I have a 1990 model iroc z. I know this site is primarily a 1st gen. web site, but i need help. My vin# shows an F meaning a 305. But all factory emissions equip. is perfectly in place and looks brand new. As though this is the original engine. All factory GM parts are there including the factory spark plugs! The emissions stickers under the hoods gives info for a 350. So i need to know how to tell a 305 froma 350 by looks, accessories, or engine #'s whatever anyone knows that works. Thanks. Maybe this is a factory mess up and this could make the car kinda rare? Her is the vin # if it would help- 1G1FP23F4LL125256

Ford,
If you can see the engine block, right behind the drivers side cylinder head, there will be a number cast into the top of the block. Should be 8 digits. Post that casting number and I can tell you if the block is a 305 or 350 block.

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Bill Koustenis
Owner
Advanced Automotive Machine
Waldorf Md
1971 Chevelle "Heavy Chevy" original owner
1973 Z-28 ..one family car...Brother bought it new in 73

I think F indicates the tuned-port (as well as throttle-body) engine. I don't have access to any books right now though...

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David
Camaro - '68 327 Coupe, '86 Z-28 IROC 305 TPI
Corvette - '73 Mako Shark II replica (http://makoshark2.com/djunod/), '79 L-82, '82 Cross-fire, '01 Coupe

on the engine in my old 83 camaro it read "5.0 litre" or something like that, anyway it read 5.0 for 305 if you can see it that might help. its right by the engine code on the back of the block, near the top bellhousing bolt. it really helps if you can read brail, the back of the engine is hard so see.

yeah you cant see the rear of the engine at all!any other ways?