my father bought a used truck and was told it was a 454,it's not, it has 4 bolts down the center of the valve cover and it is in a 91 silverado it is missing the oil dip stick and the air cleaner bolts and there is rust all over the serpentine belt i was told it needed the head gasket replaced,not sure which one so will probably change both or i will change the water pump first the p.o also cut the ends off the battery cables and clamped them on with vice grips,how red neck, oh and no bed on the pickup. so how do you tell the difference between the 307 and the 350? it is a 4x4 with a manual trans
Go here: Chevy Small Block V8 Casting Numbers - Mortec
You will need to pull the casting numbers off the block and heads to figure out what you have. This site will tell you how to do that also.
Post up what you find.
Mark
Most likely it's a 305 or 350... 307's were only made briefly many years earlier... and 400's gone by '81... the engine size should be cast onto the rear block bellhousing surface next to the distributor, driver's side... 5.0L or 5.7L... there are aftermarket SBC 454's around, but extremely unlikely you have one... Now, the '96 - '02 Vortec 350's have the power of earlier truck 454's !!! And the '91 swirl port heads 350's have good low RPMs power and MPG, but die above 4500 RPMs...
If it's the original motor, a 4x4 would probably have a 350. Look for a "K" as the eighth digit in the VIN (I believe), and somewhat-streamlined exhaust manifolds. The 305's are log type. Early Getrag-licensed 5-speeds are crap but by '91 enough improvements had been made that you got a good one if it's not thrashed. Your head gasket issue is likely a full-on cracked head, sometimes these engines have heat-cycling problems and if it gets over 250, that's that. No big deal, just have the heads checked and if needed get new ones. Some of these trucks were terrible, others went 3-400,000 miles.
i am going over there later today and writing the vin no. down as well as the casting no of the heads. i am going to take a flashlight and paper and pencil as well.
Had a '91 Silverado 454. Believe me, you don't want one, a 350 or even 305 is better in every way in those years.
No body or no part could fix this severely underpowered 8mpg big-block, the smog guy said they tuned them to run really hot for emissions purposes...the hotter it got, the less power it made then the hotter it got. Finally got so hot trying to pull a (moderate) hill, the p/s lines exploded from exhaust manifold heat. Bye-bye.
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