Clearanced my block at the intake valves

[Jerryl]

It's all good Rob.
I appreciate the healthy discussion.

What I fail to understand is how the gasket sealing can be comprimised *if* the fire ring is still fully clamped and does not protrude into the chamber.
Been a while since I studied the clearances and . . . Maybe Mike can post a picture of the eyebrow area with gasket on?

 

[Mike T]

That's all well and good. Just make sure you post the results if possible as you go.

Just be honest and share it all, The good the bad and the ugly, so others can either use or stay away from certain modifications.

Everyone who knows me will tell you that I'm an open book when it comes to successes and failures. I would be happy to post any ill effects due to what I've done here. Honestly all I could imagine (worst cast scenario) is that the block could crack at the relief but I really feel as if that's far fetched.

No way for me to prove that there were any gains or loses in power so that's out.

You have a good understanding of how things work so I would like to hear you option. One of your concerns was clamping force due to the modification....from my perspective this particular area is probably the strongest on the block because of it's location relative to the head bolt. Any thoughts on this?

 

[robzombie]

It's all good Rob.
I appreciate the healthy discussion.

What I fail to understand is how the gasket sealing can be comprimised *if* the fire ring is still fully clamped and does not protrude into the chamber.
Been a while since I studied the clearances and . . . Maybe Mike can post a picture of the eyebrow area with gasket on?

With the notch you will be forcing combustion pressure more directly at the fire ring in that area in a higher concentration and angle in that particular spot.

Physics will tell you that you have just exposed the fire ring in that area to a higher load from taking the material away and changing the direction of force generated on the fire ring in that spot.

The amount of change depends how much of the fire ring is exposed, compression, boost applied to it and so forth.

Think of it in simple terms. If you have to push up on something that has 1,000 lbs. of vertical force pushing back down at you versus 1000 lbs. of force pushing sideways which would be easier to move?

What I'm getting at is the head fasteners generate a vertical clamping force and now you are introducing a semi horizontal force. It may be a small amount or it may be a large amount. It depends on the design and application such as our motor and how much boost [pressure] you magnify it by.

The more the fire ring is exposed the higher the potential for exposing another problem that's all I'm getting at. It may or may not be an issue but it should be a consideration and that's why I hope he shares whatever the outcome is with as much detail on how much boost he runs and how often as well as any other pertinent info.

 

[Jerryl]

Rob,
Do you think it applies if yhe fire ring is not exposed and fully clamped?

 

[Mike T]

With the notch you will be forcing combustion gases directly at the fire ring in that area in a higher concentration and angle in that particular spot.

Really the same argument can be made about the stock configuration.....It's just reversed with the head being the wedge area (if we want to call it that).

 

[robzombie]

Everyone who knows me will tell you that I'm an open book when it comes to successes and failures. I would be happy to post any ill effects due to what I've done here. Honestly all I could imagine (worst cast scenario) is that the block could crack at the relief but I really feel as if that's far fetched.

No way for me to prove that there were any gains or loses in power so that's out.

You have a good understanding of how things work so I would like to hear you option. One of your concerns was clamping force due to the modification....from my perspective this particular area is probably the strongest on the block because of it's location relative to the head bolt. Any thoughts on this?

That is one of the issues I was worried about. That area is the strongest as the bolt/stud is generating the highest clamping force in that area. The common issue with blowing the H/G is detonation or lifting the head.

With the term lifting the head it describes one of two issues, head flex or fastener stretch.

When you notch the block and introduce more force in a narrow area such as you have and looking at where you have done it, it looks like it should be fine versus if you had done it in between the fasteners.

My issue is that it may push the fire ring sideways due to the angle of force now being put on it unless you have additional force holding it in place such as O-ringing the head or block.

Obviously running 20 lbs. of boost versus 28/30 could have very different results.

 

[robzombie]

Rob,
Do you think it applies if yhe fire ring is not exposed and fully clamped?

The less exposed the fire ring is the better. The angle of the notch and the depth will determine the amount of possible detrimental effects as well as the other factors of boost levels and detonation.

 

[Mike T]

Glad I don't have an engineering degree..... because then I'd really obsess about all of the potential pit falls. I'm going to stick with the simple version and that is that the forces want to blow the head straight up off of the motor and the fire ring sees the same amount of outward pressure no matter what angle its coming from. I think the side load on the gasket would have more to do with surface area than the angle that it was applied from.

Sure it may want to push out if an area isn't clamping like it should but still I think that is has nothing to do with how close or how far the fire ring is from the cylinder wall as long as it's clamped and not protruding.

 

[Mike T]

 

[turbofabricator]

Pressure remains constant in a sealed vessel. Gotta be more worried about deflecting the deck between head bolts on the intake side. Just isn't much material in the deck there. Pinning the deck in that area can help retain the gasket. More importantly is the tune up and proper fuel.
I have always wanted to test before/after under high boost notching the bores. Same with high boost and stock style intake valves and flat valves. Not sure why Buick chose the valves they did.

 

[earlbrown]

Odds are you'll find no gain from that notch. Forced induction really takes a whole lots of 'tricks' and makes them obsolete.

You lost a little bit of static compression but without knowing how far the edge of the valve was/is from the bore, there's no way to say for sure. If that notch took you from a shrouded condition to an unshrouded condition, there's efficiency to be gained. If you weren't shrouded to start with, all you did was lower the compression a little (and make it necessary to modify head gaskets.

When you notched the bore, did you put the heads in place and scribe the notch on the heads deck surface?
(or was the notch a result of the heads combustion chamber transferred to the bore?)

 

[Mike T]

When you notched the bore, did you put the heads in place and scribe the notch on the heads deck surface?
(or was the notch a result of the heads combustion chamber transferred to the bore?)

The heads were unshrouded a while back....the block is now pretty close to a mirror image of the heads in that area. There really wasn't that much material removed.

I cant tell you what the relationship of the notch and the valve is at .500 lift so that something I'll be looking at.

It all goes back to being pressurized and the air can certainly be crammed in the motor but I've also been picturing the process as a high pressure water hose. the water flowing through the nice smooth hose is expelled in a uniform fashion but stick the edge of a quarter (the block in my case) or something like that in the path and things start deflect and bounce around.

It was asked what was the goal? Hopefully the valve was unshrouded at bit and a little smoother flow path was achieved.

 

[earlbrown]

A sharp edge into smooth flow presents itself as protruding further than it actually does.

With a N/A engine you wan the air to meet back up on the other side of the valve in what Smokey Yunick called a 'flow cone'. With his testing if one side of the valve was shrouded the cone couldn't form and flow (with power) would drop.

In our case we're not relying on 14.7PSI of atmospheric pressure to push the air in, At 30PSI we actually have 44.75PSI of pressure at the valve. In that case a small lip might cause extra tumble giving a better mix and making more power since the air hitting that lip will go apeshit when it rolls off the end.

...OR... it could cause a 2 percent reduction in flow resulting in a .3% reduction in power at the tires. It's hard to say which is true (or if they both are a little)