906 heads ?

[Snoman]

Hi guys, I am in the process of rebuilding my 69 383 it has the 906 heads and i was wondering how to tell if they have been milled down, I was looking at maybe a measurement point on the head or ? The motor was built about 25 years ago by a previous owner he said he had it built up pretty good it is .30 over high dome pistons looks to be zero decked or close. healthy cam i think he said 525 lift. let me know what you guys think of the heads i am trying to figure out the cc size i think the 906s are 88cc stock. Thanks

 

[Cranky]

Unless they have been milled a lot, the best way to tell is to measure the CC's of the chambers. Open chamber heads are usually right around 90 cc uncut. I've checked them with a depth mic and they are usually close to .090" deep from the gasket surface but they can vary from chamber to chamber. I found a set of heads that varied .015" on the same head!

 

[Snoman]

ok thanks for the help

 

[coronet66]

I just had my set of 906 heads done port, polish, decked all new valves, guides, seals, 3 angle valve job all for 800. I got the motor back together 2 weeks ago and what a huge difference in performance from before. good luck with yours

 

[Meep-Meep]

A quick check to see how much your heads have been cut is to measure the thickness between the spot face for the lower row of head bolts and the deck. An uncut head should be 1".

 

[Snoman]

OK Thanks meep meep, I just got the rest of the motor apart, looks like the heads need repair, it has a cam in it that says on the end CC 305H10 and P2434 I think it is a comp cam 525 lift 305 duration, and on top of the pistons it says .030 L 2293, they are a high dome forged piston, i googled that number and cam up with a trw piston 22cc dome, anyone have any experience with this kind of combo? it also has a old torker intake and a 830 holley and headers and 4.30 gear.. Thanks for all the help guys, later

 

[Meep-Meep]

That's a pretty big cam and sounds like it has the compression to match. I hope you are planning on running race gas. If this is for the street I would get some flat tops and get the CR down to 9.5:1 with iron heads. Put a cam that will give you about 180 PSI of cranking pressure, which should be about 270 deg of duration.

 

[Snoman]

I have been running it on the street for a couple years I had a rod bearing go out on me so I am in the process of rebuilding the bottom end, What kinda HP do you think a setup like this is capable of? What do you think it is capable of with a good set of heads.. Thanks for the help guys. later