynoing the car I could see the fuel pressure! My theory is that the secondaries are robbing the primaries, because they are straight in line and thr primaries are at a 90o right angle.
I have the new MSD Pro Billet in there. I didn't have this problem when I had the car Dynoed! It has only surfaced since the new cam. With this cam I should be using a lot more fuel right? 9 miles to gallon worth! If I could watch the fuel gauge while we are dynoing the car I could see the fuel pressure! My theory is that the secondaries are robbing the primaries, because they are straight in line and thr primaries are at a 90o right angle.
Instructor
Joined: Jul 2001
Posts: 240
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From: kennett square,pa,us
Re: could this be the problem? (KenSny)
Ken,
I just took another spin. My tach is not working accurately.
Do you think I may have started to float the valves? I looked up the springs on the heads and they are as follows, single/1.32 inches/101#@178" solid height 1.22" rate 332. What do you think?
I did a wot in fourth at about 3000, it didn't like it at all! Head light warning light came on momentarly on dash.
I should have time in the next 2 weeks to get chass. dyno. We use their tach during the run so, I will know if valve float was the problem.
I just took another spin. My tach is not working accurately.
Do you think I may have started to float the valves? I looked up the springs on the heads and they are as follows, single/1.32 inches/101#@178" solid height 1.22" rate 332. What do you think?
I did a wot in fourth at about 3000, it didn't like it at all! Head light warning light came on momentarly on dash.
I should have time in the next 2 weeks to get chass. dyno. We use their tach during the run so, I will know if valve float was the problem.
Melting Slicks
Joined: Apr 2001
Posts: 3,399
Likes: 278
From: Olmsted Falls, Ohio
Re: could this be the problem? (bud snyder)
Sure sounds like something is going on with vacuum - maybe related, maybe not. See this thread: http://forums.corvetteforum.com/zerothread?id=162253
I was thinking about your initial post on the fuel lines. Did the engine just "quit" or did it sputter. I would think that if it was running out of fuel it would sputter whereas a coil voltage problem would cause a noticable pause in the engine.
Are those the springs recommended by Comp Cams for the 274? If they are the ones from your other cam they could be too weak and causing valve float at max lift (which is now more than with the other cam). I remember looking at the Comp Cams cam spring recommendations and the 274 is the same as what I'm getting for the 262 or 268 #981-16. Go there and compare the specs. Maybe with your 1.6 rockers the springs are not enough.
One other thought, get a fuel pressure gauge ($15-20) and run a hose off of your T (use clamps so you don't blow a hose) so you can see it and try to simulate the problem again.
[Modified by KenSny, 11:09 AM 10/7/2001]
PS: Just remembered that you have a gauge on your carb lines, so just extend it to where you can see it with the hood closed.
[Modified by KenSny, 11:43 AM 10/7/2001]
I was thinking about your initial post on the fuel lines. Did the engine just "quit" or did it sputter. I would think that if it was running out of fuel it would sputter whereas a coil voltage problem would cause a noticable pause in the engine.
Are those the springs recommended by Comp Cams for the 274? If they are the ones from your other cam they could be too weak and causing valve float at max lift (which is now more than with the other cam). I remember looking at the Comp Cams cam spring recommendations and the 274 is the same as what I'm getting for the 262 or 268 #981-16. Go there and compare the specs. Maybe with your 1.6 rockers the springs are not enough.
One other thought, get a fuel pressure gauge ($15-20) and run a hose off of your T (use clamps so you don't blow a hose) so you can see it and try to simulate the problem again.
[Modified by KenSny, 11:09 AM 10/7/2001]
PS: Just remembered that you have a gauge on your carb lines, so just extend it to where you can see it with the hood closed.
[Modified by KenSny, 11:43 AM 10/7/2001]
Thread Starter
Race Director
Joined: Feb 2000
Posts: 12,431
Likes: 1
From: CT
Re: could this be the problem? (KenSny)
well guys, i dont know if i have solved the problem yet but i did run two 12.97s yesterday at 103. all i did was change the rotor and cap, they had a bad build up of carbon or something and had a chip on the inside of the cap. i dont think the problem is solved yet. i still think that there is a problem at the top end. mabey related to fuel flow or just not enough HP. i may change my performer rpm to my team G intake in the next few week. just to see if it hurts or helps in my 1/4 times and mph. i will keep you posted.
[Modified by Vetteboy, 3:09 PM 10/7/2001]
[Modified by Vetteboy, 3:09 PM 10/7/2001]