Olds heads

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CamaroAdam73

Royal Smart Person
I'm building up my 403, i thought long and hard about buying a new set of edelbrock aluminum and i don't want to spend $700 more just to say the top ends all aluminum and have the same performance results as a stock set of performance olds heads.

So what would be a good set to use? and where's a good place to find a set? So far I've only found single heads on ebay. preferable a smaller combustion chamber, no smaller than 64CC however.

The crank girdle came in the mail today :twisted: Next is to get comp cams to ship me the cam kit, debating spending the extra 350$ for a hydraulic roller. Can't order the cam until I've got the heads though.
 

tt442

Not-quite-so-new-guy
May 3, 2011
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I havnt gotten to use them yet but I read the oldsmobile building horsepower book and the Edelbrock heads are pretty much what they recommended as the best available. They are big block heads and flow like a big block head so you wont need any port work. I believe it said with the smaller motors the heads are already flowing more thant needed. you will need to have them milled down to reach the CC you want.
 

tt442

Not-quite-so-new-guy
May 3, 2011
46
0
0
Also I will mention that with a part like that your really not spending that much on them b they are always worth a fair amount of money as long as they arnt ruined. Guys just like you looking for them used to save a a bit of money. So really think of it as borrowing you car the money for the heads and it has to pay you back a little less whe you sell it down the road
 

marcar1993

G-Body Guru
Aug 31, 2007
702
209
43
New Jersey
How high are you going to spin this motor? What pistons are in it? If you wanna run cheaper heads similar to e-brocks, run bb heads. But unless you have flattops or close, and a big cam, and plan to spin it up high often, its a waste. Just run small block heads. Need more info on the motor and car and use.
 

Minion1186

G-Body Guru
Apr 12, 2009
977
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I'm actually planning a 403 street motor build as well. The 403's used Big Block 80 cc chambers which resulted in a 8.0 compression, I've heard that flat top pistons and stock heads will bump compression up to 8.5 and with dished pistons and 64 cc heads with factory head gaskets will achieve close to 9.4-9.6 compression. Good small block olds heads that are worth using are-5, 6, 7 and 7a 350 heads. They are all 64cc heads. Good luck on finding them, usually you can get lucky finding them in junkyards or on various Oldsmobile forums.

Depending on valve sizes, I think stock 403 valves or even w-31 valves will do just fine in a street/strip small block.
 

marcar1993

G-Body Guru
Aug 31, 2007
702
209
43
New Jersey
I have a stock bottom end 403 with 1968 #5 heads, with real world measurements, I have 9.1:1 compression.
 

CamaroAdam73

Royal Smart Person
This 403 is going in my 88 MCSS. Hoping to have the car sitting at 3000LBS with me in it it's been a long time coming project.

I don't plan on making this engine spin it self to death, i know the 403 has limitations and doesn't like high RPMs. If i wanted a screamer I'd just continue building my 355.

I want to make the most power below or at 5000-5500 RPM. Once i know for sure what cylinder heads I'm going to run, I'll call comp cams and give them the concrete specs and have them ship me a cam kit. Matching valve train is always a plus. I've already got an intake manifold, edelbrock low-rise 3711.


Not sure on what pistons I'll be putting in it. There's nothing wrong with the bottom end now BUT, i'm installing a crank girdle, so i might as well do bearings, and being that far i'll be looking to change out the pistons. The bottom end was a short block, it's got under 10k millage on it when i pulled it from the trans am it was in. The only things i'll be reusing for certain are the crankshaft and connecting rods.
 

marcar1993

G-Body Guru
Aug 31, 2007
702
209
43
New Jersey
Ok, well for under 6k rpm, why not just stick with small block heads? Get a set of 5,6,7,7a heads (68-72 350 heads) hog out the bolt holes to 1/2" and put in bigger valves (or find big valve heads), unshround them and mild cleanup work. With stock pistons you should be in the 9:1 range. Find go search for a compression calculator online and plug in your info, see what you get. If the bottom end doesn't need an overbore, reuse the stock pistons just 0 deck the block. Maybe mill the heads for more compression if needed too.
Btw, 68-72 heads have anywhere from a 64-68cc combustion chamber from what I've heard. You'll need to cc them and then cut them from there.
 

CamaroAdam73

Royal Smart Person
Marcar1993 we're on the same page. Where can i find a set of 5,6,7,7a heads, and whats the best of those sets?

I've got a few other questions if yall dont mind. When i tear down tmy 403, being that it's a shortblock with very low millage, should i replace the stock pistons or re-use? What about the connecting rods? Replacing the crank is absolutely out of the question, i don't see any need for a forged crank anyways, i won't be spinning this engine up hard. So far the only things I'm doing to the bottom end are possibly re-ringing the pistons if i see fit, main/rod bearings, and crank girdle so it'll safely stand up to power. Any advice?
 
Oct 14, 2008
8,806
7,746
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Melville,Saskatchewan
Re ring and bearing IF every measures out within spec. Replacement pistons are always short on compression height. Even with early heads, 9 to 1 is hard to reach. Stock rods will be fine, if you keep the rpms down. KB pistons will give around 10 to 1 with the Pro Comp heads, a copy of the old Edelbrock head. They can be found for about half the price of Edelbrock heads. KB pistons would work with stock 4A, #8 or any of the big block heads. They would be too high with early 350 heads.
 
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