The Electrician
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How do you know exactly when the valves open and close? from Advertised Duration?
More explanation please.
More explanation please.
Squish!
- Thread starter 96blak54
- Start date
OP
OP
You dont, thats the cam companies "secret". I say this because a mod cam can crack a valve under .050" for a number of duration unlike a cam in block engine with tiny cam lobes and a pound of mechanical rods and levers that deflect under demand. A mod has less than .020 deflection when used with a hydraulic lasher, nearly zero when solids lashers are shimmed in. So ....long story short, if the cam manufacturer resist offering cam specs from seat to seat duration, choose a different manufacturer. Knowing the seat to seat duration offers knowledge to cam potential, engine build potential, estimated potential. Cam specs like that are set more for the old school. Although .050" lift gives a good indication of the ramps, but still vague. Lobe separation angle still is a vudoo mythical # the manufacturer spill out. I can sit here all day long an spill cam specs to particular scenario's and keep you confused with numbers, or I can educate you...little by little, so that you come to a better understanding.
The Electrician
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Please do
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My source of info
torch318
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Yes he does! Thank you for sharing the connection. This is awesome info! Although more directed towards a cam in the block explanation, still having the basic principles explained multiple ways helps shape the mind to understand.
The Electrician
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Mmm.....maybe you can find the other documents I have copies of. Thankyou.
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OP
Building onto the thread
Here are headgasket options available for a desired crushed thickness. (When torqueing down heads, the gaskets crush to a certain thickness from its manufactured nominal state)
Cometic has a great assortment of thicknesses.
Cometic 3.620bore
.027" c5118-027 & c5119-027
.030" c5118-030 c5119-030
.040" c5118-040 c5119-040
.051" c5118-051 c5119-051
.075" c5118-075 c5119-075
These gaskets cost around $150ea
Felpro 3.625bore
.036" 1141R & 1141L
Cost roughly $45ea
Felpro 3.625bore
.050" 9790pt2 9792pt2
Cost roughly $45ea
Their are more otions from cometic such as 3.700"bore and Darton sleeved aluminum block specific gaskets.
Here are headgasket options available for a desired crushed thickness. (When torqueing down heads, the gaskets crush to a certain thickness from its manufactured nominal state)
Cometic has a great assortment of thicknesses.
Cometic 3.620bore
.027" c5118-027 & c5119-027
.030" c5118-030 c5119-030
.040" c5118-040 c5119-040
.051" c5118-051 c5119-051
.075" c5118-075 c5119-075
These gaskets cost around $150ea
Felpro 3.625bore
.036" 1141R & 1141L
Cost roughly $45ea
Felpro 3.625bore
.050" 9790pt2 9792pt2
Cost roughly $45ea
Their are more otions from cometic such as 3.700"bore and Darton sleeved aluminum block specific gaskets.
OP
OP
Comforming felpro 1141L & 1141R gasket attributes.
Ive took a pic but realized the clarity is to poor to post. You guys wouldnt be able to make out the product #'s by the time reduced quality transmission through posting a pic.
Anyhow here we go.
Felpro offers modular headgasketd as permatorque gaskets in a non specified crush and .036" crush. The 9790pt series have no crush thickness specifications were as the 1141 series specifys .036" crush.
My learning experience;
Ive had a new set of head gaskets laying around for future builds, felpro permatorque 9790pt series. Desperately wanting my engine together, I decided to use their availability. Not happy with the spongee headbolts, I bailed moving forward. The headgaskets arent what I wanted and now the headbolts feel junky. 2 wrongs is a strong flag to stop. So thats what I did. Let it sit!
Fast forward, I purchased the felpro 1141 series headgaskets. Supposedly .036" crush and to my dismay. ....when I opened the 1141R package, a permatorque 9790pt-2 (right side) was in there.
This comfirms felpro's performance aspects to correct product info.
Ive took a pic but realized the clarity is to poor to post. You guys wouldnt be able to make out the product #'s by the time reduced quality transmission through posting a pic.
Anyhow here we go.
Felpro offers modular headgasketd as permatorque gaskets in a non specified crush and .036" crush. The 9790pt series have no crush thickness specifications were as the 1141 series specifys .036" crush.
My learning experience;
Ive had a new set of head gaskets laying around for future builds, felpro permatorque 9790pt series. Desperately wanting my engine together, I decided to use their availability. Not happy with the spongee headbolts, I bailed moving forward. The headgaskets arent what I wanted and now the headbolts feel junky. 2 wrongs is a strong flag to stop. So thats what I did. Let it sit!
Fast forward, I purchased the felpro 1141 series headgaskets. Supposedly .036" crush and to my dismay. ....when I opened the 1141R package, a permatorque 9790pt-2 (right side) was in there.
This comfirms felpro's performance aspects to correct product info.
OP
OP
Awesome product! Dont get me wrong here, im not bashing the product.
Im offering a warning for the product
Im offering a warning for the product
Dang, I better check my packages...
OP
OP
Exactly!
Nighttrain
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96blak54 great info, i cant think of anything to add....except....ive done my fair shair of playing around especially with sportsters. You can efectively reduce you squish, swirl patterns, at the same time increasing atomization by filling the bowl in the heads combustion chamber. There is a fine point with it especially around the valves where it will impede flow but most of the space in the combustion chamber is a waiste. Just throwing that out there
Silver95bird
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Okay, so let's apply this...
I have a few real life application questions on this.
Let's say you have a 2v car, and take the heads off to do a P&P job, or even for repairs. Traditionally, we'd look at thinner gaskets and decide the compression change wasn't enough to be worth ordering a special gasket over. Combining not just the compression, but also the squish distance, is it more worth ordering the shortest gasket that will provide a safe (say, .025") margin so the pistons don't kiss the heads? A lot of people won't be decking heads and blocks, but they might pull the heads off for porting or PI headswapping along the way. How much more timing does this reduction allow? The swirl dams often have sharp edges on them, and it's long been thought that those areas are likely among the most detonation-prone areas in the head. Is this squish issue an even bigger issue than that, detonation wise?
I'd like to posit the idea that perhaps there's more to gain from this by the fact that reducing the squish area reduces the areas of the block, heads, etc. exposed to the heat near ignition at TDC, making it more efficient by giving the lit charge less area to dissipate the heat into.
Ring lands are hugely famous for being failure prone on 4.6Ls, mainly lost to detonation. Assuming the tuner isn't a moron, does this shield the pistons a little more from heat and failure at those edges? I add the caveat, because a bad tune will kill anything if they try hard enough. I'm talking about moving the safe (non-detonating) timing borderline without causing damage versus a comparable engine.
Does sticking the piston out of the hole on a 4.6L start to cause issues since the rings are so close to the top? How far is too far?
I have a few real life application questions on this.
Let's say you have a 2v car, and take the heads off to do a P&P job, or even for repairs. Traditionally, we'd look at thinner gaskets and decide the compression change wasn't enough to be worth ordering a special gasket over. Combining not just the compression, but also the squish distance, is it more worth ordering the shortest gasket that will provide a safe (say, .025") margin so the pistons don't kiss the heads? A lot of people won't be decking heads and blocks, but they might pull the heads off for porting or PI headswapping along the way. How much more timing does this reduction allow? The swirl dams often have sharp edges on them, and it's long been thought that those areas are likely among the most detonation-prone areas in the head. Is this squish issue an even bigger issue than that, detonation wise?
I'd like to posit the idea that perhaps there's more to gain from this by the fact that reducing the squish area reduces the areas of the block, heads, etc. exposed to the heat near ignition at TDC, making it more efficient by giving the lit charge less area to dissipate the heat into.
Ring lands are hugely famous for being failure prone on 4.6Ls, mainly lost to detonation. Assuming the tuner isn't a moron, does this shield the pistons a little more from heat and failure at those edges? I add the caveat, because a bad tune will kill anything if they try hard enough. I'm talking about moving the safe (non-detonating) timing borderline without causing damage versus a comparable engine.
Does sticking the piston out of the hole on a 4.6L start to cause issues since the rings are so close to the top? How far is too far?
OP
OP
The idea behind squish is mixture motion and combustion resistance when compression is through the roof or running as lean as possible....keeping it stable just as the piston is coming to a stop. If one needs to add timing,....mixture and motion is poor. Lets think about it here.....
The piston at high rpm is moving faster than the fuel ignites and burns off....this is why advancing the timing is needed....to start the burn process before piston reaches top dead center. If the mixture is poor, rich, or stagnant advance timing will be needed. If mixture is stoich or leaner combustion will be more sparatic (auto ignition...key word...kind of what you want at high rpm). 30° advance at 5k rpm is much different than 30° advance at 7krpm. The 5k rpm engine is poor efficient. The 7k rpm engine is able to run near stoich throughout with out problems.
These guys bragging about running advance timing really only shows the builds efficiency. Yes advancing the timing wrings out the potential but can also be an indicator of efficiency.
For example
A stock 5.4l 2v can only and will not show any improvements with over 16° advance at 5k rpm. Stoich or lean. If we fatten up the mixture ...maybe so then. That would be counter productive
The piston at high rpm is moving faster than the fuel ignites and burns off....this is why advancing the timing is needed....to start the burn process before piston reaches top dead center. If the mixture is poor, rich, or stagnant advance timing will be needed. If mixture is stoich or leaner combustion will be more sparatic (auto ignition...key word...kind of what you want at high rpm). 30° advance at 5k rpm is much different than 30° advance at 7krpm. The 5k rpm engine is poor efficient. The 7k rpm engine is able to run near stoich throughout with out problems.
These guys bragging about running advance timing really only shows the builds efficiency. Yes advancing the timing wrings out the potential but can also be an indicator of efficiency.
For example
A stock 5.4l 2v can only and will not show any improvements with over 16° advance at 5k rpm. Stoich or lean. If we fatten up the mixture ...maybe so then. That would be counter productive
OP
OP
Tightening up the squish distance on a relative stock build will allow for a leaner combustion. Yea, youre right about the rings, but that's why we use stainless, thats why forged pistons are available....lol
I understand though. You want to know if doing so will benefit a stock engine....yes it will.
Lets see if I can shed light......nearly all engines today run beyond stoich. Running lean means fuel economy. This is why v8 cars are pulling off 30+ mpg. When continued driving and maintaining a constant rpm, over stoich is possible at low rpm. Actually causing a mild detonation....for long periods of time. The detonation is very mild compared to high rpm detonation. Yes detonation has levels of severity.
This said only proves the in cylinder caracteristics. A lean mixture is far more potent than a rich mixture. And I can go all day about a lean mixture actually being rich...crazy!
I understand though. You want to know if doing so will benefit a stock engine....yes it will.
Lets see if I can shed light......nearly all engines today run beyond stoich. Running lean means fuel economy. This is why v8 cars are pulling off 30+ mpg. When continued driving and maintaining a constant rpm, over stoich is possible at low rpm. Actually causing a mild detonation....for long periods of time. The detonation is very mild compared to high rpm detonation. Yes detonation has levels of severity.
This said only proves the in cylinder caracteristics. A lean mixture is far more potent than a rich mixture. And I can go all day about a lean mixture actually being rich...crazy!
Silver95bird
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I agree with what you're saying. Lean isn't really a problem in the conditions you're talking about - steady state cruise on a flatland - you can really lean it out and gain MPG that way. Heck, they've been experimenting with that since the advent of eec-iv. Too lean in those circumstances creates emissions problems, if nothing else.
It seems that load plays a big factor in that equation though. Same timing, same A/F, but going up a big hill, and it'll knock like crazy. It's just that WOT is basically maximum load, and we're not just talking about 1200rpms worth of detonation under low load, but more like 6000 under maximum load. The engine just can't dissipate heat as well at that rpm.
I get where you're going with the timing discussion. That's why diesels are so efficient. Unfortunately, it's not just purely combustion efficiency we have to deal with. There's also keeping temperatures low of things like exhaust valves and catalytic converters we have to deal with. That has a lot to do with setting the WOT A/F ratios, and ignition timing becomes the movable variable. That's more where I'm going.
Whether I build an engine NA or SC, I'm not going to vary my A/F ratio because I changed my piston to head clearance, but I might be able to change the ignition timing and make a few hp more without blowing the dern thing up.
Great discussion.
OP
OP
Ah...see said the blind man. Your car build must remain stock for a particular class of racing? Yea, heat will be detrimental to cats. You dont need that. I get you now.
So does running a tighter squish improve efficiency on an otherwise stock engine? Not having much experience with stock built scenario's,...it would only make sense to run tight as you can get it., so yea...run the thinner gaskets.
So does running a tighter squish improve efficiency on an otherwise stock engine? Not having much experience with stock built scenario's,...it would only make sense to run tight as you can get it., so yea...run the thinner gaskets.
Silver95bird
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I'm not so much building to a set of rules, as much as I'm trying to apply the theory to what 90% of those reading this are more likely to experience. There aren't that many people blueprinting modular engines in their home garages, but there's bound to be a good number of headswappers or those who buy a set of TF or ported heads who will want to make the most of it. Leaving .025-.030 as a safety margin, once stretch in the rods/pistons/crank is considered becomes essentially zero. There's a similar margin taken into account for checking PTV clearance with a cam change. Unlike PTV though, this changes where the heat is distributed in the chamber.
With PI heads, the chambers are very small, so essentially the deck face is the zero point for clearance. With the NPI heads, the swirl fin may be about the only part that would directly contact the piston. If someone had a set of ported NPIs with the swirl fin layed back, would that make much of a difference on how the clearance would be set up, or is the diameter of the chamber on the heads narrower than the pistons such that the pistons would kiss the head anyway? I'm mainly talking about the F5AE castings, since that's the main one Mustang NPI'ers would be dealing with.
With PI heads, the chambers are very small, so essentially the deck face is the zero point for clearance. With the NPI heads, the swirl fin may be about the only part that would directly contact the piston. If someone had a set of ported NPIs with the swirl fin layed back, would that make much of a difference on how the clearance would be set up, or is the diameter of the chamber on the heads narrower than the pistons such that the pistons would kiss the head anyway? I'm mainly talking about the F5AE castings, since that's the main one Mustang NPI'ers would be dealing with.
