Dyno ?
Thread Starter
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Senior User
Joined: Mar 2005
Posts: 135
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From: indiana
Dyno ?
i have a question...what all do u guys need to know about my engine to know the hp estimate?
410
perfect circle pistons #381P shaved .061
Edelbrock performer cam
Streetmaster intake
68cc heads
longtube headers
holly 750 carb
410
perfect circle pistons #381P shaved .061
Edelbrock performer cam
Streetmaster intake
68cc heads
longtube headers
holly 750 carb
Post Fiend
Joined: Jan 2003
Posts: 8,600
Likes: 4
From: Iowa
Well I'll use the least optimistic numbers.
Why did you shave those pistons? You now have .091" deck clearance by my calculations. They would have been much better stock.
Not knowing the dish volume, I'll figure 10cc since they were probably more before you had them shaved. The increased deck clearance will negate the reduced dish volume though.
I calculate your compression ratio at 8.91:1, with Fel-Pro head gaskets.
Still, it's showing:
341hp @ 4500rpm
472ft-lbs @ 3000rpm
I would have run a dual plane intake and Holley 600cfm carb on this motor. I believe it would better match the cam.
Why did you shave those pistons? You now have .091" deck clearance by my calculations. They would have been much better stock.
Not knowing the dish volume, I'll figure 10cc since they were probably more before you had them shaved. The increased deck clearance will negate the reduced dish volume though.
I calculate your compression ratio at 8.91:1, with Fel-Pro head gaskets.
Still, it's showing:
341hp @ 4500rpm
472ft-lbs @ 3000rpm
I would have run a dual plane intake and Holley 600cfm carb on this motor. I believe it would better match the cam.
Thread Starter
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Senior User
Joined: Mar 2005
Posts: 135
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From: indiana
well i thought i had different pistons whten what i had so thats why i messed up.....is a 600 holley big enough? and whats wrong with a single plane? but thanks for the numbers rusty
Post Fiend
Joined: Jan 2003
Posts: 8,600
Likes: 4
From: Iowa
The carb and manifold you selected are more for a high revving motor. This motor is a high torque low rpm stump puller. It's characteristics would be better optimized with a dual plane and a smaller carburetor.
You lose a *LOT* of torque on the low end by not going with a dual plane.
Numbers with a dual plane and 600cfm carb:
330hp @ 4500rpm
492ft-lbs @ 2500rpm
So you lose 11hp off the top end but gain 20ft-lbs of torque.
I guess, if you're going with the single plane and 750cfm carb, please, please put a bigger cam in it! I suggest a Crane 343941.
With your single plane, 750, and the mentioned cam:
419hp @ 5500rpm
459ft-lbs @ 4000rpm
But it still would have 399ft-lbs @ 2000rpm, so it would still be plenty drivable.
I guess it comes down to what you want to do with the motor.
You lose a *LOT* of torque on the low end by not going with a dual plane.
Numbers with a dual plane and 600cfm carb:
330hp @ 4500rpm
492ft-lbs @ 2500rpm
So you lose 11hp off the top end but gain 20ft-lbs of torque.
I guess, if you're going with the single plane and 750cfm carb, please, please put a bigger cam in it! I suggest a Crane 343941.
With your single plane, 750, and the mentioned cam:
419hp @ 5500rpm
459ft-lbs @ 4000rpm
But it still would have 399ft-lbs @ 2000rpm, so it would still be plenty drivable.
I guess it comes down to what you want to do with the motor.
Thread Starter
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Senior User
Joined: Mar 2005
Posts: 135
Likes: 0
From: indiana
ok...well il try to get that cam then....it will probably be when i get my 428 cj heads done...just ryin to get truck on road b4 graduation....but thanks alot for the help rusty...i appreciate it
Trending Topics
Elder User
Joined: Jun 2001
Posts: 508
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From: Corpus Christi, Texas
Do your pistons sit that far down?? . I know you were trying to build a clone to my engine, but mine sit .004 over the deck. You said you got the wrong pistons?
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FE "Freakin Expensive"
Joined: Dec 2003
Posts: 6,461
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From: Smith Mountain Lake, VA
LOL..there's really gonna be FIRE in the hole on that build at .093" in the hole..wont be any quick burn there... If you dont hve the short block done..I would square and deck the block some..and then "IF" you have to..open the head chambers up some to bring the CR back into range..
There re a few ways of going around the syndrome you have... But it just takes some parts specs and crunching some number's..
RJ
There re a few ways of going around the syndrome you have... But it just takes some parts specs and crunching some number's..
RJ
Elder User
Joined: Jun 2001
Posts: 508
Likes: 0
From: Corpus Christi, Texas
I used the higher compression stock pistons on my build. you must of got sme lower compression truck pistons. I was looking last night for my order form on the pistons I got but could not find it. Also was trying to remember what the copmression height was (the distance between the top of the piston and the wrist pin) ..... I am debating on redueing my engine at the end of the year or next year. i want a little more compression and some better heads!!!....Russ has got me a little jealous of his new build!!!LOL
Thread Starter
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Senior User
Joined: Mar 2005
Posts: 135
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From: indiana
Yeah it sounds like Russ engine is gonna be good...yeah i got the pistons off ebay...compared what i got and what i ordered and i got the low compression pistons...im pretty bummed and pi$$ed. but i think ill start on another block anyways cuz i wanna go bigger...i have a 427 i can get to if i needed it so i mite take up on it...