307 long vs 307 short
- Thread starter jeromeg79
- Start date
Are you referring to LONG BLOCK (Block and Heads) vs SHORT BLOCK (Block rotating assembly only) from a rebuilder, or crate engine supplier?
It's probably easier, and includes a better warranty if you go with the LONG BLOCK, however that really depends on your skills and confidence in doing the hands on for the SHORT BLOCK option.
Only thing I would mention is I believe 85-87 307 Y/9 engines had roller cams, which if you're just replacing engine without regards to originality would be the preferred option imho. That 307 Y engine was used in so many vehicles in the 80's finding a decent one shouldn't be too hard.
en.wikipedia.org
HTH
It's probably easier, and includes a better warranty if you go with the LONG BLOCK, however that really depends on your skills and confidence in doing the hands on for the SHORT BLOCK option.
Only thing I would mention is I believe 85-87 307 Y/9 engines had roller cams, which if you're just replacing engine without regards to originality would be the preferred option imho. That 307 Y engine was used in so many vehicles in the 80's finding a decent one shouldn't be too hard.
Oldsmobile V8 engine - Wikipedia
en.wikipedia.org
HTH
85 Y and 86-up Y and 9 had roller cams.
85 VIN 9 only, and all 84-earlier 307s had flat tappet cams.
Flat tappet cammed 307s used 5A heads. Roller cammed 307s used 7A head. 350 intakes can fit on a 307 5A head car. It'll physically bolt up, but the peanut port 7A heads won't match up port-wise.
Just ensure you know what you're buying. Personally, I'd get a 5A head 307 flat tappet for an 83 if you get a choice. JMO.
85 VIN 9 only, and all 84-earlier 307s had flat tappet cams.
Flat tappet cammed 307s used 5A heads. Roller cammed 307s used 7A head. 350 intakes can fit on a 307 5A head car. It'll physically bolt up, but the peanut port 7A heads won't match up port-wise.
Just ensure you know what you're buying. Personally, I'd get a 5A head 307 flat tappet for an 83 if you get a choice. JMO.
So could you use the (presumably) "better" 5A heads on a later roller cam block? Just wondering why you wouldn't want the roller cam over the flat tappet, regardless of the heads assuming they are compatible with either block?
I guess you could put the 5A heads on the roller engine. But then you need to use the better exhaust and A4 intake (7A's used the 5A) or you will have bad mismatched port issues. The roller pushrods can be used on the 5A heads as well. Plus, you're killing the entire reason for the factory roller grind which was made for better combustion and more efficient operation. (to take advantage of the swirl port). You may lose torque. Never done this swap, but I'm sure it's do-able. If you put a bigger cam in the roller 307 at that point, why not get a 350 or 403 and build that instead?
I do want to mention there was a 6A roller head used briefly. I think it was in 1985 and the pre-cursor to the 7A. I don't recall specifically because after the 5A, I didn't care.
I do want to mention there was a 6A roller head used briefly. I think it was in 1985 and the pre-cursor to the 7A. I don't recall specifically because after the 5A, I didn't care.
Great info, so there was some compatibility concerns, makes sense.
I think I did read somewhere the roller cam actually bumped up the torque slightly, but lost a little HP. Couldn't agree more on the 350/403 swap if performance is the primary goal, and if I had to over again on mine I would have gone that route. My original 307 Y was yanked out of my 87 Salon with 20K miles, while still under the 6/60 GM Powertrain Warranty, and in went the first SBC TPI setup. That was around 1989, crazy the time goes by...lol
Old pic, before the age of mainstream digital cameras....LOL
Never did understand Chevies always seemed to put their starters on the wrong side. 
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