Trying to understand how much I have under the hood...

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Haffnez72Scamp

72 Scamp 340
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Just looking for a rough idea fellas... 350, 400, 400+?

68 340 -30 overbore
x-heads gasket matched to LD340 Intake
Holley 750 (too much carb, I know)
Keith Black Pistons
Comp Cams - Mutha Thumpr Cam (.522 intake .509 exhaust)
Pro-Race eladtomer bind Crank Dampner
Headers to 2.5 to x pipe, dynomaster mufflers
2800 Stall in 727

If any of you are running something similar let me know!

Cheers!
 
SGBARRACUDA said:
I agree 350. Why do you think a 750 is to much?
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Thanks guys. In terms of the Carb, I am getting about 100-125 miles to a full tank with 323's in the rear. She is thirsty! Also gotten that feedback from a circle track crew chief and engine builder. Could be wrong, just assumed since it chews through a tank so quick.
 
what is your compression? and that is a pretty lumpy cam - sometimes less really is more - have you tried a 650 on there? 2cfm per HP is a general guideline - not a rule. If you really are at about 350hp, then it probably is too much carb. I have known several people who had nice 340's - the 650 worked really well - double pumper -mech. secondaries- the 750 seemed to over juice the engine, unless they were racing..
 
I'm going to say 325-350. Which Holley 750?
 
justinp61 said:
I'm going to say 325-350. Which Holley 750?
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I agree, depends a lot on compression and what your cam duration is at .50 inches of lift to get a better idea. This is all on paper though, your tune can make actual HP a lot less, a time slip with your MPH and weight will get you real #'s.
 
Understanding how to properly time your combo is critical, setting initial, adjusting the mechanical and vacuum advance to dial in your total can be verified here. While close, the cam you are running is likely not optimal for maximum performance and mileage.

One thing I didn't see you comment on is what your A/F ratios are at various throttle settings. Until you verify your A/F ratios with a wide band A/F meter, you will likely be leaving significant performance and mileage attainable on the table.

98.9% of us are unable to properly tune carbs or EFI systems through their entire rpm and throttle position settings by simply reading the spark plugs. It's a time consuming trial and error process that's an elusive art perfected by a relative handful of people on the planet. My self included.
 
Install a vacuum gauge and do a full throttle run and see if your carb is to big. Bigger carb doesn't mean your engine getting more fuel than it needs. If to big it would have poorer fuel atomization. Does it run good was it a bear to get in tune ??
 
Thanks guys,

Runs very well. Couple of pumps and turn the key. It shifts incredibly early which is where I am starting. Taking it to my mechanic once out of winter storage (so soon!). I bought a TCI shift improver kit and will have it installed this spring. Thanks for the advice re: time slip, weight and MPH. jbc426 thanks for the detail, I'll work with my guy on that.

Appreciate all of the advice and comments.

Cheers!
 
weigh it and run it through the 402m (Canadian 1/4 mile) and plug it into a HP calculator.
 
Ok in my opinion, and it is just that. The 750 is not to big. What you need is dialed in. Not just main jetting but, air bleeds and the other circuits. Accelerator ramps and the vacuum spring too The 750 will give best top end HP. These old hot rod engines were never built for mileage!!!! For street throttle response? The same type but 600 cfm. is awesome, and a little kinder on fuel. LD340 manifold, block off the heat crossover. With a mandrel clean up the runners of all casting nubs as far as you can reach. Have the center divider wall under the carb milled down to 1/2 inch tall, a 1/2 inch heat dissipation plate is good here also. In my opinion..........
 
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