What heads for 421 SBC?

[sleeper sedan]

Having been involved with many "street" builds over the years street cars are often tire and chassis limited... so killing off the excess torque and placing the peak numbers higher in the curve is not a bad thing at all. Other things to take into account [obviously] is the camshaft, rear gear, etc.

Me personally, I would go with a larger head and tune/tinker finding the torque that your '80 G-body will handle.

Ckark

[user-9274568]

Having been involved with many "street" builds over the years street cars are often tire and chassis limited... so killing off the excess torque and placing the peak numbers higher in the curve is not a bad thing at all. Other things to take into account [obviously] is the camshaft, rear gear, etc.

Me personally, I would go with a larger head and tune/tinker finding the torque that your '80 G-body will handle.

Ckark

I totally agree with this! Everyone wants 600hp for the street but the truth is it's undriveable in most cases. Someone calls me for that request and I tell them exactly that. A honest 500hp on the street is a good goal. Affordable, pump gas able, FT cam able, and lastly dependable..

[900HP]

Having been involved with many "street" builds over the years street cars are often tire and chassis limited... so killing off the excess torque and placing the peak numbers higher in the curve is not a bad thing at all. Other things to take into account [obviously] is the camshaft, rear gear, etc.

Me personally, I would go with a larger head and tune/tinker finding the torque that your '80 G-body will handle.

Ckark

I totally agree with this! Everyone wants 600hp for the street but the truth is it's undriveable in most cases. Someone calls me for that request and I tell them exactly that. A honest 500hp on the street is a good goal. Affordable, pump gas able, FT cam able, and lastly dependable..

LOL. A number of years ago I did a hot street 505 BBC for a spoiled rich kid type. He was in too much of a hurry to go play with his new engine to be burdened with dyno time so I don't have actual dyno figures but I'm guessing it was around 600hp and 600tq or a little better. This went in a '69 Chevelle with a 4-speed and 275-50-15 BF Goodrich Radial T/A tires and stock suspension. His only concern was that he had 600 horsepower (he told everyone that it had over 600 hp even though it was never dyno'd).

The car would do rolling burnouts at 60mph in 4th gear. 1st gear and 2nd gear were completely unusable at anything over 1/2 throttle. It was a lot of fun to drive but my mid-11 second Buick would have annihilated him in a stop light drag race, the car was too difficult to drive.

He was happy though I guess. He came back after a test drive and his eyes were the size of dinner plates, he may even have been shaking a little. His only comment was "I was pulling on the interstate and got on it and it started doing a burnout!" The guy that was riding with him said he would never get in that car again. ever. I can only imagine what the dumbass was doing

[Wolfplace]

thanks for the all the posts.
CamKing said:

Just as a round number, I look at 650-700hp.
If you want to make above 700hp, I'd go with 18deg heads.
If you're looking for less then 650hp, I'd go with the 23deg heads.

this pretty much sums up the thought of going with 18deg heads. this is not an all out max perf build. 600hp or a little more is just fine for me.

Chassis is a mid 80's G-body.

Cam is by no means locked in. I was just posting up what Carl used just to have it out there.

No nitrous planned at this point but that's not set in stone either.

Carl,
You said if you would do it all over again, 235's or 245's but would need more rpm's. How much more would you say? Based of your build I was thinking I only needed to spin this thing to 6500.

I'm with Carl on staying with the SHP block.

.904" lifters are included in this build.

I'm a little concerned the 235's will be too big for the street hurting the lower end torque. If I stay with the 220's I can use standard stud mounted rockers and still get 600hp but 227's or 235's will need shaft mount rockers to be done right and I'm ok with that.

So, I'm still stuck with which head to use....220, 227, or 235? Thanks for all your post. I really appreciate it.

The 235 are in no way too big
Here is another 421 I did a while back
http://www.chevelles.com/forums/showthread.php?t=350309

http://youtu.be/sFI5Ar4EOR4

[1killerolds]

Thanks everyone for the replies.

I am going to go with the 235's. I found some other posts with guys running the 235's and it seems to be the way to go.

Good thing is I talked to CP yesterday and they said the pistons I have selected will work with the 235's 60/40 valve split. Said it might be a little close in the area between the valve reliefs so careful checking is definitely needed.

Thanks again for the info

[CNC BLOCKS]

Thanks everyone for the replies.

I am going to go with the 235's. I found some other posts with guys running the 235's and it seems to be the way to go.

Good thing is I talked to CP yesterday and they said the pistons I have selected will work with the 235's 60/40 valve split. Said it might be a little close in the area between the valve reliefs so careful checking is definitely needed.

Thanks again for the info

Are you going to dyno your engine when its done??

[1killerolds]

Yes, I am going to dyno this when it's done.