I am (slowly) rebuilding the 302 from my 73 Maverick. I have had the machine shop work done and am now getting ready to reassemble the engine. It is going to be a daily driver which will potentially occasionally see the strip (eventually). I am now trying to decide on which heads to use. I would like to use some good iron heads to avoid the cost of the aluminum heads. I had decided on the GT40p's after considering them, ~68 351W heads, and E7's. However, now I am looking at the Roush 200 heads. Their flow performance appears to be very nice for the money. I am wondering if they would be worth the extra money, and if they will work in my application. In my rebuild, I am planning on switching to a 600 CFM 4 barrell Holley Carb, an Edelbrock Performer Intake and Performer Plus Cam (both rated for Idle to 5500 RPM). I am planning on initially using the stock exhaust manifold, then changing to headders and dual exhaust in 6 months to a year. I have been told that the GT40P's will work with the stock exhaust, and the Roush 200's say that they will work with stock intake and exhaust manifolds, but I assume that means Mustangs with stock manifolds. Will they work on a Maverick with stock manifolds? Realizing that the 64 cc chambers will lower my compression from ~9.0 to ~8.5, is the extra flow worth the extra money (~$300 for new parts)? Also, am I limiting myself too much by looking at cams/intakes rated for Idle to 5500 vs 1500 to 6500 rpm? How rough will the 1500-6500 cam/intake idle? Thanks, 73Mav
Just my opinion You have not mentioned this, but for me, I would suggest anytime you build a motor with more than stock parts and you are going to build more horsepower, you need to put a stahl converter in. I think alot of guys are running like a 2500 stahl, it will help with a lopey cam. And also gives you a little more go go stuff. Always my .02 pennies.
you may be limiting your breathing potential from the start by using performer goodies. if this is how you are going to finish your engine you could probably port the exhaust side of 351W heads and port match the intake and never be wanting for more. However if use performer RPM goods you would benefit from going with better heads. The performer RPM air-gap in a test I read recently gave up nothing on the bottom and gave more on top than a regular performer. Doesn't the P-castings require P-headers? the plugs come out at a different angle or something like that? some things to consider. Also roush 200's have 2.02 intakes, wouldn't that require machining valve reliefs in the pistons? check out the roush 180's, 1.94 intakes, 180cc intake runners, many of the same features as 200's. Admittedly only $40 less per pair but for street use? maybe a better deal. If they say they will work with stock I would think they mean stock bolt location and port location. they should work with your manifolds.
My .02 cents.... The GT-40P's aren't worth the money. The valves are SLIGHTLY larger than stock. They are decent for porting, however. I do believe they require a different exhaust manifold, double check though. The early 351W heads have much larger valves and can be had for much less, plus they don't have the AIR injection ports and can be ported to much larger than the P's. Only disadvantage is the larger plug. Haven't headr much on the Roush heads, can't be bad for the money though?
MY OPINION! If it were me, I would save up my money and go for the entire perfomer rpm system, aluminum heads and all! I have found, in my limited experience , that you will be better off in the long run if you save up a little more and get the aluminum heads!! Personally, I will never use a set of cast iron heads unless i'm doing a stock rebuild!! Aluminum is the way to go!!!!!
I have the exact combination you describe. GT40P's, 600 cfm Holley, Performer intake and matching cam, Blackjack headers on a 302. The heads I had previously were a set of fully ported and polished '70 351W's, three angle valve job, screw in studs and roller tip rockers. The GT40P's beat them hands down. All I did to them before bolting them on is polish the valve pockets and exhaust ports and remove a hiccup in the roof of the exhaust port. The stock exhaust manifolds I've had laying under the bench for the last 30 years fit the GT40P's better than the headers when using stock spark plugs, but with these heads you really should have the breathing provided by headers. With the headers I have to use special shorty Accel spark plugs and put distributer cap style terminals on the plug ends of the wires. The headers need to be loosened up to take the plugs out and an ignition amplifier is needed to fire the large gap plugs, but I would still do it all over again. The combination works very well. For more info on GT40P's check out http://www.geocities.com/motorcitymustang/gt40p.html
It all depends on what you want to do with the car and how much power you want to make. From what you have indicated, it sounds to me like you are looking for a daily driver with a little extra power (something with a bit more torque). I would go with the the GT-40's if that is the case. The Roush heads will be overkill due to larger port volume and lower compression (both of which adversely affect torque).
I'd be interested in seeing a flow comparison between the stock P's and the stock early windsor heads. I have seen the ported figures (of course, now i can't find it in my bookmarks!) and as i recall the windsor heads outflow the P's, but stock for stock, who knows? The small (.02" larger than stock E7 heads) exhaust valve worries me a bit, compared to the 1.56" on the windsor heads, and the 1.60 that is fairly standard on all performance heads (aluminum and otherwise). Sounds like the P's might be more trouble than they're worth, with an better ignition, those accel shortie plugs (i'm pretty sure they're made by Nippondenso, since they are the only plug with a U-shaped ground electrode, and i'm a little shy about putting japanese plugs into an american engine), loosening the headers just to replace plugs, etc. I mean, daily driver and all, you don't want the hassle. I just thought of something, but you'd have to get input from the other guys as i have no experience with them: PAW sells reman'd iron heads that are ported and have 1.94/1.60 valves installed. Pretty cheap too at $550/pair, (that's what the P's cost, isnt' it?) and you can specify with or w/out AIR passages. They are small chamber, 60cc i believe, which would put your compression right about where it should be for a D/D. Anyways, just some thoughts....
I'm not sure where your getting your info from but, the 69-74 351w heads have 1.84 intakes and 1.54 exhaust and the "P" has 1.84 intakes and 1.46 exhaust. The flows are similar but, where the P's have the advantage is in combustion efficency. If you have noticed Ford replace the regular cast iron GT-40 heads which is the 69-70 head design with the GT-40p's because they are better. By using the P's you can save money on the rest of the valve train, pedestal rockers and push rods. With the other heads you need guide plates, hardend push rods,and adjustable rockers with this setup you usually need different valve covers, if you use roller rockers. with the pedestal type you can remove the spash plate on the stock cover and they will work. There are different types of header avalible for these heads the thing to look for is to make sure the primary tubes go down then turn to the rear, most headers go down and to the rear at the same time. The heddman 88400's shorty's go down and then back and work with the P heads I think Mac and JBA make headers for this head in the 65-66 mustang which should fit.
ditto on the spark plugs.. its not a fun change in a maverick... been there done that. Had the first produciton old school windsor dart heads and had the same problem. but i'm use to it... i just sleve the spark plug boots with nomex and just always check the plug just in case they come loose. Also I had a set of ported 65-289 52cc heads with 1:84 and 1:60 valves in them and just did a swap with just the Wsr heads... yep and didn't do much was an over kill for my set up at the time. Car lost MPH and only gained an average of a 10th in the 1/4 mile. As far as the 200 Roush heads i can't complain but then again the motor was made to work with that set up. If your worried about lower compression just think about how much money your gonna waist on gas if you drive it every day. Also this is just my 1 cent but you can still make some decent horse power at 9:1 also don't forget to look into the AFR heads they are a nice piece. good luck in what ever you do.
Most engine dyno tests reveal about a 4% gain for every point in compression, provided other components match. I would worry about the half point. The nice thing about aluminum heads is the weight savings and the fact that they dissipate heat better, so you can run higher compression or more advance without detonation.
Now hey, i'm not trying to start an argument here, but my understanding was that iron heads dissipate heat better, and aluminum tends to keep the heat where it starts (in the chambers, mainly). I don't recall exactly why you can run more compression with the aluminum heads....
naa, aluminum is light weight, and by design loses heat and gains heat very quickly. Why do you think those little japanese 4 bangers heat up so fast in the morning, and your cast iron v8 takes a day and a half to warm uP? Iron is very thick, and retains heat for much longer
Aluminum heads dissipate more heat-right into the water jacket. Energy (heat) is used up three ways in an internal combustion engine- pushing the piston down, through the exhaust, and through the cooling system. The last two mentioned are a waste of energy and the reason the average car engine is only about 50% thermally efficient. Aluminum heads are less efficient in their use of generated heat but they allow you to bump up compression and ignition timing to raise cylinder pressure and get back what you lost. Where aluminum heads really shine is the approximately 45% weight savings. Removing 50 - 60 lbs from the front of your car does wonders for the power to weight ratio and front to rear balance of the car. You probably “feel” more of a power gain from that than for any other reason. Also since most aluminum heads have the ports and chambers finished in a CNC machining process they are more consistent from cylinder to cylinder in size, shape, and surface finish, so right off the shelf you may get a small advantage in flow.
For a good comparison, we ran ported '68 302 heads on our bracket car for years, then I saved up the ca$h to buy some RPM heads. With no other changes, no jetting, no timing changes, no gearing changes, nothing....we picked up .7 second. Went from 10.40's to 9.70's. Losing 45 lbs weight helped, but I cant see the weight loss totally responsible for .7! I'm sold on aluminum. To add more on the compression deal, you can run higher compression (up to 11:1) with aluminum easily, which generally increases bottom-end torque and responsiveness. Makes the car feel 1000 lbs lighter! I still remember the aluminum head swap...trying to do a burnout and keeping engine rpm under 7000 was tough cause I was so used to the iron heads holding it back
