Fox T-Bird/Cougar Forums

Technical => Engine Tech => Topic started by: vinnietbird on October 11, 2005, 09:29:54 AM

Title: GT40 iron heads and flat top pistons...
Post by: vinnietbird on October 11, 2005, 09:29:54 AM
Will the Gt40 iron heads from an Explorer work with flat top pistons in my T-Bird?
Title: GT40 iron heads and flat top pistons...
Post by: V8Demon on October 11, 2005, 09:41:35 AM
Depends on the cam your gonna run.  What do you have in store?
Title: GT40 iron heads and flat top pistons...
Post by: vinnietbird on October 11, 2005, 10:08:32 AM
I wasn't planning on changing cams right now.The engine in my '88 'Bird is an H.O. from an '87 Lincoln LSC.I'm using the Explorer intake on it already.Factory headers,H-Pipe with hollowed cats,dual exhaust.What do you think?My pistons wouldn't hit the valves would they?
Title: GT40 iron heads and flat top pistons...
Post by: CougarCoupe88 on October 11, 2005, 11:22:25 AM
if it's a true Ho you should be good with the stock cam. people do it all the time. and the motor should have the valve relifes in it. only the good HO's got them.
Title: GT40 iron heads and flat top pistons...
Post by: vinnietbird on October 11, 2005, 11:39:51 AM
I don't want to change my cam,I just want to know if I can use GT40 iron heads on my H.O. with flat tops.
Title: GT40 iron heads and flat top pistons...
Post by: Ether947 on October 11, 2005, 11:44:48 AM
Yes you can.
Title: GT40 iron heads and flat top pistons...
Post by: vinnietbird on October 11, 2005, 11:49:56 AM
That's great.I keep hearing conflicting stories,and don't really know what to do.I can get the very low mileage heads for $150.00,ready to go.1/2 the people say no,the other half yes.I haven't found any print that says either way.
Title: GT40 iron heads and flat top pistons...
Post by: Tbird232ci on October 11, 2005, 11:52:06 AM
an 87 HO should have valve reliefs, not the flat tops you think of in a standard output engine, or an 86 GT engine
Title: GT40 iron heads and flat top pistons...
Post by: vinnietbird on October 11, 2005, 12:05:41 PM
Well,actually,I say it's an '87 engine because it came from an '87 car,but,it does have flat top pistons.
Title: GT40 iron heads and flat top pistons...
Post by: Sick88Tbird on October 11, 2005, 04:01:07 PM
Make sure you get the GT-40P specific headers.  I believe Mac makes a set of full-lengths that are compatible as well as BBK(if you have a stick).  Ford racing also offers shorties for those heads but they are rediculously expensive.
Title: GT40 iron heads and flat top pistons...
Post by: vinnietbird on October 11, 2005, 09:32:44 PM
These are not the "P" heads.Just the cast iron GT40 heads.
Title: GT40 iron heads and flat top pistons...
Post by: Sick88Tbird on October 12, 2005, 08:52:47 AM
No need to worry about headers then...if ya find anyone with the "P" specific headers let me know...lol.
Title: GT40 iron heads and flat top pistons...
Post by: cougarman on October 12, 2005, 09:43:48 AM
Quote from: Sick88Tbird
No need to worry about headers then...if ya find anyone with the "P" specific headers let me know...lol.


BBK shortys fit the P heads just fine.:D
Title: GT40 iron heads and flat top pistons...
Post by: Innes on October 14, 2005, 12:51:04 PM
i just pic-ed up GT-40 heads to off an explorer i notetied the rockers on them have a 5 on them does that mean ther 1.5 rocker ratio. cause i wannted to put on 1.7's rollers. i know the cobra came like that but are the heads exacly the same.am i going to have piston problems and do i have to machine the heads (push rods ect.) to make the 1.7's work.havent decided want kind of cam yet.
Title: GT40 iron heads and flat top pistons...
Post by: TurboCoupe50 on October 14, 2005, 01:48:55 PM
For the price I'd grab 'em, but you are taking a risk of using them on the flattops. Only way to know for sure, would be to clay the pistons with a head installed and very gently turn the engine by hand. Then you remove the head and measure the thickness of the clay where the valves made the indentions, anything .100 or more and you're OK.

BTW. The '87 LSC 5.0 is the flat top piston 200hp engine, same as the '86 Stang and LSC. The Mark VII DID NOT get the 225hp HO till '88....
Title: GT40 iron heads and flat top pistons...
Post by: vinnietbird on October 14, 2005, 04:00:42 PM
Thanks a lot.How much do these heads go for usually?If I can't use them,I'll sell them and try to at least get my money back.Thanks.
Title: GT40 iron heads and flat top pistons...
Post by: vinnietbird on October 14, 2005, 04:02:08 PM
I've got the Explorer intake on it,and it's running great.How much horsepower would you guess the heads would make....if they will work?
Title: GT40 iron heads and flat top pistons...
Post by: TurboCoupe50 on October 14, 2005, 08:47:14 PM
Quote from: vinnietbird
I've got the Explorer intake on it,and it's running great.How much horsepower would you guess the heads would make....if they will work?


Over the E6s I'd guess 35-40 hp with the stock HO cam, the Explorer intake and a 65mm T-body. You may need to increase the fuel pressure 3-4 lbs to get max HP. Ideally with head mods you should go with Mass Air.

I sold a well used set of the std GT40 irons for $300 about a year ago.
Title: GT40 iron heads and flat top pistons...
Post by: vinnietbird on October 15, 2005, 09:44:05 AM
I'll go get them.I may have to wait to install them,because I don't have anything for Mass Air yet.I was planning on that for next spring.Do you think the car would run well enough without Mass Air until then,or wait?I want more horsepower (doesn't everybody?),but have to go one step at a time.With the kids in school.and a LOT of expenses,that's just how it has to be.I'll start watching E-Bay and gathering parts,like the Mass Air wiring kit,Mass Air Sensor and intake tubing,then the computer.For now,the heads are on my list first while I have access to them.I have E7 Heads in the garage,but,i figured if I'm getting the GT40 heads,I'll go ahead and get the new seals in the E7's and only use them if the GT40 heads don't work out for me.
Title: GT40 iron heads and flat top pistons...
Post by: 86Tbuzzard on October 16, 2005, 02:43:20 PM
If I use the explorer cam with the GT40P heads, and the explorer intake...would that mess up the pistons?
Title: GT40 iron heads and flat top pistons...
Post by: vinnietbird on October 18, 2005, 03:35:10 PM
Well,I can get the heads for $100.00 if I pull them myself....NO PROBLEM !!!! I wonder if my combo ('86 H.O.,Explorer intake,Explorer GT40 heads) would run decent without Mass Air.Anybody?Turbo Coupe50?
Title: GT40 iron heads and flat top pistons...
Post by: t-bird85 on October 18, 2005, 03:52:58 PM
I dont understand something, If your going throught the trouble of changeing your heads why not just do a clay test and save your self the dought,  Every motor is different to say your not going to have PVC problems.  To many factors to take into account. I agree with coolcat that you wont but its better to be safe.
Title: GT40 iron heads and flat top pistons...
Post by: vinnietbird on October 18, 2005, 09:01:45 PM
I thought I already stated I was going to use the clay.My mistake.Yes,I plan on it.Cheap insurance.
Title: GT40 iron heads and flat top pistons...
Post by: TurboCoupe50 on October 19, 2005, 02:44:30 PM
Quote from: vinnietbird
Well,I can get the heads for $100.00 if I pull them myself....NO PROBLEM !!!! I wonder if my combo ('86 H.O.,Explorer intake,Explorer GT40 heads) would run decent without Mass Air.Anybody?Turbo Coupe50?


As long as you keep the HO cam and 19lb inj it should run fine on the S/D. You should install a adj fuel pressure regulator, and increase the F/P to 42-45 lbs to get max power out of the combo.
Title: GT40 iron heads and flat top pistons...
Post by: vinnietbird on October 19, 2005, 02:53:08 PM
I'll look around for one of those.A good used one would be nice right about now.I'll check E-Bay.Thanks a lot.TC50.I have a lot to give you credit for on my 'Bird.You've helped more than you know in the past few months.Thanks a lot.