Head experts and compression ratio guys in here please?

[mustangman70]

Allright, im getting ready to build this motor up, its a 67 block with 67 heads, but i have a set of 70' 302 heads with the letter "B" casted into them, and i am going to port match these heads to my RPM airgap intake. will these heads change my compression ratio???? I will also be putting a cam kit in, the cam specs are 230/230 @ .050 and the lift at the same is .512/.512. Now i understand i have to swap screw in studs in, so i will have a machine shop do that, but im going to port the heads and intake my self, now my questions are these, I need to buy new valves as the valves are cracked, so which ones should i get size wise??? I was looking at manely's, but they say that they are .050 longer Is this going to be a problem? the cam is kinda high on lift so i dont want the length of the valve to be a clearence issue also, which pushrods are good to use Would it be smart to use guide plates??? keep in mind this is a daily driver. I will also be spraying the car with a 100 shot of nitrous...hey 10sec...On friday i will paypal you the $$$$

So what kind of power will you think i will put down with

Ported heads and ported air gap intake (port matched)
.512 lift cam
roller rockers and all of the mods listed in my sig

 

[mustangman70]

Nobpdy

 

[mustangdave]

I'm no expert but with the screw in studs, I would add hardened pushrods and guideplates or you're likely to bend or break a pushrod causing major engine trouble. I also think you may have piston to valve clearance issues so clay the pistons, install everything and turn the engine by hand. Disassemble and check your clearances. There is also the issue of the lack of compression needed for that cam to work. Your not going to get that with those heads; the chambers are too big to give you a high enough compression.

 

[hrspwrjunkie]

Allright, im getting ready to build this motor up, its a 67 block with 67 heads, but i have a set of 70' 302 heads with the letter "B" casted into them, and i am going to port match these heads to my RPM airgap intake. will these heads change my compression ratio???? I will also be putting a cam kit in, the cam specs are 230/230 @ .050 and the lift at the same is .512/.512. Now i understand i have to swap screw in studs in, so i will have a machine shop do that, but im going to port the heads and intake my self, now my questions are these, I need to buy new valves as the valves are cracked, so which ones should i get size wise??? I was looking at manely's, but they say that they are .050 longer Is this going to be a problem? the cam is kinda high on lift so i dont want the length of the valve to be a clearence issue also, which pushrods are good to use Would it be smart to use guide plates??? keep in mind this is a daily driver. I will also be spraying the car with a 100 shot of nitrous...hey 10sec...On friday i will paypal you the $$$$

So what kind of power will you think i will put down with

Ported heads and ported air gap intake (port matched)
.512 lift cam
roller rockers and all of the mods listed in my sig

For that combo, you are going to need way more than stock heads. Way more.

You may consider backing off on the cam size (224/232 is almost too big for a street 302, you may want something down in the 218/224). The Performer RPM intake is also too much intake for those heads. It's all about combination, not the individual parts. You can send your heads to PC Automotive and have a nice port job done or pick up a nice aftermarket set. You will also need a good set of headers for that combo...generally speaking, with a little less cam 1 5/8" long tubes with a good 2.5" mandrel bent exhaust will be fine.

Compression for that motor will be fine at somewhere between 9:1 and 10:1 with less cam. The '70 heads will not make you lose compression over the '67 heads, as they are both 54cc heads...but again, I wouldn't run that combo.

I just read that this is a daily driver...don't run that combo. Pick something in a cam with no more than the 218/224 grind as that will still provide a rough idle. I'd stay small, like 212/218. Check out Comp Cams Extreme Energy line, you will be very happy with it. You will also need much better heads...ported or aftermarket...and forget the Air Gap, cold start problems will make driveability a bear.

 

[mustangman70]

Thanx for the input, drivabilitly and "warming up" is not an issue to me. I suppose i could save money for a couple of weeks and get a se of aluminum heads, if i went that route what set would be good for that cam?? iVE HEARD NOTHING but good things about the aluminum edelbrock RPM heads, what would be a nice head to give me a good bump in compression????

 

[69Rcode_Mach1]

Why not go 351 while you are at it? Can't cost you much more and the power will be a lot better.

 

[302 coupe]

none of the aftermarket heads will bump your compression. The combustion chambers on them are all more than 54cc.

I'm not a fan of ported stock heads. Sure its cheap power, but once you add the cost of machine work for screw in studs, plus the hardware, then bigger valves and the machine work for that, plus the hours spent porting often with unknown results....well, it becomes a toss up. I'd be much happier with a set of used aftermarket heads for about the same price.

As for the air gap intake, I have a hard time understanding cold start issues, especially when you live in Florida. I live in Georgia and I've never even needed to use the choke on mine.

I don't know what tranny you have, but if its an auto, anything more than 218 or so duration at .050 will be much happier with a higher stall converter. My cam has 228 at .050 and I run a 3500 stall, car seems to really like it. I could get by with less stall, but future plans call for a more agressive cam, and I didn't want to have to do the converter twice.

 

[mustangman70]

I have plans for the stall, yes it is a c4, so if i got a set of aluminum heads with 64cc chambers my compression would drop, so i want a set of heads with the smallest possible CC???

 

[mustangman70]

I also DONT have cold start issues either lol, even with my air gap, i havent had to use a choke in years

 

[hrspwrjunkie]

Thanx for the input, drivabilitly and "warming up" is not an issue to me. I suppose i could save money for a couple of weeks and get a se of aluminum heads, if i went that route what set would be good for that cam?? iVE HEARD NOTHING but good things about the aluminum edelbrock RPM heads, what would be a nice head to give me a good bump in compression????

There aren't any aftermarket heads that will give you a bump in compression. Edelbrock Performer RPM heads are a perfect match for your intake. I would still pick a smaller cam, though. A Comp 268 will give you a nice 350+ horsepower out of that engine with 1 3/4" headers. A great set to go with would be AFRs...I've seen a set of 165s with 1 5/8" long tubes, a 216/224 grind hydraulic roller cam, Performer RPM Air Gap and 750 Holley go 396 horses. It's hard to argue that one. And that could be matched with a Comp 262XE flat tappet.

 

[meanroy]

Thanx for the input, drivabilitly and "warming up" is not an issue to me. I suppose i could save money for a couple of weeks and get a se of aluminum heads, if i went that route what set would be good for that cam?? iVE HEARD NOTHING but good things about the aluminum edelbrock RPM heads, what would be a nice head to give me a good bump in compression????

I see the responces saying "there's no head you can get that will raise compression", and I think they are somewhat mistaken. Whether you can afford the price is another story.

You can get Edelbrock heads with chamber volumns from 47CC to 75CC.
Some of the lower chamber vols. require different pistons, Jessel rockers, etc.

Many of the popular Edelbrock would actually LOWER your C/R if the chamber size posted above is correct ( ... both 54cc heads ... ) since the chamber vol is 60CC.

The same is true for the FRP GT40 heads and AFR which come in 64CC and 58CC.
The Holley Systemax has 61CC chambers.

Ford Motorsport (SVO) Yates heads are full race heads which come in 68CC and 40CC. These are Nascar heads and will cost you a BUNCH!

The biggest benefit you will gain from going to an after-market heads is the improvement in flow.

Roy.