Engine displacement

[jcd9730]

Maybe this is a dumb question, but I'm still learning about the inner workings of these engines.

My question is, tomorrow I will be taking the heads off to replace a head gasket. When I bought the truck, I was told it was a 350 block stroked to a 383. If it is a 383, its a pretty mild one, but I wasn't too worried about it. The engine size wasn't really a big factor in buying it.

It is a 350 block (checked the cast number), and if it does have a 400 crank, it isn't externally balanced. With the heads off, short of taking the whole rotating assembly out, is there a way to tell if its a 350 vs 383? Measure the stroke maybe?

[haysonj]

Originally Posted by jcd9730

Maybe this is a dumb question, but I'm still learning about the inner workings of these engines.

My question is, tomorrow I will be taking the heads off to replace a head gasket. When I bought the truck, I was told it was a 350 block stroked to a 383. If it is a 383, its a pretty mild one, but I wasn't too worried about it. The engine size wasn't really a big factor in buying it.

It is a 350 block (checked the cast number), and if it does have a 400 crank, it isn't externally balanced. With the heads off, short of taking the whole rotating assembly out, is there a way to tell if its a 350 vs 383? Measure the stroke maybe?

If it is a 383 the bore would be 4.030 and the stroke would be 3.75 On a 350 the stroke is 3.25.

[jcd9730]

So I could just measure the difference from TDC and BDC, and it would be either 4.030 or 3.75?

[jcd9730]

3.75 and 3.25 I meant...

[budman k20]

I agree measuring the stroke is a good way to confirm the displacement. A 327 has a 3.25 in. stroke and a 350 has a 3.48 in. stroke. Using a tape that would be just under 3.50 inches. Both a 327 and 350 have 4.0 in bores.

[jcd9730]

A 350 has a 3.48 or 3.25 stroke?

[c10srule]

could check the casting numbers on the crank

[Tx Firefighter]

Google will show you the stroke of a 350 Chevy. Measure from bottom dead center to top dead center and compare to your google information.

Questions like this its much easier and faster to look up than to wait for an answer on a forum board.
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[jcd9730]

yeah i already googled that. I just didnt know if this was a good way to find out what the displacement was, which is why I asked.

[haysonj]

I was wrong on that the 350 is 3.48 and the 383 is 3.75

[Tx Firefighter]

You're on the right track with your measuring. You should be able to determine basically what stroke the crank is by using a ruler or tape measure. In this case, you're measuring to the quarter inch not to the thousandth or anything so close enough will tell you what you have to work with. It will be either 3.5 inch or 3.75 inches.
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[jcd9730]

Cool, thanks for the help!

[70blackfish]

383 I believe the Balancer will be a 8 inch and the flex plate will be weighted because of the 400 crank

[haysonj]

Originally Posted by 70blackfish

383 I believe the Balancer will be a 8 inch and the flex plate will be weighted because of the 400 crank

Not necessarily my 383 is internally balanced and has a neutral balancer and flex plate

[LONGHAIR]

Yeah, you can't trust the lack of a counter-weighted balancer as proof of a 350 crank. There are internally balanced aftermarket cranks out there.