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Old 10-27-2008, 07:30 PM
GMR GMR is offline
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block deck height 8.990

A sbc 350 with a block deck height of 8.990 - will there be problems fitting an intake, heads, distributor. Wondering what, if any, machining costs might be involved. This would be a mild performance street motor. Haven't bought anything yet.

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Old 10-27-2008, 07:42 PM
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no problem really, just make sure you run a .050" head gasket.
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Old 10-27-2008, 07:56 PM
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If the 8.990" is the dimension of your stack, I think I'd be shopping for pistons with a taller compression height to prevent cutting the block decks so much.

In other words, on a 350 for instance, half the stroke is 1.74", the rod is 5.7" and a good quality piston will have a compression height of at least 1.560". Added up, this makes the stack 9.000" and will prevent having to cut the decks so much to arrive at a zero deck.

With zero decks, a head gasket should be used that will measure between 0.035" and 0.045" to allow a tight squish to allow operation with full ignition lead on pump gas without detonation. There are many gaskets available that measure 0.039", 0.040" and 0.041".
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Old 10-27-2008, 09:12 PM
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Quote:
Originally Posted by techinspector1
If the 8.990" is the dimension of your stack, I think I'd be shopping for pistons with a taller compression height to prevent cutting the block decks so much.

In other words, on a 350 for instance, half the stroke is 1.74", the rod is 5.7" and a good quality piston will have a compression height of at least 1.560". Added up, this makes the stack 9.000" and will prevent having to cut the decks so much to arrive at a zero deck.

With zero decks, a head gasket should be used that will measure between 0.035" and 0.045" to allow a tight squish to allow operation with full ignition lead on pump gas without detonation. There are many gaskets available that measure 0.039", 0.040" and 0.041".

Go with what the "Tech" sez, the 9.00 makes life much eaiser!
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Old 10-28-2008, 07:13 AM
How fast is fast enough?
 
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It was my understanding that it was already cut to 8.990"- since his pistons are only .010" out of the hole he can just run a thicker gasket- to get his .040" quench.
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Old 10-28-2008, 08:17 AM
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We cut alot of blocks 8.990 and with a 3.480 stroke the Wiseco, JE, CP,Diamond pistons if we use a 6 inch rod and the pistons has a 1.250 CH that would be zero deck and on the 5.7 rod their CH is 1.550 which is zero deck.

The same piston and rod combos with a 3.500 stroke crank would be 9.000 deck for zero deck.

There has never been a fitment issue with the intake as most of the performance intake gaskets are thin which helps in these cases.

Some of the SRP pistons have a 1.260 and 1.560 CH

Last edited by CNC BLOCKS NE; 10-28-2008 at 09:12 AM.
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Old 10-28-2008, 09:18 AM
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Thanks fellas and apologies for not making myself clear. The block I'm looking at is already cut to 8.990.

CNC, I'm looking at Felpro intake gaskets and see they are mostly 1/8" or 1/16" thick. So I will most likely need the 1/16" as opposed to the 1/8". This will give me enough gap at the front and rear for silicone? Is that what you were saying?
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Old 10-28-2008, 09:28 AM
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Quote:
Originally Posted by GMR
Thanks fellas and apologies for not making myself clear. The block I'm looking at is already cut to 8.990.

CNC, I'm looking at Felpro intake gaskets and see they are mostly 1/8" or 1/16" thick. So I will most likely need the 1/16" as opposed to the 1/8". This will give me enough gap at the front and rear for silicone? Is that what you were saying?
With the thinner intake gaskets it will make the intake set lower which will halp make up for the low deck heights.
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Old 10-29-2008, 09:22 AM
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thanks CNC
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Old 10-29-2008, 12:53 PM
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Quote:
Originally Posted by GMR
A sbc 350 with a block deck height of 8.990 - will there be problems fitting an intake, heads, distributor. Wondering what, if any, machining costs might be involved. This would be a mild performance street motor. Haven't bought anything yet.
This should be fine as long as the heads are not also milled. This cut will lower the heads by .035 inch which is getting on to the max one should consider without correcting the intake just as if this was a situation where the heads rather than the block had been milled. Just keep in mind that milling the block deck and milling the head (if any) are additive to each other in respect to how the head is positioned relative to the intake. That's to say the heads will set closer to each other making the distance across the V narrower; also, the ports are lower. The usual solution is to mill the intake sides to narrow it and the bottom to lower it. However, if the movement is only .035 total, this should be accommodated by the gaskets.

Many aftermarket pistons consider the deck will be milled and they are already shortened between the pin and crown, but check this dimension upon assembly to be sure. If the crown projects above the deck, this will drive selection of a head gasket that will maintain .045-.050 inch of space between the piston crown and the squish/quench deck of the combustion chamber. Less than this risks collision between the piston and the head, more than this diminishes the effectiveness of squish and quench. Head gaskets can be stacked to get the right dimensions if one can't be found to have the suitable height.

Bogie
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Old 10-29-2008, 03:04 PM
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Thankyou for the explanation Oldbogie, very helpful.
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