Gt40 Questions

[TOOLOW91]

Ok so a buddy of mine got me a set of gt40 3 bar heads from a lightening for 200 bucks . I know that you have to use a stepped head bolt .
My question lies in the combustion chamber size some say they are bigger then the cobra castings yielding in having to mill them to stay at stock comp ratio some say there the same . I need advice on what is what so I know what to do with them . The plan is to run 1.6 rr Ed Curtis cam and possibly trick flow upper lower with it .

 

[srtthis]

they should be roughly 61CC...

 

[RangerJoe]

You're going to need upgraded valve springs anyways. If you let a shop do the springs, just get them to cc them. I would mill em anyways, compression is easy HP.

Joe

 

[TOOLOW91]

how much should i have them milled ? 59cc? 60cc i dont want to run into ptv issues either

 

[TOOLOW91]

this car might see a blower in the future too

 

[RangerJoe]

Well, if its going to see a blower then I would leave the compression alone. If not, then .030 would be a safe bet on milling, but you may want to research your cams first. For example, the AFM N41 cam is designed for GT40 heads, but takes advantage of all the clearance available with stock pistons. Really doesn't leave much room for milling.

Joe

 

[TOOLOW91]

how is the n41 drivability wise ? I'm sti ll dding this thing for now

 

[RangerJoe]

how is the n41 drivability wise ? I'm sti ll dding this thing for now

I've never driven one, so I can't really say. They recommend a 3.73 gear as minimum. I was told that it will buck a little at low speeds, but thats going to happen with alot of cams. It is lower on their list of cams as far as extremeties go.

Joe

 

[TOOLOW91]

yeah something to look into . car is getting 3.55 I'm sure it would
be a big deal