Vibration and blow by (engine tear down)

Thank you Paul for your advice.
I will set initial timing to 15* and total without vacuum 34* @ 2500 RPM, how much with vacuum on? 40* ?
Before i start the engine i will show here my timing curve for proper values

A lot of people smooth out and polish the cylinder head to minimize the risk of hot spots, so i did though why not do the same on piston... here are the result: First pictures original other two shows the modification

 

Robert

We do the same with all of our pistons. You can also round all the other sharp edges on the piston top where the valve pockets were cut into the piston top.

Would you also put the cylinder head on the bare block with 2 head bolts and scribe the bore circle on to the head.
I would like to see how much of the edge of the combustion chambers (around the spark plug) are exposed in the cylinder.

Paul

 

Yep, looks like detonation to me as well.

As far as the balancer goes, did you mic up the crank and balancer ID to make sure the press fit was right? Usually we have to hone those for proper fit. At minimum, I dust off the black oxide finish on the hone so it doesn't gall on the way on. You have to use a good high pressure lube when installing them as well.

I"m really surprised the the crank didn't break or bend hammering it on if it was actually so tight that it seized part way. I've seen it happen many times.

 

Aluminum heads generally like 34 deg max. Iron heads best to stay at 30 deg. Your bearings and rings will thank you.

There was a guy at the local track that was new to Buicks and said he ran 87 octane on his 70 GS 350. I told him he was leaving a haze on top end. I told him he would be better off running 93. After a while I didn't see him coming to the track. Showed up later with a Chevy and I said what happened to the GS. He said the oil light was coming on and he put some heavy oil in and sold the "POS" to a young kid.

I'm sure he pounded the rod bearings right out of it. And the rings too....from detonation.

 

Paul here two pictures i hope this helps, if not i will make like you said.
My car runs very rich at idle and i guess the spark plugs are to cold. I bought a wideband setup LC-2 from innovate to confirm proper AFR.
I had luck, all bearings are fine i don't know why, but i guess the proper oil system and clearance helped a lot protect it.

@ Ron, i used a sand paper and grind a bit of the surface.
The new balancer was in the engine shop with the recommend press-fit numbers from ATI so this issue should be solved.

 

Here is a before and after of my pistons... I would roll the edges a bunch to reduce the sharp edges:

http://smg.photobucket.com/user/sea...rage Pics/aa_zps62d0f026.jpg.html?sort=4&o=53

http://smg.photobucket.com/user/sea...ics/DSC00766_zps511b6e18.jpg.html?sort=4&o=62

 

Robert

You will need to clean the head surface so we can see the circle.
Here is an Edelbrock head I did as an example.
Notice how the intake valve side of the combustion chamber wall is in the cylinder.



Once you scribe the bore circle onto your head I will suggest that the chamber wall be move out to the scibe line.
Here is a cast iron chamber where I used a die grinder to bring the chamber out to the scribe line.
It will drop the compression ratio a little and unshroud the valves for better flow.



Also don't miss what Sean posted above #26 concerning piston edge rounding. Nice Job!

Paul

 

Here Paul, what you mean about it?

 

Remove the material shown by the zig zap lines.




It should look like this when you are done.



Paul

 

Thank you Paul for your adice. I will asap do the modification. Whats are the benefits from this? decreasing compression rate and ?

kind Regards

Robert

 

Better flow from around the valves and the edge of the combustion chamber is not in the cylinder where it can disrupt flow to and from the valves.

Paul

 

Update:

Im working on the heads and the new pistons are 0.0011" (0.03mm) than the old ones.
I bought head studs and ARP recommend 110 ft/lb torque. By the hone plate was a paper with a recommendation of 80 ft /lb.
Which torque numbers should be used by honing on the machine?

Unfortunately i did file the rings to the old size and they have 0.020 top and 0.024 second gap.
With the new oversize of 0.03 mm * 3.14 the would increase by 0.004" up to 0.024 top and 0.028 second to big?

Thanks for your advice

Robert

 

Use 110 ft/lbs on the torque plate

Try the rings in the cylinder after you hone it and see what you actually have for gap.

Paul

 

With vacuum advance working, total timing could be around 45-50 at low vac (part throttle)(assuming 34 initial plus mechanical). 50 or more deg total timing at low throttle opening should be no problem, although most people like to limit vacuum adv to 10-12 degrees or so. Just make sure vac advance drops away under heavy throttle and you end up with 34 total.

 

Here can you see the progress from my head, i hope its not to late...

 

Looks good.

Can you check the volume in the combustion chamber?

I believe this is what Robert did last time. Thanks for the reminder.

Robert

Don't forget to use an old head gasket under the torque plate.

 

Is the first picture the "after" and the second picture the "before" ?

 

Yes I see the remaining quench band. Thanks for taking the time to post pictures.

For what it is worth, I had this same conversation with Randy Gillis face to face concerning effective quench bands.
Randy was on the development team for conical dish pistons at JE. He is now part of RaceTec.

The conversation concluded that a 3/8" quench band width provides sufficient quench.
As the quench band width decreases from 3/8" the volume of air being "pinched" decreases and the resulting "squish velocity" or turbulence becomes less effective.

The small squish band adjacent to the spark plug is not significant compared to the large squish area adjacent to the chamber.

The Edelbrock head shown in post #27 does have an effective quench area adjacent to the spark plug.

 

Hey folks i did sleep very bad tonight, i still hope i can re-use my head.
Should i remove the valve's and unshrouded the area around the valve?

This progress will add some cc and my static compression is 11:1 so i guess its not necessary to bring it back to this level? just grinding the bottom to get in 10.0:1 -10.75:1 area..

Block is now honing on with 110 ft/ lbs middle (1,3,5) and remainder 100 ft/lbs . Old orange crush gasket between the block and hone plate.

 

Your head is fine to re-use. See my reply in post #43.
Yes, unshroud the area around the valves.
buicksstage1 has a very good picture of unshrouded valves in post 40

A 10.75:1 compression ratio would be good.
That would bring the dynamic compression ratio under 8:1

Paul