I just mounted the edel 6006 heads in preparation for checking valve clearance, and I noticed the valve edges are very close to the cylinder walls. I installed the #1 piston, and left the rest out so I could look up and see what was going on with the valve to cylinder clearance. I still have to mount up the rocker arms to check piston to valve, but when I saw how close the valves were I thought ask you guys about it. Is it necessary to bevel the cylinders in way of the valves? If so how much? How close constitutes "shrouded"? As always thanks for the info.

Gears... 4.10 rear and 4.09 front. C6, NP 203. Right now open differentials both ends, looking at the "no-slips" from Power-trax. Tires to be......35's probably, still looking and figuring. It's a work in progress, if you know what I mean. L2291f30 pistons, deck machined to achieve 0 deck, about .020" removed. .010 under on crank and rod journals. Line honed. Balanced, Harland Sharpe roller tip rockers with "rocker Arm Specialties" stands with end supports. ARP everything. Stans tri-Y headers, the balance of the exhaust to be determined..... probably 2-1/2", maybe with X/H pipe equalizers. Windage tray, HV oil pump, and the Oil mods on everything except oil to the rockers, at this point. Edelbrock performer RPM heads, manifold, carb(750), and cam
Tom

 

Shrouding is a term to describe how close the valve is to the combustion chamber and the cylinder wall. All valves are shrouded it is just a matter of how much. The 6006 heads will work on a standard bore 390 pretty good so since you are .030 over you should be just that much better off. Sounds like you have a very nice build going. You are going to use the performer RPM cam with a 4X4 truck? May want to go with a little smaller cam with a dual pattern. You can go smaller and not give up peak horsepower and gain low end torque.

 

I wouldn't worry about the valve clearance. The 6006 head has the same valve size and spacing as the CJ head and lots of folks have been putting those on their 390s for years without chamfering the walls. They'll flow plenty good as is.

That RPM cam is pretty big for a 4X4, might want to consider a smaller grind from some other vendors. Also that X-pipe can make your engine sound a little buzzy at high rpm, I'd go with an "H" instead. Other than that, it sounds like you are well on your way.

Barry

 

Thanks for the info. Would a little chamfering be a bad thing? The length of the combustion chamber measures about 4.160", It looks like more. I am thinking I should atleast chamfer enough to match the cylinder to the combustion chamber. Or do you think it's a waste of time?
I am still thinking about the cam. In another post I listed some of my other choices. Right now, I am putting everything together checking all the clearances. Then I'll make the final decision on cams. I am taking things slow and sure.....Unfortunately, work is intefereing with my project! (LOL)
Thanx again for any input
Tom

 

One thing to remember is that the valve spacing is not the same as the 428. You have to shim the intake rocker .060" away from the rocker to get the correct alignment between the rocker and valve.

The heads will fit the 390 - that's what I have on mine. What Edelbrock recommended to me when I asked was to check the valve to bore clearance on the exhaust because they felt that it was most extreme on the exhaust side. Also some un-shrouding of the bore on both the intake and exhaust sides of the bore would be helpful. Remember to be careful to notch only above where the top ring seats at TDC. Do not remove too much material as the block could be weakened or you could break into the water jacket.

That was Edelbrocks recommendation. Remember that the stock bore on the 428 was 4.13" and the 390 .030 is 4.08" This leaves a difference of .050" in diameter so you are looking at removing about .025" of material on the bore by each valve.

Personally - check your clearance. If it looks good leave it alone. If you feel the need on remove a little. Remeber the more you remove the lower your compression ratio will be.

Reggie

 

Just a little note on rocker spacing. I ordered a kit from dscmotorsport.com that had more than enough shims to space everything out and had aluminum spacers to replace the springs. It worked very well.

 

Thanx for the info. The stands and endsupports I got from Rocker Arm Specialists, came with an assortment of shims and the spring replacement spacers. ANybody know what the side clearance should be?
Tom

 

"Eyebrowing" or grinding a shallow notch where the valves would meet the cylinder block is a fairly common operation when prepping engines for high performance use. Typically it's done for valve clearance reasons though, not necessarily to improve mixture flow, when you install a high lift cam. Check and see if there are any high performance ford books at your local library or possibly even do a search on that type of mod on the internet.

 

In my opinion it is a VERY GOOD idea to match the chamber to the block.
be careful of the top ring and the water.

It is a simple mater of square edges in the flow path - it is better if they are not there.