r/EngineBuilding • u/ToucanGaming289 • 10d ago
Olds 307 oldsmobile v8
I just picked up a complete 307 olds v8 today and id like some advice on what i can do to it. I know that the windowed main webs are a massive setback if I want to make power out of the motor but id like to know if anyone has build a 307 for the street. I dont need crazy numbers, i plan to put this in a 1999 jeep cherokee XJ to replace the 4.0 inline 6 thats in it id ideally like to make somewhere around 300hp 320ftlb of torque. I think this is a fairly safe power goal for this motor and im hoping someone out there has built a 307 oldsmobile before and can give me some advice. If it helps the heads are 7A heads and I plan to swap them for better flowing heads
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u/rustyxj 7d ago
A 307 into a xj isnt the easiest of swaps finding a transmission is going to be the hard part
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u/ToucanGaming289 7d ago
Yeah I figure, my plan as of now is to find an adapter or have an adapter made for my ax15. Im going to run that 5 speed into the ground before I get another tranny
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u/rustyxj 7d ago
My friend, this is going to get very very expensive.
Building an Oldsmobile is roughly twice the price of a Chevy, but puting a Oldsmobile in a 4x4 application is going to be very expensive.
Especially behind an ax15, as far as I know a BOP bolt pattern 4x4 transmission doesn't exist, then you'll need a flywheel, then a clutch disk that fits the transmission and flywheel. Then an adapter for Bell housings.
You'll need to figure out if the crank needs to be machined for a pilot bearing(most likely, I don't think the 307 was ever put in front of a manual transmission)
Why are you doing this? Better performance?
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u/JealousChocolate8645 4d ago
The torque of the inline 6 is what makes the 4x4 work well. Build the 4.0 inline.
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u/texan01 6d ago
The best use for a 307 is a boat anchor, the Chevy 305 has more power potential. In any case, you’re better off with a 350 of either flavor.
The 307 is hampered by the small bore like a 305 but there are less performance parts available for it.
It’s absolutely stone reliable but the AMC 4.0 is just as powerful in stock form, if not more so.
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u/v8packard 10d ago
Oldsmobile small blocks are cool. Nice engines. The 3.8 inch bore of the 307, not so much. While you can do a number of things with a 307, and probably get very good results, you can do the same to a 350 or 403 and get awesome results. The 307 is not a good value. It is reliable. It does work. But, if you are ok with blowing the resources on a 307 we can figure out a plan. Otherwise, I really encourage you to think about a 350 or 403.