Edelbrock RPM Heads on 383 - Bore notching for valves

[road chicken]

Does anyone have first hand experience bolting these ( 84 cc) heads onto a 383 with a +.030 over bore (4.280) ?
My question is about notching the bores for clearance.
I looked at the instruction and they say to check and give .035" between any part of the valves and the engine. The Mopar Engine Bible says the big valve heads ( 2.14 and 1.81) will fit the 440 bore ( 4.32) no problem and the others should be checked and clearanced (sp?) as necessary. Ok I wasn't planning on the extra 40 hours to do this,if necessary.

Then I see this article:

http://www.moparmusclemagazine.com/tech ... ewall.html

Same configuration I have-( except my pistons are actually .015 down in the bore) and I am looking at cometic head gaskets with a 0.027 thickness and 4.350 bore to bump the compression from 8.94 to 9.5.


So what gives, did these guys just decide to wing it and hope 0.015 clearance was just enough? Or do the Eddys have enough clearance as bolted on?


Thanks, RC

[moparite]

Same configuration I have-( except my pistons are actually .015 down in the bore)

Do you have everything exactly as they did? Same cam rockers etc.. It seems in the article they did a bit of calculation before hand. If you are not sure there is an old school way of figuring valve clearance. Put some clay on the top of the piston and then see what the actual clearance is.

[road chicken]

Old School Best School. I will do that regardless because that is the only way to "KNOW" whats there for the piston to valve clearance. The cam lifts are close and the duration is less on mine. But the Valve to Bore clearance is my concern, which the clay will also reveal. I just wondered what the rule of thumb is on that. 10, 15 20 thous ?

[moparite]

If it where my engine i would go with more the better. You don't know whats going to happen down the road. Valve hop or a spun bearing could cause things to go catastrophically wrong. I'm wondering if you built the engine from the article or what? If it where me i would have thought this out long ahead of time and chosen the parts accordingly. Some reading for you...
http://www.racingheadservice.com/rhs/pi ... nce-guide/

Did you get any info from Edelbrock with the heads? I would see what they recommend.
http://www.edelbrock.com/automotive_new ... /index.php

[road chicken]

Yeah..ummmmm....no, I 'm not asking about piston to valve clearance- I'm interested in the cylinder bore wall to valve clearance. What is the clearance called for there and how is that figured? As I stated Edelbrock says .035 from the other engine parts- certainly piston to valve is included, yet no one ever mentions doing cylinder bore notching- or even checking the valve to cylinder bore wall clearance- when bolting these heads- or any mopar head with the 2.14/1.81 valve combo on a 383. In fact the ONLY time I have seen this talked about is with the 1.88 Max Wedge exhaust valve.

The engine was built after long hours in the "bible" and even they only make mention of it, not how to check it and what are the parameters for doing so, when, and why. What are the tolerances for side to side valve play and at what ratio to the lift from the seat? What expansion rate is there in the metal and , since Al going to expand at twice the rate of the iron block, how does that need to be taken into account? Does it affect the inner two cylinders clearance less than the outer valves of the outer two cylinders? If so, how does that need to be compensated for?

and an edit- the clearance is 0.150, not 0.015- I miss typed that. So It won't/ shouldn't be a problem, but now I want to know why that space is required. Unschrouding ( sp?) of the valve for flow ( obviously) and play in the valve.

At least, apparently, I wasn't the only one that missed this section of Engine building 101

[moparite]

If i understand you correctly you are worried about the valve touching the cylinder wall? it shouldn't be an issue. If you put the head on with no spring and then let the valve drop into the cylinder you will see it's beyond the point of your cam lift and rocker arm ratio. I think the valve spring would bottom out before the valve would touch the cylinder wall.

[road chicken]

If i understand you correctly you are worried about the valve touching the cylinder wall? it shouldn't be an issue.

Exactly- thats what i was worried about. As it turns out I had transposed a number in my calculations , so I thought I only had 0.015" clearance when it is actually 0.150" clearance to the bore. Stupid mistake on my part.. Sorry about that.