Could I swap out my 305 heads for stock 350 heads? Can I leave the stock cam? I do not have the funds to buy heads but I do have a set from a 350 in good shape in my garage. will this work? Will I see a gain?

 

Yes it will "work".

No you will probably not see a gain, although you might. Most likely you would see a significant loss. That would depend on exactly what 350 heads you have, since there is an enormous variety of them.

 

The bigger valves may hit. The formula is: Cylinder Bore x 0.52 = Max intake valve diameter (and taking that number x 0.80 for max exhaust diameter).

About the performance gain...NOPE (you will lower your compression)

But it would benefit Nitrous or Forced Induction.

 

I don't know that it is right or wrong, but how can you have a formula to determine that? I would think that valve placement in relation to cylinder bore centerline would throw the formula out the window. Surely all SBC heads don't have the intake valve in exactly the same place. Who came up with that formula?

 

This guy says so:

Mr. Wagner - High Performance Engines - Ferris State University

 

Wow, dead on formula! 305bore(3.72") x .52 = about 1. 94" intake ... and the intake size times the .80 = 1.55" exhaust. Good to know. Wonder if this formula is for clearance or efficient combustion.

 

I believe its more for eficient combustion, there are head designs where that causes clearance problems. but yes a set of factory 350 heads with 1.94 intake and 1.5 exhaust will fit your 305, however, your compression ratio may be lowered from the larger combustion chambers these heads have.

 

I agree with both points. 1) The standard 1.94 intake valves will clear the small bores of the 305 and 2) The standard 64cc combustion chamber will greatly reduce compression on a 305 and result in serious power loss

But, if you chose the Aluminum Vette heads (113 castings) that have a 58cc combustion chamber, they will keep your compression ratio up and you can in fact mill them down to either your stock 54cc or even smaller as aluminum heads support higher compression. Alternatively you can use a thinner head gasket to help bump up the compression on the 113s.

Also, the Aluminum 113 heads have one of the best exhaust ports (D-port) for a GM head (at that time) which is a bonus and can easily be ported to increase flow. Before there were a lot of Aftermaket heads available, TPIS use to port the Aluminum 113 heads and obtained some pretty high flow rates that rivaled the AFR 190s. Also, aluminum is really easy to work with (good for experienced porters, bad if you are new and slip with the die-grinder).

Aluminum 113 heads were one of the most popular GM heads until recent years, but they are still very popular with guys who want to build their 305. In fact, most of the FAST 305s that I've seen all used Aluminum 113 heads.

 

The 113's are probably a great head to use on a 305 like Grim Reaper said. The smaller chamber's a plus for the 305. In fact, World Products S/R Torquer heads for the 305 have the same 58 cc chamber IIRC. If you're building a fairly wild 350 or 383, I can see where the 113's wouldn't provide enough flow. In that case, you're better off with a set of AFR or Trick Flow 195's. But with some port work, the 113's should provide more than enough flow for just about any 305 buildup. In fact, you probably wouldn't even need to do any porting unless it's a really wild 305.

 

Actually there is another bonus to the Aluminum 113s; they are now reasonably priced. When they first came out and EVERYONE wanted them, they were very pricey (and we know how most 305 guys are on a tight budget).

But, now that there are a TON of great Aftermarket 2.02/1.60 heads for guys with 350 (and up) to chose from, the Aluminum 113s are not as desireable anymore - and considerablly cheaper and more available today. You might even get lucky and find one that had some porting work already done to them.

Just be careful if the valves have been swapped for bigger ones. Typically, they used 2.00/1.55 valves in a valve swap and those will probably hit the bore walls on a 305 (unless you notch the block). But even if you notch the block, they are so big that they are probalby shrouded by the bore and won't give you any benefit over the stock 1.94/1.50 valves.