The Stovebolt Site Forums The Shop Area Engine Shop 305 marine heads on a 350?

I pulled a good running 350 out of my '56 and plan to put it in my '77 Searay Boat. One of the heads on the 350 has a stripped bolt hole so I want to use the 305 marine heads on the 350. Doable?

Don't see whay not, other than the 305 heads might have smaller valves. Is it a bolt hole in the head itself? You could Heli-Coil it if you want to save the head, even if you don't use it in the boat.

Take the head to a machine shop and let them fix it up. They may want to weld the hole shut and redrill and tap it. The 350 heads would definately help it to breath better,
Scott

Cletis if you have a shop (drill press vise etc ) and a lil time the heli-coil idea works well i use them were there's not a lot of meat around the offending stripped out threaded hole. and threaded inserts were there is more meat around the stripped out threaded hole. one place on the web to get the heli-coils is. www.mcmaster.com
cat#112 pg3096-3099 and threded inserts on pg 3100-3104. as far as useing car head on a boat i'm not sure of the differents between them the 305 to 350 i think there here spring and valve sixe differents .Later Earl

305 heads have smaller intake valves than a 350, and the head volume is 58 CC instead of the 76 CC heads that are standard on a low-compression 350. The 305 heads bring the compression ratio on the 350 up to about 10.5:1, which requires at least mid-grade gasoline, or premium as a better choice. If you're ready to spend about 20 cents per gallon extra, go for it.

I use 305 heads on some of the claimer engines I build for round track racing, but I open the ports up for 1.94" intake valves, and 1.6" exhausts, plus some extensive porting and polishing. This type of head work usually adds $1,000.00 or more to the price of the engine, but it allows a racer who wants to bend the rules a little to claim he's running a stock 305 head due to the casting number. The head won't pass a teardown inspection, but the protest fees are so high at most tracks that the cheaters can get by with modifications that aren't obvious to the usual tech line checkout.
Jerry

Thanks Jerry. That's info I can use. Guess I'll try to fix the 350 heads. I don't need a high compression fishing boat.

Thanks to the rest of you, too. Not sure if there's enough meat left for a heli-coil but probably enough for an insert.

Is there any meat on the broken bolt at all? One thing that has worked for me in the past is to take a nut and place it over the broken bolt, weld in the space and then use a wrench to try to turn the remainder of the bolt out. Either that or a screw extractor... Good luck with the repair!
Dano

MrDanB, there is no broken bolt. It's a stripped out and oversize hole.

I reread your original post.... Stripped out holes are a ral PITA. I would stick with the 350 heads over the 305's if you can get the hole fixed at a reasonable price. Good luck wiht her just the same!
Dano