Hello experts

I have a 1973 Camaro with a 307 engine and I am going for a mild performance increase. I could not find out so far, the stock head specs. Any ideas would be appreciated. I got new heads ready, but still wondering about the original specs before I tear down the engine....

 

Remove the valve cover and find the casting number.
Then search the 'net, or nastyZ28 site for the specs.

 

These are the head numbers found on 307 Chevys.
3911032 (1968, 70cc)
3917290 (1968, also used on some 327s)
3917293 (1968, 75cc)
3931633 (1968-1973)
3986388 (Used from 1968-1976 on 307 and 350 engines)
3927185 (1969-1976 307/327/350, 70cc)
3932454 (1969-1973)
3927188 (1970, 74cc)
3986339 (1971 307/350)
3998991 (1972-1973 307/350, 75cc)
3998993 (1972-1973 307/350, 75cc)

None of them are what we would consider "great" heads, or even good. If you have a set of Chevy performance heads, or good aftermarket heads, either will make more HP than any stock 307 head. These are not terrible engines, but with their reverse bore/stroke, they tend to be a little tougher to get big HP numbers. The right heads, cam, and intake will really help, so if you're going to replace the heads consider doing a cam and intake, plus headers also.

 

My first 69 had a 307. When I rebuilt the engine, I put on 327 heads which had bigger valves. If you're after getting some performance out of the 307, then those heads make for great paper weights.

 

Most of the 327 camel hump heads did not have the holes drilled for the alt. and power steering. I would get a set of vortec heads with the holes 64cc chambers bigger valves and they make around 30HP over the old hump heads. With a little porting on the exhaust side they are right up their with the better aftermarket heads for about 1/3 the price.

 

lol. Wasn't suggesting he go looking for 327 heads. Just that if he has a stock head budget, there's something better than what he has.

 

Its hard to beat the Vortecs if your on a budget.

 

Thank you guys for the infos. As I purchased Trick flow heads, 175 cc, 56 cc combustion, 1,94/1,50 valves, I was wondering how much difference to the stock head they are. But seems anyway better than stock, as your comments are saying.
I will add a mild cam (CC 12-205-2), and a 4 barrel vacum carb from summit.

 

Your engine presently has a compression ratio of 8.5:1. Those 56cc heads are going to give you a c.r. of 10.69:1, provided you use the same compressed thickness head gaskets as what your 307 came with. Yes they're way better than the stock heads, just know that you're going to be using premium gas. To me that's not an issue, as my car is a toy, not a daily commuter. Don't know what you're building yours to use for?

 

I will use mine for weekend fun, no daily use. I am surprised by the cr you mention. The tech guy from summit racing told me I would come to 9.5. Gasket with 0.039 compressed. I would prefer to stay below 10, to keep the engine smooth. HP is not such an issue, just more torque would be nice. How do I calculate correctly? Anyway, I will have to measure it with new heads on, and maybe choose a thicker gasket. What do you think?