hp limit on bbc o port heads?

crazycuda · Post by **crazycuda** » Wed Mar 22, 2006 3:53 pm

I know this is probably a crap shoot question but using the hp to flow numbers is there any power cap (from your experences) on the oval port heads.

Using a stock unported set what mods would you do to acheive maxium flow/ hp potential?

67RS502 · Post by **67RS502** » Wed Mar 22, 2006 4:25 pm

Upper 600s are pretty easy with clean up and bigger valves.
But over 700 gets tuf.
I've seen welded up / epoxied 049s done by Casey at SAMs that flowed over 400... they were on their 470cube motor back in the day, the car was running low-mid 9s from what I remember.

Donnie1126 · Post by **Donnie1126** » Wed Mar 22, 2006 6:42 pm

Here's a link to some BBC flow numbers. Don't know if they will be of much help but I think it has some stock flow numbers. Might give you an idea of the power you can get from unported heads.

http://www.carcraft.com/techarticles/116_head_bbchev/

highVE · Post by **highVE** » Wed Mar 22, 2006 8:34 pm

If your talking about old iron heads, like the 781 castings. Then you can get some semi respectable power from them. Like 69RS502 said, bigger valves. 2.19"/1.88" with bowl work, and 11/32" stem. match that with a nice solid roller grind and a victer oval port intake with some compression 650HP is acheivable all day long on a 505. (4.350bore w/4.250stroke)
I've done it a few times for street/strip cars.

Mike Theroux
www.mikesportingservice.com

shawn · Post by **shawn** » Wed Mar 22, 2006 8:34 pm

I've always been a big fan of a good street/strip bracket bb chev w/049 or 781 oval ports, as long as it's under 480"'s or so. I've done a bunch of .100 over 454 with a good crank (gm steel) and stock rods with good bolts,good dome piston (13.5-1 or so) that is fairly light weight to save on the bottom end. A set of 049's with 2.25/1.88 valves and good port work (something that would flow in the 330/340 area), a roller in the 265-275 @.050/.700 lift department and a dart intake with a 1050 will get you about 700hp. Obviously there is always more to be made with any combo. If you want to run it like a super stock motor and put a ton of cam in it, spin it up,port the heads to the ragged edge, and angle mill them for a bunch of compression, you might be able to add 100hp more to that.
shawn

DOTracer · Post by **DOTracer** » Wed Mar 22, 2006 10:53 pm

Here's some data on the 781's I've run for a couple seasons.

These are not ported, rather a basic bowl blend, 3 angle valve job, intake gasket match and large valves ( 2.25/1.88 ).

Machine is a Superflow SF-600, Brizensky fixture plates, 4.310" bore fixture.

lift intake exhaust exhaust w/2" straight pipe
.100 69 70 69
.200 142 110 114
.300 210 140 146
.400 256 166 176
.500 285 180 195
.600 276 188 204

Probably alot left in them as the chambers were untouched as were the valve guide bosses and both intake and exhaust runners.

Performance wise, they were on a 13.1 to 1 compression 461 ci bbc. The car is a 3515 lb 79 Malibu running a quick as 9.994 @ 132.87 mph on 9" wide radial tires and mufflers...normally aspirated. Have no idea of true HP, but the "dream wheels" and online calculators show around 675 hp IIRC.

Joe Mendelis · Post by **Joe Mendelis** » Thu Mar 23, 2006 1:38 pm

67RS502 wrote:Upper 600s are pretty easy with clean up and bigger valves.
But over 700 gets tuf.
I've seen welded up / epoxied 049s done by Casey at SAMs that flowed over 400... they were on their 470cube motor back in the day, the car was running low-mid 9s from what I remember.

Casey was my Cylinder Head instuctor at S.A.M. He does some impressive stuff.

PWMAX · Post by **PWMAX** » Thu Mar 23, 2006 2:57 pm

I have made over 750hp, on a 496, with 049's. This was more than a "clean" up though, it was a fricken lot of work, lol. 2.19/1.88 valves. I gaurentee with a little more playing around with the heads, more compression, the motor was 12.9:1, and more camshaft, it was under .700 net lift, I know I could have made over 800hp with them. There was no vaccum pump, or any ring tricks, nothin, a very basic bracket motor. 68 Camaro, went 9.29 at 146. Switched to a set of ported Candield 310's, no other change, except they had a 113 chamber, which bumped compression to 13.8:1, and porting the Victor-o 4500 to rectangle port status, the same cam, everything, car went 9.000's to 8.9xxx's at 149, every once in awhile, would go 150 and change. The Canfields were a "basic" full port job, nothing fancy.

DOTracer · Post by **DOTracer** » Thu Mar 23, 2006 3:11 pm

PWMAX wrote:I have made over 750hp, on a 496, with 049's. This was more than a "clean" up though, it was a fricken lot of work, lol. 2.19/1.88 valves. I gaurentee with a little more playing around with the heads, more compression, the motor was 12.9:1, and more camshaft, it was under .700 net lift, I know I could have made over 800hp with them. There was no vaccum pump, or any ring tricks, nothin, a very basic bracket motor. 68 Camaro, went 9.29 at 146. Switched to a set of ported Candield 310's, no other change, except they had a 113 chamber, which bumped compression to 13.8:1, and porting the Victor-o 4500 to rectangle port status, the same cam, everything, car went 9.000's to 8.9xxx's at 149, every once in awhile, would go 150 and change. The Canfields were a "basic" full port job, nothing fancy.

Was just curious to know what kind of race weight that Camaro is/was?

67RS502 · Post by **67RS502** » Thu Mar 23, 2006 5:09 pm

PWMAX
What were the cam specs and how high did you spin it?

crazycuda · Post by **crazycuda** » Fri Mar 24, 2006 1:00 pm

Thanks for the input on the heads.
I am slowly putting together a bbc together for my 78 Trans Am. I am still at a toss up between going 454 or 427. Any one have any opions on what would be a better way to go for a hot street play toy. I personally lean to the 427 because I can turn it like a small block but the tork loss from the 454 has me a little ify because the ta is a 3800lb car. I have the parts to go with either setup.

doctorpipe · Post by **doctorpipe** » Sun Mar 26, 2006 1:53 am

I would have to go to the shop for the flow numbers, but I did a set of heavily reworked closed chamber oval port heads, with 2.08" intake and 1.94" exhaust valves. They were 5/16ths stems, and the customer had the .650" lift cam I had to work around. The engine is a 496 for bracket racing. I don't have dyno numbers but it runs consistently 10:30 on alky, in a 3950 lb. 1975 chevelle. It turns 6800 rpm max. The problem is the exhaust ports force the engine to shut down at high rpm. Cash in on the torque, that's what big inches with small heads do best. It has been bullet proof for 3 years, unfortunately the tranny's and rear end weren't. The intake was modified for a 1150 dominator and heavily modified also, and it had custom 2 3/8" headders.
Doctorpipe