gt-40 heads and performance

I know there are many threads on these heads...anyway a couple questions.

I have a set of cast gt-40s (marked GT) on my 302 in a mustang(low hrs), PO had them just installed before I bought it...I am thinking of swapping them to the 302 in my 72 SN. Is it as simple as unbolt and swap?

Also...what kind of performance should I see if I just swap heads and no more?

Will performance be much better if adding an edelbrock alum. performer intake?

I would be tickled pink if I could gain 2-3 mph on the top!

Also...I have a complete 302 sitting in the garage(good shape)...Might want to see what I could have done to that engine and use the heads on it...any performance recommendations?

Chris...They would go from one 302 to another 302...no drilling !

What diff in performance could result from just a head swap?

How much better with another intake(edelbrock )?

Any one know what the torque speck are...good rainly day project, and it's been raining...plus my wife won't know that I took the gt's from her boat and her's should not be faster than mine right?

He-- yes it is!

TRBenj...that is enough motivation to go to the garage! Thanks!

Chris ...what are your thoughts on performance intakes in addition to the swap?

Thanks TRBenj and Chris! I checked ebay for the professional products "Typhoon " Intake...145.00 + 20.00 (shipping) for polished alum. That looks like a good deal! Looks cool too!

Any clearance issues?

Always tinkering Right!

Big price diff on the intake!I think I will go ahead and get the typhoons... I like the polished look too. Sense I already have the heads...won't cost much ! Still have a some time to get them on and play a while

Thanks all for the input!

Chris...regarding parts boat...do you have the black round floor access ports(what ever they are called)?

I agree that the slight increase in CR helps- but I dont think its the biggest factor. The GT40's outflow the stock heads all across the board by a pretty significant amount. I would think that the better breathing is what allows you to pick up several hundred RPM at the top end.

To see a good side-by-side comparison, check out the Ford head flow chart here: http://www.allfordmustangs.com/Detailed/630.shtml

Actually, the chart shows flow from .100 to .600 of lift. I agree that a race motor that turns high RPM is not comparable to our boat motors that generally turn 5k max. However, I dont think that low end torque is the most important factor on our motors either- I think its all about the midrange power. The cam I chose for my boat makes power from 2500-5200 and it works great. Holeshot is much stronger than stock, and the midrange power is terrific- a great ski boat motor. Since I get 3k+ RPM out of the hole, I dont see the need to make huge amounts of power below that point. The 400+ RPM I picked up on the top end can be attributed to the higher flowing heads and intake (and the cam that can support them).

How many RPM do you turn with your new setup?

Great info and thanks! I am keeping things somewhat simple...swap heads and intake!If I pick up 2-3 mph it's a success!Low end and mid now are strong.

Tim,

On the gps...I am seeing 46mph...tach reads 4000 and is most likely off a bit(original tach 1972).
Hole shot is great and midrange too...0-40 is fast, but top end is not there like I want it! 49- 50mph for a 302 in a SN would be nice! Funny thing is...in the fall last year right after I brought it home, it was hitting 47 and that was before I removed 300lbs of soaked foam and drained two year old gas out???
I also switched to an EI ign...reset timing. I think the carb can be fine tuned a bit as well as minor timing tweeking.That with the head and intake should get me there!
Or just go out and find some old gas!

46 is no slouch for a 302 in a Ski Nautique, thats for sure. Strange that it was faster before though... Where was the soaked foam? Ive noticed that we can pick up a solid MPH by putting a few people in the back seat.

I bet that the heads, intake and a full tank of gas will get you there!

Oh, and I would say its a pretty good bet that your tach is off. With a new 540 and 46MPH on GPS, 4k RPM doesnt make much sense.    

That's pretty consistent with what Ive seen. With stock sized props, both 1:1 and 1.23:1 boats seem to run pretty close on RPM vs. MPH. You can see some differences due to hull efficiency though. Once you start changing prop sizes, that can skew everything as well. Before my mods, for example, I was seeing 43MPH @ 4600RPM.

Boat Dr, I see that Cam Research did your cam- I have been impressed with mine. Did you have to source them the reverse rotation blank? When I ordered from them they said they could not get them.

It does run pretty strong...I'm trying to reach close to the 50 mark with it with out major machine work...that would be pretty good for a 302!
I figure the rpms should be closer to   4400-4500 at that speed .I think I will put on another tach and see.

Soaked foam was removed everywhere..but it was not heavily soaked...once I got started, I just got it all out...even up under the bow.

Yeah...it has to be...with the federal 13x13 before the 540...same thing low rpms...it sounds like it's rappin out pretty well.It's an old tach.