forced Induction cylinder heads

-
canadian duster

canadian duster

Well-Known Member
Joined
Oct 29, 2015
Messages
145
Reaction score
17
Location
lloydminster alberta
so my plan was to use 30 heads 74combustion chamber open up to 2.02 intake valves on my 408 stroker with 6v71 (plan for 6 psi boost).

ive run into issues get a machine shop in the area (Lloydminster sk Canada) to do this work. typically they are wanting to charge upwards of $1500 or this work. It seems quite high to me considering a new set of iron heads can be had for ~1900 cad. the is the smaller combustion chamber

I assume I would be limiting my engine too much if I stay with the 1.88 intake valves?
does anyone have recommendations for aftermarket heads that have a larger combustion chamber?
 
As far as I know, there are no as cast large open chambered aftermarket heads. You could search for a older set of W2 heads and run them as is, stock, if they can be found as cast, stock &
unported, they flow pretty good.
(Draw back, expensive rocker arms.)

I don't know how far you can open up any aluminum head in the chamber.

Working on iron heads is time consuming making them expensive. The 308 is a good OE head. Better when ported.
 
The Edelbrock aluminum heads for the early 340's are machined .060" in the chambers to clear the 340's proud of deck pistons. They have a 65cc chamber that's basically an open chamber. https://m.summitracing.com/parts/edl-60179

I've got a '68 340 with the pistons .018" over the deck so I wanted open chamber heads too. I had a set of 308's cut for 2.02/1.60 valves, cut for dual valve springs, chambers cleaned up after the valve job and heads stage II ported, ended up flowing 264 cfm @.500 with a 65cc chamber. By the time I was done I had almost $1,500 into them (US), and pretty much could have just bought the eddy's.
 
Same here as 72 bluNblu. However, at the time, the Edelbrocks were a little cheaper than today. I also paid cash at a speed shop on a price matching. $1200.

An aluminum head (as you probably know) can run a point high in compression ratio and not require a fuel grade change. If it ran on 87, it will still run on 87.

Again, how much you can carve out of the chamber I do not know.

Are your pistons at a positive deck height? How far down the hole? Have you done any math on the subject?
 
Thanks guys. I have the math (sitting at home though). If I remember correctly this 74cc we cc'd the chamber at have us a 8.2:1. To switch to the daddy's or aftermarket with the combustion chamber size available we were driving into the 8.6 ballpark range which then limits my boost potential on pump gas.

It looks like Brian at Imm sells an iron head that he will open up to 72cc that I'm going to investigate.

When it comes to aluminum vs iron, I've read you may gain up to a 1 point cr change with an aluminium?
 
Yes. But the math is important to do so you know exactly how much gain there is.
While in a boosted application, no matter the head material used, I would aim for a low ratio. Better off a bit low than a smige high.

Brian is a good fella. He'll set you up.
 
Ever thought of a thicker head gasket?
Like 0.054 thick. Felpro makes them.
 
What is the intended use of your car?
%100 drag car, swap heads
Street/ strip car, leave the heads, save your money for other performance upgrades as the blower will not care if there are 1.88 or 2.02 valves. Performance increase just by swapping heads will be minimal, unless you're changing the cam too.......
 
It will be a 99% street car. Upgrading cam as well.

What I'm really curious about is the potential impact of 2.02 to 1.88 intake valves.

Is it really worth the additional 2000+ dollars to change heads?
 
IMO, and for a street car, the blower will overcome any deficiency in valve size. At around 8.5:1 static comp you'll have snappy throttle response cruising around town when you're not making boost (which is most of the time). With 5-6 psi you'll have no trouble running premium pump gas.
 
MiradaMegaCab and 70Duster440 are saying pretty much the same as I said in my PM. The heads are just not that important when comparing head to head. The money you save in not changing heads can be used in more important areas, like carbs or FI, exhaust, cooling or even a custom cam.

Jack
 
You must log in or register to reply here.
-

Back
Top