o.k.,I'm sort of new at this and I hope this isn't a dumb question,but can I use 350 heads on my 305 sbc? What would the problems be? Just looking for reliable cruising,not lighting up the tires.Engine was free and heads are in good shape and almost free.Thanks ahead of time for any and all help.
Give a man a fish, he eats for a day, teach a man to fish, he eats forever -- plus, he spends all his money on tackle and beer, and you'll never see him on the weekends again. http://www.mortec.com/borstrok.htm Which I found by typing "+chevy +305 +bore" into google
In order to run the 350 heads on the 305 you have to relieve the top of the cylinders to keep the valves from hitting. The bore on the 305 is too small for 350 heads. Find a set of 305 or 307 heads they are plentiful and not too expensive.
There were some 350 heads with small valves, but at 76cc, your compression would be very low. It's best to stick with the smaller chamber 305 heads.
.....besides, even if you did relieve the block the intake port would be so shrouded that you'd be better off with the small valve heads anyway.
How about the other way around? Running 305 heads on a 350? Even just to 'get me by' for a few months? I wouldn't run into a valve clearance problem (as aforementioned 350 bore is larger than 305), maybe just stroke problems? Ben
Ben, your compression ratio would raise up, but it will otherwise work fine. They are really not performance heads per-se, as the 305 heads have small valves and ports. taj, you should use 305 heads as stated by several people for the reasons listed.
i run 305 heads on my 350. Its a great little torque monster with the higher compression. I don't do a ton of highway driving with mine so for around town cruisin, they're great
Virtually any 350 heads will work on a 305. The high compression 350 heads are similiar in combustion chamber size & intake valve size to the 305 heads & will give a 305 the same performance as if using 305 heads. But the low compression 350 heads (the ones with the 1.94"/2.02" intake valves) will give a 305 less performance because the compression ratio will be lowered. But it'll give it somewhat better performance at higher rpms due to the bigger intake valves. It'll also make it burn more gas.
You gotta use high octane gas (Premium) when using 305 heads on a 350. Because the compression ratio will over 9:1. Otherwise, if low octane gas is used, the engine will eventually "burn up." (Start smoking, burning oil, back-fire through the carburetor, etc.) But then again, 10% ethanol is added to most "low octane" gas nowadays, which makes it high octane.
I have never had a problem running 350 heads on a 305. I like the power they make they have good high RPM power. I have run pop up pistons in this combo too, but if you have any questions or concerns use some modeling clay or playdough and put it on the piston and see what kind of clearance you have between you valves and piston. Then you will answer a lot of your questions. You can also run steel shim head gaskets to adjust your combustion chamber and valve clearance so you can get the proper clearance you need.
World Products S/R 305 heads. 58cc chamber 1.94 intakes. I am running them on a 262" SBC and top end is strong. I bought them a decade ago for about 20% less than the current price, but I'd do it again at current prices. http://www.summitracing.com/parts/WRL-042750-1/ They space the valve stems closer together than stock so the valves don't interfere with cylinder walls. Use a head gasket for a 350 on these regardless of the blocksize. Also, someone mentioned steel gaskets, use them! Composition gaskets will add about 6 cc's to the chamber size, dropping the compression at least one ratio number, the steel ones are way thinner.
Not true. Gasoline with 10% Ethanol is no higher octane than what the decal on the pump says. Maybe you have some special fuel where you are, but it is 87, 89, and 91 here. The refineries are able to use lower octane gasoline in the mix, to get the total numbers to the "usual" amounts, so it is a boon for them.
You'll have all kinds of soot buildup on the deck around the bore openings which creates hot spots and detonation where the gasket's fire ring should be..
Here's a nice list I found while looking for 1970 LT-1 head casting #'s... Stash it in your files!!! http://webpages.charter.net/darrell1/casting_numbers.html
Yea, I'm sure. Like I said, I'm running them and the head chamber is the same opening spread as a head for a 350. If you try to use a 262 gasket it's small opening sealing edges are all hanging out inside the chamber. They cover the block just fine but don't fit the head. That's from personal experience. I don't know about carbon build up because it hasn't been apart since the Winter of 2000.
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