Power after head replacement

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Power after head replacement

Unread postby dudedog » Sun Jun 22, 2014 4:42 pm

Its been a long time but I have my LS running. Last fall I lost my head. Winter put a hamper on things. I was going to rebuild but found a new head. I had help at the time but I could not get him back so between the head and my engine its been fun piecing it back together. Came to me in pieces. I feel good about getting it back together. The engine fired up and sounds good. The problem is I dont seem to have all my power. I was wondering what the input is about this issue. I am believing I did not get the head torque enough or I am a cog off on timing. Maybe a vacuum issue but I cant find one. Any input is appreciated on this matter. I am so happy to have this running again. I would like to be travelling again. I seem to be gaining some power driving it around town. The head bolts torque to 70lbs. I never felt that to be tight enough. Easy torque.
Thanks Again for any guided help as to what is likely causing my lack of power.
Fred

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Re: Power after head replacement

Unread postby scott.edwards » Sun Jun 22, 2014 8:33 pm

Hello Fred,

You may want to list the year, model, engine, transmission. If you do, you will probably get more help.

Cheers, Scott
91 LeSharo


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Re: Power after head replacement

Unread postby 'derfnarb@yahoo.com [Lesharo-owners] » Sun Jun 22, 2014 9:10 pm

1988 5sp renault. Just cant get enough power after head replacement. Should I have full power immediately. Engine slightly backfires at low rpm. Acts like timing is out.


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Re: Power after head replacement

Unread postby scott.edwards » Sun Jun 22, 2014 9:19 pm

It sounds like the timing is out..... agree! Check your rotor and cap as well as the ignition wires..... make sure in ok shape.

Yes, full power immediately.... no backfires, and should idle immediately as well.

It is easy to check the timing on the 88.... line up per the manual, using the rear viewing window in the cam cover. It's in the manual.... should be dead on, or it may be out a tooth.

Cheers, Scott


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RE: Power after head replacement

Unread postby 'Mark' » Sun Jun 22, 2014 11:56 pm

Sounds like timing belt off a by a cog.




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RE: Power after head replacement

Unread postby Rick Heslop » Mon Jun 23, 2014 5:07 am

Fred,

Have you checked the valve lash?

Also did you torque the head as per the pattern in the book?

Not sure when, but you should re torque at some point.

Hope it helps,

Rick




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Re: Power after head replacement

Unread postby 'derfnarb@yahoo.com [Lesharo-owners] » Mon Jun 23, 2014 11:04 am

Yes, I torqued the head as the book. 3 times. As I mentioned the final torque of 70 lbs did not seem all that tight considering how hard they were to get out. Its a brand new head. Old bolts. Hopefully I dont have more lower end probs. I adjusted the valves also. Hopefully to spec. If that were a prob I feel I would hear noise. The engine runs good and starts but there is idle hesitation. Does the lower timing mark point straight up or slightly to the right pointing at the bolt shown on the pics in book. I was told I should see this through the cover. I previously did this with the cover off. I am a backyard mechanic. I had no choice by doing this myself. I am going to tear this down and look at the timing close. It should be torqued to spec. Is it possible to get the fuel injectors hooked up wrong?. The idiot who originally helped me tore down fast and would not give me time to observe hookups. He was never found again. A know it all kid.
Thanks for the comments. I feel its ether the head torque or timing. The oil appears fine. No mlky look. I did find a lot of water in the oil pan prior to the head replacement. I feel I took a huge gamble trying to save this. They are old and getting very difficult for parts. I had no choice but to use a cracked exaust manifold. You cannot get new ones anymore. This should not effect this I believe. Small crack.

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Re: Power after head replacement

Unread postby 'Mark' » Mon Jun 23, 2014 11:23 am

I don't see this as a head torque issue. Insufficient torque will usually show up many months later after the gasket has been heated and cooled many times. An undertorqued head will seal for some time (relatively). If it is running rough at idle, with a consistent roughness, you probably missed the timing belt. Did you recheck this? As far as injectors, given the injector harness, it's usually pretty difficult to mix them up. Even so, it would probably result ins cyclic roughness when it runs, like a galloping horse (sort of).



Mark




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Re: Power after head replacement

Unread postby 'Scott.Edwards' » Mon Jun 23, 2014 11:38 am

Hi Fred,

You check the timing with the cover on.... there are 2 windows, one on the
front, one on the back..... just take your time, read the procedure, follow
it, it will them make sense to you. Yours will be the newer style set up in
the book (there are 2 procedures, it outlines both), not the one with the
dial gauge on the distributor. I cannot remember, but think you need the
dist cap off so you can identify tdc when the dist rotor is pointing at cyl
1...... cyl 1 is at the transmission end of the engine.

Start with that, then move on if this is not it. Low power and the slight
backfire says to me that you are probably off on the timing.

Take care,

Scott
91 LeSharo


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Re: Power after head replacement

Unread postby 'derfnarb@yahoo.com [Lesharo-owners] » Mon Jun 23, 2014 1:43 pm

The timing looks as close as I can imagine. The pics in the book can be deceiving. One picture shows both dowells on crankshaft straight up and another shows them at 30 deg. I have the notch straigjt up. Cover is off. I cant see crap with the cover on. Notch is straight up on cam and crank. I am going to move over one cog and see what happens. Timing belt is off now. It really looked like the timing was correct. It sure wont run right. I wish I would have taken this out back and shot it before putting more money in.


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