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which bbc head to use

2K views 7 replies 7 participants last post by  Impala5967 
#1 ·
ok I am rebuilding a 427 chevy and have a set of oval and rectangle port heads. I was told years ago that oval port heads were used in trucks for torque and the rectangle heads were used in cars and for a hot rod the rectangle heads were the best choice. I just seen a dragster today with a 427 and it had oval port heads and needless to say it was very fast, which now makes me confused as to which heads are best. the oval ones I have are new out of the box, but I would have to rebuild the rectangle heads. it's all going in a very lite weight car with a 4 speed and 4:56 rears, the engine is balanced, if that makes any difference on which heads to use.

I did a search on this topic and found nothing; just to let you know that I've done my homework...
 
#3 ·
It depends more on the type of cam and rpm range your intending to run BWG, most streeters do just fine with the oval ports and will likely outperform the rect heads in around town driving.
 
#5 ·
I would have to agree on the ovals unless you are going to take the motor to 8000 like someone else said. I am building a pump gas 496 being rapped to 6500 rpm, and I am still using a set of polished and ported 781 ovals. You could use rectangular in my case, but I was after the torque.

Good luck
Adam
 
#6 ·
I would also agree with everyone on the ovals even though I have a 396 w/ rectangular ports. Here's a question though, a BBC in a street car has enough torque to typically smoke the tires at will, can you really use more low end torque than what the rect ports will provide? Other than just doing big smoky burnouts:)
 
#7 ·
I know there is going to be a little torque overkill, but we already had a set of polished and ported 781's, that we were going to use on a 461. Then we found a cheap 496 short block and decided to use that. The motor is going into a tube chassis 1967 Nova, it has a full interior and eveything, and the body is all steel except bumpers and hood, and weighs 2700lbs with a big block, so that is just more reason to not need the torque, but the car should be fun to drive.

Adam
 
#8 ·
I completly understand your question and you should really weigh in the benifits and disadvantages of each design.
1) Oval ports- Generate very high intake velocities and generally flow well up to 6000RPM. This will give crisp acceleration at amy RPM. Dis-addvantages they are pretty much all done at about 6000RPM. These are very drivable street heads. If you are going stock lock for casting 049, 290, in closed chamber. Port the bowls out and run big valves. 2.19I 1.88E
2) rectangular ports- Do not run all that well below 3000RPM. They are terrible around town. Have a noticible chug ( I think fuel actually condenses in these if you idle araound. Over 4000RPM hold on, there is nothing like them. they will flow great after and keep flowing well above 7000RPM.

I speak from experience as I ran both in my '68 Vette 427 tie-power. Currently I am switching back to the ovals and reserving my rectangulars for a 489 stroker. I personally think the rectangular ports are to big for a street 427, 402, 396. If you design your engine to make power over 6000RPM go rectangular. If not the Ovals will perform better on the street.
 
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