Disappointed with my engine

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joemish said:
Way too much carb. I have a 670 on my 383 Road Runner. works great.
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Do you happen to know what the venturi and throttle bore diameters are on a 670 and 870 street avenger carburetor? From what I've seen, they are much smaller than their 'cfm rating' would suggest.
 
Dartswinger70 said:
**** J heads....**** J HEADS !? SMH...:soapbox:
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mill them or rework tem did u c the heads page i sent u ? put 1 size bigger valves in the, & do a mild porting job it will help
the 340 hp heads will help too call clayton they have a lot of them if u r close to st.louis mo go to his resteration ysrd its at 674 wideman rd cattawissa mo

clays card (2).jpg
 
Martin Koiryohann said:
mill them or rework tem did u c the heads page i sent u ? put 1 size bigger valves in the, & do a mild porting job it will help
the 340 hp heads will help too call clayton they have a lot of them if u r close to st.louis mo go to his resteration ysrd its at 674 wideman rd cattawissa mo

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Cheers Mate but I'm on the other side of the planet
 
Not to get into a middle of a fight, but I see a lot of miss-match on the build. First, is the motor. Only my opinion, I would of started with a short stroke 318, being a short track racer. Yes, will cost a little, but putting in 202's would make a improvement in the "J" heads, while the 160's exhaust are already there. As others have stated, I would go with a smaller carb set up, then fine tune everything else and have some FUN.
 
mopowers said:
Do you happen to know what the venturi and throttle bore diameters are on a 670 and 870 street avenger carburetor? From what I've seen, they are much smaller than their 'cfm rating' would suggest.
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What gives here with Holley? According to the size chart the only difference between the 870 and the 750 is a sixteenth in the back venturi the 750's way ?? Unless I misunderstood the chart?
 
Retroboy said:
What gives here with Holley? According to the size chart the only difference between the 870 and the 750 is a sixteenth in the back venturi the 750's way ?? Unless I misunderstood the chart?
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You should call them and ask. I know the "670" street avengers have the same size venturi and throttle bores as a 600cfm 1850 too. Strange... Maybe it has to do with different booster designs or venturi shapes? Who knows.
 
Isn't it true the carb will only air flow what the engine pulls or needs? Also I thought it has been said that you double the displacement for example a 340 X2 = 680 that's what size carb or you could run a 700 cfm carb. as a starting point...:)
 
Dartswinger70 said:
Isn't it true the carb will only air flow what the engine pulls or needs? Also I thought it has been said that you double the displacement for example a 340 X2 = 680 that's what size carb or you could run a 700 cfm carb. as a starting point...:)
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if u r turning 6000 rpms then a 750-800 cfm i used a catrr thremoquad on my 400 i was turning 6-6500 i also had 95# pf oil presure (there is a rule of 10# of oil pressure for every 1000 rpms) if u run lower oil prssure u run the chance of staving the bearlings of oil. i have seen guys blow mopars up. but do as u like i really dont think fuel flow is the isse i thonk the camshsfy dose not match the rest . i only used mopsr performance cams Now how much faster do u want to be?
 
Retroboy said:
Okay Mr Rusty RR what was your input?
Was it you that said Mopar heads were the pick of the bunch way back when ? Ha ha ha what a joke. Have you ever looked at a Ford Cleveland from 1971 - 86. I don't think you guys had 302 C in the US did you? Maybe you should have said that they have a higher exhaust port than a Chev which would have made them the pick of a bad bunch It was inferred by myself in my origional post the heads were the issue.
The other thing you suggested was overall car set up. I'm 64 mate and first went down a racetrack in a FED more than 40 years ago. I can promise you this, there is Zero, did you get that, Zero, similarity between a door car set-up and a 1400 lbs slingshot. None.
I welcome your and anybody else's input but keep it real.
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I'm very familiar with Cleveland heads, since I have a complete 70 M code 351 in my spare bedroom. And yes, I've seen a couple of 302C engines. NOT Boss 302. 302C. They are different.
 
Retroboy said:
What gives here with Holley? According to the size chart the only difference between the 870 and the 750 is a sixteenth in the back venturi the 750's way ?? Unless I misunderstood the chart?
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CFM differences are not all in the throttle bores.
 
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