Hold up in SBC?
Hold up in SBC? Bored .040 over 388CI SBC
Eagle crank and rods, yada yada, bottom end is stout, will hold 8000 rpms. Rods are either 5.7 or 5.6
Trick Flow 23 degree alum. heads (not ported)
Comp Cams XE284 flat tappet cam
Summit 'Black' aluminum roller rockers
1 3/4" Long tubes into true dual 2.5" pipes
650 double pumper that was modified to flow more
Edlebrock Victor Jr intake (believe that's good up to 9k rpms or so)
Camaro T56 6 spd 4:10 gears
What's going to be the hold up here? Some people say the cam (manufacturer specs suggest up to 6500rpms), some people say the heads.. I would like to spin the car up to 8000 rpms, or at least 7000! Wanted to hear suggestions of making more powaaar and higher rpms. Should I go with roller high rpm cam? Some say it will lose power on low end...etc etc.
Discuss. Thank you.
__________________
Eagle crank and rods, yada yada, bottom end is stout, will hold 8000 rpms. Rods are either 5.7 or 5.6
Trick Flow 23 degree alum. heads (not ported)
Comp Cams XE284 flat tappet cam
Summit 'Black' aluminum roller rockers
1 3/4" Long tubes into true dual 2.5" pipes
650 double pumper that was modified to flow more
Edlebrock Victor Jr intake (believe that's good up to 9k rpms or so)
Camaro T56 6 spd 4:10 gears
What's going to be the hold up here? Some people say the cam (manufacturer specs suggest up to 6500rpms), some people say the heads.. I would like to spin the car up to 8000 rpms, or at least 7000! Wanted to hear suggestions of making more powaaar and higher rpms. Should I go with roller high rpm cam? Some say it will lose power on low end...etc etc.
Discuss. Thank you.
__________________
Last edited by kukri; Oct 28, 2005 at 11:00 PM.
On The Tree
Joined: Sep 2005
Posts: 101
Likes: 0
reality check....you are not going to get an 8000RPM motor to respond well down low with good torque. Two VERY different camshafts, a roller will make more power everywhere if done correctly, but don't expect power over that entire range.
I also doubt the heads will make good power up there, get them ported or something else.
BTW, a .040" 350 with a 3.75" stroke is a 385"
I also doubt the heads will make good power up there, get them ported or something else.
BTW, a .040" 350 with a 3.75" stroke is a 385"
Also, If you want to spin 7-8000 RPM's I would suggest going to a 6.0" rod. There will be a great deal of strain and wear on the the crank and cylinder walls with the 5.7 rods. Solid Roller will also be needed to spin that far up reliably. Higher flowing heads would be nice as well, probably over a real 300cfm. Go to the carcraft head flow test to find something in this range. DO NOT believe the advertised ratings. My Iron Eagle Platinums flowed 284cfm out of the box. Advertised was 322cfm. Huge difference. Just my .02
TECH Regular
Joined: Dec 2004
Posts: 492
Likes: 0
From: Newark, Ohio
Are you being serious, or just pulling our leg?
First of all, neither the cam or heads will be happy above 7. And if you do push it to 7, I think you'll still be outside the cams optimum range.
Why are you interested in those rpms? If its a must, then you'll need to port the heads, and go a solid roller with a minimum of 260 dur. @ .050.
I know the Stock guys do this but they are forced into making these combos work, you are not.
First of all, neither the cam or heads will be happy above 7. And if you do push it to 7, I think you'll still be outside the cams optimum range.
Why are you interested in those rpms? If its a must, then you'll need to port the heads, and go a solid roller with a minimum of 260 dur. @ .050.
I know the Stock guys do this but they are forced into making these combos work, you are not.
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First problem is the cam & heads (I completely agree that heads that flow at least a real 285 CFM @.600 is a minimum). Cam choice for something like this would have to be in the near .600 lift and .050 around 265 to 270. Next is the carb, to move that much air (and make power) at 7000+ you'll need at least 900 CFM, a small carb might get you there but won't make power there. Next is the headers, a 385 at 8000 RPM would need at least a 1 7/8 header to work right (Engine Analyzer Pro suggested the my combo would loose 40 HP at 7000 with a 1 3/4" over a 2"). I'm building a similar combo for my car right know I have a 385 short block, GMPP Fast Burn Heads (actual flow 275@.600-stock for now), a raised runner Victor 4500 intake w/a dominator carb, Big Shot kit and a Crower cam .547/.575 and 262/272@.050 and installed with a 108 intake centerline. I'm building a set of 2" primary tube headers for it as we speak. Finally if you're going to drive this on the street you'll have poor drivability because it wont start making power until around 4000 RPM, if you had an automatic trans with a 4000-4500 conv it wouldn't be as bad, but trying to cruise with this at 2500 will be tuff.
Your best bet would be to stick with the combo you have and shift it at 6000-6500 RPM.
Your best bet would be to stick with the combo you have and shift it at 6000-6500 RPM.
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