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Discussion Starter · #25 ·
Running the math with those shim gaskets and assuming a 0.025 deck clearance, the compression ratio with flat top pistons (4-valve relief) gets me 10:1. Assuming a 0.020 deck clearance bumps me up a tenth.
With the tighter quench clearance, I’m good with that.

Are the 1094’s going to reliable for a street motor? I only ask because the description references racing applications.
 

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Running the math with those shim gaskets and assuming a 0.025 deck clearance, the compression ratio with flat top pistons (4-valve relief) gets me 10:1. Assuming a 0.020 deck clearance bumps me up a tenth.
With the tighter quench clearance, I’m good with that.

Are the 1094’s going to reliable for a street motor? I only ask because the description references racing applications.

The issue with shim gaskets and aluminum heads is that aluminum has a larger rate of expansion when heated and contraction when cooled than does iron or steel as in block and shim gasket. Given we’re starting with two good quality mating surfaces of the block deck and the head’s mating surface there is nothing bad about a shim gasket with one exception.

That is the thermal movement of the head compared to the iron block and steel gasket. The head as it expands and contracts with temperature changes scrapes along the fire ring eventually eroding the aluminum where contact is made with the fire ring. The FelPro 1094 has a polymer coating that flexes with this movement and is self lubricating to facilitate a sliding moment instead of an abrasive one. Obviously there is a life span to this but a data point is Subaru uses a similar type gasket which functions just fine through their warrantee period and longer.

The other answer to surface abrasion of the aluminum head which I should first mention that aluminum is softer than iron or steel which is why the head takes the greater amount of wear. A partial answer is hardening the aluminum to condition T4 or T5 but this is expensive and you don’t see it till you're buying the high price heads. The somewhat gooder news is all aluminum work hardens so just using it dynamically eventually improves its surface hardness.

Anyway got lost a bit there, the subject is how to reduce this surface abrasion with gasket choices. Here both MLS and composite gaskets allow for differential movement across the gasket so rather than the aluminum head doing all the sliding on the fire ring these type gaskets allow some of the movement be taken across the thickness of the gasket. Another solution is found in gaskets using a copper fire ring rather than the more typical stainless steel. Another is the pro racers solution of a stainless O ring but we’re talking some serious money with this trick.

You can make your own MLS by stacking shim gaskets but even stacking a pair of .015’s delivers the sum of .030 and that is in the range of composite gaskets that are available down to .028 or .026 inch.

I had started a long dissertation on this your post but I keep getting distracted in getting my Harley back together after a tire blow out. Parts are slow to arrive and the damage took longer to fix than anticipated. I think about doing things like I’m a 20 something but do them at the pace of being an 80 something. I vaguely remember my mother saying something about ‘biting off more than I can chew’.

Anyhow to use my now venerable Frankenmouse engine as an example it has crankshaft dyno papers of developing 430 ft pounds of torque at 4200 and 412 horsepower at 5600. It uses LT1 heads that are coolant modified to the standard 880 block with the vent system enlarged and repurposed to be an external coolant return to an water neck box mounted on a GMPP LT1/4 intake manifold. Plus they have port and valve mods that showed 257 cfm intake and 194 cfm exhaust both at .6 inch lift. These heads are mounted with a GM gasket of .028 inches that is stainless faced on one side and graphite on the other. Those torque and power numbers came with a 670CFM TBI, it currently runs an 800CFM Edelbrock AVS-1.

I can actually get this to run on 87 octane E10 during the winter without changing any tune or jetting. Early spring and late fall and actually most frequently during the winter it runs just fine on 89 E10, Late spring through early fall it has to have 91 E10 which is what it’s tuned for. The 87 octane was the rare test to see if it could limbo that low.

I need to add that it uses a forged 4032 alloy, 10cc D dish piston that is .025 in the bore on a 5.7 rod. The head chamber measures 53 cc’s and the SCR is 10.65 with a calculated DCR of 9.23 for the LT4 HOT cam. The power comes in plateaus rather than peeks especially the torque with not less than 420 ft lbs from 3600 to 4800 RPM while horsepower is at or over 400 from 5400 to 6000. Needless to say this is one potent street engine with lots of torque and power right where you need it on the street.

Bogie
 

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Fel pro 1094 is a coated steel shim head gasket.
Yes they are reliable with aluminum heads. The literature that comes with gaskets even states they are fine to use with aluminum heads. If you do a search you,ll fined many people using that gasket with aluminum heads with no problems. Or you could send your block to the machine shop and have it zero decked and use a standard size type of gasket, but i surly wouldn't tear an engine down just for that. You will have no problems using that gasket, make sure heads surface are nice and smooth and spray the gaskets with Cooper head gasket sealer.
 

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Discussion Starter · #29 ·
I’m really liking the coated shim gasket. That gets my quench and compression ratio exactly where i was hoping to get it. I’m thinking that is going to be the plan.

so right now the build is looking like flat top pistons with a ball hone. 65cc aluminum heads with 2.02/1.60 valves and the z28 springs. Taking an earlier suggestion on the cam and found the comp cams high energy 268h cam. 268/268 - 218/[email protected] 110 LSA/106 ICL.
I’m thinking that with the higher compression and the tighter LSA this should be a fun little build.
Have to tear the block down now to see if a simple hone and re-ring with flat top pistons is going to work clearance-wise.
 
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