I just picked up a complete 1972 402 big block with 3999241 heads on it. I got a set of 049 heads in the deal. I am totally new to big blocks. Which set is better to use? I would like a little more compression than 8.5:1. Can I or should I mill one set of heads down to raise the compression? Any ideas as to about how much would be safe? I'd like 9.5:1 or so static compression. Thanks guys.

If your not going to rebuild the whole motor you would probably be better off with a set of closed chambered heads. If your planning a complete rebuild and with new pistons then the 049's would work great. If not they have such a large combustion chamber, compression is going to be at a minimum. Tell us more of what your going to do with this motor.

Matt

I'm not really able to rebuild right now. The bottom end looks good. I want to run more cam for a little lope at idle, but am afraid of killing my dynamic comp with only the 8.5:1 static comp. What I am looking at is a stock bottom end, one of these two sets of heads, factory cast iron intake(low rise), 750 Q-Jet,1-3/4" headers, 2-1/2" exhaust and an HEI. I am still in the air for cam. It is going to depend on what I can do with the heads. The stock 72 bottom end has domed pistons I found out. How much of a dome is it? I wanted to do a little better calculating since I was just guessing last night. This will be going in my 72 Nova with an M-20 and a 3.08 open or 3.73 posi rear. I will run either rearend, but I figured the 3.08s would be a better match to the big blocks torque.

I was contemplating a Comp 270/270 Magnum cam if I can get the compression to 9.5:1 static. Or a Crane 260/260 if I have to live with the 8.5:1 static comp.
Thanks for the help.

EDIT:forgot exhaust specs, pretty important graemlins/clonk.gif

If you want to up your compression I would think about selling the 049's and buying a set of 215's or 063's or 290's or any other closed chambered head. My 206's have the smallest chamber @ 97cc. That would give you a lot more compression.
I don't know what pistons your motor has, I'm assuming flat tops in a 72, but I'm not for sure. If somebody knows what pistons you have that would help a lot.

Matt

I believe with a set of closed chambered heads that will give you the 9.5-10:1 range your looking for. Like I said though we need to find out what your pistons are.

By the way is this going in that nova?(Nice Car)

I believe if I had the 3.73's I would go for them, that will wake it up a lot.

Matt

I have not been able to find out so far, I am also very curious because it would help me get a better handle on what I can do. I know they are domed, I just can't find how much.

This car is only going to be a street fun car really. It may see just a couple trips to the track, but it won't be a campaign car. I want to make the 13's on a stock bottom end. I think that shouldn't be too hard. Maybe even possible with the low compression. The Nova only weighs 3500lbs with me in it and a full tank of gas.

Are you going to go with an Auto, or stay with a 4-spd?

Matt

No 396/402's ever came thru with flat tops..all of them had domed pistons.The 71/72 style dome is about .110 tall..closed chamber heads really wake these motors up..assuming a .030 piston/deck height,101 cc chambers,and .039 head gasket you'll be around 9.5 to 1
Use a cam that builds cylinder pressure too..the 270H Comp should be a decent choice..especially with 3.73's and a convertor in the 2800-3000 flash stall range.

I think I will have to stick with the 4speed. If it was me alone I'd probably try the automatic, but it is my dad, brother and I's car, so we are doing a majority rules type of thing. Everybody gives and takes a little.

Thanks mr 4 speed, now I can at least pretend I know what I am doing now instead of guessing until things looked about right.

I am thinking I will run the 3.73 gears....then I can adjust my "gearing" with tire height.

What should I assume as a safe redline on this engine? 5500rpm? I am going to put new springs in so I don't have to worry about the valves floating on me, but that will be the only real upgrade to the heads. I'll be using stock everything but the cam/lifters and valve springs.

Originally posted by mr 4 speed:
..assuming a .030 piston/deck height,101 cc chambers,and .039 head gasket you'll be around 9.5 to 1... Isn't that going to be a little long on quench height?

I usually figure stock pistons are either .020-.030 down in the bore..anyway,as I mentioned,the closed chamber heads on 71/72 402's really wakes them up..I've down a few budget 402's this way,and it work out well.

They work well enough to make 498 hp and 564 tq. At least on mine they do. :D
Regards,

Originally posted by USFATL:
They work well enough to make 498 hp and 564 tq. At least on mine they do. :D
Regards, What's your combo Steve?

I too am going to run a pair of these heads. Its nice to know that they do support making HP/TQ.

http://www.chevelles.com/cgi-bin/forum/ultimatebb.cgi?ubb=get_topic;f=4;t=020094

No 396/402's ever came thru with flat tops..all of them had domed pistons.The 71/72 style dome is about .110 tall..closed chamber heads really wake these motors up..assuming a .030 piston/deck height,101 cc chambers,and .039 head gasket you'll be around 9.5 to 1
Use a cam that builds cylinder pressure too..the 270H Comp should be a decent choice..especially with 3.73's and a convertor in the 2800-3000 flash stall range.

This is a ? for Mr.4 speed Im doing a 71 402 open chamber head to close chamber head swap. I have the close chamber 063 heads Will i get by get by with any head gasket or will i need a special head gasket? I have a thumper cam with a 498 gross lift. Im going to run roller rockers with hyd. lifters. How much more hp, will i get will it be noticable?

I have a set of each,the 049s measured 119 cc,the 241s were 113,flow was basically the same I opted for the 241s ,minimal planing to get to 110

I'm doing a 71 402 ls3 820 open chamber to 063 close chamber head swamp.Can someone tell me will i need a certain size head gasket or can i use a stock head gasket? Also I will be running the 063 close chamber heads,roller rockers, thumper cam 11-600-4 with a .498 lift, aluminum intake, headers. What compression will i be at? How much HP? Will i notice more Power?