They are either 60cc or 62cc.. I found conflicting information. And the gt40s used on F150 Lightnings 351w are 64cc. How can you tell if they are the 302 Cobra head or the 351w Lightning head?
64 sticks in my head. as for lightning over cobra thats new to me? Sure if there diff sombody here knows.
If they are 64cc on a 72, you get 7.99:1 If they are 62cc, 8.15:1. If you can go back with a thinner gasket, say .035"-.038" compressed, you can get back .05 to .1 of that. Then milling should gain about 1cc per .008" milled. So, mill .020", .038" gasket, supposing 62cc head, and get 8.5:1 compression. Or back to stock...
There's a big difference between............ and......... Scott's heads are NOT fully ported as the program assumes and they do not have 1.94" intake valves. You're comparing apples to asparagus. His heads have the thermactor bump removed and some polishing done to the outer portion of the port. Big whoop. Your engine analyzer program is using a fully ported head as it's basis for the improvement in horsepower. Now then......Scott, do you really want to see an improvement in power with ported heads?
the gt40/gt40p head is a fantastic head. I have the gt40p's in my 86 mustang (actually have the entire 97 ford explorer engine with the explorer/gt40 intake and gt40p heads in my stang) for my maverick, I'll be using regular gt40's which I've bought already, as I don't want to mess around with the header issues, and it will be going on a rebuilt late model 5.0 roller cam block, with either a stock HO cam, or a tfs stage 1 cam. I've done a ton of research on this, and with a late model roller block motor with a small cam such as a tfs or e cam, gt40/gt40p heads, a good intake, and 1.6 roller rockers, it's common to put down between 250-275 at the wheels, or 275-300 at the flywheel. Now, if you're putting this on an original 302 block from the early 70's, this will be a whole different story. Remember, the early 70's blocks were only putting out 141 horse stock. IMO, switching to this head should give a 25-50 horse increase, 50 being on the high end, but I wouldn't expect to see 200 horse out of the swap. With a cam, I'd expect 200ish at the flywheel. IMO, the best thing you can do is stick those heads on a late model 87-01 5.0 roller cam shortblock, use a good roller cam such as the tfs stage 1 cam, and you'll gain nearly 75-100 horse over your current block. this is all bench racing of course, and using the simple statistics of the oe 70's block at 141 horse vs the 87-93 5.0 block at 225 horse, vs what most people are getting with these heads and a cam on top of a stock late model block.
The block is NOT the issue. The low HP came from many restrictive parts that were done away with when the 5.0 became fuel injected. A 4v carb/intake, dual exhaust, headers, and decent ignition opens the early engines right up. Good heads are just the icing on the cake. You can get well over 200 hp before you even figure in a cam. Dave
Well the gt40's had 65cc's so I passed on them. How about c6oe 289 heads with 1.84/1.50 valves and 52-55cc's? .. found them on e-bay. Will these pick up power over my stock heads?
Those will add back compression but if the GT40 heads as ported & had larger valves in them, I dont know for sure if the 289 heads will out perform GT40 heads. Look at Powerheads.com. They have airflow chart of 289 heads & E7TE heads off the 5.0 mustangs & they are close to the same when ported or unported. GT40 heads do a little better than these 2 heads.
I wouldn't give up on the 40s because of a bit of lower compression. You will still be picking up quite a bit more flow and HP. Like I said, I have 8:1 compression and still picked up a phenomenal amount of "seat of the pants HorsePower". It really was a completely different car after I swapped the heads out. In fact, if I am not mistaken, the reason for having more cc's is because the shape of the combustion chamber is more domed to allow better flow and better burn. When you dome the chamber and pull the spark plugs toward the center, you will have to pick up a bit more volume, but the design is a little bit more like a Hemi in that it allows much more efficient use of the flow and burn area.
You did good IMO. 65cc will put you down in to 7.9:1 compression. I know it might work, but 7s are for blowers and turbos, not performance NA. You want some 69-73 Windsor heads. The 289 heads are no better than what came on your 302. They might bump compression a touch, but that's it. The .060" larger intake valves will do little for you. The Windsor heads will have larger valves AND ports, stock. If you port them, they really are one of the best. (Notice I did not say THE best... I don't want an arguement from GT40 fans.) Good luck Dave
Early 351w had 64cc. If you want a set of 70 351 heads drive over to this end of the state and I`ll sell them to ya for a $100 bucks but they need to be cleaned up.
69-75 had 60cc with big valves and ports. 74-75 are less desireable due to excessive smog plumbing in the ports.
