BBC Heads

TimAT

Addict, Cruise-In Bird-Run 1 Veteran
Joined
Mar 24, 2008
Messages
1,970
Location
Gladstone, Missouri
OK, still looking at Ol' Red getting a new heart- Got a 4 bolt block being bored and line honed, so that part is done. Found a 496 forged rotating assembly, so that's pretty well done too.

Now looking at heads-

AFR, Brodix, Dart, and RHS are all very pricey and advertise having "open" combustion chambers. The difference is pretty visible looking at open and closed side by side.

What's the advantage to open over closed, other than in the upper RPM numbers??

Anyone ever played with the difference? I know you can put open chamber heads over closed chamber pistons, but you can't go the other way without making lots of very small pieces that you can't use anymore.
 
OK, still looking at Ol' Red getting a new heart- Got a 4 bolt block being bored and line honed, so that part is done. Found a 496 forged rotating assembly, so that's pretty well done too.

Now looking at heads-

AFR, Brodix, Dart, and RHS are all very pricey and advertise having "open" combustion chambers. The difference is pretty visible looking at open and closed side by side.

What's the advantage to open over closed, other than in the upper RPM numbers??

Anyone ever played with the difference? I know you can put open chamber heads over closed chamber pistons, but you can't go the other way without making lots of very small pieces that you can't use anymore.


Called TSCH and the heads are Open Chambers 115cc.:cool:

I'll do the flow numbers for you in the next few days.:noworry:
 
OK, still looking at Ol' Red getting a new heart- Got a 4 bolt block being bored and line honed, so that part is done. Found a 496 forged rotating assembly, so that's pretty well done too.

Now looking at heads-

AFR, Brodix, Dart, and RHS are all very pricey and advertise having "open" combustion chambers. The difference is pretty visible looking at open and closed side by side.

What's the advantage to open over closed, other than in the upper RPM numbers??

Anyone ever played with the difference? I know you can put open chamber heads over closed chamber pistons, but you can't go the other way without making lots of very small pieces that you can't use anymore.


Called TSCH and the heads are Open Chambers 115cc.:cool:

I'll do the flow numbers for you in the next few days.:noworry:



Ran the flow number on the specs we talked about.

598 hp at 5500
634 flbs at 4000
633 flbs at 4500


Damn!!!!!!!!!:drink:


BTW: 551 flbs at 2000 rpm. Double Damn!!!!!!!!!!!!
 
Last edited:
How much compression ratio drop will you see when going to those open chambers? When I ran the canfields on mine (110 combustion chamber versus stock 100) with no other changes, CR dropped to 10 from 10.7.
 
OK, still looking at Ol' Red getting a new heart- Got a 4 bolt block being bored and line honed, so that part is done. Found a 496 forged rotating assembly, so that's pretty well done too.

Now looking at heads-

AFR, Brodix, Dart, and RHS are all very pricey and advertise having "open" combustion chambers. The difference is pretty visible looking at open and closed side by side.

What's the advantage to open over closed, other than in the upper RPM numbers??

Anyone ever played with the difference? I know you can put open chamber heads over closed chamber pistons, but you can't go the other way without making lots of very small pieces that you can't use anymore.


Called TSCH and the heads are Open Chambers 115cc.:cool:

I'll do the flow numbers for you in the next few days.:noworry:



Ran the flow number on the specs we talked about.

598 hp at 5500
634 flbs at 4000
633 flbs at 4500


Damn!!!!!!!!!:drink:


BTW: 551 flbs at 2000 rpm. Double Damn!!!!!!!!!!!!

Talk about a monster BB...Dayum
 
Stuff a .650 to .700 cam in that and the numbers should get pretty big-- and quick.

I went another direction. Lowered the lift and closed the LSA a little.

This is the Comp Roller (jetboat) XR296HR
112 LSA


.566 lift

242 int
248 ex .050.

With the DUAL Quads:

612 hp at 5500
636 flbs at 4000

547 ftlbs at 2,000.
10.22 cr.
I like this combo--even though it's a Comp Cam.:yahoo:


I know this is a Jetboat cam. BUT!!!!!! When I was building BB boat engines in the 70's --- yea, a long time ago-- I found that Jetboat cams to work very well in street engines. I like the lift of this cam --cause it will be easier on the valve train for a street driven vehicle. I like it when you don't break springs and rockers going down the road.:tomato:
 
Last edited:
Stuff a .650 to .700 cam in that and the numbers should get pretty big-- and quick.

Ok, for fun::D

675 lift

260 duration at .050 -- solidroller


112 LSA ---------------------------------------- 108 LSA

662 hp at 6,000 rpm ------------------------ 657 hp at 6000
635 ftlbs at 5,000 rpm ------------------- 624 ftlbs at 5000

479 ftlbs at 2000 rpm. ------------------- 466 ftlbs at 2000

:suspicious:


VERY ROUGH IDLE-- Big lope!:bonkers:


You think RED attracts attention now, with this.....................:eek::bounce:
 
Last edited:
I think I like the numbers for the Comp Cam. HP is 600+. I think the fun part will be the 551 torque number at 2000. WHat would happen if you opened up the lift and kept the LSA and duration on the split pattern

Maybe some other BB guys will step in and throw out some other ideas too.
 
I think I like the numbers for the Comp Cam. HP is 600+. I think the fun part will be the 551 torque number at 2000. WHat would happen if you opened up the lift and kept the LSA and duration on the split pattern

Maybe some other BB guys will step in and throw out some other ideas too.


Tim:
Remember that the heads are limited to .600 lift with the current springs on them. I'll run some more numbers tomarrow.:noworry:
 
I think I like the numbers for the Comp Cam. HP is 600+. I think the fun part will be the 551 torque number at 2000. WHat would happen if you opened up the lift and kept the LSA and duration on the split pattern

Maybe some other BB guys will step in and throw out some other ideas too.


Tim:
Remember that the heads are limited to .600 lift with the current springs on them. I'll run some more numbers tomarrow.:noworry:

That is correct. But I've always been a big fan of matching the springs and the cam.
 
I think I like the numbers for the Comp Cam. HP is 600+. I think the fun part will be the 551 torque number at 2000. WHat would happen if you opened up the lift and kept the LSA and duration on the split pattern

Maybe some other BB guys will step in and throw out some other ideas too.


You know I'm not a Comp Cams fan. But Comp does have a Cam 304HR that is close to the specs you asked about.

.612 lift

244 at .050

110 LSA


603 HP at 5500
633 ftlbs at 4000 t0 4500


553 ftlbs at 2000

Anthing with higher lift from Comp will be a solid roller and with more effective duration -- 250+.:smash:

These are from Comp Cam Book specs.
 
Last edited:
Crane Cam 139021 HR

610 int
632 ex

.050
234 int
242 ex

112 LSA


591 hp 5500
655 flbs 4000
652 ftlbs 3500

585 ftlbs at 2000


Wow- on the low end torque.:twitch:
 
Last edited:
So are you going with the AFRs? If so, let me know which ones and I'll redo everything with their flow numbers.:idea:


I was in the shop looking at my 454--thinking 496.:nuts::rolleyes::bonkers::wink:
 
Yep-- AFR's. For the little difference in the $$ I can't see not using AFR. And the 325's seem to be the best fit short of going to the all out CNC'd parts.
 
Yep-- AFR's. For the little difference in the $$ I can't see not using AFR. And the 325's seem to be the best fit short of going to the all out CNC'd parts.


Yea, that's the way to go. Let me know the ones you get so I can get the flow numbers. Did you look at the numbers on the CNCed 315cc? Quite good.:nuts:
 
I looked at the 315's- numbers look good, but the full CNC steps the bucks back over 3k. I'm going to do the 325's as cast, CNC chambers, all parts. I need to check, but I may have to drop back to the full "as cast" heads. From what I have read, the CNC thing jumps the chambers to 121cc- too big.
 
Top