stdyhand

My question is regarding the GT40 heads. I've done a lot of reading regarding the "Gt40 vs. P head" debates and in their untouched state I am lead to believe the majority see the P heads as better performers due to their smaller chambers, higher flow, and revised spark plug.

However, the regular GT40 head does have a larger exhaust valve compared to the P heads which some believe to be better for performance.

My question is do the regular GT40 heads have the same amount of metal that can be removed during porting to make them perform better than the P heads, assuming they were ported as well.

I am able to get my hands on either heads fairly cheap but I was wondering if both sets of cylinder heads were ported would the P heads still out flow the regular GT's or would the larger exhaust valve on the gt40's allow it to now outperform the P heads due to porting?

I've seen a lot of threads about these heads but not too many on what the flow numbers were like after porting both sets.

Oh, one more question not related to this topic. I was considering upgrading to some 3.73 gears. How will this effect the engine idle? Will it idle higher and how does it effect how fast you shift through gears? I know the shift points are basically the same, but assuming I am starting off in first like normal I would be shifting gears much sooner, right?

67mustang302

The p heads performs slightly better than the regular GT40s, but they also require a special header. There's more to power than flow numbers, the revised plug/chamber is one of the bonuses of the p head.

And gears won't effect your idle at all, your top speed in each gear will be slightly less in terms of mph, and cruise rpm will be a bit higher.

stdyhand

Aside from the plug/chamber design, would the P heads still outflow the gt40's if they were both ported or would they perform about the same?

AdderMk2

you cant really compare that until they ARE ported... you can always port one just a little bit more. the P's make better power OOTB. porting them is a wast of money though. By the time you finish paying for the port work, you can buy a set of used aluminums.

nitrous_bob

i like the real 40's better than p's

i have never yet witnessed a p headed car run well...ever

i think some mild porting is well worth it on a real gt40 head though, my buddies '93 ran 11.80's on a 125 shot and 4.10's, with iron 40's just slightly ported exhaust and decked a bit. comp valve job (i would do this even on brand new heads since most do not have a good valve job anyways) all that can be done for about $300 and assuming you can get the heads for $300 it's a $600 investment

it's hard to find aluminums for that... and they still need some work

i am a big fan of iron 40's for a high 11 second car, easy and cheap

and as far as gears.... dont be afraid to go 4.10, on a mid 12 second car 3.73 will still bog a bit and not enuff.

expect your rpm's at any given speed (not idle) to be about 250 more per gearset. so if you do a 2.73 to 4.10 swap, you'll be running about 1000 rpm more than before. that should explain shift point question a little easier to understand

87Stallion

dont bother with either

Venomantidote95

+1 unless ur really not looking for a good performance gain.

Blown408

X2, You will just upgrade down the road later. Save up for a nice set of aluminum heads. Cant beat the performance and the weight loss that you gain with them...

stdyhand

The problem I have found is that almost all aluminum heads, with the exception of the TW (same valve, different angle) and maybe smaller AFR 165 heads have the 2.02 intake valve so I know I would have to flycut the pistons. I don't really want to do that. Nor do I want to get an aluminum head with such large valves and not be able to get the most CAM I can.

It seems I will have no choice but to just rebuild a short block. I've already purchased an engine stand from harbor freight and looking at an engine hoist now.

I'm trying to decide whether to get a bare block already prepped for a stroker from Fordstrokers or if I might get a block locally and get the machine work done a little cheaper.

I'll be looking at some forged pistons with valve reliefs capable of handling heads with the 2.02 intake valve and deep enough for a higher lift.

Question though, which blocks were roller blocks? I know the earlier blocks weren't but which newer blocks were considered to be roller blocks? Was it just the 87-93 Mustangs or are the 302's from Explorers also roller blocks?

Also what does machine work for a block normally cost? I'm looking at boring .030" over, decked, align honed, shot blasted, etc.

I know my local NAPA sends blocks off to be machined but the only cost I have heard of was someone getting their block bored for like $20 per cylinder. That wasn't including any other work so it seems like the cost could add up rapidly and I could have already purchased a fully prepped block and saved that time.

sn95_331_GT_ yellow

solution:

2.02 heads

+

custom cam (FTI, cam innovations)

all done...

ask MJR about his similar set up, he wont bitch about it