We are in process to build a street built 403 for our 64 Cutlass and need some advice.

Block decked / bored 0,30
Stock Rods
Big Pan / HV Pump
Balanced & grind Crank (403)
no Halo Girdle
maybe straps ?

Goal is about 9,5:1

We are not sure if stand with stock 83 cc 4A heads (bowl job) along with a Cometic .027 head gasket and maybe bigger valves and stock style pistons

or

go with 7A 350 (64cc) heads (port bowl job) stock valve with maybe the KB´s pistons.

 

You kinda got it backwards, with stock pistons and 4A heads, CR will be 8 to 1, with 7a heads and KB's, mid 10s. I'm doing this off the top of my head, so don't hold me to the math. If I was doing a 403 (which will end up 409 after boring) I would use big block heads and the KB or other pistons with a small dish. Cr will end up in the high 9.xx range and the engine will use the added volume of the heads. IMHO.

 

Once again, if BBO heads work on a 400 cu in BBO, why restrict your 403 with smaller SBO ports? At a minimum, I'd use C heads, and preferably some aluminum ProComps as ported by Bernard Mondello. Yeah, you'll need to match chamber size and piston dish to get the right CR, but that's normal for building a motor. Just keep in mind that you make HP by maximizing airflow through the engine. Using heads with small ports does not accomplish this.

 

Get a Chinesium Girdle:

http://www.ebay.com/itm/151173321106...84.m1555.l2649

:-)

 

That is TOO friggin funny!!!!!!!!!!!!!!!!!!!!!!!!!!

 

Lightweight is the way to go these days. Like I said, engine technology has come a long way. Octania, how do you make any profit on these girdles, you are practically giving them away!

 

Nice part of aluminum heads on a 403 with the quality hyper and forged pistons will put you at mid to high 9's compression, with the right cam, a very torquey motor.

 

Well with the exotic materials used, I lose money on each one
but, I make it up in VOLUME!

 

@ captjim & padavano

BB heads & Alum heads are not a option...
So whats your opinion:
7A 350 heads with with stock style piston
4A 403 heads with KB´s

to bring compression in the 9-9,5:1 range

 

Because you don't want to spend $150 on a set of C castings?

I mean, you're going to have what, $4K or so into this motor?

If you must use one of the two sets of heads that you apparently already have, then it doesn't matter. In either case, get 2.070/1.625 or larger valved installed. Select pistons to match the chambers of the heads that you use.

 

The 4A heads are plain awful on the exhaust side, similar to J heads. Seeing your in Germany, either put on early SB heads on the stock short block with a better cam or upgrade the pistons and port the heads.

 

If those are the choices the KB/4A combo is easiest. Those pistons were made for guys to use the 4A heads and get 9.5 to 1 CR. But again, as Joe stated, for almost nothing more, the BBO heads are a MUCH better choice.

 

With your options I too would bolt the KB/4A combo on and get it running (sounds to me like you're at the point of needing to get this build on the street). We just hate to see you hamstring your build with low flow heads. But then again, you can always bolt on BBO heads at a later date.

 

That's actually the best reason I've heard for going with the 4A heads and KB pistons. Of course, once again assuming the 4A heads need a valve job, spend $150 and get the C cores now.

 

Can you get C heads in Germany for $150? Maybe that's not the case and the source of the reasoning behind the one-or-the-other decision.

 

I have the 403 with .024 kb -6cc pistons and "zero decked block"(if my memory is right) and shaved 4A heads with 1.7 ratio rockers and the cam is 249-CL42-222-4 and im looking into some aluminium heads myself but the machine shop guy asked cam and rocker specs so i assume he shaved the heads to get the most compression out of it. What im worried about is if i buy heads that have lower cc chambers then i could be geting into having too buy new cam or rocker arms for valve clearance. does anyone have any knoledge to bestow apon a young man with limited experiance in this area lol ?

 

Don't worry, valve/piston contact SHOULD NOT be an issue in your case, with any Olds factory/aftermarket head. It needs A LOT more lift..

 

Thanks alot, i got some heads im looking into since i got pletty room i might get bigger cam for the hell of it haha

 

I would stick with the cam that yields maximum performance. Duration figures are more important than lift. Timing figures dictate, to a certain extent, the dynamic compression and exhausting the cylinder of waste. Throwing a bigger cam in when unnecessary will just make your engine inefficient.

 

Well im thinkn on geting a roller cam and it will still be a street car but i was thinkn i could get away with bigger and still be ok as far as streetable goes, slowly workn my way to being more race car lol goin have to do more reasearch to come up with best one for a weekend warrior that i can drive 50 miles then race then drive back. Gas mileage is of no issue haha any suggestions?