Dreaming of 6 litres...........
04-30-2018, 05:34 AM
#21
At that CR, it's going to feel lethargic at best.
Use a .040 head gasket, that will get the CR into the upper 10's or if you're feeling really spiffy, use a Cometic .021 gasket.
That'll get you into the mid 11's for CR. With a good tune it would be completely safe but you'd probably have to run premium.
Use a .040 head gasket, that will get the CR into the upper 10's or if you're feeling really spiffy, use a Cometic .021 gasket.
That'll get you into the mid 11's for CR. With a good tune it would be completely safe but you'd probably have to run premium.
04-30-2018, 07:58 AM
#22
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Now that we know what your doing we can get a more accurate picture.
IIRC an LQ4 piston has an 8cc dish.
1st, Why bore the engine .060 over??? There is no advantage to that and the engine will actually run hotter the thinner the cylinders get.
2nd, Why .075 thick gasket? This will take away from the quench area and reduce compression lower to like around 9.2:1. Typically the factory pistons stick out of the hole on these Iron blocks. Each one is a little different I typically use .006 out of the hole for rough calculations. Ideally you would want to run around a .040 quench which is why the factory uses a .052 thickness gasket.
If you want a 9.7:1 ratio I would build an LQ4 with a .020 over bore with a factory head gasket and 69cc head.
I have a comp cams pushrod length checker 7702-1
IIRC an LQ4 piston has an 8cc dish.
1st, Why bore the engine .060 over??? There is no advantage to that and the engine will actually run hotter the thinner the cylinders get.
2nd, Why .075 thick gasket? This will take away from the quench area and reduce compression lower to like around 9.2:1. Typically the factory pistons stick out of the hole on these Iron blocks. Each one is a little different I typically use .006 out of the hole for rough calculations. Ideally you would want to run around a .040 quench which is why the factory uses a .052 thickness gasket.
If you want a 9.7:1 ratio I would build an LQ4 with a .020 over bore with a factory head gasket and 69cc head.
I have a comp cams pushrod length checker 7702-1
P.S. yeah, can I reuse the factory head gasket? Been looking at cometics and the smallest size I've found is 4.030 bore
Last edited by Mark Johnson; 04-30-2018 at 08:17 AM. Reason: additional questions
04-30-2018, 11:56 AM
#24
It's the gasket that is 4.060 (don't plan to touch block bore) and .075 thickness allowed for my target compression with the heads milled to yield that 69cc combustion chamber. Hmm, but also didn't take into account the .006 outta the hole, or the 8cc dish. Thanks- gonna crunch some more.......
P.S. yeah, can I reuse the factory head gasket? Been looking at cometics and the smallest size I've found is 4.030 bore
P.S. yeah, can I reuse the factory head gasket? Been looking at cometics and the smallest size I've found is 4.030 bore
04-30-2018, 02:04 PM
#25
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Factory gaskets good enough- great! yeah- 69cc combustion chambers and the factory gaskets will get me to the 9.7x I want to be, overlooking the obvious.. Say, recommendations on a pushrod length checker...........
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Mark Johnson (04-30-2018)
You said budget....
