yogi18m

my iroc currently has a 305 tpi engine in it and i want to put in a 350, i have been told i should just buy a 350 block and use the heads off of my 305 tpi engine to boost the compression and get more power. what do you think should i do that or would the engine preform better if i would just use 350 tpi heads? if i should use the 305 heads should i just rebuild them to the factory setting or what do you think should be done to them.

DuronClocker

iTrader: (1)

Use the 305 heads and put bigger valves in them. Stock 305 has 1.84/1.5 valves and stock 350 heads have 1.94/1.5 valves. I don't know what the chambers of the 305 heads can do but if possible go to like 2.02/1.6 or 2.00/1.55, etc. 1.94/1.5 will work, but of course the more airflow the better.

Grim Reaper

The better setup is to use aluminum L98 heads. They have a 58cc chamber and 1.94/1.50 valves to start. Plus they were the best flowing head (especially on the exhaust) of that vintage. In fact, most guys only work on the intake, the exhaust on the aluminum L98 heads is that efficient.

That is what I am using. And with a .029" gasket (TPIS has a "thin" gasket for aluminum heads), I get a compression ratio around 10.2:1.

DuronClocker

iTrader: (1)

Yeah, that'd be a great way to go if you have $500+ and can find a pair.

Then again, a decent valve job on the 305 heads with valves will run you close to $400 or more depending on where you go.

Grim Reaper

But even the CHEAPEST aftermarket head (even if iron) is still in the $700 range (i.e. World Castings S/R Torquer which also respond well to porting). I don't consider Vortecs only because you need to buy a different intake and should change the springs - thus not making they quite the cheap deal they initially appear. But the Vortecs are a great inexpensive head, and also respond very well to a "little clean up". And they still have a 64cc chamber.

Yeah, you don't see as many aluminum L98 heads as you use to on e-Bay. Somebody must be hording them or something. But I still do see them, just not as often as I use to.

I do see a number of people selling old "double humps" these days, but I get scared with "old iron heads" & cracks. You can make the deal "subject to passing inspection", but try and get your money back if they turn out to have fine cracks. Also, a lot of guys put the term "as is" (which is a BIG RED FLAG as far as I'm concern).

DuronClocker

iTrader: (1)

I was just comparing the price to porting and getting a valvejob with new valves on his 305 heads. The reason I suggested them is because they'd raise his compression a bit as well.

But yes, agreed, if going to buy new heads and want something at a decent price, find used aluminum L98 heads....or aluminum LT1 heads. Those things are so cheap, can be had for $150-200 a pair. I got mine for $250 shipped including 24# injectors and the intake manifold But, they do require quite a bit of machinework (require welding aluminum on the bottom and then getting milled) and a lot of coolant hose re-routing with the use of a remote t-stat housing.

There is no way I'd attempt it though unless I was already planning on the LT1 intake manifold (which I was and I had most of the conversion parts already).