Thread: 350/305 ???

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Ok I just need some clarification on the difference between a 305/350.
I have two experienced people telling me two different things.
1. 305 and 350 are the same block, with a different Bore and the same stroke
2. 350 and 305 are different blocks, with different cranks and bore.

I pulled an engine that is supposedly a 350 and replaced it with another 350. However the flywheel would not fit on the new 350 (because the center whole was two small) My dad suggested that this may be a different because one block is a 2piece rear main, and the other is a one piece rear main.

Reason I want to know if because I was given the old block, however I am now uncertain weather it is a 350 or a 305... If it is a 305 I need to know if it is compatible with my 350 parts (I.e. will the 350 heads/crank fit properly in the 305 block) The whole engine is in really good shape, the guy I'm working with spun a rod bearing (but the crank and the bearings still look really good there is just a little play in them) But the guy has plenty of money and likes to spend it... so he bought a brand new 350 lol.

Thanks for any info in advanced

well the 305 is a 305 shares the same crank with the 350, but the bore is much smaller, just measure the diamaters of the blocks with a tape measure or ruler, if there the same you got 2 350 blocks, diffrent, the smaller 1 is a 305 or smaller. If the engine you got from the guy spun a bearing, your going to at least have the crank checked by a machinest, and all new rod bearings, if a bearing spun, it's no good.

Ok thankz.. Do you mean the Diameter of the piston bore?
I know for a 350 its 4" so if its smaller than 4" its probably a 305?

Originally Posted by weylinthedirty

Ok thankz.. Do you mean the Diameter of the piston bore?
I know for a 350 its 4" so if its smaller than 4" its probably a 305?

yep. if it's smaller, also check the stroke by measuring from BDC to TDC, you can do it with a dowel in the spark plug hole if the heads are on, mark for BDC then bring it to TDC and mark, set next to a ruler and check. 305/350's are 3.48 " stroke, 267's are also but it rules out the 265-327's as they all used diffrent strokes.

ill put it on the engine stand tomorrow and do some mesurments...
Thanks a bunch

Ok well the engines on the ground (upside down) so I just kinda stuck a tape mesure down there and I measures the pistsons... They are 4" across (diameter).
Now my next question is... If they are in fact both 350 engines, then why does one have a smaller flywheel button. (button I.e. end of crankshaft where the flywheel bolts on and the center of the crank kinda comes throught the center of the flywheel.
I think the one I have is a 2 peice rear, and the new one we bought is a 1 peice rear (could that be the difference?)

Old design crank vs. new design crank is all...

10-4 Change came ~1987 look @ valve cover mounting 87 newer v/c bolts throuh the center ,87 back v/c 4 bolts on outer flange. Flywheels/flex plates heads ,intakes all differant. 31 5w

what are the block casting numbers or suffix codes? thats all you need to have.. check em here: http://www.mortec.com/ or http://www.chevymania.com/partsid