I have a 1983 Hurst Olds thats completely stock other than the previous owner installed an edelbrock 2711 intake and demon carb. I'd kind of like to keep it stock but i have a 403 that needs to be rebuilt. I also could get a hold of a 350 with 6 heads on it. What would it take to get the turd 307 up to around 350 HP. Can you stroke a SBO? The car is just a weekend warrior, help firestone out here and there. Any thoughts? Also does anybody know of a good machine shop for olds in southern minnesota?

 

A SBO can be stroked, I am nearing completion on mine- I am using sbc rods(Scat I beam) and pistons (ICON 4437) ( 4.155 bore) and offset grinding the crank to increase the stroke from 3.38 to 3.5. I am in the St. Paul area so not too far from you. If you wanted to have it done up here check, with Kelly's Machine on Payne ave in St. Paul. CutlassEFI ( Mark) has been awesome in helping me out with information and he came up with a custom ground cam to match my rebuild which I just got last week.
Use the 307 as a boat anchor.

 

Any engine can be stroked, it just requires custom machine work and selecting the right custom rods and pistons. Now, in the case of the SBC, the 383 is popular because you can simply take a stock 400 crank and put it in a 350 block. Unfortunately, all SBO motors use the same 3.385" stroke, so any increase will require custom offset grinding.

Of course, the BBO is really just a "stroked" SBO...

 

The 307 can be stroked by offset grinding the crank and using sbc 2" or 1.88" rod journals with expensive custom pistons. Not worth it with the 307, the heads need a lot of help plus the small bore and windowed mains. Bore your 403 .024" over, use KB hyper pistons and either work the hell out of those awful 4A heads or better yet for a few $$$ more get Procomp heads. You should be around 9.3 compression or better with Procomp heads, get them from Benard Mondello. J&S machine has girdles for the bottom end. The 403 is the 307 with a much larger bore. The 68-76 350 is a great motor and benefits from a much stronger bottom end, it can also be bored to 4.155", nearly .100" over.

 

For 350 hp I'd go with the 350 or 403. Custom work means more $.

 

Before you start any engine upgrades define a realistic budget.


Your best bang for your buck is to swap in a good running 403. If you have a little more dough you can upgrade that 403 with some easily obtained parts.


If you have more money build a 68-72 350 to your needs. If you want to build a stroker small block look for a D or DX block & go wild.


Don't forget the minute you start making more power than a stock 403 you will also need to start upgrading the transmission, differential & fuel system etc.


Good Luck

 

Good point about the trans and rear. A good overhaul with a 10 vane pump, hardened pump rings and stator, billet servo, deep pan and shift kit with bigger boost valves and a huge trans cooler will be the bare minimum for the 2004R trans. A billet foward drum is another upgrade to seriously consider. Check out Dr Dan's thread on ROP for the 2004R trans, he knows these trans inside and out. The 7.5" rear is another can of worms. Expect the spider gears to explode just hitting the gas pedal, eventually. Either a 8.5" GM or 9" Ford rear would be best. If no slicks are planned, get a True Trac posi with Moser axles and a girdle cover.