Head Gasket Suggestions

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nm9stheham said:
Just to be clear..... the .039 compressed Felpro is the Felpro 1008. The .050" compressed Felpro is the 8553PT. 2 different gasket PN's; the 8553PT is the standard kit PN.

If you go from the .050" to .028" think head gasket, that is about 0.35 points in compression so is not negligible. You will indeed feel it on the butt-dyno. How much trouble anyone would have on their particular engine with the Mr Gaskets, IDK. But I'd take the precaution to at least have the heads skimmed.

I used very similar composition gaskets to the Mr Gasket for thousands of race miles on my turbo Mitsu rally engine running 14-15 psi boost. Blew a grand total of 1 when the engine got hot and the head warped a bit. Otherwise, A-OK. So it seems to be a mixed story.
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Yea that is about what I came up with too uncompressed my felpro 8553 was .054 and the compression difference was around .4 it took me from 9.6 to 10 or something like that for the difference in price and the negative reviews I didn't think .4 was worth the risk.
 
Justin Sykes said:
I have a 1984 Model 318 in my '69 Dart.

I have Hooker longtubes, Edelbrock Performer intake, and recently put in the Comp XE268 cam. I picked up a set of "302" heads from a pull-a-part for $60 and intend to get em to the machine shop for a freshening up with my new components that come in the cam kit. Aiming to just get them surfaced so no major milling. I am aiming for anywhere from 9.2 to 9.5-1 compression.

What thickness head gasket should i aim for? What are some good wallet-friendly solutions?

*I am also open to good header gasket suggestions*

View attachment 1715536410
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I know I seen the post on fb but cant remember now but what are you doing with the bottom end? I went thru just about every scenero planning a 318 build I can help you out lol. What did you decide to do with your valve springs ? I remember you asking about the stock ones with that cam I suggested you not use them lol
 
nm9stheham said:
Just to be clear..... the .039 compressed Felpro is the Felpro 1008. The .050" compressed Felpro is the 8553PT. 2 different gasket PN's; the 8553PT is the standard kit PN.

If you go from the .050" to .028" think head gasket, that is about 0.35 points in compression so is not negligible. You will indeed feel it on the butt-dyno. How much trouble anyone would have on their particular engine with the Mr Gaskets, IDK. But I'd take the precaution to at least have the heads skimmed.

I used very similar composition gaskets to the Mr Gasket for thousands of race miles on my turbo Mitsu rally engine running 14-15 psi boost. Blew a grand total of 1 when the engine got hot and the head warped a bit. Otherwise, A-OK. So it seems to be a mixed story.
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I guess I wasn't clear. I never mentioned a part number. The 1008 is the gasket I was talking about.

It's my personal preference to run the FelPro gaskets. I wouldn't run a Mr Gasket head gasket on a briggs and stratton. They make a few good things, but ironically, gaskets ain't among them, IMO.
 
freak
you have any quench possibilties?
if so you shot yourself in the foot quench wise as well as leaving efficiency on the table
 
dartfreak75 said:
I know I seen the post on fb but cant remember now but what are you doing with the bottom end? I went thru just about every scenero planning a 318 build I can help you out lol. What did you decide to do with your valve springs ? I remember you asking about the stock ones with that cam I suggested you not use them lol
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nothing bottom end. All stock. I have the proper springs for the cam that came in the kit, but im just using stockers for break in purposes. Have some 302 heads that are getting the correct springs.
 
Splittin hairs. Quench won't get you 20 more HP so screw it. It's way over rated.
stone age true only with race gas
Not more hp,maybe less in a race car
but way more torque, less advance, less fuel sensitivity, less detonation
 
pishta said:
Cometics MLS type? All of them MLS gaskets require a high RA (smoothness) on the head and block but I think iron on iron are an exception as the AL on iron block heads expand at a different rate and can stress a gasket in a sheering force, the MLS gaskets and the high RA finish prevents this type of stress. Iron on iron expand at the same rate, so there is no sheering force on the gasket.
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But they still spec a smoother surface...just had this conversation with my engine machinist
 
What did he say about the smoothness, could he elaborate on why they spec that high RA?
 
Wyrmrider said:
Splittin hairs. Quench won't get you 20 more HP so screw it. It's way over rated.
stone age true only with race gas
Not more hp,maybe less in a race car
but way more torque, less advance, less fuel sensitivity, less detonation
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Horse ****. Compared to "WHAT"?
 
RustyRatRod said:
Horse ****. Compared to "WHAT"?
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Pump gas?
I don't really understand the whole quench thing. Seems to me like a whole lotta trouble to go through for a street engine. I understand it may be useful when trying to squeeze every last drop of power out of it for a race car. Tbo I dont even know what quech is concerned? Its the distance between the piston and the head?
 
dartfreak75 said:
Pump gas?
I don't really understand the whole quench thing. Seems to me like a whole lotta trouble to go through for a street engine. I understand it may be useful when trying to squeeze every last drop of power out of it for a race car. Tbo I dont even know what quech is concerned? Its the distance between the piston and the head?
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Yes, it the gap between the piston and head; it is over just part of the piston surface. it needs to get down below .060" to even start having an impact and something like .035" is pretty darend good. Too tight and you risk the piston hitting the head as everything wiggles around at high RPM.

The idea is two-fold:
  • The tight compression of the gases to the piston head allows the piston head to pull some heat out of the compressed fuel-air mixture, and so makes it less prone to detonation. That is the strict definition of quench.
  • It also squishes the fuel air mix out of the tightening gap at high speed, and that promotes swirling and mixing of the fuel-air mixture in the chamber and gives a more complete and faster burn. This is known a 'squish' but we tend to lump that in with quench and call it all 'quench'. The faster burn makes the mixture less prone to detonate. (BTW, any time you speed the burn rate up, then any tendency to detonate decreases. which is why closed chambers tend to detonate less than open ones.) The benefit of the more complete burn is obvious: more power and efficiency (including better mileage and lower emissions).
If you are seeking optimum performance, you plan this in. You can run higher compressions and/or more advanced timing and still have better detonation resistance. The added compression and timing mean more torque and power and efficiency.

There is no argument that this works; it has been common in engine design since the 40's-50's and used in hot-rodding since the 60's, my 1st engine in 1975 had quench-dome pistons. The only valid arguments are if it is worth the trouble to the individual; it limits parts selection and often invokes more machining costs. I value it for being able to run more compression, which means more low RPM torque on a street engine, which is of great value in that use. I also like the better detonation resistance; I can be lazier in setting timing LOL
 
nm9stheham said:
Yes, it the gap between the piston and head; it is over just part of the piston surface. it needs to get down below .060" to even start having an impact and something like .035" is pretty darend good. Too tight and you risk the piston hitting the head as everything wiggles around at high RPM.

The idea is two-fold:
  • The tight compression of the gases to the piston head allows the piston head to pull some heat out of the compressed fuel-air mixture, and so makes it less prone to detonation. That is the strict definition of quench.
  • It also squishes the fuel air mix out of the tightening gap at high speed, and that promotes swirling and mixing of the fuel-air mixture in the chamber and gives a more complete and faster burn. This is known a 'squish' but we tend to lump that in with quench and call it all 'quench'. The faster burn makes the mixture less prone to detonate. (BTW, any time you speed the burn rate up, then any tendency to detonate decreases. which is why closed chambers tend to detonate less than open ones.) The benefit of the more complete burn is obvious: more power and efficiency (including better mileage and lower emissions).
If you are seeking optimum performance, you plan this in. You can run higher compressions and/or more advanced timing and still have better detonation resistance. The added compression and timing mean more torque and power and efficiency.

There is no argument that this works; it has been common in engine design since the 40's-50's and used in hot-rodding since the 60's, my 1st engine in 1975 had quench-dome pistons. The only valid arguments are if it is worth the trouble to the individual; it limits parts selection and often invokes more machining costs. I value it for being able to run more compression, which means more low RPM torque on a street engine, which is of great value in that use. I also like the better detonation resistance; I can be lazier in setting timing LOL
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So with "quench" can you still run pump gas? It seems to me with a .035 distance between the heads and pistons you would have an extremely high cr like 12s or 13s. Also what about the piston to valve clearance? How do plan that out ahead of time seems like you would be extremely limited on cam selection
 
dartfreak75 said:
So with "quench" can you still run pump gas? It seems to me with a .035 distance between the heads and pistons you would have an extremely high cr like 12s or 13s. Also what about the piston to valve clearance? How do plan that out ahead of time seems like you would be extremely limited on cam selection
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I’m running 11.25:1 on pump gas right now and my “quench” is at .065 which is the “danger” zone according to the powers that be.

I’m changing the head gaskets to get close to 11.75:1 and I’ll see what that does.

I’ve typed out literally thousands of words about quench right here, on this forum so I’m not going to do it again.

I will say it was tested plenty and the ONLY thing we ever determined was closing the quench gave power increase not because of “quench” but because the increase in compression ratio.

If you have 10:1 compression and say...IDK let’s say .070 quench and you decide you need more quench, so you drop the big $$$$$ to get pistons to get you your quench, but the CR remains exactly the same, you will find ZERO horsepower. None.

Now, on junk **** heads with a horrible plug location, like the SBC and the BBM, you might find you can reduce the total timing some, because you are compacting the air/fuel charge, and we all know a denser A/F charge requires less timing, but horsepower? You won’t find any.
 
YR, can u explain this. Stock 74/5/6 360 motor. Remove factory heads and install 318 heads with smaller CCs. Car runs lots better. More power and torque. Quarter mile time 1/2 second better. No other changes. Shift rpm 5000. Kim
 
dartfreak75 said:
So with "quench" can you still run pump gas? It seems to me with a .035 distance between the heads and pistons you would have an extremely high cr like 12s or 13s. Also what about the piston to valve clearance? How do plan that out ahead of time seems like you would be extremely limited on cam selection
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The quench is in just one area of the piston-to-head clearance. All the computations that you go for compression ratio through still apply. You can have a deep dished piston with low compression ratio but still have one edge of the piston come up very close to the bottom of the head and create a quench/squish gap. Don't think of just flat top pistons.....

One of the ideas behind quench/squish is so you can run pump gas with higher CR.

Piston-to-valve clearance is an entirely different matter.
 
oldkimmer said:
YR, can u explain this. Stock 74/5/6 360 motor. Remove factory heads and install 318 heads with smaller CCs. Car runs lots better. More power and torque. Quarter mile time 1/2 second better. No other changes. Shift rpm 5000. Kim
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So you changed heads, gained compression and it went faster? That makes sense to me. Compression covers a multitude of evils. The engines was less affected by airflow and more affected by compression ratio.

That makes perfect sense to me.
 
not about max hp
it's about more torque all along the curve
plus what nm said
but as yr said not much more top end hp
but much less likely to ping or worse around max torque
 
yellow rose said:
So you changed heads, gained compression and it went faster? That makes sense to me. Compression covers a multitude of evils. The engines was less affected by airflow and more affected by compression ratio.

That makes perfect sense to me.
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Yep. Changed the whole torque curve (moved it down in RPM and the peak was probably higher) and it just worked out to be better with the car weight, drivetrain setup, etc. It is like what we talk about with cams and 'more area under the curve', only here it was 'more total energy under the curve'.

So what is that, that I keep hearing about flow trumping compression every time? LOL
 
Well flow trups compression if you can get enough of it
7:1 with a turbo for example
 
nm9stheham said:
Yep. Changed the whole torque curve (moved it down in RPM and the peak was probably higher) and it just worked out to be better with the car weight, drivetrain setup, etc. It is like what we talk about with cams and 'more area under the curve', only here it was 'more total energy under the curve'.

So what is that, that I keep hearing about flow trumping compression every time? LOL
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Flow does trump compression IF you have enough compression and IF you’re not killing flow to get the compression.

As an example (this is exactly what happened) I took on a set of BBC heads. I flowed them as they came in, after the valve job and then after porting so I had all the numbers.

The owner claimed 14.5:1 CR, but all I had was the heads, so I couldn’t verify if he knew what it exactly was or not, but that’s what he said.

Both valves were extremely shrouded by the chamber. So I unshrouded them first, then I made some changes to the shape of the chamber, because it wasn’t what I like. In fact, I did what is called “softening” of the chamber, even though it was an N/A deal.

The up shot is, by the time the work was done, he was at 13.9:1 compression, but his flow numbers were up. A bunch. Plus I got about 6% lower reverse flow numbers, so that was a bonus. The customer was livid he lost that much compression. I told him the flow gain was much more important.

Fortunately for me, it was going back on the dyno where the engine was done in the first place. It picked up power on the dyno, but the shop said it won’t matter...in the car it will not show an ET reduction because of .6 less CR.

Unfortunately for that shop, the dyno numbers and the new ET matched exactly what they should have been.

So yes, airflow does trump compression, if you are losing airflow to gain compression.

Another example is my junk, and FABO member Zigs builds. I stick the piston out of the hole so I can reduce the dome. I didn’t actually give up CR, but I made compression the correct way, less dome, more CR.

Zigs’ is the same way. I milled down his dimes but stuck the pistons out...how much I don’t remember, but if he doesn’t care I’ll post it up when we put it together. But he will be a measure 10.25:1 when it goes together. Should be a real neat engine for his car.
 
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