retarding the cam from 4 degrees to straight up

[Bigchief632]

Essentially, yes, that's what I am saying. I've done this scenario numerous times over the year. Build engine, max compression pump gas for example. Engine gets run for years. Comes back for freshen up. Hone, re ring, bearings, etc. Say for example, a 406. 11.5:1 with flat tops, and 64cc. Mill heads .010. I had a .041 thick gasket on it originally, to maintain same compression, I switch to .051. These are usually re dynoed too. I see the difference. Same dyno, that repeats very well. Usually, they make a touch more power, certainly not less.

Did you cc's the heads after cutting them? I don't see any way cutting the heads 0.010" and then adding 0.010" to the head gasket doesn't reduce the CR.

Stan

Heads started at 65cc after chamber work and a lite mill when they were new. Compression was 11.5:1. After, I milled them .010. the chambers ended up around 63. I "estimated" that based on .006/cc. No point in wasting time cc'ing them again to know if it was +/- .2 cc different. It's just not that important. So, if you do the math, it was roughly 11.46:1 after using the .051 gasket with .010 more squish clearance, quench distance, piston to head clearance or however you want to define it. It would have been around 11.9:1 if I would have used the same .041 thick gasket, and would have pushed it over the limit for pump gas. Ironically, it made slightly more power. It certainly didn't hurt it. And that was the whole point of bringing this example up. And it still runs to this day, and has had nothing but 91 ethanol premium unleaded ran through it. This is a 610hp 406 sbc.

[digger]

Essentially, yes, that's what I am saying. I've done this scenario numerous times over the year. Build engine, max compression pump gas for example. Engine gets run for years. Comes back for freshen up. Hone, re ring, bearings, etc. Say for example, a 406. 11.5:1 with flat tops, and 64cc. Mill heads .010. I had a .041 thick gasket on it originally, to maintain same compression, I switch to .051. These are usually re dynoed too. I see the difference. Same dyno, that repeats very well. Usually, they make a touch more power, certainly not less.

Did you cc's the heads after cutting them? I don't see any way cutting the heads 0.010" and then adding 0.010" to the head gasket doesn't reduce the CR.

Stan

Heads started at 65cc after chamber work and a lite mill when they were new. Compression was 11.5:1. After, I milled them .010. the chambers ended up around 63. I "estimated" that based on .006/cc. No point in wasting time cc'ing them again to know if it was +/- .2 cc different. It's just not that important. So, if you do the math, it was roughly 11.46:1 after using the .051 gasket with .010 more squish clearance, quench distance, piston to head clearance or however you want to define it. It would have been around 11.9:1 if I would have used the same .041 thick gasket, and would have pushed it over the limit for pump gas. Ironically, it made slightly more power. It certainly didn't hurt it. And that was the whole point of bringing this example up. And it still runs to this day, and has had nothing but 91 ethanol premium unleaded ran through it. This is a 610hp 406 sbc.

was it zero deck? more specifically what was the original squish clearance?

[mt-engines]

Whats it matter... he just showed that he increased the clearance and it gained power.

[skinny z]

Surely there's more to it than that.
There are an equal number of internet posts that reflect the opposite.

[Bigchief632]

Did you cc's the heads after cutting them? I don't see any way cutting the heads 0.010" and then adding 0.010" to the head gasket doesn't reduce the CR.

Stan

Heads started at 65cc after chamber work and a lite mill when they were new. Compression was 11.5:1. After, I milled them .010. the chambers ended up around 63. I "estimated" that based on .006/cc. No point in wasting time cc'ing them again to know if it was +/- .2 cc different. It's just not that important. So, if you do the math, it was roughly 11.46:1 after using the .051 gasket with .010 more squish clearance, quench distance, piston to head clearance or however you want to define it. It would have been around 11.9:1 if I would have used the same .041 thick gasket, and would have pushed it over the limit for pump gas. Ironically, it made slightly more power. It certainly didn't hurt it. And that was the whole point of bringing this example up. And it still runs to this day, and has had nothing but 91 ethanol premium unleaded ran through it. This is a 610hp 406 sbc.

was it zero deck? more specifically what was the original squish clearance?

Yes, 9 inch deck height set off BHJ fixture, SRP 2 valve relief pistons, zero deck. .041 original to .051 after. Pretty self explanatory I thought.

[Bigchief632]

Surely there's more to it than that.
There are an equal number of internet posts that reflect the opposite.

It's representative to what 99% of all you guys are doing and working with. Nothing magic. Like I said, lots of reverse inverse of reality in this hobby based on 40+ year old concepts that have stuck for some reason.

[digger]

Heads started at 65cc after chamber work and a lite mill when they were new. Compression was 11.5:1. After, I milled them .010. the chambers ended up around 63. I "estimated" that based on .006/cc. No point in wasting time cc'ing them again to know if it was +/- .2 cc different. It's just not that important. So, if you do the math, it was roughly 11.46:1 after using the .051 gasket with .010 more squish clearance, quench distance, piston to head clearance or however you want to define it. It would have been around 11.9:1 if I would have used the same .041 thick gasket, and would have pushed it over the limit for pump gas. Ironically, it made slightly more power. It certainly didn't hurt it. And that was the whole point of bringing this example up. And it still runs to this day, and has had nothing but 91 ethanol premium unleaded ran through it. This is a 610hp 406 sbc.

was it zero deck? more specifically what was the original squish clearance?

Yes, 9 inch deck height set off BHJ fixture, SRP 2 valve relief pistons, zero deck. .041 original to .051 after. Pretty self explanatory I thought.

thanks for clarifying, given seen some people run pistons in the hole wanted to make sure it wasn’t going from 0.060 to 0.070 or something that is misleading

[skinny z]

Surely there's more to it than that.
There are an equal number of internet posts that reflect the opposite.

It's representative to what 99% of all you guys are doing and working with. Nothing magic. Like I said, lots of reverse inverse of reality in this hobby based on 40+ year old concepts that have stuck for some reason.

True enough.
And what works in one case may not work in another.

[mt-engines]

Surely there's more to it than that.
There are an equal number of internet posts that reflect the opposite.

From book salesmen that don't actually build or test their own stuff? And tell the guys that actually do it for a living that they are wrong.

[HQM383]

Whats it matter... he just showed that he increased the clearance and it gained power.

Because it was part of an overall refresh so a number of things could have contributed to a slight increase in power over the original power reading. Quench was not isolated as the only change.

[skinny z]

Surely there's more to it than that.
There are an equal number of internet posts that reflect the opposite.

From book salesmen that don't actually build or test their own stuff? And tell the guys that actually do it for a living that they are wrong.

Not sure of what to make of it mt.
It's all internet related to me. Further to my comment, it seems that there are an equal number of arguments on both sides.

With respect to the shortblock on the stand right now, I've a flat top piston that measures.008" down.
My go to gasket is the Mahle .026" version.
That'll be a .034" piston to head clearance.
I may work on the chambers and ultimately increase the CC's from the present 65.4 but as it is, I'd see 10.2:1 which is just about right.
So, increasing the chamber volume may put me in the position to have the heads milled.
Am I better off taking more than what's needed to get the 10.2:1 back and go for a thicker gasket but increasing that quench to something closer to 50 thou?

EDIT:
To further complicate things, one iteration of this engine might be track specific (as in the drag strip). Another might be a fall back to everything else I've built, driven (everywhere) and raced as well. More of the traditional street/strip combo.
(Carbed 357 hydraulic roller deal).

[Stan Weiss]

How close is the piston to head clearance?

NASCAR Engines 101

https://www.youtube.com/watch?v=rBZCnG1HwDM

Go to the 39 minute mark and watch for a couple of minutes.

Stan

[mt-engines]

Surely there's more to it than that.
There are an equal number of internet posts that reflect the opposite.

From book salesmen that don't actually build or test their own stuff? And tell the guys that actually do it for a living that they are wrong.

Not sure of what to make of it mt.
It's all internet related to me. Further to my comment, it seems that there are an equal number of arguments on both sides.

With respect to the shortblock on the stand right now, I've a flat top piston that measures.008" down.
My go to gasket is the Mahle .026" version.
That'll be a .034" piston to head clearance.
I may work on the chambers and ultimately increase the CC's from the present 65.4 but as it is, I'd see 10.2:1 which is just about right.
So, increasing the chamber volume may put me in the position to have the heads milled.
Am I better off taking more than what's needed to get the 10.2:1 back and go for a thicker gasket but increasing that quench to something closer to 50 thou?

EDIT:
To further complicate things, one iteration of this engine might be track specific (as in the drag strip). Another might be a fall back to everything else I've built, driven (everywhere) and raced as well. More of the traditional street/strip combo.
(Carbed 357 hydraulic roller deal).

All I'm trying to say. Is its not as this huge power increase or det resistance concept to tighten quench.. there are too many other factors to worry about. Just make sure you have enough clearance so you don't hit the heads on an over rev.


Just like MLS vs Composition style head gaskets. I've seen some engines last longer between freshen up with composition over MLS.. and for some reason it was alway the engines that wanted very little timing. Im sure Bigchief632 has probably seen that as well.

I used to overcomplicate too many aspects of builds only to realize what was more important. At the end of the day will it run?

I would hate to tell you to run .028" when its worked for me only to fail on you.

Sneak up on your tolerances is the best way to learn.. starting too tight doesn't give you much to learn from.


Your build specifically if its an automatic trans and you keep the revs below 7k.. I don't think its an issue.. but it could be. You never know. Heck maybe you could use this as an opportunity to try for yourself different thicknesses.

[mt-engines]

How close is the piston to head clearance?

NASCAR Engines 101

https://www.youtube.com/watch?v=rBZCnG1HwDM

Go to the 39 minute mark and watch for a couple of minutes.

Stan

Our cup pistons were not flat they were concave.

And these engines don't have .48bsfc numbers either like most of these pump gas guys.

[Stan Weiss]

How close is the piston to head clearance?

NASCAR Engines 101

https://www.youtube.com/watch?v=rBZCnG1HwDM

Go to the 39 minute mark and watch for a couple of minutes.

Stan

Our cup pistons were not flat they were concave.

And these engines don't have .48bsfc numbers either like most of these pump gas guys.

That is a new one for me. What does BSFC have to do with squish clearance?

Stan