Question for big block gurus !

[454 blazer]

Hey guys ive recently put my engine back in , different heads and cam , rectangle heads , 270 comp cam 4x4 extreme energy, my question is what torque converter would you recommend as ive got a 3000 stall which is WAY to much , do you think a stock one would be good? The trannie is an overhaulded th 350 with np205 runs 33s with stock rear gears, which i assume is 3.07.

 

[folkenheath]

A 270 adv. duration is pretty mild I would think you would be fine with stock RPM or maybe 200 RPM higher. Just make sure it's a strong enough unit for the big block.

 

[80' 427]

personnally I would change gears. 2000-2500 would be a better converter but you are moving a heavy truck. The gears will help the engine move and will allow the stall to come down some.

 

[blueblazes44]

I would call a tc company and explain (1) what you have and (2) how you intend to use you truck. I went with Boss Hog behind my bbc and have been very pleased. Great tech support,great product and best price I could find. www.accperformance.com

 

[1-ton]

I would have to agree that you do not have enough cam for a BB with square port heads. Square port heads are high RPM racing heads, and you have a low RPM torque camshaft in it. your heads and torque converter would great for drag racing, but not for low RPM off roading.

IMO, the square port heads on your engine are too much for off roading purposes.

 

[4X4HIGH]

I would have to agree that you do not have enough cam for a BB with square port heads. Square port heads are high RPM racing heads, and you have a low RPM torque camshaft in it. your heads and torque converter would great for drag racing, but not for low RPM off roading.

IMO, the square port heads on your engine are too much for off roading purposes.

Glad someone else brought it up. I was going to say that square port BBC heads don't belong anywhere near a 4x4 engine. They don't even start making power until 3000-3500 rpm so unless this is a mud truck only spinning lots of rpm ditch those heads to a racer and buy some "781" large oval port heads.

 

[80' 427]

he has been over this before. Think now that its together he just wants it to work properly.

 

[1-ton]

he has been over this before. Think now that its together he just wants it to work properly.

In that case, changing to a cam that has an advertised duration of about 298 degrees will help, along with a converter with about 900 RPM stall at most (set the idle at about 750 RPM). This will make it at least drivable.

I had a 1970 SS Chevelle with a square port 454 (12:1 compression, 298 cam, 900 RPM stall, 4:11 gear, twin 450 CFM carters, tunnel ram intake, 1-3/4 inch primary headers, accell electronic distributor, 11.90's in the quarter mile), and it was a mostly, but not always, fun, drivable, on a sunny weekend only, without too much hassle type of hot rod.

 

[80' 427]

Gear, add gear first.

 

[folkenheath]

I think you guys are over reacting with the heads. Are they optimum for his engine, no, should he go out of his way to change them because he already has a running engine he likes, I don't think so. GMPP puts the rectangular ports on the 454HO crate engine, and it makes slightly more torque and power at 1750 RPM than the 502HT with oval ports on it, and that has more cubes. Step up to the 502HO and it adds rectangular port heads and the whole entire torque curve raises. Probably has more to do with the cam, but obviously with only 211/230 duration at .050" it's somewhat mild even with rectangular ports. I guess my point is even though they aren't optimum for low end torque, you can still make some with them, it is a big block. I used oval ports on my big block, but I have built with rectangular ports too for other applications, they can still make torque. He already has them on and running. I say enjoy it. He should probably regear though.