Finding GT40 heads, but are they worth the trade from 58cc chamber to 64 ?

1996 Explorers with v-8s are hard to come by in P&Ps. All the Mountaineers seem to have v-8s but they are all 97 and up. I only recently learned that there are NO 96 Mountaineers, only ones manufactured in 96 as 97s. There are two 97 mountaineers with a manufacture date in the door of 9/96, and I saw the three bars on one. So, there are heads to be had. Can anyone tell me if they are definitely worth the trouble to swap?

 

If you are going 4bbl & free flowing dual exhaust, they beat the stockers by a wide margin...

Problem is beginning in '73 deck height increased to cut compression, dunno what the final ratio will be...

 

according to part numbers, my block is a 71, and I dont know what current heads are other than they are iron. If original to block, am guessing 58 chamber. already have headers and 4 bbl. I can get the heads for about 90 bucks....just have to spend my time pulling them. I hate to loose any compression, but if it is a net gain I wont be sad.

 

Iv got a real nice set I did some port work on and had some top notch machine work done to them. I have flow numbers if you'd like to buy them. But, keep in mind I have truly spent to much on them they won't be cheap. Honestly,if I had it to do again id buy a set of Edelbrock e street. They have a rebate till the end of the month.

 

71 heads were not 58cc. Should be around 62-64cc. Swap like that with no other changes should be worth an easy 20 horsepower. Even more if you nip them another .030-.040 thou/few cc's and run thinner head gaskets with no more than .060 bore size. Will need a bit shorter pushrods but the compression ratio gain will be worth the extra effort.

 

According to one of my books, '68 to '76 302s had 58 to 60cc heads.

 

One of the two motors looks like the top end was off recently. I was going to target that set, but I may need to measure a chamber to see if someone already did some milling? Also, how much can be taken off before intake issues come into play?

 

For this build, I am going on the cheap. From what I can see, aluminum heads are about 800 bucks away....at least some are. This time around is a hands on learning experiment, and if there is a next one, selling this one will finance it.

 

I'd say you would be better off dumping the cast and getting a set of aluminum heads,much better and save some weight. especially if you have to do any machine work on the cast iron ones also.

 

My build started out on the cheap also. But,by the time i had the valve guides replaced and a good performance valve job paired with the cost of the heads and magnaflux I was very close to the cost of those aluminum heads.

 

GT40 & GT40P heads are basically the same but there are some differences = GT40Ps bump compression due to smaller chambers, GT40s breathe a little better due to larger chambers, both Should have stronger valve springs installed ... even if they are for their stock motors let alone a Mustang H.O cam or anything "built" and topping them off with roller rockers is a nice addition. I have been told this by many motor builders from mild to mean & nasty . If you can't afford the aluminum heads then these are the next best thing vs older heads for the best breathe-ability.

 

yeah, no big surprise there really.. books tend to lump things together like that. I've CC'd many different castings through the years and they are not all the same. Might not be huge differences but it is there. You can literally see the quench pads, especially on the exhaust flange side of the chamber, disappear as the years went on and they got larger in volume. Not counting the teeny 260 heads.. 64-66 289"s were in the range of 53-55 cc's. 67-70 stayed fairly consistent at around 60-62cc's. 71' on up got even larger upwards of 64-66 cc's. Add the shorter piston pin heights, slight dishes and then taller decks of the 74' blocks and the lowered compression took a major dump on the torque curve.

And FYI on those GT40 heads. Supposedly slight chamber sizing differences between the Cobra GT40's and the 96/97 Explorers. Either way.. none of those castings ever even came close to 58cc's. Always at least 60 cc's or more. GT40P's got closer to that 58 number.

As for the bang for the buck of factory heads?.. it barely exists anymore these days due to the major influx of Chinese parts and tons of good used aluminum castings which saturate the for sale ads. Machine work keeps going higher just like any other auto shop rates these days. Unless you need to do absolutely nothing to them to get them ready for use?.. seems rather unlikely though.. you will end up tossing cash at them to end up halfway or better towards the cost of a vastly superior aluminum casting. This is what these guys are saying and they are absolutely right on target. Been there done that many times. mainly because it's all I had or could afford to work with at that particular moment. Times have drastically changed for the SBF though so it's wasted effort these days unless you class racing by design.

Then again.. if it puffs a little more smoke because you didn't do the guides and install nice Viton positive seals?.. oil is cheap again these days. Install 2 steps hotter on the plugs and run full synthetic so the oil doesn't foul the plugs so quickly and go have some fun. lol

 

Yep groberts101 is right. In the long run you'll spend almost as much money to still have a mediocre heavy iron head that performs about a 1/4 or at best 1/2 as well as even a decent but cheaper aluminum head. I would suggest do what your budget allows IF you have to swap heads but if not then save it for when you have scraped together the cash for the better heads.

If & when I build a 302 for the '72 Maverick it will have to be a low budget junkyard motor and unfortunately as I wish I could afford a 347 stroker motor pushing somewhere between 350-450+ hp to the wheels I know that's Realistically Never going to happen. Nothing wrong with building what you can afford because of course there's some guy who can always 1 up you somewhere or some how whether it be money or ingenuity.

 

Well, the desire to build "good" junk is always appealing to me....but I do see the wisdom in aluminum. A set of 90 buck GT40 heads sounds better BEFORE leaning over mountaineer fenders for 5 hours, but I collected the "spider" and "dogbones" while I was in there and the deed is done. I plan on lapping the valves to see if the seats are still decent, cleaning, checking the springs and probably replacing those, install new valve seals, and see if she smokes! Gonna think about milling .020 off the bottom, but not completely sold on it yet. need to do more reading, but I would really like to have 9.5:1. This engine is going to get what it gets as it came in the car and will be used more or less as is. The next motor build will get aluminum. Ok. I'll admit it. I am a junk-a-holic.

 

Ok, your plans are what mine was and I got carried away with the heads. Maybe with more self control you can do it but the new $800.00 Edelbrock heads seem to good to pass up for me if I had it to do again . Good luck with it.