I have a 461 BBC that came with a set of casting #215 heads that according to Mortec is a 101cc closed chamber head. The pistons in the motor are Speed Pro L2349F which is also a closed chamber piston. I have a chance to buy a set of freshly done casting #781 heads with 2.25 intake and 1.88 exhaust valves but they are open chamber heads. This motor will be for drag racing only, no street use. My question is, can I use the 781 heads without changing anything? Which head would be more appropiate for my application (drag race)?

You'll drop compression. Seems like the wrong way to go with a drag motor.

I am running a closed chamber piston with a .580 dome and canfield 310 open chamber heads . I have no clearance issues. BUT im not sure about your 781 heads? i would think you could grind the domes around the corners to work !

I just went through this and BELEIVE me you will hate it. It was not by my choice the guy who did my machine work did the combo. It was the biggest 454 slug you ever saw, a YUGO could have taken it on the street. I did not pull the motor the 2nd time. I went with closed chamber heads milled down to get compression up and a Lunati Voodoo cam. Double the power.

DON'T DO IT!!!!!!!!!!!!! my 2 cents worth

I just went through this and BELEIVE me you will hate it. It was not by my choice the guy who did my machine work did the combo. It was the biggest 454 slug you ever saw, a YUGO could have taken it on the street. I did not pull the motor the 2nd time. I went with closed chamber heads milled down to get compression up and a Lunati Voodoo cam. Double the power.

DON'T DO IT!!!!!!!!!!!!! my 2 cents worth

I don't know if a low compression 454 can be called a 'slug' several on this site are running some good times,but for a drag motor you do want more compression.

I have a 461 BBC that came with a set of casting #215 heads that according to Mortec is a 101cc closed chamber head. The pistons in the motor are Speed Pro L2349F which is also a closed chamber piston. I have a chance to buy a set of freshly done casting #781 heads with 2.25 intake and 1.88 exhaust valves but they are open chamber heads. This motor will be for drag racing only, no street use. My question is, can I use the 781 heads without changing anything? Which head would be more appropiate for my application (drag race)?

Last set I put on one of mine were in the 114CC range. Although mine was the L2268F 427 11-1 slugs, they are down the same road as far as compression, CC the 781's and see what you find. The 215's will be way more compression and if it's race only, I'd be sticking with the 215's for comp. I would do some pocket work on those.
The 781's will flow much better and would be my choice on a street/strip combo. If using the 781's set them on the motor and turn it over to ensure there is no contact on the chamber to piston. If so it's a easy clearance task and it's common using the factory 11-1's with a head that originally ha small valves (they are not unshrouded for the larger valves like the rectangles are from the factory).


I just went through this and BELEIVE me you will hate it. It was not by my choice the guy who did my machine work did the combo. It was the biggest 454 slug you ever saw, a YUGO could have taken it on the street. I did not pull the motor the 2nd time. I went with closed chamber heads milled down to get compression up and a Lunati Voodoo cam. Double the power.

DON'T DO IT!!!!!!!!!!!!! my 2 cents worth

How much of a slug, like as in 14-15 second 1/4 mile power? My combo had no problem burning the hides in all four gears and make passengers grab the role cage in fear.

I don't know if a low compression 454 can be called a 'slug' several on this site are running some good times,but for a drag motor you do want more compression.

I don't remember calling his nor anyone elses a slug but mine. It was the worst BBC combo I had ever seen. Flat top pistons with open chamber heads, wrong cam. Mine was a slug

I don't remember calling his nor anyone elses a slug but mine. It was the worst BBC combo I had ever seen. Flat top pistons with open chamber heads, wrong cam. Mine was a slug

The combo Joel refers to had a calculated CR of 7.8 combined with way too big of a cam. :sad: IIRC, cranking compression was in the 110-120 psi range on a fresh engine.
It WAS a slug. ;)

I don't remember calling his nor anyone elses a slug but mine. It was the worst BBC combo I had ever seen. Flat top pistons with open chamber heads, wrong cam. Mine was a slug

I could see that with that combo.

Michael,

Darryl/Doc/FRYNTYR posted pics of the chamber areas to watch for contact in the BBC INFO Sticky, top of the ENGINE section

If it is drag only and you will put adequate race gas in it the 215's will out run the open chamber heads.

If both sets of heads are prepared the same I would guess the 215 heads will be at least two tenths faster in the quarter, maybe more.

All good info, thanks everyone. I think I'll stick with the 215's and have them reworked. :beers:

Very good choice.

Did you ever take it back to the track? MPH? ET? LJ

Very good choice.

Did you ever take it back to the track? MPH? ET? LJ

Yeah we took it there before we knew it had head problems, ran 12.6 @101. I knew this should run better than that. We tore into it because it was blowing oil from somewhere at high RPM's and we could'nt fiqure out where it was coming from and found a flat cam lobe, one bent pushrod and 6 broken inner valve springs. We have just now freshened it up with all new bearings, a 294S x .595 lift Comp cam with new lifters and Comp cam Hi-Tech pushrods. I think the guy that had the motor before me had actually used some 396 pushrods with a .544 lift cam and they was not stout enough. When we pulled the pushrods out, I mic'd one and they were only like 0.300 OD. The new ones are actually 0.375 with 0.80 wall Chrome Moly. Been looking for a set of aluminum heads with a small cc chamber to keep my compression up but we may have to resort to having the 215's reworked.