[Chevystr383]

yeah my static is 9.9 with the .041 quench and 9.4 with my .062 quench

[383SBC]

Hey Chevystr383, I'm in the EXACT same position as you right now, same heads, measurements and everything! So I got a question then on how the factory does things given that every 350 they produce is going to have the pistons 0.025" in the hole. Either they use a 0.015" gasket to get the ideal 0.040" quench or they run a much higher quench figure. Which is it?

[ericnova72]

Originally Posted by 383SBC

Hey Chevystr383, I'm in the EXACT same position as you right now, same heads, measurements and everything! So I got a question then on how the factory does things given that every 350 they produce is going to have the pistons 0.025" in the hole. Either they use a 0.015" gasket to get the ideal 0.040" quench or they run a much higher quench figure. Which is it?

From the 50's into the 90's, they used a steel shim from the factory in most cases(Aluminum head engines being different).

[cobalt327]

Originally Posted by 383SBC

Hey Chevystr383, I'm in the EXACT same position as you right now, same heads, measurements and everything! So I got a question then on how the factory does things given that every 350 they produce is going to have the pistons 0.025" in the hole. Either they use a 0.015" gasket to get the ideal 0.040" quench or they run a much higher quench figure. Which is it?

Shim gaskets.

[Chevystr383]

so 383sbc do you plan on zero decking the block? How do you like the afr 180s?

[oldbogie]

Originally Posted by 383SBC

Hey Chevystr383, I'm in the EXACT same position as you right now, same heads, measurements and everything! So I got a question then on how the factory does things given that every 350 they produce is going to have the pistons 0.025" in the hole. Either they use a 0.015" gasket to get the ideal 0.040" quench or they run a much higher quench figure. Which is it?

The factory does not idealize quench they lie about chamber size instead on their specifications. Every chamber I've ever measured on a factory spec head is 2 to 6 ccs bigger than advertised. Now they'll tell you this is done to give stock car engine builders space to mill the head and still be legal against the spec. So I'll ask, what else has anyone see the factory do to production parts to help racers pass tech inspection, my experience is nada.

They reduce real compression ratios and use circular dish pistons to lower their production costs and reduce the likely hood that an engine will encounter detonation, thus reducing both their emissions qualification problems on NOx and the expense of warranty problems.

All the old guys here have heard this from me before, the classic of let the customer pick up the extra cost of poor combustion chamber design or just reduce the engine's performance is well seen in the production of the Ford and Lincoln Y blocks. On both engine's the heads started out with a tight chamber with the spark plug located to favor the exhaust valve and beak the projected from the squish/quench deck. This is classic Ricardo chamber design (as in Sir Harry and the High Speed Internal Combustion Engine) which today is the Vortec and Fast Burn at GM or the GT40 at Ford or the Magnum at Chrysler. But back to my story; Ford decided to simplify the chamber and these features were gone by 1955 simply letting the consumer either add octane to make for the mechanical octane's the chamber no longer made with high swirl (squish) and effective quench or live with a de-rated power output. This is not to pick on Ford as everybody did this in one form or another.

It took the government setting emission and fuel mileage standards to finally drive the manufacturers back to adequate engineering of their product instead of selling things designed for the lowest manufacturing cost. This is how today Ford's new Mustang V6 is rated a 300 horse and gets 30 mpg highway, the result of putting some genuine thought into their product at long last.

Bogie

[383SBC]

Hey thanks for the info guys, that makes more sense now. So I think in my case I will have the block zero decked, I already got it decked and told them to deck it to 9.000" but when I installed my crank/rod/pistons and measured I am around 0.020" in the hole........ this tells me they only took 0.005" off the deck and DIDN'T deck it to 9.000". I plan on calling them and telling them it wasn't decked to 9.000" like I asked and hopefully they will take that extra 0.020" off for free so I will be zero decked and can use a 0.040" Permatorque MLS gasket. I would rather be right at zero deck and do it right then use some ultra expensive custom gaskets, besides it would still probably be cheaper to pay and have that 0.020" taken off then to buy those custom gaskets. I wonder though, what difference would it make to run a 0.060" quench (where I would be right now with a 0.040" MLS) opposed to a 0.040" quench when my compression isn't all that crazy at 10:1. I mean its already been decked and it completely flat so that wouldn't be an issue, just a larger than optimum quench would be the only issue. And regarding the AFR's, I have the 195cc eliminators and haven't had any use out of them yet so I can't say one way or another but from all I have read they are among the best bang for your buck CNC ported heads you can buy, easily capable of 500hp.

Keith

[Chevystr383]

other than the increase in compression, whats the difference from .060 quench and .040? any increase in gas mileage, horsepower, throttle response, etc?

[techinspector1]

Originally Posted by 383SBC

I already got it decked and told them to deck it to 9.000" but when I installed my crank/rod/pistons and measured I am around 0.020" in the hole........ this tells me they only took 0.005" off the deck and DIDN'T deck it to 9.000".

What you are assuming may not be true, so be sure what you are doing before you step in doo-doo and make a bad relationship with your machine shop. You may have used rebuilder-type pistons, which are 0.020" shorter on the compression height.

Using 5.7 rods and 1.425" pistons, the stack is 9.000". Using 6.0 rods and 1.125" pistons, the stack is 9.000". If the pistons are shorter, the stack is shorter.

You told them what block deck height to cut the block to. You did not tell them to zero deck the block to the pistons. Be careful.

[ericnova72]

Yep^^^. Got a part # for those pistons, so you can confirm their compression height??

[oldbogie]

Originally Posted by 383SBC

Hey thanks for the info guys, that makes more sense now. So I think in my case I will have the block zero decked, I already got it decked and told them to deck it to 9.000" but when I installed my crank/rod/pistons and measured I am around 0.020" in the hole........ this tells me they only took 0.005" off the deck and DIDN'T deck it to 9.000". I plan on calling them and telling them it wasn't decked to 9.000" like I asked and hopefully they will take that extra 0.020" off for free so I will be zero decked and can use a 0.040" Permatorque MLS gasket. I would rather be right at zero deck and do it right then use some ultra expensive custom gaskets, besides it would still probably be cheaper to pay and have that 0.020" taken off then to buy those custom gaskets. I wonder though, what difference would it make to run a 0.060" quench (where I would be right now with a 0.040" MLS) opposed to a 0.040" quench when my compression isn't all that crazy at 10:1. I mean its already been decked and it completely flat so that wouldn't be an issue, just a larger than optimum quench would be the only issue. And regarding the AFR's, I have the 195cc eliminators and haven't had any use out of them yet so I can't say one way or another but from all I have read they are among the best bang for your buck CNC ported heads you can buy, easily capable of 500hp.

Keith

I'll second or third the piston comments, you need to know whether these are the so called rebuilder pistons that restore the crown to deck clearance of zero decked blocks or whether the deck wasn't zero decked and has the standard crown height 1.56 inch instead of the rebuilder length of 1.54 in there.

I'll add going back to stuff I wrote earlier that I wouldn't mill anymore off the deck than is necessary to make it flat. These thin wall blocks need all the support they can get. If it wasn't cut to zero, my choice to establish a tight quench would be a .028 thick multi-layered gasket. These will wrestle the shear stress at the interface between the aluminum and iron parts and still hold the total quench to .048 which is darn good.

Going crazy over quench between .060 and .040 is the stuff of professional racers with big bucks and egos to match on the line. For a street engine or hobby racer this kind of stuff isn't that significant. Some years ago Chevy High Performance magazine took a Mexican made Mr. Goodwrench 350 up to about 420 HP using the stock bottom end with cast round dish pistons, powder metal rods, and a cast crank with nothing more than a not to radical Comp 268 cam, 1.6 comp roller Rockers, a 750 Holley on a Performer RPM intake and 1-3/4 dia headers all on 92 octane unleaded. to try and put some compression into this mix they did use the FelPro .015 thick rubber coated shim gasket. But that's not something I recommend outside the dyno room. but if one assumes that the block had the spec .025 piston/deck clearance the squish/quench would have been .040 where the edge of the piston came closest to the head, but must of its crown would have been about another .080 lower in the bottom of the dish for .120 over half or more of the squish/quench deck.

So cleaning up the pistons to get the compression and squish/quench up and something healthier for a cam there isn't any reason why this combo couldn't have been knocking on 500's door.

They we're somewhat surprised that it held together for 250 or more dyno pulls so imagine what you could do with a 4 bolt bottom end, forged crank, alloy rods, and forged pistons, a balance job, and reworking the lube system to be sure it could support the 6000-7000 RPMs you turn it to.

So all-in-all I'd be inclined to retain as much meat in the deck as I could so if it wasn't milled to zero, I recommend leaving it unless it's warped.

Bogie

[383SBC]

http://www.summitracing.com/parts/WIS-PT017H4/

My pistons, note the 1.125" compression distance. I have eagle H beam 6.000 inch rods. Do the math and I should be at 9.000". I am however sitting 0.020" in the hole so I am 1000000000000% sure they just skimmed the decks to make them flat. All of this aside, I do completely agree with you Oldbogie on my situation and the course of action to take, however, if you can show me that 0.028" MLS gasket to use please do because the thinnest compatible gasket I can find is 0.039" felpro permatorque MLS. I have been searching and I have been told by others I won't find an MLS gasket or any gasket for that matter that can be used with aluminum heads smaller than what I have found. It is unfortunate they didn't take a little more off the first time around but I am where I am at now and the decks are flat so I have to work with what I got. Basically all I need now is the thinnest possible COMPATIBLE gasket to use in my situation yeilding a 0.050" quench which I could live with since, like you said, it is street/strip and not putting food on the table. If you or any of you could show me such a gasket (if one exsists) I would really appreciate it. If not my only other options are get it re-decked to take off more material which you strongly advise against or run a 0.060" quench which I am still uncertain of the consequences of doing so.

Thanks,
Keith

[oldbogie]

Originally Posted by 383SBC

http://www.summitracing.com/parts/WIS-PT017H4/

My pistons, note the 1.125" compression distance. I have eagle H beam 6.000 inch rods. Do the math and I should be at 9.000". I am however sitting 0.020" in the hole so I am 1000000000000% sure they just skimmed the decks to make them flat. All of this aside, I do completely agree with you Oldbogie on my situation and the course of action to take, however, if you can show me that 0.028" MLS gasket to use please do because the thinnest compatible gasket I can find is 0.039" felpro permatorque MLS. I have been searching and I have been told by others I won't find an MLS gasket or any gasket for that matter that can be used with aluminum heads smaller than what I have found. It is unfortunate they didn't take a little more off the first time around but I am where I am at now and the decks are flat so I have to work with what I got. Basically all I need now is the thinnest possible COMPATIBLE gasket to use in my situation yeilding a 0.050" quench which I could live with since, like you said, it is street/strip and not putting food on the table. If you or any of you could show me such a gasket (if one exsists) I would really appreciate it. If not my only other options are get it re-decked to take off more material which you strongly advise against or run a 0.060" quench which I am still uncertain of the consequences of doing so.

Thanks,
Keith

GM 10105117 has stainless steel faces on both sides. http://www.summitracing.com/parts/NAL-10105117/ I'd use Copper Kote on both sides of this gasket.

GM 14096405 has stainless steel on one side and graphite on the other.
http://www.summitracing.com/parts/NAL-14096405/ I'd put the graphite side against the head, apply Copper Kote to the block side of the gasket.

They both have a compressed thickness of .028 inch.

Another but thicker choice is FelPro 1010 at .039 inch.
http://www.summitracing.com/parts/FPP-1010/ I'd install this dry. These use a copper fire ring which really reduces the fretting of the aluminum, but you'll give up some quench and compression with them.

Another choice is a set of custom Cometic MLS in stainless these can be had down to .027, they are costly about 150 bucks.
http://www.4secondsflat.com/cometic.html

Another trick with these thin gaskets is to put a thin coating of Yamma Bond around the coolant and oil holes on both sides of the gasket. This stuff is sold by Yamaha for sealing vertically split motorcycle engine cases. Seals really well but is an SOB to get apart next time, lacquer thinner helps make that easier. This however doesn't work with Copper Kote, one or the other.

For these gaskets the surface they contact has to be straight and smooth. Mating surfaces need to parallel each other to prevent the less stiff component (the head) from warping when the bolts are torqued. Follow the recommended torques and the rotation which is basically from the inside out of the mating parts. Pull up in small increments with aluminum heads, I use from 5 to 10 rounds depending on the head, less thick heads like the L98/ZZ4 get the most as do the Edlebrock E-Streets and anything imported.

Pay no attention to claims that gaskets don't need to be retorqued, aluminum and cast iron sandwich's always want to come apart. These parts need to cycle a few times and get comfortable with each other, so plan on going back the first time soon and then again in a couple weeks, then check 'em yearly after that. But remember that aluminum expands and contracts a lot more than iron. So once heated up it pushes with a lot more force against the fastener's head than would be seen if the head was also iron. So to start with it wants to unwind the fastener. If it can't the force has to go somewhere and will distort the aluminum, depending upon casting quality the aluminum can actually plastically flow around the bolt head which will reduce the clamping force of the fasteners when the engine cools off and the aluminum contracts away from the fastener. This is one reason why when you buy heads you want to see that they've been hardened at least to T4 condition and preferably T6 and that the base material is something like 356 to start with.

Securing the intake is nearly as important as putting on the heads. The angle the intake bolts have to the head will want to pull them sideways which causes internal strains that have to work themselves out. Follow the manufacturer's torque values and rotation process.

Every bolt that is pulled to a torque value to hold a seal needs a hardened washer between the bolt head or for studs the nut. These need to be lubricated so that aluminum isn't galled by then rotating against it and the torque values are not distorted by friction between the bolt head/nut, the washer and the part being fastened.

Bogie

[383SBC]

Thanks Bogie!! I don't think those first 2 GM gaskets you listed would work for me though, they are listed as 4.000" bore and my pistons are 4.040". Those gaskets must be for a 305 since even a 350 has a 4.000" bore. I am interested in the cometic gaskets since they are MLS and I could run the smallest one at 0.027" and still maintain a reasonable 0.047" quench. I'm debating if paying the extra for those gaskets is worth it opposed to the felpro 1010 cost and having the block taken down. A lot of options right now!!

[oldbogie]

Originally Posted by 383SBC

Thanks Bogie!! I don't think those first 2 GM gaskets you listed would work for me though, they are listed as 4.000" bore and my pistons are 4.040". Those gaskets must be for a 305 since even a 350 has a 4.000" bore. I am interested in the cometic gaskets since they are MLS and I could run the smallest one at 0.027" and still maintain a reasonable 0.047" quench. I'm debating if paying the extra for those gaskets is worth it opposed to the felpro 1010 cost and having the block taken down. A lot of options right now!!

The GM gaskets will fit a 350 with overbore. They actually measure 4.1 inch and are listed for 302, 327, and 350 engines with aluminum heads, Edlebrock also lists them for 302, 305, 307, 327, and 350 with ETech heads.

My experience with these show they are somewhat quirky gaskets, they need good surfaces and careful alignment, but work well when you get them right.

Bogie