403 Head Question

[500/600]

Did you hit water jacket?

 

[TURNA]

Did you hit water jacket?

Nope If i did they would be in the scrap pile.

Used a shallow 7/32 seat normally used in a fuelie head

 

[olds307 and 403]

Using 2"/1.625" valves? How much porting time do you have on the exhaust side? Nice job BTW.

 

[TURNA]

Using 2"/1.625" valves? How much porting time do you have on the exhaust side? Nice job BTW.

None really used a bore cutter to hog them.

Not going nuts with them. This is a driver.

They will flow great for up to 400HP

I should be around 325-350

 

[Texas82GP]

It's a "cruiser".

 

[500/600]

It's a "cruiser".
View attachment 129747

My mind was thinking short stroke + halo + big valve heads = 7500 cruisable rpm.

 

[TURNA]

My mind was thinking short stroke + halo + big valve heads = 7500 cruisable rpm.

If it wasnt for the webbed block

It could have been the best engine ever built

huge pistons short stroke a real screamer

 

[olds307 and 403]

My mind was thinking short stroke + halo + big valve heads = 7500 cruisable rpm.

Yeah, God bless the late 70's. Surprised your Cad V8 wasn't lightened as well. Pontiac also stripped meat out of their bottom end on the 400 in 77. The intake port is Ok on the 403 4A heads. The exhaust port is a different story pretty constipated, even the J and 8 heads are better after a bowl hog. Talking 195/119 stock. Hopefully the 1.625" valve and opening the bowl at least equal stock early SBO heads.

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[pagrunt]

"Cruiser"

 

[500/600]

Yeah, God bless the late 70's. Surprised your Cad V8 wasn't lightened as well. Pontiac also stripped meat out of their bottom end on the 400 in 77. The intake port is Ok on the 403 4A heads. The exhaust port is a different story pretty constipated, even the J and 8 heads are better after a bowl hog. Talking 195/119 stock. Hopefully the 1.625" valve and opening the bowl at least equal stock early SBO heads.

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jsmachineoldsmobile.com is your first and best source for all of the information you’re looking for. From general topics to more of what you would expect to find here, jsmachineoldsmobile.com has it all. We hope you find what you are searching for!

www.jsmachineoldsmobile.com

The 472 and 500 were always heavy duty. By the time the 500 went away and the 425 took over the lightening had begun.
Lots of people are building 425s. I have no idea why. Must be for fuel economy 👍