Vibration and blow by (engine tear down)

I appreciate your points and concern. Here is a more detailed version of mine.

My conversation with Randy was mainly because I was getting ready to order another set of pistons for a 1970s wedge head engine.
I needed to know how far out from cylinder wall a quench pad needed to be to create enough squish velocity to be effective.
The answer was 3/8.
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The further the squish area extends out from the cylinder wall, the sooner the piston will move air latterly across the cylinder.
The piston is also at a higher velocity resulting in a higher squish velocity.

As you decrease that distance the squish air volume also decreases and the piston must be closer to TDC to produce the same squish velocity.
The problem is, as the piston gets closer to TDC its velocity decreases and at some point is moving too slow to squish air at an effective velocity.
It was determined that 3/8 distance from the cylinder wall is sufficient and less than that gave diminishing returns exponentially thanks to the decreasing piston velocity as it approaches TDC.

Looking at the very small pad extending out from the spark plug side of the combustion chamber that is far less than 3/8, it would seem that any contribution would be very small and insignificant compared to the quench being created by the major squish area.

Also the major squish area is creating turbulence early in the combustion process where the minor squish areas act later where combustion is more complete making them less effective.

The edge of the combustion chamber protruding out along the top of the cylinder wall certainly poses a restriction to exhaust gas flowing towards the exhaust valve and that same edge can hold heat increasing the chance for detonation.
If it is not large enough to be beneficial as quench then it is better being removed.
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Another reason that the chamber is smaller than the 455 bore might be so it will work with the smaller bore of the 430.

Paul
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Actually the only part of my reply that belongs to Randy is the 3/8" dimension. The rest of the info is from me and I stand by all of it.
I simply was giving you my reasons for not having concerns for removing the small amount of material that you consider crucial.

This combo has problems because the cylinder head came in with less combustion chamber volume than the expected 64 cc
and the cam was ground with a smaller LSA than was specified.

At this point we can respectfully disagree and leave it at that.
What I don't want to do is continue going back and forth to the point where no one wants to read or can find what both of us previously wrote.

Sometimes I change the font so I can easily find the info I wrote for future reference.

Paul

 

What engine problems did you see after you mistakenly modified the combustion chambers?

 

Collecting data is extremely important to our shop.
Would you please share some of the details of how your engine responded after the heads were modified?

Paul

 

Chris and Paul, i don't want a battle here. Its like the oil guys, everyone means he knows the best oil, but they only have an opinion for the best oil...
Im sure both are right an a bit wrong. But Chris, why write you so aggressive agains Paul? why you don't answer what happens with your engine?
My target here is get good information to built a reliable engine. I'm very thankful for any advice's and i will not touch the other head since this issue not clarify.

I take some photos for better analysis and i have did start the grind around the valves:

 

Chris

I apologize for being hesitant to reply to your posts. That was rude of me.
I was hesitant to do so because of some of your previous interactions with other board members.
I appreciate the fact that you are passionate and are willing to contribute to the success of others.


I'm only going to share this next part because you asked about our research and in no way do I want this to mean I think we are a big deal.
This past year was a humbling experience for me as we ventured out into new racing territory on water.
We managed to take the points for the year, got rooky of the year and set the 1 mile course record but it was costly as the learning curve asually is.

We (as in the shop and race team) have spent hundreds of hours of track time developing our program.
We continue to work with some of the best head shops including Al Dicksen who is still our main source for heads and technical info.
Thanks to Al Dicksen, Driver and shop owner Kirk Rogers was able to win the Nascar northwest tour championship in 1993.

Having said that I know very well that what works for racing in the way of quench is not the same requirement for street/strip.

You are not wrong in suggesting quench reduction is not a good thing.
I was simply pointing out that there is a point where a squish area can be too small to be effective and is better off being removed for other reasons.

For what it is worth, if you look at a squish velocity calculator you will see that one of the inputs is the percentage of quish area to total area.
Simply put, The more the squish area, the more air is going to be quished and the higher the squish velocity.
So the inverse is also true to the point if not being effective.

By the time the piston is to the point of firing the spark plug, the gasoline droplets should have changed state into a gas by the heat of compression and we should only have to consider dealing with a gas and very little or no liquid at all in flow considerations.

Paul

 

Robert

You are doing a nice job.
I sometimes like to use a smaller used intake and exhaust valve that sits low enough on the seat to be out of your way when grinding but just enough to cover the seat so if you slip with the grinder the seat will not be damaged.

Paul

 

Update:

1-3-5-7 Head is just finished, it was my first time, i hope its looks okay...
Tomorrow i will check the valve in the seats for proper fit.
After that i will try to measure the cc, any advices?
The cc numbers will give me the amount of thickness for mill down the heads for proper total cc

 

Robert

Very nice job!
Don't mill the head.
We are looking for a compression ratio around 10.75.

If you need to it would be better to mill the block and have the pistons even with the top of the block. The quench would be improved.
If I remember correctly the pistons were .005" down.

Paul

 

Thanks Paul, i will tomorrow measure how much the pistons are in the hole. Last time with calculation was 0.05" down, never measure it.
I must mill the heads a little because i did slip of with the grinder but the scars aren't deep...

Why is 10.75 compression required? I have seen engine with less and they make also great power...

 

Robert

Sorry about the way I phrased my sentence.
I meant to say 10.75 or lower where 10.75 is the limit. no problem with less.

Larry is correct on your DCR goal.

The intake valve doesn't close (.006" lobe lift) till 78* ABDC which makes it look like a bigger cam as far as DCR is concerned.

Paul

 

It looks like the runout on the valves is off.
It also looks like the intake valve seat is deeper on one side. Hard to tell with the dark deposits.

The original pistons were set right at zero deck. The spherical replacements sit .005" in the hole and have less dish volume.
Robert is going to check deck clearence again.

These heads came in with 62cc chambers according to the paper work.
I'm waiting to see what they actually cc at and then we can go from there.

One of the requirements was for a stock like idle so Robert ordered a TA cam with a 118 LSA. The actual LSA on the cam is between 116 and 117 depending on what cylinder is checked.

Paul

 

Robert lives in Zurich Switzerland
Original pistons were Speed Pro
TA set the heads up.
Paperwork is shown in post# 24 in the thread below.
Chamber volume was 61cc not 62 as I stated earlier.

http://www.v8buick.com/showthread.php?221766-Compression-amp-Ignition-Question

 

What is the runout of the valves? And need you more pictures of the intake valve? what you mean with deeper?

 

little update:

First a big thanks for the good support here :TU:

I measure the piston in the block, they are 0.006"-0.008" down. I haven't build a bridge as you showed me chris. I did use an magnetic arm many times, after that i use feeler gage to confirm the numbers. I know not the best method but i saw the are just very slightly in the hole. So the 0.06"-0.08" should correct. I take the 0.006" value and made a compression caclulation with 68cc and 72cc see below:

And all valve are sealing great in their seat. Tomorrow i will measure the chamber volume out and than i give the job for the machine shop to do the surface. Unfortunately i haven't a picture from the grind fail...

 

Chris

Robert had piston to valve contact during the first dyno runs.
I'm thinking that some one local to Robert repaired the heads and they may not be in the same condition as when received from TA.
Thanks for your help with this.

Robert

I believe you had some bent valves.
What was done to the heads to repair them.

Paul

 

Paul:
Last time i did check the valve straightness and only one valve was bent. I replaced the valve and checked all valve and seat for proper seal.

Update:

I measure the cc of the heads, they volume are 65cc - 66cc, i guess it would would be no problem to get 67-68 cc and i will do this weekend.

 

Update:

- Head chamber is now corrected on 67 cc
- Head are milled 0.002
- Engine complete assembled and cam degreed intake centerline 114

Next Step:

- Re-torque the head gasket
- Checking flexplate to starter clearance
- Mount the crank trigger and program a proper timing curve for the MSD 6530
- Clean out engine bay

 

Final Update:

Thanks for everyone that gave me here advice's and hope to get this thing done. I'm proud to say, it was only possible with this forum with the great people here.
Special thanks to Paul, Larry, Jim, Chris, Devon, Sean and another people which don't know they names sry.
Pictures are on Photobucket and there are a lot more, just click on the image thumb.












The Car has also become a new interior and hotchkis suspension :TU:

From this



Eeastwood mats


TMI Sport R Seats




New Carpet and repainted console with new chevelle floor shifter -> works great and easy installation



Here a video from the first start after the rebuild. The smoke on the passenger side was a leaky radiator hose connection to the firewall. Driver side was a bit brake fluid (silicion based)

[video=youtube;pA6qeUq9IMs]https://www.youtube.com/watch?v=pA6qeUq9IMs&feature=youtu.be[/video]


Yesterday started the progress to seat my rings. I push it hard (1/2 throttle) and engine has awesome power. I really like the monster torque and the tires doesn't .
The new suspension works awesome, way better feeling on the steet. The car drives so amazing... unbelievable how it moves in the corners. I can very recommend this!
To drive with an AFR gauge is amazing and showed me there is some tuning required to the Holley 870 Street avenger.
The engine idles 14.3-14.8 most time 14.5 that's great but...

Here come the problems in:

When i open the throttle more 1/3 very fast, it get way to lean 16-17:1
If i open it slowly to 1/3 it will get up to 15-16:1 with a moderate acceleration. Is the transmission in second gear it will spin the tires and press you in the seat and the car will go straight forward.
I would like to see an AFR from 13-13.8 :1 under this load situation, any one confirm that? After the acceleration the AFR goes down to 12.5 and after few seconds it goes back to 14.5.
So i guess the installed Power valve opens to late, original is #45 installed 2 x 4.5 = 9" of Vacuum. My engine has 12-13" vacuum at 900 RPM, so when i drive around town there is often 13" available.
13" / 2 = 6.5 correspond to Holley PV #65 . I bought a #55 and #65 and a cam set for the acceleration pump. I have also one 1 higher / lower number of jets for the mains primary and secondary.

Any suggestion how i should tune the carb? I thought install a #65 PV and a cam that activate the acceleration pump sooner and but lesser in lift.

Tanks for the help

Robert