Rebuild heads or new heads

Funwithfox · Aug 31, 2020

I have a 93 LX with 5-speed. Noticed that #8 spark plug was getting build up on it. Also was losing some oil somewhere (not on ground and didnt notice any smoke). I have a mild build on the car. CAI, 65mm throttle body, GT40 (explorer) intake, 28lb injectors with MAF calibrated for them and throttle body, GT40 iron heads, Comp cam (duration @ .050 intake is 218 and exhaust is 224, lobe lift is .3210 and lobe separation is 114). All of this stuff was done by the prior owner. I took the heads off this weekend and they clearly need to be rebuilt. Lots of buildup on the valves of #8. Other valves shows signs of this as well. Also, should mention there was standard lifters and not roller rockers.

Question, should I rebuild these heads and install roller rockers or should I get new heads? I am not looking for crazy power as I want the car to be a nice streetable driver. I will most likely never take it to the track. Maybe somewhere around 300hp or just north of that would be nice. I am by no means an expert on this technical stuff, but have been reading around about how some heads are better than others depending on what cam you have. Any help would be appreciated. Thanks

90sickfox · Aug 31, 2020

What kind of heads are they ? Thats the most important question. Some heads are worth it....some are anchor weights.

Funwithfox · Aug 31, 2020

They are GT40 with the 3 bars. Does that help? New to the mustangs so trying to get to know them.

2000xp8 · Aug 31, 2020

IMO, it comes down to your budget.
If you are pulling them off, you already own them so that money is gone, you could have them valve jobbed with bowl work fairly cheap. My guess is $250. Would provide a little power bump too.

But, you could easily get to 300rwhp with a set of twisted wedges and a few more tweaks (maybe even 325rwhp+ with well matched parts).
Most likely be a good 35-50rwhp than you have now and be 50lbs lighter in the nose.

Not sure they price of tw's these days, but they used to be $1100.

So now you see why the budget is so important.

I'm of the belief that gt40 irons fall in the anchor weights category.

General karthief · Aug 31, 2020

How many miles on it?

KRUISR · Aug 31, 2020

I would bet with the GT40's rebuilt, add roller rockers and go with some electric fans (contours are my preference) you would be close to your goal of 300rwhp.

Do you actually need a rebuild or just valve seals?

Another questions for you. Does your lower intake have a small mesh insert below the PCV valve?

It fits under the rubber grommet at the back of the intake. The reason I ask is my Explorer intake did not have one and I kept fouling #8 plug (3 hours of continuous driving would do it). The reason is without the screen more oil vapor is pulled out of the lifter valley and the PCV hose connects to the Explorer upper intake inline with #8 cylinder. If you are only seeing oil crud build up on cylinder head by #8, that might be your problem. If sucking enough oil #7 cylinder could be affected too.

2000xp8 · Aug 31, 2020

The electric fans at this point would be like throwing money away, especially if the stock fan works fine.
A gt40 iron setup is typically 250rwhp to 265rwhp. Pretty far from 300rwhp. Fan is worth like 5rwhp.
Electric fans, k members, tuning should be left as advanced mods after all the things that make real gains (like aluminum heads) are done.
I say the same thing all the time, all the power is in the heads.

General karthief · Aug 31, 2020

Look it comes down to budget, if you have it, the right aluminum head is just a few benjamins more than rebuilding the gt40 heads. A few ponies comes down to money. If you're just schlep 'n around town do the iron heads with some roller rocker arms, a 373 rear gear and it will be fun to drive. That is if you don't need to rebuild the bottom end.
It all comes down to a plan.

HemiRick · Aug 31, 2020

I agree the stock heads are the cork in these engines. I have a set of Blue Print pedestal mounts on the way ($820 for pair shipped) to replace my stock E7's. Should pickup close to 100 HP. I buying the bare heads and having my local machinist build them. I also got a Comp 35-349-8 cam same basic dur but more lift (.10 .444 vs .544) than stock.

HemiRick · Aug 31, 2020

Electric fans dont gain any HP, what you gain by removing fan you loose w the bigger alt and the load its places on engine to run fans.

KRUISR · Aug 31, 2020

Only when the fans are actually running. From experience, most of the time the fans are not running, therefore, freed up horsepower instead of constant hp sucker.

From experience, if I run a 1/4 mile run (on the street) I have yet to have my electric fans running during that run. Therefore my engine has more horsepower available to propel me down the road. It doesn't make more, it looses less and therefore has more available.

General karthief · Aug 31, 2020

HemiRick said:
Electric fans dont gain any HP, what you gain by removing fan you loose w the bigger alt and the load its places on engine to run fans.

the op has gt40 heads, better than e7s,
and I would like to see the difference in hp between the e fan draw on the alternator and without e fans.

HemiRick · Aug 31, 2020

The stock engine driven fan has a clutch and when its cool it hardly places any load on the engine.....so much similar to an electric setup load wise. It only works when it needs to.

KRUISR · Aug 31, 2020

So when its cool you don't feel any air being blown toward the engine. Ok. You run a clutch fan and I will keep my electric fan. Now let's get back to the OP's question.

HemiRick · Aug 31, 2020

I think his GT40's are probably fine and he's missing that screen. IF you want more power, the heads are where to find it....no way to get 300HP or more IMHO w stock heads. I've heard GT40 were worth like 35 HP so 225 plus 35 is only 260.

Adieu · Aug 31, 2020

HemiRick said:
I think his GT40's are probably fine and he's missing that screen. IF you want more power, the heads are where to find it....no way to get 300HP or more IMHO w stock heads. I've heard GT40 were worth like 35 HP so 225 plus 35 is only 260.

You can port, polish and mill your way past 300hp with stock heads, my old 302 put down 267 at the rear wheels through a C4 automatic with a set of heavily worked over D5AE castings from the smog era. That's over 300 at the crank. That said, I don't recommend that route to anyone. Duplicating that work these days would cost as much as some of the cheaper aluminum castings... that make as much, if not more power, and save a lot of weight and reduce heat retention.

KRUISR · Aug 31, 2020

HemiRick said:
I've heard GT40 were worth like 35 HP so 225 plus 35 is only 260.

If you are going to try and justify by adding up to a number that is only part of the actual engine, try doing the whole combination...

Funwithfox said:
CAI, 65mm throttle body, GT40 (explorer) intake, 28lb injectors with MAF calibrated for them and throttle body, GT40 iron heads, Comp cam (duration @ .050 intake is 218 and exhaust is 224, lobe lift is .3210 and lobe separation is 114).

So lets start the math over again...

Stock engine, heads, intake - 225
GT40 heads +30
Explorer intakes +20
Comp Cam (XE270HR - by the specs) +30
65mm TB +5
28 lb injectors +5

Total = 315

New parts I suggested:
Add a little porting/smoothing of the heads +10 (maybe more)
1.7 roller rockers +5

New total = 330 (with clutch fan)

Switch to electric fans frees up +20

New total at flywheel = 350

That on a 5 spd car will be really close to 300 at the wheels if not over. Yes these numbers are crude and could go up or down a little as every engine reacts differently to the same changes. My point - 300 rwhp is not far away from his existing combo.

Funwithfox · Sep 1, 2020

Thanks for all the replies. If the GT40 heads give me 30hp, what do a set of new heads give me? I know it varies, but a general range would be good.

Funwithfox · Sep 1, 2020

KRUISR said:
I would bet with the GT40's rebuilt, add roller rockers and go with some electric fans (contours are my preference) you would be close to your goal of 300rwhp.

Do you actually need a rebuild or just valve seals?

Another questions for you. Does your lower intake have a small mesh insert below the PCV valve?

It fits under the rubber grommet at the back of the intake. The reason I ask is my Explorer intake did not have one and I kept fouling #8 plug (3 hours of continuous driving would do it). The reason is without the screen more oil vapor is pulled out of the lifter valley and the PCV hose connects to the Explorer upper intake inline with #8 cylinder. If you are only seeing oil crud build up on cylinder head by #8, that might be your problem. If sucking enough oil #7 cylinder could be affected too.

I just went out to look and I do have this mesh insert in my intake. Also took another look at the heads and they are actually GT40P heads (4 bar). Here is a pic under. You can see #8 is not great and #6 is starting to get bad.

2000xp8 · Sep 1, 2020

You guys should stop with the flywheel talk.
In 99.9 percent of cases it's not provable.

gt40 iron heads with a cam and gt40 explorer intake will make 250-265rwhp. That's really not opinion, it's been done thousands of times.

TFS kit will make 290-310rwhp. Again, i consider this to be fact.

It goes up from there, custom cam's, better intakes, afr heads you can stretch it all the way to 359rwhp (which is the best i've personally seen from any stock 302).

Electric fans should not be any type of priority on a gt40 iron setup, if you have an extra $400 it should goto the heads long before that. You have the best parts already? Go ahead, just don't expect a lot of return for your money.

For the OP, what makes you think the heads are the problem and the engine isn't burning oil?

Rebuild heads or new heads

Funwithfox

New Member

90sickfox

Wasn't a pretty sight...and I've got big hands

Funwithfox

New Member

2000xp8

General karthief

wonder how much it would cost to ship you a pair

KRUISR

2000xp8

General karthief

wonder how much it would cost to ship you a pair

HemiRick

I'd be looking at jacking under the house

HemiRick

I'd be looking at jacking under the house

KRUISR

General karthief

wonder how much it would cost to ship you a pair

HemiRick

I'd be looking at jacking under the house

KRUISR

HemiRick

I'd be looking at jacking under the house

Adieu

Easy there, this ain't a dating site.

KRUISR

Funwithfox

New Member

Funwithfox

New Member

2000xp8

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Rebuild heads or new heads

New Member

Wasn't a pretty sight...and I've got big hands

New Member

wonder how much it would cost to ship you a pair

wonder how much it would cost to ship you a pair

I'd be looking at jacking under the house

I'd be looking at jacking under the house

wonder how much it would cost to ship you a pair

I'd be looking at jacking under the house

I'd be looking at jacking under the house

Easy there, this ain't a dating site.

New Member

New Member

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