Reply With QuoteThe bolts should be ok. If they are streched out, put in ARP"s studs. First squart a few drops of oil in the hole maybe one of the rings is leaking.
I am going to pull the heads for the first time to do a valve job. I used ARP's and they are in Edelbrock RPM Performer heads (alum). Do I need to replace these head bolts? I have a # 7 cyl. down 25%. All of the others checked good on the leak down I did on a warm motor. The heads had a full port and polished by Chapion Marine in FL. The heads had 236 hours. The hyd. rollers have 361 hours.
With just pulling the heads should I replace anything else while I have the heads off? The cam is a Crane 1391741 Hyd roller with about 625 lift. I do a lot of cruising in the 2500 to 3000 range and WOT is just in short spurts. Change oil every 25 hours.
Thanks for any help, Mike
The bolts should be ok. If they are streched out, put in ARP"s studs. First squart a few drops of oil in the hole maybe one of the rings is leaking.
# 7 cyl. down 25%,
From what???
sorry, I did a leak down last fall and #7 was leaking on the exhaust. Just don't know why yet.
Yeah I think I'd pull the heads if you have one leaking out the Exhaust. At least the one for sure to see why, but sounds like time to kiss the seats
That's what I'm kinda thinking GC, thanks.
Hey Mike...Is the valve closing all the way? Is this an aspirated motor or blower set up? Did you have the exhaust manifold off when you did the leak down?
Before teardown, I would determine if #7 is leaking from the exhaust. Many times with aluminum heads, the valve seats go out of round slightly and causes some exhaust leakeage. Also if your valve job is marginal on that particular valve, a weak valve spring may add to the leakage problem. 25% leakage is not that bad if you know it's leaking through an exhaust valve. Many times when the engine gets hot, the valve will seal much better. There's not a real noticeable power loss with a cylinder leaking 25%. Doubt you will feel any performance difference.
Fiat48 reminded me of something. idea when we ran Southwest tour I remember checking valves & doing leakdowns & finding some of the holes leaking from the exhaust valves. Sometinmes they got so hot that when cooled & the moter stopped they didn't always stay straight when that valve was open! After we learned this we put a little heat in the motor & whamo, leakage down below 5% if I remember right because the valves were then able to straighten themselves out with enough heat & seat pressure!
You never know
Gnarley,
When I first started running alcohol we used to knock the valve seats out of round in a couple passes. 25 to 40% leakdown most of the cylinders, leaking right out the exhaust ports. Rapping the valve when hot with air pressure applied, we'd get most of them to seat back down to 10% or better. Lapping seats by hand was done after qualifying. That's back in the days when we ran small stock valve seats, the motor fat and the timing laid back. Took us a while to realize all we were doing by laying the motor back was causing extreme exhaust valve temps. I saw 2500 degrees on the Pyromteter more than once. Todays heads are much better (come with much heavier seats) and we do a valve job about every two years, unless we miss the tuneup real bad.
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