291 BBC Heads

[BBPanel]

I'me going to run a converted Hilborn stack unit on a 489 BBC for the street. I have a set of 290 closed chamber heads w/large valves but there is going to be a significant mismatch between the rect port intake and the oval port heads. Would I be better of going to a set of 291 rect closed chamber heads? Will I be giving up too much low end going from the ovals to rect head relative to the gains from properly matched ports? Or will I have a torque problem at all (this will be my first BB). Probably looking at 10:1 CR and a cam w/mid 240/250 duration @ 0.050 in 55 Belair. Appreciate your comments. -Bob

[Wolfplace]

BBPanel said:

I'me going to run a converted Hilborn stack unit on a 489 BBC for the street. I have a set of 290 closed chamber heads w/large valves but there is going to be a significant mismatch between the rect port intake and the oval port heads. Would I be better of going to a set of 291 rect closed chamber heads? Will I be giving up too much low end going from the ovals to rect head relative to the gains from properly matched ports? Or will I have a torque problem at all (this will be my first BB). Probably looking at 10:1 CR and a cam w/mid 240/250 duration @ 0.050 in 55 Belair. Appreciate your comments. -Bob

=
Is this converted to EFI?
If you have the rect heads run them or at least open the ovals to match the intake.
I do not like mismatched ports & neither does air.
This was done 30 years ago when the best intake by far was the factory GM rect one & there seems to still be a few hold-outs but today there is no reason to be doing this.
I would also be putting a little more cam in a 489 assuming it is a solid.
Don't be afraid of some cam, bigger engines like them,,,
I would be looking at something about 8-10 degrees longer.

[BBPanel]

Yes, it will be converted to EFI. No, I don't have the heads yet - been looking for a set. Want to run flat top pistons and the closed chamber heads will help me there w/compression. Would love some aluminum heads (like AFR 305) but there are 2 things holding that back. One the budget can't afford the Al heads and two I have a set of Jesel shaft rockers and they only fit OEM heads - the cost of new stands to use them on an Al head is just too much also for the budget.

The difference in the intake ports is large between the 290 and 291 heads (265 vs 315 or 320 I believe) - that was my concern as to losing a lot of lower end torque.

I understand the stack injection tames a cam quite a bit - jumping up to 250/260 probably won't hurt anything - I'd like to run a solid roller. Thanks for the reply - any other suggestions?

[69 Nova]

You shouldn't see a torque problem on lower end with the longer stroke.

[Wolfplace]

BBPanel said:

Yes, it will be converted to EFI. No, I don't have the heads yet - been looking for a set. Want to run flat top pistons and the closed chamber heads will help me there w/compression. Would love some aluminum heads (like AFR 305) but there are 2 things holding that back. One the budget can't afford the Al heads and two I have a set of Jesel shaft rockers and they only fit OEM heads - the cost of new stands to use them on an Al head is just too much also for the budget.

The difference in the intake ports is large between the 290 and 291 heads (265 vs 315 or 320 I believe) - that was my concern as to losing a lot of lower end torque.

I understand the stack injection tames a cam quite a bit - jumping up to 250/260 probably won't hurt anything - I'd like to run a solid roller. Thanks for the reply - any other suggestions?

=
If you want to keep the ovals, I would recommend you get in touch with Mike Stark & see what it would cost to match your heads to your rect intake.
Can't speak for him but my guess is it would not be a big deal,, probably a hell of a lot cheaper than doing a new set of heads up.

If you do decide you are lookin for a set of AFR or Brodix Race Rites now that they have a rect one shoot me an email & I can probably save you a few dollars on either one