head planing

[Don Dulmage <big-d@xxxxxxxxxxxx>]

[AD removed for archives]
-------------------------------------------------------------------
Help us support US Troops ? Just Register Here.
caadlVxbOyW3Na/Permission Data
-------------------------------------------------------------------


First lets do a bit of thinking. The b and Rb engines are designed to have a compression ratio of 10 to 1 (in round figures) This requires a specific deck height and a specific combustion chamber volume. Proper chamber volumes are 80 cccs (i believe one year is 79.5)  and that would be for what we know as engines with 906 heads. (346 and 452 are similar. )
So when we bring a clyinder head to that spec we are not planing a big "gob" off and making it super thin etc etc, we are just bringing it to factory specs or the specs it was designed to be in the first place. 
Typically I find many of these heads when measured are over 90 cc or better than 10% oversize. Why? Because the factory just didnt worry about it. (0 cc requires 090" to be removed to get to 80cc. (.010" per cc) So it is not unusual to need to remove 080 to 090 just to get the heads at stock specs. Those who are already shouting please read that last line again " just to get the heads to stock specs"
I cant help that , it is just the way it is. 
As for pushrod lengths. I always check to make sure the lifter is no more than half way in its travel.(or even a bit less or higher) I do that before I put the intake  and tray on.
A few thing work into this. Are both head machined the same (rocker arm height  which can very from casting to casting, deck hieghts of the actual block which can vary quite a bit on some blocks and are right on on others. Is the cam bored in the centre of the block(They are not always so. This week we had a Ford that was 030 to the pass side of the block)) All these thing afffect the pushrod length and fit so we alway check it and shim iof necessary which is by the way a piece of cake. Also so cam manufacturers including one of the most famous brands around dont always make their base circles the same as stock cams  . This can be a real problem and it is why they often recommend adjustable rockers. Pushrods are available for most engines overnite that are plus .100" and that helps too. On the 400 cheapie we have a set of 346 heads with 2.19 intakes and 174 exhaust. the heads were ccd to 79.5 which required I think if my memory serves me .091 on one side and .095 on the other head. later beciase we were using Felpro Blue gaskets which are approx 020" thicker than the original factory steel gaskets we removed  another 020" to allow for the thicker gaskets without lowering compression.  On the 400 we ran them with stock rockers and 045" shims. 
It seems to me we couldhave run them without and they would have been ok but just. Most lifters have quite a bit of travel because of manufacturers tolerence so there really is no fixed answer to your question. Just check anytime you wander of the stock production path. It only takes a minute and shiming s no big deal. 
Another thing which causes huge amount of trouble with stock non adjustable rockers is valve stem heights. many shops which are chevy oriented are not aware tese must be set on Sb and BB mopars , Olds engines and Ford FEs. I see thsi probalm almost montly. I have a recently done 340 hee done by another shop which has burnt valves anddamage because thestem heights were not set anda couple of valves never actually touched te seat. 
Sorry for the long post but there is no easy answer. When in doubt check it out
Don  
Author of
Return to Deutschland (True Adventure)
Old Reliable (Mopar)
http://stores.ebay.ca/Don-Dulmage-Enterprises
[Non-text portions of this message have been removed]

[AD removed for archives]
-------------------------------------------------------------------
Investigate just about anyone and anything with Web Detective!
caadlCmbOyW3Nf/Web Detective
-------------------------------------------------------------------

----
Please address private mail -- mail of interest to only one person -- directly to that person.  I.e., send parts/car transactions and negotiations as well as other personal messages only to the intended recipient, not to the Clubhouse public address. This practice will protect your privacy, reduce the total volume of mail and fine tune the content signal to Mopar topic.  Thanks!

'62 to '65 Mopar Clubhouse Discussion Guidelines:
http://www.1962to1965mopar.ornocar.org/mletiq.html. 



bOyW3N.