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| Opinion on head recodition https://www.ausmini.com/forums/viewtopic.php?f=2&t=41828 |
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| Author: | clubmn [ Thu May 08, 2008 7:02 pm ] |
| Post subject: | Opinion on head recodition |
OK so i droped two heads off to get reconditioned. First one: avonbar tuned 12g940 turbo head. Second: Stock: Cooper 12g295 Well good news is they both were not cracked, but now what should I do to them, Should I do the works (cost me stacks, valves, guides......) do you think its a good idea to put hardened valve seats in both? Finanly i dont really want to skim the cooper head incase I decided to use it on a different application. Should i, must I if i want to use it on a stock moke donk? and how much should i skim. 50 right? |
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| Author: | 1018cc [ Fri May 09, 2008 8:44 am ] |
| Post subject: | Re: Opinion on head recodition |
clubmn wrote: Well good news is they both were not cracked, but now what should I do to them, Should I do the works (cost me stacks, valves, guides......) do you think its a good idea to put hardened valve seats in both? Finanly i dont really want to skim the cooper head incase I decided to use it on a different application. Should i, must I if i want to use it on a stock moke donk? and how much should i skim. 50 right?
It is up to you how far you go with them but if it was me I would go the whole hog (it is already off the car anyway). Personally I would put hardened valve seats in because they aren't bringing super/leaded/Lead replacement back! You don't have to skim the cooper head but your compression will end up lower than stock if you don't (not good for power and have no balls down low). GR reckons that if you take anymore than 0.060" off in turbo applications you will blow gaskets, and any more than 0.080" off in N/A motors you will blow gaskets. The more meat you leave on the head the better IMHO (to a point). If you took 0.050" off there is still heaps of meat left - but I would be sure that's what I wanted to do with the head though. My 2c |
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| Author: | Mike_Byron [ Fri May 09, 2008 10:32 am ] |
| Post subject: | |
Your recon bloke will have a pretty good idea of what each individually will need. Usually for both, they need skimming as 80% of all heads are warped. Also they will need valve guides, maybe valves and certainly valve seat and valve reface and an acid dip to get rid of all the water way gunk. Now on the individual heads 295 - just aweek back somebody posted about a 295 head and the replies gave the std deck height measurement which from you can calculate has already been skimmed - taking off .050 thou is quite common to increase compression. You don't need to go higher because then you run into problem with octane ratings. Fitting hardened exhaust valve seats is easy and not expensive. I have had several heads done and the cost is around $300. I supplied the valve guides (ex-ebay) which were bronze though. 940 - much of the above applies except that in my case the recon bloke wouldn't fit hardened exhaust seats because some of the valve seat is in the direct explosion area and he was uncomfortable with uneven expansion and contraction of the seat and the risk of the seat coming loose at high revs - if that happens, the engine is all over, red rover. Thats been a debate on here several times with a number saying he was wise and others saying it hasn't happed to them. For me - I just use flashlube. Mike |
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