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Post by Deleted on Aug 13, 2012 19:36:04 GMT -5
What has changed since your recent dyno time? Ign, carb, intake?
Do you have a good ground system?
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Post by real57vetteguy on Aug 13, 2012 20:14:01 GMT -5
Bill,
Thats what is so confusing... nothing, I am taking it back up this week. The only thing I can think of is its under a different load out on the road. It really acts like its starving for fuel.
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Post by mongoose on Aug 14, 2012 5:29:10 GMT -5
How is your fuel system set up?
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Post by stan65cutlass on Aug 14, 2012 10:55:54 GMT -5
if it was fuel it would probably run poor at full throttle off the line. im thinking elsewhwere. valvetrain tight floating? (would be popping i think) centrifugul advance shorting a wire when plate rotates? or plugged high speed jet, i guess the injector pump would override it on launch
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Post by real57vetteguy on Aug 14, 2012 14:31:04 GMT -5
I'm running a Holley mechanical fuel pump, brand new tank, brand new lines and a 750 Quadrajet. I took it to a Quadrajet guru today and the secondaries are not even opening, although it it super responsive in park, under a load it isnt doing so well. I may try to change to a quick fuel or Holley street avenger 770.
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Post by real57vetteguy on Aug 14, 2012 14:40:11 GMT -5
if it was fuel it would probably run poor at full throttle off the line. im thinking elsewhwere. valvetrain tight floating? (would be popping i think) centrifugul advance shorting a wire when plate rotates? or plugged high speed jet, i guess the injector pump would override it on launch I agree but keep in mind I have never driven the car with the new engine, it feels strong to me off the line but It may have a lot more power if it were getting the proper fuel amount, where you can really notice it it at about 2800 RPM and above. no popping, no noise, just a loss of power, I know the valvetrain is adjusted properly, as it was adjusted, double checked and then triple checked before the valve covers were installed. I am also running the points dist with a petronix flame thrower kit, everything seems to check out on the ignition side.
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Post by shane on Aug 14, 2012 14:59:10 GMT -5
Do you have a fuel pressure gauge ?? Just because your fuel pump is new doesn't mean its not faulty. There are a couple of members on here that went threw the same scenario and there engines would loose power around 4000rpms do to faulty new electric fuel pumps. Also are you running a fuel pressure regulator ?
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Post by stan65cutlass on Aug 14, 2012 16:47:38 GMT -5
vacuum or mech secondaries? not opening has to be it. it will run out of gas when they are supposed to open
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Post by real57vetteguy on Aug 14, 2012 18:09:15 GMT -5
vacuum or mech secondaries? not opening has to be it. it will run out of gas when they are supposed to open BINGO my friend!!!!!! Vacuum, but the car has plenty of vacuum. They will open sitting still if you get into the throttle but under a load... not a chance. I have thought about replacing the Qquadrajet ever since I bought the engine, It run fine on the engine with a 440 lift cam, stock manifolds and small exhaust, but since the change to a 572 lift, headers, better exhaust and some "head massaging" I dont think it is up to the task. I know the quadrajet can probably be tweaked to perform fine, and that might be the best route, on the other hand it looks like fido's ass and I have my eye on a new Holley Ultra street avenger 770 cfm, any thoughts?
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Post by real57vetteguy on Aug 14, 2012 18:11:21 GMT -5
Do you have a fuel pressure gauge ?? Just because your fuel pump is new doesn't mean its not faulty. There are a couple of members on here that went threw the same scenario and there engines would loose power around 4000rpms do to faulty new electric fuel pumps. Also are you running a fuel pressure regulator ? I am not running a regulator, I did however check the fuel pressure which is 7PSI which should be fine, I know some of the Edelbrock Carbs dont like more than about 5PSI but the Quadrajet shouldnt have an issue with 7PSI.
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Post by Deleted on Aug 14, 2012 19:20:39 GMT -5
What size fuel line are you running? I remember you posting some impressive dyno numbers. Are you running a line large enough to support that power under a load? If you're not pulling enough fuel under a load to raise the engine rpm under load, you won't pull enough to open the secondaries.
I have been more than happy with my Quadrajet from the Carb Shop in Ontario, CA.. It's a stage two. Jets are 74, pri rods are 53c and sec rods are ax. I do agree that they look like poo.
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Post by real57vetteguy on Aug 14, 2012 19:40:01 GMT -5
all the lines are 3/8. But keep this in mind ( I had to go back and look at what happened because the dyno run has me confused) This is a long drawn out story but please bear with me. The engine when purchased ran strong (VERY strong) according to folks I have talked to that were on the power tour or that had rode in it. The Quadrajet was set up for that motor before I had it, When I got the engine we went from a 440 lift cam to a 572 lift cam that was ground by Mark (curlassefi), we also went from stock manifolds to headers, and better exhaust and did more port work, originally the edelbrock heads were done by dick miller with a mild port, there was an additional 2500.00 in port work done, then we did some work on the exhaust side. When I took it to Dave (the dyno shop) he was insistant on running a quick fuel carb on the engine (in which I was talking to him about buying the carb from him) so he changed the quad to the quick fuel. (I totally forgot until I called him today that we were running a quick fuel carb on the dyno) after a few jet chaanges it did very well. So when I left (he was trying to sell me this 700.00 dollar carb) I told him I would let him know, I then called the original owner of the engine in which he assured me that Quad was a great carb. I should've just bit the bullet and bought the quick fuel, I've had so much going on doing this build in the short amount of time that I am forgetting things (old age and beer also) so from that point the quad was back on the car, idles perfect, sounds great, get it on the road and BLAAAAAAA
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Post by real57vetteguy on Aug 14, 2012 19:46:22 GMT -5
on another note about new carb selection, (guys remember and laugh all day at this comment, this is my first carb engine REALLY) vacuum VS mech secondary? I am not going to be drag racing its a driver, lots of sitting in traffic, stop and go etc what do you suggest? why?
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Post by Deleted on Aug 14, 2012 20:07:19 GMT -5
I would really look at that carb. "IF" I'm remembering correctly from CO.com that engine started at roughly 340hp? I'm willing to bet your Q-jet is way off. I prefer the vacuum secondaries on the street, especially in an overdriven trans car with an auto. Call your dyno guy and talk with him a little more. I am no master tuner, in fact I will be taking mine to a friend in a couple of weeks to see if he can get any more out of it. He's an older gentleman with many years of experience under his belt who has a great understanding of Q-jets, HEI's along with all the others and how to tune them well (suspension also).
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Post by real57vetteguy on Aug 14, 2012 20:26:35 GMT -5
I would really look at that carb. "IF" I'm remembering correctly from CO.com that engine started at roughly 340hp? I'm willing to bet your Q-jet is way off. I prefer the vacuum secondaries on the street, especially in an overdriven trans car with an auto. Call your dyno guy and talk with him a little more. I am no master tuner, in fact I will be taking mine to a friend in a couple of weeks to see if he can get any more out of it. He's an older gentleman with many years of experience under his belt who has a great understanding of Q-jets, HEI's along with all the others and how to tune them well (suspension also). Bill, your about dead on, when Paul has it dynoed the first time it made somewhere in the 340-350 range in HP, it was making gobs of TQ, that was at the rear tires. Before I bought the engine I called the fellow that did the dyno tune, I asked him about the engine and the relpy was this. This is a Mustang dyno, (which I am very familiar with the mustang brand dyno, they usually run 15% -20% lower in dyno results than any otehr brand) he claimed the dyno had never been calibrated and that Pauls motor was very strong, he said all he did is use it for tuning purpose and it wasnt really meant for accurate dyno purpose. It could be BS or the truth, but I also seen the build sheets on the engine and talked with several people that claimed that car was wicked, there was roughly 21k spent on the engine. as a rule of thumb if your making 450 hp you will see about 350 at the tires. One major point that the engine builder made to me was that the cam was way too small and it was running stock manifolds with ported heads which will rob HP. its what the owner chose to run. We chacked everything when i got it, and the work was very impressive.
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Post by real57vetteguy on Aug 14, 2012 20:47:50 GMT -5
I wanted to add this. It took me a few minutes to look this up, but in 2009 I had a supercharged fox body mustang. I had it tuned by a fellow that had a mustang dyno. The car made 385 rwhp, I was a little let down and he told me this, "Man this brand dyno always registers the lowest dyno HP of any, mustang clailm they have the only TRUE hp numbers but its always tremendously lower that any other" a few months later I put the car on a dynajet maching and it pulled 465 hp, I told that guy about the dyno on the mustang machine and he said the same exact thing, "man they are terribly low, we have seen 200 hp different on turbo cars. with that being said the dyno results didnt scare me, I felt even if they are only 10% low its making in the high 380's plus with a tiny cam and horrible exhuast and a stock type quadrajet. high 380's at the rear tires would be 450 plus at the flywheel. So when I got the motor you could see that the exhuast was smaller than the exhaust ports, there was a roller rocker that the pin had broken and the pushron was riding on the rocker its self, and the previou owner warrentied that, and the intake gaskets were smaller than the port work. with all the above corrected, a good degree job an a custom grind cam, and no telling what the correct intake gaskets, and headers added, but i think fuel was the big thing.
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Post by Deleted on Aug 15, 2012 17:32:01 GMT -5
Ooooh 340 to the tires....nice numbers.
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Post by real57vetteguy on Aug 15, 2012 19:54:48 GMT -5
Do you really think 340 to the tires is good?
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Post by real57vetteguy on Aug 16, 2012 5:25:43 GMT -5
Its time to make a carb decision, I am leaning towards a Holley Ultra Street Avenger 770 or Quick Fuel SS 780 looking at V.S. for either, any advice?
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Post by Deleted on Aug 16, 2012 11:44:50 GMT -5
Do you really think 340 to the tires is good? I don't think it's bad. It's probably in the range of what my car should be putting down. Sure I would love to have more power, but the money and maintenance involved is a bit much for me. I could never have afforded to build my car from scratch (well not while the kids are still in the house lol). Come to think of it, my Dad wasn't able to build a car this nice until us kids were out of the house lol.
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