performance rebuild question
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Junior User
Joined: Apr 2004
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From: Jacksonville, Florida
performance rebuild question
I've been tearing into my first rebuild and I have a few questions. First off it's an 81 F-150 custom 4x4 with 3.00 gears.
when removing rocker arms does that particular cylinder have to be at TDC? I've read that it does but I'm replacing the cam anyway.
What cam do you reccomend for a daily driver and part time hauler/ tower? I would like to use Crane because they also have rockers and pushrods that i like.
I was thinking the H-272-2 (503941 part #) or the H-260-2 (503901 part #)
Oh yeah, almost forgot I was planning on using an Edelbrock 500 cfm carb, and headers.
any suggestions would be great.
when removing rocker arms does that particular cylinder have to be at TDC? I've read that it does but I'm replacing the cam anyway.
What cam do you reccomend for a daily driver and part time hauler/ tower? I would like to use Crane because they also have rockers and pushrods that i like.
I was thinking the H-272-2 (503941 part #) or the H-260-2 (503901 part #)
Oh yeah, almost forgot I was planning on using an Edelbrock 500 cfm carb, and headers.
any suggestions would be great.
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When you assemble the engine they need to be at TDC.
Crane makes a 260/272 camshaft p/n 270-503901, that would give you a little from your first choice and a little from the second.
If your interested more in peak low end torque, the 260 and a smaller carb might be of interest to you, if your gonna run unported heads.
Good luck
Crane makes a 260/272 camshaft p/n 270-503901, that would give you a little from your first choice and a little from the second.
If your interested more in peak low end torque, the 260 and a smaller carb might be of interest to you, if your gonna run unported heads.
Good luck
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Thats a tough question.
An example, I am sure you've seen col_flashmans post on his built 300. He used an rv torque camshaft, which should peak tq real low, yet his tq peaked if I recall correctly around 3500rpm, which IMO means the head must have been ported real good to raise the tq peak.
Rough guesstimate, with a mild port, I would say either would do fine. Your gears are pretty low though though, IMO you'd want a lot of low end tq to get that sucker rolling...so I might lean towards the smaller grind.
It was brought to my attention recently about some isky camshafts, if I were you, I'd call comp cams, isky and crane, see what they say, I think isky offers an even smaller grind that should peak tq a little lower, I was told the 256 supercam by isky (I believe p/n 331256) would make a good tq and mild performance cam...who knows? good luck
An example, I am sure you've seen col_flashmans post on his built 300. He used an rv torque camshaft, which should peak tq real low, yet his tq peaked if I recall correctly around 3500rpm, which IMO means the head must have been ported real good to raise the tq peak.
Rough guesstimate, with a mild port, I would say either would do fine. Your gears are pretty low though though, IMO you'd want a lot of low end tq to get that sucker rolling...so I might lean towards the smaller grind.
It was brought to my attention recently about some isky camshafts, if I were you, I'd call comp cams, isky and crane, see what they say, I think isky offers an even smaller grind that should peak tq a little lower, I was told the 256 supercam by isky (I believe p/n 331256) would make a good tq and mild performance cam...who knows? good luck
Last edited by jwtaylor; Jan 7, 2005 at 11:43 AM.
Laughing Gas
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Actually, if you have the positive stop style they don't need to be at TDC. The Isky is a good cam, if you want I'll post the specs. Headwork is always a good idea on the 300, no matter which cam you decide to go with, and EFI manifolds would work well for your build. Matt.
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From: Jacksonville, Florida
thanks again. just one last question though, regardless of the cam, I'm planning on a 6 inch lift and 35 in. tires, I know the 3.00 gears are gonna suck for that so what does everyone reccomend, I've heard 4.10 or even 4.56, I still want to be able to tow and hook chains with the stubborn stumps and with some of my buddies that doubt my 300's potential.
thanks again
thanks again
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Originally Posted by mattri
Actually, if you have the positive stop style they don't need to be at TDC.
By positive stop I assume you mean pedastel mount, and it would be a good idea to have the cylinder at TDC even with those, as pedastel mount are torqued down to a certain spec, get it wrong and you could end up with a broken bolt or loose rockers.
Originally Posted by ford_muddbilly81
thanks again. just one last question though, regardless of the cam, I'm planning on a 6 inch lift and 35 in. tires, I know the 3.00 gears are gonna suck for that so what does everyone reccomend, I've heard 4.10 or even 4.56, I still want to be able to tow and hook chains with the stubborn stumps and with some of my buddies that doubt my 300's potential.
Once you have the tires size you plan to use regardless, then you need to search the web for a forumula, probably on any 4X4 forum, that allows you to punch in different gears and tire sizes to determine your rpm at any given speed. If your looking for towing application, ideally you would want your average cruise speed and peak torque at the same rpm. Good luck
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This here's a mighty fine site with the proper conversion gizmo's. Never mind the jeep thing, numbers is numbers:
http://www.novak-adapt.com/knowledge/gearing.htm
http://www.novak-adapt.com/knowledge/gearing.htm
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From: Kalispell, MT
here's a formula i got off of Superlift.com....
rpm=mph x gear ratio x 336/tire diameter
ex. assuming your final transmission gear other than most OD trannies is a 1:1 ratio (3rd in a 3 spd, 4th in a 4 spd), if your gearing is 3.73's, your tires are 33" tires, and your speed is 65 mph, see the following:
2468=65 x 3.73 x 336/33
as a general rule (with Ford, anyway, I believe) 5th gear is approximately 0.75:1....to find exact ratio, most likely contact a dealer or tranny shop with transmission ID number...with OD tranny, mulitiply ring/pinion gear ratio (3.73) by 5th gear ratio (0.75)
ex. 1851=65 x 3.73 x 0.75 x 336/33
MontanaFord
p.s. hope this helps....it helped me out a lot...
rpm=mph x gear ratio x 336/tire diameter
ex. assuming your final transmission gear other than most OD trannies is a 1:1 ratio (3rd in a 3 spd, 4th in a 4 spd), if your gearing is 3.73's, your tires are 33" tires, and your speed is 65 mph, see the following:
2468=65 x 3.73 x 336/33
as a general rule (with Ford, anyway, I believe) 5th gear is approximately 0.75:1....to find exact ratio, most likely contact a dealer or tranny shop with transmission ID number...with OD tranny, mulitiply ring/pinion gear ratio (3.73) by 5th gear ratio (0.75)
ex. 1851=65 x 3.73 x 0.75 x 336/33
MontanaFord
p.s. hope this helps....it helped me out a lot...
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