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intake isuue

664 Views 7 Replies 6 Participants Last post by  JB.Racing
Intake ports sit high .25in from head ports after engine rebuild. Calc. CR to be 8.5:1. Chambers are measured to 45cc. I have not measured deck height. In order to match ports, I need to shave .187in off of the intake mounting surface. This seems wrong to me. Any suggestions???
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Better check the deck height. Sounds like that's where the problem lies.
How much was the block decked?

Were the heads resurfaced at any point in time?
I measured the deck height using two different methods. The results are 9.558 and 9.551. So, there was not alot of material removed on both the heads and the block.

I took the ported intake back to the vendor and we compared it to another intake which was being shipped out to a customer and both intakes had the same critical dimension. I am not sure what to do next. Any suggest, other then to spell "issues" correctly?

Is it typical to have .25 inch of miss-match between the head and intake ports? If I take off .088 inches (this is alot) from each side of the intake, this will leave only an 1/8 inch mis-match and I believe I can port match this difference. Does this seem correct???

What head gasket are you using?
The copper head gasket is .043in thick. Below is a paste of a MS-Excel file of the combustion ratio calcs and the deck height calcs. Please review and see if I made a mistake.

I am going to take the intake to a local machine shop and have them cut .088 in off each side. I hope this will drop the intake down enough where I can port match the rest.

bore = 3.82 in
stroke = 3.4 in

main journal dia. = 2.478 in (cut .020 in under)
journal to deck = 8.3125 in (measured with calipers on right and left side of block)
deck height (1st method) = 2.478/2 + 8.3125 =9.5515 in

connecting rod length (journal to journal) = 6 in
piston pin height = 1.85 in (from JE pistions data sheet)
piston deck clearance was measured = 0.008 in (measured by calipers using cam degree wheel)
deck height (2nd method) = 6 + 1.85+ 3.4/2 +.008 = 9.558 in

piston dish depth = 0.245 in (from JE data sheet)
piston dish dia = 3.08 in (measured with calipers)

combustion chamber vol = 45cc (measured by speed shop)

head gasket thinkness = 0.043in (measure with calipers)
head gasket cylinder Dia = 3.85 in (measured with calipers)

gasket vol = 0.500 cubic in
piston dish vol = 1.824 cubic in
deck vol = 0.0916 cubic in
chamber vol = 2.746 cubic in
chamber vol = 2.746 cubic in
swept vol = 38.947 cubic in (swept vol = stroke * pi * (bore / 2)^2)

total vol = 44.110 cubic in (total vol = swept vol + chamber vol + gasket vol + deck vol + piston dish vol)

compress ratio = 8.544 cubic in (cr = total vol / (total vol - swept vol))
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All depends on Gasket Combo.
What is the actuall stock Head Gasket thickness?
Close to .070"
What kind of Intake Gaskets are used?
When the Intake is NOT torqued, it will sit higher. Check when it's well torqued down ( 30-35lbs) Then make a decision.
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