Engine Valve Spring Question With Gt40x Heads And Moderate Cam On Stroker Engine?

[Gearbanger 101]

I have a set of GT40X heads on the way here for my newest venture. I plan on running an off the shelf CompCams XE274HR with these heads atop a 10:1 331 (yeah....I know, it's a wimpy top end). What I'm shooting for is plenty of jam down low, with nice low speed drivability.

My question is in regards to the springs. I'm not sure that the stock M-6513-A50 springs that come with these heads are going to be up to the task? I'm currently looking into the 986-16 spring Comp recommends for this cam. The seat pressure and open pressure between them is pretty close GT40 springs are [email protected]" closed & [email protected] vs. the Comp springs that are [email protected]" closed & [email protected]" open.

I'm currently wondering if anyone has ever shimmed the original M-6513-A50 springs to increase their closed pressure a little? I wasn't sure if doing so was a good idea, as it also increases their open pressure. From what I remember, it's about a 1:1 ratio (someone correct me if I'm wrong), so if I were to shim the valve X-thousands in height in order to make up the almost 10lb closed seat pressure difference, I would also increase the open pressure approximately 10lbs as well? That being said...I'm not really sure if an increase of 10lbs of open spring pressure is really such a big deal in the grand scheme of things?

Anyone know for certain? Any ideas? I'd really like to run these springs if at all possible. I'm trying to put this engine together on a budget (as you can tell by my choice of head).

 

[MikeH686]

I think the springs i had in my edelbrock heads had the same spring rate of 123lbs and based off what my machine shop told me was that the cam that was in it it needed heavier springs because the owner prior didnt know what he did but he bent every single valve because the valve wouldnt close fast enough

 

[2000xp8]

You should be able to shim them.
Gt40x are actually pretty decent heads.
But my advice, take them to a machine shop and have them valve jobbed, at the same time have them shim the seats to 130lbs. The ford valve job on them isn't that great, taking care of the seats and doing a 3 angle valve job and bowl cleanup adds quite a bit of power.

While i don't know all the math and calculations involved, i know for a fact my buddy had all gt40x and y's seat pressure set to 130lbs.
He also required all heads that he installed to be valve jobbed, whether you wanted it that way or not, he said that the heads themselves, the valves, seat pressure and bowl jobs varied so much, that the $200 was great insurance.

 

[Gearbanger 101]

Yeah, the heads themselves have been recently rebuilt. I picked them up from a reputable member on here last week and just waiting for them to ship. They were decked (minimally), with new guides, and valve seals. His machinist apparently "checked" the valve springs as "good" and a valve job was performed, but I don't know the exact details. They've also already got minor port work done to the exhaust side.

I plan on disassembling them and checking the over again and doing a little work of my own to the ports, throats and bowl areas. I know by reputation that these are kind of a middle of the road head performance wise as it is, so it's gonna need all the help in can get trying to feed a 331.

I know there's more power to be had with better heads like Trick Flow or AFR's, but I like the idea of staying with the Ford top end components and I figured for the price (less than half the cost of a new Trick Flow or AFR casting) it was tough to beat.

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[srtthis]

you should take some time and clean up the casting flash in the runners

 

[Gearbanger 101]

you should take some time and clean up the casting flash in the runners

Yeah, they're going to get a going over.

Does anyone know what kind of material a person has to work with in regards to the runners and throat area? Is there a lot to work with, or are the water jackets just ready to burst at the seams at the mere sound of my carbide cutter?

 

[srtthis]

id talk to rick or tmoss about that...

 

[clement]

you can shim them and it should be just fine because 300lbs of open aint .

 

[Noobz347]

I picked them up from a reputable member on here last week...

That's it... Now I KNOW your full o chit!

 

[Gearbanger 101]

you can shim them and it should be just fine because 300lbs of open aint ****.

That makes me feel a little better. I'd rather spend $30 on shims, than $200 on springs.

That's it... Now I KNOW your full o chit!

I think he stumbled in here by accident.

 

[clement]

just watch that you dont get into coil bind at open when you shim them

 

[Gearbanger 101]

just watch that you dont get into coil bind at open when you shim them

I can't imagine I'd have to shim them much to achieve 10lbs? That is assuming if the seat pressure they're rated for is accurate. I did a quick google search and saw a lot of guys posting that some of them have seen as little as 90lbs on the seat with these springs at times.

Anyone know where I can pick up a decent shim kit made up of various thicknesses?

 

[Gearbanger 101]

Anyone ever use Alex's shim kit? Seems simple and effective enough?

http://www.alexsparts.com/products/...,-351C,-BB-FORD,-FE-FORD-1.500"-x-1.031".html