Engine Build Questions
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5th Wheeling
Joined: Apr 2021
Posts: 30
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Engine Build Questions
I am getting a machine shop to fix up a '96 351w out of a F250. This is going into an estimated 4,000-4,500 Lbs mud/trail truck. I am new when it comes to engine building and looking for a little help from the masses. Knowing nothing and just doing research on the internet, I am thinking I want a Holley Truck Avenger 670 carb, an Edelbrock Performer RPM Intake, AFR 185 Renegade heads, Extreme Energy 224/232 Cam from CompCam, the cylinders are already bored to 30 over. Reusing the stock/OEM crank shaft so no stroker for this motor. Running Hedman 88400 headers. I have 5.38 gears spinning 38.5" tires(Will go bigger when these tires wear out.) This is meant to play in the mud but want to do grocery runs occasionally or go pick up the kids.
The machine shop I am working with is telling me that they have a pair of AFR195 heads that will work well for my application and will make good power down low, where I want it, with the correct cam being used. Then saying to use a 750 CFM Carburetor. I just don't want to get a motor built that is built to run 3,000 to 7,000 RPM but I have a cam only running up to 6,000. With this set up will I still have the low end torque I desire? Don't want a dog off the line that right when it is getting to the meat of the power, the cam is done and it falls on it's face.
Are these changes negligible in the grand scheme of things?(What I have been told and want to believe)
Thanks for any and all input. If you have a better idea, please provide it and explain why.
The machine shop I am working with is telling me that they have a pair of AFR195 heads that will work well for my application and will make good power down low, where I want it, with the correct cam being used. Then saying to use a 750 CFM Carburetor. I just don't want to get a motor built that is built to run 3,000 to 7,000 RPM but I have a cam only running up to 6,000. With this set up will I still have the low end torque I desire? Don't want a dog off the line that right when it is getting to the meat of the power, the cam is done and it falls on it's face.
Are these changes negligible in the grand scheme of things?(What I have been told and want to believe)
Thanks for any and all input. If you have a better idea, please provide it and explain why.
Hotshot
Joined: Jul 2020
Posts: 10,331
Likes: 2,585
From: Near Salt Lake City
You need an RV cam to make power down low
Just about any high lift, long duration camshaft will up your RPM band
Meaning it won't pull the skin off a grape below 3000 RPM
I hear you say you are using the OEM crank
You might want to reconsider stroking it
Just about any high lift, long duration camshaft will up your RPM band
Meaning it won't pull the skin off a grape below 3000 RPM
I hear you say you are using the OEM crank
You might want to reconsider stroking it
Cargo Master
Joined: Mar 2007
Posts: 2,786
Likes: 1,009
My pea-brain input is the 195's are too big. They are more interested in getting them off the shelf than assist you on your build.
Check the specs of the head. There is a reason why they have a dual pattern exhaust manifold bolt pattern.
I would keep the EFI.
Check the specs of the head. There is a reason why they have a dual pattern exhaust manifold bolt pattern.
I would keep the EFI.
FTE Legend
Joined: Jun 2006
Posts: 31,930
Likes: 1,499
From: Ottawa, Ontario
IMO AFR185's or only just big enough for a 5.8 so I don't see these 195's being much of an issue in this case, the cam has a much larger effect on engine powernband so that is the part you have to get right on the money.
None of these parts will work wil the OEM EFI system.. in case anybody thought it was an option.
None of these parts will work wil the OEM EFI system.. in case anybody thought it was an option.
Cargo Master
Joined: Mar 2007
Posts: 2,786
Likes: 1,009
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Cargo Master
Joined: Oct 2020
Posts: 2,648
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I would avoid the Avenger carburetors they are notorious for having drivability problems at part throttle especially with a cam as big as that one. I'd ease up on the duration especially on the exhaust side and run something like a 4777 Holley. I have one of those that I had built with down leg stepped boosters and we ran it to 8200rpm last summer on a 355 Chevy in a circle track car. Worked great, tech department didn't like it even though up to a 750 was allowed by the rules.
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