GT-40's are back from the shop with flow numbers.

Zero Signal · Dec 12, 2005

Well I don't know if this is tech or not these days, but I finally got the GT-40 irons back from the machinist. I bought them back in August for $200 off an Explorer along with the intake. I spend $40 on a porting kit and did the porting myself. The machine work bill was $350. So fully worked GT-40's for less than $600. It took forever becuase of some internal issues on their part, but it was worth it.

Their work included: magnaflux, bake, check valve guides, all new flat bottom valves (1.94"/1.63"), 3-angle valve job, mill heads, spring lift and seat pressure check, full assembly (shimmed up the springs), new stem seals, EM-varnish, painted exposed surface, and last but not least a flow bench test.

I don't have many good pics of the port job, but I have the numbers that will be used to pick (or design) the cam. I compared the data of my ported GT40's to what we have posted in the FAQ sticky. I noticed they they are somewhat comparable to the Edelbrocks they have there. My exhuast falls off at around .300" but it's still a lot better than the stock port and waaaaay better than stock E7TE anyway, here is what my port job did for me.

Notice the exhuast flow at .300". I think that number might be messed up, I'm thinking it should be right on top of the Edie. That would even out that curve. But the low lift flow will help a lot. It's all gonna come down to the cam with this one.

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Anywa, just thought I would share. I'll follow up with the cam once we're done with that this week.

Blackened302 · Dec 12, 2005

wow, that's awesome, especially since you can get the gt-40's themselves for pretty cheap!

urban96 · Dec 12, 2005

how do the ported compair to a set of p's?

final5-0 · Dec 12, 2005

Way to go John

Hope it all works out like you expect!

Grady

Zero Signal · Dec 12, 2005

They will flow about 5% more than the P's on the intake and 10% more on the exhuast.

bjl95mustang · Dec 12, 2005

How much was the port work?

bimmertech · Dec 12, 2005

i'm gonna go out on a limb here and say that an "E" cam would work pretty good here--as far as off the shelf grinds go. good job, those are some good low-lift numbers.

Zero Signal · Dec 12, 2005

Port job was $40 since I did it myself. But mind you, it took me maybe 16 hours to do it. If I did it again, it would probably be somewhere around 10 hours.

As far as the cam goes, the machinist I went through (Denny Wyckoff, Motor Machine & Supply) is also the local cam genius. He's going to design the cam and try to find an off-the-shelf match. If he doesn't find one, I might go custom grind. I can get the grind cheaper through him than through FTI since he does most of his business with Crower.

I attribute most of the low lift bonus to the 3-angle valve job. It's unfortunate that we are stuck with 30° seats. A 45° seat could do us a ton of good in the low lift region.

DFG 5OH · Dec 12, 2005

i've been considering self-porting mine. Did you use the SA porting kit? How hard was it? my heads have already had all the machine work, and if i port them, will i have to redo the machine work?

Zero Signal · Dec 12, 2005

i've been considering self-porting mine. Did you use the SA porting kit? How hard was it? my heads have already had all the machine work, and if i port them, will i have to redo the machine work?

Yeah I got it from Summit. Get the deluxe kit or whatever the big one is. Whatever you do, don't port them unless you plan on getting a valve job done afterward, becuase the seats will be totally screwed up. Mine were all completely rounded down after cleaning/polishing the chambers. Still, with 16 valves, you are most certainly going to kick some seats with the grinder. I hit a few pretty hard and I was being careful

Also, I used a 1/3 hp flexible shaft grinder with a 1/4" chuck. I would highly recommend something with variable speed. Don't use those single speed jobs from Sears and Harbor Freight.

Last thing, don't bother with a carbide bit. The 40 grit sand cantriges cut faster than you would think.

Joes95GT · Dec 12, 2005

Do you have any info on what kind of flow bench they were tested on? What size bore, what pressure level, and was the exhaust flowed with a pipe (and if so, what size)?

One thing that I would REALLY consider doing is finding a WAY smaller intake valve. Even a 1.6 is a bit overkill in those heads. In comparison (although it may not be a very fair one), Blue Thunder 4.3 heads still use a 1.6 exhaust valve with 2.125" intake valves.

Joe

Zero Signal · Dec 12, 2005

All I know is that it was done @ 28" Hg but anything else can be accounted for with the cam.

BPA · Dec 12, 2005

Too bad you dont have any pics of the porting job you did darn.. Anyways good #'s

95snoozer · Dec 12, 2005

Zero Signal said:
They will flow about 5% more than the P's on the intake and 10% more on the exhuast.

opened up Ps will far outflow the exhaust on your heads

a basic port job with 1.6 exhaust will flow 170+ in fact

blksn955.o · Dec 12, 2005

Actually, the P's cannot be ported as much as the reg. gt40 heads due to some water passages...with a good valvejob and port work they should run or outrun a set of ported gt40p heads IMO from what I have read on the subject.

Zero Signal · Dec 12, 2005

I was only refering to the stock P's which is what he was refering to. But I couldn't find a pair of P's for $200. This whole thing is revolving around the cost.

igotyofire · Dec 13, 2005

i wonder what killer95stangs flow at, hes the one who made 300rwhp on gt40p's. i dont remember if his were flow benched,heh ill try searching later

95snoozer · Dec 13, 2005

blksn955.o said:
Actually, the P's cannot be ported as much as the reg. gt40 heads due to some water passages...with a good valvejob and port work they should run or outrun a set of ported gt40p heads IMO from what I have read on the subject.

I didnt say that

HIS HEADS flow anemicly on the exhaust worse than a P with mild work

not to mention the 59cc cobustion chamber with better quench

igotyofire said:
i wonder what killer95stangs flow at, hes the one who made 300rwhp on gt40p's. i dont remember if his were flow benched,heh ill try searching later

see my sig,

I also have one of these little gt40p combos

Zero Signal · Dec 13, 2005

The P's are just a better head all around. If you can find them AND they are priced well, they would be the best choice. For me, I had to get a hold of the state's auto recycler's association to find just these heads.

blksn955.o · Dec 13, 2005

Zero Signal said:
I was only refering to the stock P's which is what he was refering to. But I couldn't find a pair of P's for $200. This whole thing is revolving around the cost.

yes stock for stock the p is a good head for a good price if you get ones that dont need alot of work.

GT-40's are back from the shop with flow numbers.

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