Hi,
If you shave the heads a full thousand, it will bring the CR
up to high 9s low 10s depending on head gasket thickness,
& if he can afford it, get adjustable push rods.

For the cam click below
http://www.hotrodders.com/kb/search...ent=pub-9386959356855737&cof=FORID:10&q=how+to+choose+a+camshaft&sa=Search#1471

 

Shaving, milling,resurfacing,decking,etc

I am no expert on Mopars but a most definite compression increase will be a result of head shaving (surfacing) since a Mopar does not have adjustable valvetrain your head will sit lower therefore your pushrods are slightly longer by the amount of the milling and when you tighten down everything (rockers) you may wind up with valves slightly open, the cure is adjustable pushrods or in some cars you can insert little spacers (shims) under the rocker pedestals to bring every thing back up for adjustability, follow this increase in compression with a budget exhaust (duals) , a crossover pipe will also build some low end torque, which is what will result in the seat of the pants feel and get your buddies distributor curved to accomodate more initial timing, check with the mopar guys on whats best, then some jet work and presto you stand a gain.....
warning this may result in increased referrals to you as a tuning guru......lol
good luck and go ahead!!, just keep us all posted on how it worked out!

 

Thanks for the responses guys. What I'm looking for are some hard numbers from Mopar guys that have built these before like Richard Stewart 3rd provided with the .100 bumping the CR to high 9's. Does anyone know if its better to shim the rocker shaft or to install adjustable pushrods to correct the geometry, I guess what I'm asking is which of the 2 is a better more dependable approach.

 

Hi,
The adjustable rockers are the way to go but they are expensive, they come with a tube so if one were to shatter it wont take a bunch of other things out with it. I have to go out for a few hours, when I get back I'll get back on here & give you some help, there are other ways of doing the push rod lengths. This is a Canadian truck correct, as these trucks were Warlocks or Little Red Express trucks here in the US they're pretty cool truck's & fairly quick as well.
Rich

 

No its a US truck, like the one pictured below.

 

Hi,
Wow that truck is way cool, sorry it took so long getting back,
I have looked everywhere & I can't find the push-rods,
I had a set of shortened rods leftover from when I put the adjustable rockers in,
& from looking at what you have there,
you (your friend) should use the adjustable ones also.
Rich

 

Imo, your best best is to get closed chamber heads. Taking .100 off the 906's will mean the deck thickness of the head will be getting kinda thin and especially so if core shift is in the wrong direction. I've done them .100 before and well, it's much better just to get the closed chamber heads. 516 heads are dirt cheap but most came with the 1.60 exhaust valve but will respond pretty good with some mild porting and the 1.74 exhaust. Just don't think running the 2.14/1.81 will be cost effective on that combo. Also, the 78cc number came from a book, right? That's been a long time lie or is what the NHRA says they CAN be for stock class racing but don't quote me on that because it's been many years since looking at a rule book. All stock uncut open chamber heads I've measured (bunches) were not less than 88cc and most were 90cc. Closed chamber run around 80cc. A cheap alternative is to use a cam that builds a lot of cylinder pressure. RV cams is a type of cam that does that. It makes a low compression engine 'think' it is a higher compression engine. Problem with that is the combustion chamber design on the old Mopar heads isn't that great and you will have absolutely no quench so once the engine is up around 180-190, it'll ping. Best bet with the 906 heads is to use reverse dome pistons. You'll up your compression plus have good quench and with the right combination of cam, intake, carb, etc, that 400 will run dang good. Quench is important but with a piston that's .100 down (not even close to having any), 906's with a roof that's around .090 high than ad in your gasket thickness...then throw in old tech combustion chamber design...it's a recipe for poor quality performance. Good quench (no more than .040), decent compression (I like 10-1 at least for a street motor), a custon ground cam, it'll be sweet and will run fine on pump gas. Btw, I never use off the shelf cams for me Mopar engines or anyone else's that I do. They always run better with custom cams and that includes better than the Purple Shaft cams from Mopar Performance. And yes, that is a cool looking truck! Used to have a 69 and wish I still had it....along with about 20 other cars I let get away lol

 

A 3906 headed 400 has obviously already been apart...

I've had decent success with 400s by cutting the heads .030, running the FelPro composite gaskets and a 268 Comp Cam. With headers and a decent intake they pull pretty good.
The stock steel shim gaskets are around .020 and the Felpro composite gasket is .040 so it's really not much of an increase in compression, but it allows composite gaskets to be used without LOWERING the compression ratio and there is no monkeying with rocker arms or pushrods needed...
I use two of the "light" stock distributor springs to bring in the advance, the aftermarket "curve kits" have springs usually too light and the advance can cause the idle to be tempermental. I've seen advance pulled at idle with a Mr Gasket curve kit, quality piece that it was!

As was said above, 2843906 and later heads are usually slightly larger than claimed in books as far as chamber CCs go. I've had most iron 452 heads come in 84cc-86cc.