21 replies to this topic

[Quinn]

Back Story,

Rebuilt the motor in an 87 SI.  Had the head milled.  Not sure exactly how much was milled (will measure tonight).  

 

Events :

 

Primed motor with no fuel injectors hooked up, fuel pump disconnected, and ignition unplugged.  Saw a good amount of oil pumped up to head.

Started engine.  Had a big vacuum leak (brake booster disconnected). Engine rev'd up fairly high before i could turn it off.

Connected booster.  Restarted car.  Idled great for an I-4.  Finished fixing all the minor leaks and let it idle until the thermostat opened and the radiator fan kicked in.  Verified the temperatures with a laser thermometer.
Next day I lowered the car down and drove it around the neighborhood.  Power felt adequate but I didnt exactly goose it to see how it would respond.  Was running open loop (no 02 sensor) and the brakes are still iffy.

Drove it home and park it in my driveway while I hook up parts to pass local inspection.  Hour later cant restart the car.  Pull valve cover and realize 1 in every pair of intake valves is "sticky".  Cylinder 2 particular is bad and wont come back up.

 Before removing the head I verified the cam timing was as I set it (note : as i set it could have been wrong but doubt it).  I did a leakdown and the only air loss was through rings on 1,3,4 (as I expected to find, 2 miles on motor).  Number 2 i had real bad air loss through the intake valve.  Tear down head and find the four intake valves all hit the top of the piston. #2 being the worst.   Head gasket looked in great shape. No evidence of coolant breaching the chamber.

 

 

So long story short....what happened?  My theories :

 

1) Maybe the valve guide/valve stem geometry/clearance were off?  I dont recall if they did all intake valve guides or just some.  This is my present theory of choice.

2) Could the head be milled so far that I need a cam advance gear?  I did not clay the piston to valve clearance. I can do this tonight.

3) My cam timing was off.  I used the proper marks.  I spun the motor over 20 times+ by hand to verify no binding. I will remove the cam gear tonight to verify that my key was in the 12 o clock position.

4) Weak valve springs and the high rev startup condition could have caused the impact?  Why did it idle and drive great afterwards though....  Why is it that one in every chamber took the load?  Does one valve open before the other for a swirl effect?  Is this so dramatic that only one would ever hit if the clearance is close?  Maybe when the engine was warm the valve guide/stem clearance increases and I was able to continue driving it.

 

 

I find it odd that the 3 valves that made impact but still seal (1,3,4) are still "sticky".  They could be slightly bent which I think would explain their lack of enthusiasm for closing?  I'll take it to the machine shop tomorrow morning and have them help identify the issue.  I'm sure they will blame the engine timing/me.  

 

I'll try to post pictures below.

 

 

Quinn

Edited by Quinn, 31 July 2014 - 02:55 PM.

[Quinn]

Here is a link to an image of the bottom end :

 

http://imgur.com/HDYEnzv

 

 

Here is one of the head itself :

 

http://imgur.com/ksrjvi2

[cbstdscott]

#3 is the answer.

[Quinn]

cbstdscott :  I will try tonight to verify that my cam keyhole notch is indeed 12 o clock in reference to the marks.  have you ever seen it not be?  How could that even be a possibility?

Here is the photo of the cam+camgear :

 

http://imgur.com/BT48JmJ

 

Are you thinking I have this upside down?  Would that not totally screw with the firing order or does it run wasted spark and I lucked into some operating condition? 

 

 

Quinn

[cbstdscott]

The question is: What is your crank position? Both the crank and the cam have keyhole notches. Both of them must be at 12 O'clock.

[Quinn]

Certain the bottom end was at TDC.  White mark on timing cover mark.  Verified that with the head off as well .  Easier to see the piston locations with no head!

Quinn

Edited by Quinn, 31 July 2014 - 05:02 PM.

[Quinn]

Pistons are in the exact same orientation and location as when removed.  Valve reliefs must be for exhaust and done so to minimize part numbers of unique pistons?

[Quinn]

Notice your drawing shows valve indents on the exhaust side.  

 

 

Here is another example :

 

http://www.redpepper...showtopic=43898

Edited by Quinn, 31 July 2014 - 05:05 PM.

[Quinn]

All of those above posts were in response to a question regarding piston orientation.  

 

Quinn

[cbstdscott]

Certain the bottom end was at TDC.  White mark on timing cover mark.  Verified that with the head off as well .  Easier to see the piston locations with no head!

Quinn

 

The white mark on timing cover is the ignition timing mark X degrees (I have forgotten the exact number and I am too lazy to look for it) before TDC. That is not a mark of TDC. The best check for TDC is to check the notch on the crank.

[Mark L]

All of those above posts were in response to a question regarding piston orientation.  

 

Quinn

Sorry, I deleted my post before.

I really think you pistons are in backwards.

[cbstdscott]

That would do it.

[Mark L]

Check out this tread

http://www.redpepper...=1

[Quinn]

This motor was never dissassembled until me.  That is the orientation the pistons were in from hondas factory.  Your service manual drawing even shows it the same way.  I realize its counter intuitive.  I thought they were backwards when i removed the head.  I've had a long history of backwards piston debate (old d16z6 build was a vitara 300whp turbo).

 

Ignition timing marks are not white. The white mark and the timing belt cover arrow do line up as TDC.  I have no head on my car.  You are correct that the ignition timing marks which are not white are in fact before TDC. This is at least valid on my car.  I can snap some photos if it goes against the normal convention for these motors.

 

Took the cam gear off.  The woodruff key was correct and at 12 o clock.  This was also the same position it was in before dissasembly.  So unless the belt is jumping back and forth I feel confident the bottom and top end were in alignment.  Or at least not off enough to have valves contacting pistons for gods sake!!!

Any other ideas 

Edited by Quinn, 31 July 2014 - 07:09 PM.

[rallyxcrx]

  Looking at another dia. of pistons, it looks like the pistons are in right. I've never heard of anyone hitting an intake valve, only exhaust, timing has to be way off. Set the engine at TDC with the head off when putting it back together, the keyway position doesn't matter, just the 2 marks on the camgear. Best not to use an adjustable cam gear unless you have more than .020 off the head, Dave                        

Edited by rallyxcrx, 31 July 2014 - 09:19 PM.