351w with GT-40 (or 40p) heads

[Zorm]

I know its not jeep but I am putting it in my 83 Cherokee (last year of the Grand Wagoner size ones), the 351w. Its a non-roller block, 93 I think. Found a set of GT40 and 40p heads in a local junk yard, which one would be better then the stock heads. Not really looking for huge hp, just want better breathing engine.


If I go GT40 or(40p) heads, keep the non roller cam/lifters or do the retro fit to the roller rockers


Also don't know if I want to try and rebuild the MPFI using the Explorer upper intake or just get a 650 Holley with a Edelbrock duel plane 4 bbl intake. Or use the cheby TBI set up I got. I also found a 80's ford LTD with the 5.0 and a real low upper intake.


thanks for any input.

[JoshT]

Either one would be better (depending on your stock heads), but I'd stick with the GT-40 heads. Supposedly the GT-40p are a little better out of the box, but they have an odd spark plug angle that makes fitting headers/manifolds/exhaust a bitch. Are you aware that 5.0L GT-40 (or GT-40p) heads will need the head bolt holes drilled out for the larger 351 head bolts? IIRC 5.0L uses a 7/16" head bolt, while 351w uses 1/2" bolts.


Do you have roller rockers now? If so, keep them. If the heads you are considering are from an Explorer (biggest source of these heads) they won't have roller rockers and probably not worth swapping unless you need to.

Roller cams are nice, especially when installing and breaking in a new cam. Can't say if it's worth converting to roller cam. If it were mine and I wasn't planning to replace the cam or lifters, I wouldn't convert. If it were mine and I was installing a new cam, I'd most definitely consider swapping to roller. To me the ease of breaking in a roller cam would be enough to justify the cost.

Explorer intake is a nice set-up, but 5.0L intakes won't fit a 351w. Due to the taller deck on the 351, the 5.0L/302 intakes are not wide enough to fit. To run the GT-40 upper intake, you would have to find a Ford Lightning lower intake. Good luck with that, if you find one it'll be high $$$. Cheapest one on Ebay right now is $450, lower intake only and it looks rough.

Don't even bother with an 80s EFI intake, doesn't matter if it's 5.0L/302/351.

You'll probably be best off going aftermarket on the intake for carb or EFI. If it were mine, I'd probably go with an aftermarket EFI intake and a Mustang EFI system, but I'm biased towards EFI.

[Jacksdad]

I'm switching out my tired 352 FE for a 351w, and I'm going to be using GT40P heads. My short block is a non roller '89, probably from a cop car going by the casting numbers. A roller would have been nice, but it was in great condition and cheap.

JoshT is right - 302 heads will need to be drilled out to 1/2" to accept the Windsor head bolts. A machine shop can do it, but a lot of people just go with a good bit and a drill press. As mentioned, a 302 intake won't work on a 351w, and Lightning lowers fetch a premium. I'm going with an Edelbrock Performer to simplify my swap, but an aftermarket fuel injection system might well find it's way on there eventually.

I got real anal and did a lot of research before settling on the P heads over the GT40s.The biggest complaint you hear - as JoshT mentioned - is the plug angle on the P heads. It was changed along with the combustion chamber for a more efficient burn. It can cause problems with fried wires and plug removal with some exhaust manifolds and headers. I settled on BBK unequal length Fox body shorty headers, but MAC headers seem to come highly recommended too. I haven't got the motor in yet, so I'm not sure what kind of underhood clearance I'll have, but I'm banking on the extra space we have over a Mustang making them a bolt on. I guess we'll see.

One thing I did find was lots of people making GT40P heads work with all kinds of headers. That's not to say all brands will work, but the key in most cases is 90 degree plug wires, and sometimes ceramic boots and/or heatproof sleeves and shorter plugs. Depending on the brand of header, some plugs can be a pain to remove, but the trick is a shortened plug socket with a slot cut in the side that allows it to slide over the plug from the side before pushing it down onto the hex. You use a wrench on the socket to loosen or tighten. Given the performance you gain from dropping GT40P heads on, it seems like a small sacrifice.

I went with GT40Ps over GT40s not only because they make a little more power, but also because the chamber is smaller. On a stock block like mine, they'll bump the compression up about half a point from 8.8 to around 9.3 without the expense of a piston swap. I don't really need any more for my use, so I'm happy with that.

P heads will make about 30hp over smog heads like E7's, but (like GT40s) they have one major weakness - the stock valve springs suck. You have two choices depending on your application. For a performance motor that you want to spin a little faster, or one with a bigger cam (over .500") you can buy drop in spring kits from TFS and Alex's Parts for around $200.

My intended use doesn't call for a high revving motor, so I looked into the feasibility of using new stock replacements. Turns out that some other builders had the same idea and documented their experiences online. New stock springs will work with a mild cam, and they float at around 6200 rpm from what I've read. My build is geared toward as much grunt as possible from idle to 5500rpm with .483/.499 lift, so I should be safe using them. A new set cost me a little over $40 from Rock Auto. I'm on a tight budget and really don't see the sense in spending another couple of hundred on springs that will allow me to spin it well past the point where the motor has stopped making power. It's money I can use to buy other stuff I do need.

This chart shows the improvement in flow you get over E5/E7 heads. I know flow and HP don't necessarily correlate, but you can see the difference. A mild build like mine should net around 300-320hp with P heads - a lot more than my 352 is making right now.

24883567_10102172342255951_8890256156939506805_o.jpg

[JoshT]

One thing I did find was lots of people making GT40P heads work with all kinds of headers. That's not to say all brands will work, but the key in most cases is 90 degree plug wires, and sometimes ceramic boots and/or heatproof sleeves and shorter plugs. Depending on the brand of header, some plugs can be a pain to remove, but the trick is a shortened plug socket with a slot cut in the side that allows it to slide over the plug from the side before pushing it down onto the hex. You use a wrench on the socket to loosen or tighten. Given the performance you gain from dropping GT40P heads on, it seems like a small sacrifice.

I'm using a 98 Explorer 5.0LGT-40p long block in a 86 Ranger. High mileage, but got the whole running Explorer for $500. Explorer manifolds won't really work in the little Ranger, so got a set of Hedman Headers that should fit with a little work. Got 90 degree ceramic plug wires and heat sleeves to use with the headers. If I hadn't gotten the explorer engine like I did, I don't think the Ps would have been worth the added work. Just my opinion on that.

P heads will make about 30hp over smog heads like E7's, but (like GT40s) they have one major weakness - the stock valve springs suck. You have two choices depending on your application. For a performance motor that you want to spin a little faster, or one with a bigger cam (over .500") you can buy drop in spring kits from TFS and Alex's Parts for around $200.

Meant to mention that about the valve springs. Stock springs were barely good enough for a stock Explorer cam once they had a few thousand miles on them. I put 1.7 roller rockers on my otherwise stock explorer engine and went with a set of upgraded springs from Alex's parts. Not even close to having the engine running yet.

[Jacksdad]

As long as you don't have any issues with them, you're way better off with the Hedmans. The Explorer headers have to be the worst I've ever seen from a performance standpoint. Just switching them out for decent headers has to be worth a good few hp.

[Zorm]

Sweet, ton of great info. I am planning on drilling out the bolt holes, got a drill press. Non roller valve train, and if I really don't need to, no plan on changing. It's a big jeep, I would be amazed if I get it passed 45kRPM. That said, thoughts on maybe a little better cam then the factory stock? Would the stock springs from the factory heads work on the gt40p? Or what should I look for.

I do have a chevy 350 tbi set up I was thinking of using, that or a 600-650 4bbl Holley. I already have the 4 bbl intake. This will be a weekend driver, maybe tow something one in a while, and go play on some trails, no heavy mud bogging though.

Again , your thoughts are welcome

[Jacksdad]

I'm going with a relatively mild Lunati Voodoo cam and lifters. It's maybe a step up from an RV cam, but still under .500" lift. I did find someone online that was running an Explorer 302 with an F303 cam (.512" lift) with GT40P heads and stock replacement springs, and had no issues revving it to six grand, so anything with less lift should be fine. If I were you, I'd go with a build that gives you gobs of torque off idle, with a nice broad power curve to 5000-5500rpm. A small carb (600- 650 cm) and dual plane intake would be a good fit for a motor like that.

Just make sure you ditch the valve springs that came with the heads.

http://www.lunatipower.com/Product.aspx?id=2359&gid=287

[Zorm]

Any one that has done this, gt40P heads on a 351w, non roller, what push rods did you use? Picked up great set of gt40p heads machined about 2 years ago, only on the 5.0 for about 5 months before the engine block cracked. Just need to clean up. I am also looking for shorty headers that would bolt up to a stock exhaust, kinda.

[Zorm]

I got a Edelbrock Performer 351w duel plane manifold (picked that up for $75), to go on and was thinking of a 600 or 650 cfm Holley carb. Going to keep the flat tappet stuff, maybe a bump in the cam, .400 lift? any thoughts on cam?

I have two options for tranny, cheep because I already have them. 1] the Cherokee has the Jeep T176 4 speed mated to the Jeep NP208 xfr case in it now. I can use the Ford bell housing I picked up (external slave mount) which bolts in place of the Jeep bell housing and go that rout. 2] Use a Jeep NV3550 5 speed I was going to use on another project, get the adapter, mate that to the ford bell housing and see if the NP208 will bolt up to it.

thoughts welcome?

[Jacksdad]

The transmission I can't help you with, but I'd go bigger on the cam. Those heads would be wasted with that kind of lift. Get an RV style cam with a dual pattern grind to help out the exhaust (it's a Ford thing) and find one which matches your intake's power band - 1000 to 5500rpm if memory serves.