Building 400 for mud racing
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Elder User
Joined: Apr 2004
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Building 400 for mud racing
Need some opinions here, from experienced people hopefully!!! Will be picking up parts from the machine shop soon, but havent picked a cam yet (have been keeping an eye on this site, but nothing seems to really match what I'm doing) Rig is a 78 Bronco being run in a obstacle type mud race(stock class) The main idea is to use the 400's natural ability to make torque and some 4.10 gears to run in high range for wheel speed. So far this is the recipie- 30 over forged TRW pistons in stock configuration, Aussie cylinder heads for some compression and a supposedly 3000rpm range torque converter. Due to being in stock class the engine will have to run the factory exhaust manifolds, mufflers (has a good dual exhaust on it) and intake and carb (will be using the larger 429 2v carb) I'm leaning towards the Comp cams XE274H- adv duration 274/286, @.050-230/236, lift 562/565, 2000-6000 rpm range, 2400+ stall, 3.73+ gears. Keeping in mind that this is not driven on the street and IS for racing so it will be seeing RPM's, any opinions on my cam selection--- Pulling the converter out and going back to stock wont be a big deal if that doesnt work out, but I'd rather not have to change out the cam if I get that wrong. Thanx
Cargo Master
Joined: Dec 2004
Posts: 2,232
Likes: 3
From: NE Texas
There seems to me to be a few "holes" in your recipe. To begin with things don't seem to match up well. When building a high performance engine it is very important to have the correct combination of pieces so that everything works together in the same RPM range.
For instance you are running a 2 barrel carb, which in any size will choke the engine and prevent it from taking advantage of that much cam. Also, if you are going to run so much cam and plan on such high rpm, you will not be taking advantage of the long strokes ability to build mid range torque.
If you are limited to a 2 barrel carb by class rules, then use the big carb you talk about, increase the compression as you indicate, but use less cam so you can keep the powerband in the area where the carb can feed it and you can take advantage of the long stroke ability to build mid range torque. Then gear it for your race speed to be with the engine running no more than about 5000 RPM, because I don't think you can feed that thing to make power any higher than that with your carb restriction.
I would think that the cam should be no more than about 220 duration @ .050.
My $0.02,
Doc
For instance you are running a 2 barrel carb, which in any size will choke the engine and prevent it from taking advantage of that much cam. Also, if you are going to run so much cam and plan on such high rpm, you will not be taking advantage of the long strokes ability to build mid range torque.
If you are limited to a 2 barrel carb by class rules, then use the big carb you talk about, increase the compression as you indicate, but use less cam so you can keep the powerband in the area where the carb can feed it and you can take advantage of the long stroke ability to build mid range torque. Then gear it for your race speed to be with the engine running no more than about 5000 RPM, because I don't think you can feed that thing to make power any higher than that with your carb restriction.
I would think that the cam should be no more than about 220 duration @ .050.
My $0.02,
Doc
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Elder User
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You have pretty much mirrored the doubts I had in the back of my mind about too much cam for the restricted breathing!! I guess maybe the Comp Cams high energy 268 would be a safer pick- anybody else have any input??? how about opinions on the converter???
Elder User
Joined: Feb 2000
Posts: 775
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From: Temperance,MI
For your cam do this call 1800-426-2261 or check them out online, www.camcraftcams.com he will make a cam for what you need not what they want to put on the market, i just got mine for the 331 I'm building for my friends bronco. Decently priced too give them a call you wont be disapointed.
Curtis
Curtis
Laughing Gas
Joined: Feb 2003
Posts: 1,234
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From: In the woods of Oregon
you can feed a revving 400 with a 2v carb, it just needs to be opened up and such so it can flow the cfm needed. lots of carbs shops in the back of numerious magazines offair this modification with flow bench results.
Cargo Master
Joined: Dec 2004
Posts: 2,232
Likes: 3
From: NE Texas
If you use a cast iron 2V manifold, make sure you use a hand grinder and ensure that the turn below the carburetor is a smooth transition. Just round it off. Ford manifolds are already cast with a rounded off turn, but can be improved. GM manifolds on the old small blocks were just a sharp edge and benefitted greatly from a little hand grinder work.
Good luck,
Good luck,
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