Power after head replacement

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Power after head replacement

Unread postby dudedog » Tue Jul 01, 2014 2:26 am

I have been posting about a power issue after installing a new head. I am fairly confident about timing and not feeling its plugged exaust. Its been brought to my attention that I may have done the valve adjustment wrong and before I redo I would like the group input. I tried to follow the manual instructions. I believe I did my first adjustment explained at #1 tdc. I have been told I should have done the first adjustment on the first mark clockwise from tdc. Can I get this confirmed. Im told this is will greatly effect the power.. Looking forward to this conformation. I am hoping this will solve my problem as I would like to take this to Alaska.. Fred

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RE: Power after head replacement

Unread postby 'Mark' » Tue Jul 01, 2014 3:20 am

Here's my 2 cents. I have done many valve adjustments on high performance engines. After doing so many, we rarely looked at timing marks. We simply pointed the cam lobe away from the rocker arm. This is usually the lowest point of the cam. Generally, if it weren't for the fact that engine components expand as they get hot, we wouldn't have any valve lash at all. Usually, the exhaust valve lash is larger than the intake lash as this valve gets hotter than the intake valve thereby expanding more which in turn, need more clearance. Basic thermal expansion. The worst thing you can do is have the valve adjustment with no clearance as this will hold the valve slightly open during the compression stroke. This will both reduce power and burn the valve and seat. Having too much clearance will generate a lot of clatter. Luckily, the manufactures have taken all of these elements into consideration and have come up with the optimal valve lash adjustment specs. There will be minor cam timing differences with different valve lash but shouldn't affect power dramatically (unless you are holding valves open).

Now for the other note. I haven't done a valve adjustment on this particular motor yet. It looks pretty standard to me, though. I imagine that some of the others may have thing to add.



Mark




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Re: Power after head replacement

Unread postby RonOhler » Tue Jul 01, 2014 7:54 am

Hi,
I don't use the process of - set the engine at this position and adjust these valves - turn to this position and set these other ones. I've seen it be so fussy that it is real easy to be slightly wrong in location and mess up the lash setting. There are only 8 to do. I'm far more comfortable recommending only setting both at the same time while on the compression stroke of each cylinder. I usually use a wrench on the alternator nut or crankshaft harmonic balancer bolt to roll the engine over.
Best,
RonO



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Re: Power after head replacement

Unread postby ingles_hank » Tue Jul 01, 2014 8:12 am

there are complete service manuals in the "files" section. The engine sections give easy method for adjusting valves.

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Re: Power after head replacement

Unread postby 'b.elliott' » Tue Jul 01, 2014 10:25 am

Hi Ron
,Rick and others
Maybe he has my problem ,one of the timing marks was all but invisible I
screwed up the first time until I saw the "missing"mark
Brian


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RE: Power after head replacement

Unread postby 'Mark' » Tue Jul 01, 2014 10:41 am

This is why the process that both Ron and I described don't actually use the timing marks. He makes sure it's on the compression stroke and I usually point the lobe away from the rocker. For those that understand engine operation, it makes sense to use the base radius of the cam, especially when it might be difficult to find the timing marks. Besides, it's usually much easier to see where the cam lobe is pointing with respect to the rocker, at least for me.



Mark




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Re: Power after head replacement

Unread postby Jim Kielty » Tue Jul 01, 2014 10:52 am

Remember #1 is at the firewall end instead of at the front where it's
supposed to be. ;>)

Jim K



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Re: Power after head replacement

Unread postby 'derfnarb@yahoo.com [Lesharo-owners] » Tue Jul 01, 2014 6:07 pm

Thanks for the responses. I dont have any rocker noise and so for I really have no gotten this very hot. I have only driven it a few blocks so far. Is there a consensus that this could be my problem?


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Re: Power after head replacement

Unread postby 'Mark' » Tue Jul 01, 2014 10:00 pm

I assume that you mean you have little rocker noise. Unfortunately, one cannot measure valve lash by noise (However, you can usually tell if one is horribly out of adjustment). When I would adjust valve with a rocker style engine, we would verify that each valve had some clearance by wiggling the rocker to make sure there was clearance before the adjustment. If the valve was tight, there was always the possibility of a burned valve. The point that I'm trying to make is that tight valve as far worse that loose valve lash. Time to get the feeler gauges out!



Mark




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Re: Power after head replacement

Unread postby RonOhler » Wed Jul 02, 2014 12:04 am

With these being push rod engines you can't see the camshaft lobes. So = you have to use a different approach. But it's simple once it's understood. Oh - for the day's of working on Chevy Vega's and Ford Pinto's with their open overhead valve - top mounted camshafts.
Best,
RonO



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