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Just to put your mind at rest, after close inspection I can report that the pistons have not touched the cylinder head surface. We are using a .040" Cometic head-gasket and we run .036 squish gap to the head surface, which obviously means the pistons are out of the bore by.004"
More when we complete the hot block pressure test hopefully today.
Cheers,
Mark.
I'm very happy for you thanks for the update, I'm thinking you may want to pressure test the block individually with sleeves in mind.
As a result of finding water in the oil of my new 435ci engine build, we decided to remove the engine and set up a test rig in order to best determine were the water ingress into the oil was emanating from. The accompanying pictures show how we went about determining and understanding the cause and the fix.
Pressurizing the engine block, through a Schroeder Valve to 35 PSI.
Inspecting the pressurized 200ºF hot engine block.
The coolant heater, pretty standard equipment in Dirt racing to preheat the engine, and well worth the investment for serious racers.
We discovered that the Cometic gasket, applied dry as per Cometic's recommendation, does not have a very effective seal around the inner studs flanking the pushrod cavities and that water can and was seeping up the head studs and finding its way down the oil drain and pushrod bores.
The fix in our opinion is to run a bead of Locktite liquid gasket seal around the base of each stud, as well as separating the 3 layers of the .040" metal gasket [by removing the rivets] and spraying each layer with adhesive copper coat letting that dry and then re-assembing the casket etc.
We will also fill the small slot between the flats of each sleeve with two pot epoxy and scrapping if flat and level with a razor blade.
I'm surprised when you applied the thread lubricant to the studs that didn't create a good enuf seal. Glad it wasn't the block!
Hi GN,
We checked the stud bore,s and they are all blind, plus the studs were coated with thread sealant so no issue, we are of the opinion that the issue lies with the incomplete casket bead around the base of each stud. We are of the opinion that the gasket should be stamped in such a way as to form a raised bead in a complete circle around each stud.
However the gasket is also leaking, as I stated in my first post, across the narrow 'bridge' between the cylinder bores, so logically there is either a bit of porosity in the really thin aluminum wall or perhaps a tiny crack, either way we think we can fix that with cleaning out that cavity and epoxy sealing it.
Its also hard to see such a tiny leak getting into the oil as logically it would vaporize under combustion conditions.
I'm very happy for you thanks for the update, I'm thinking you may want to pressure test the block individually with sleeves in mind.
Hi Camster,
I assume that you have read my separate post on the Hot Block pressure testing that we carried out, so I wont repeat it here, as I think this thread has come to it natural conclusion, and should just fade away now that we have found the cause of the issue.
For this reason, I went ahead and merged the two threads together to keep the original updated.
Hi KCS,
Understood no issue on my part.
DB, your question:Any idea why is this happening now and not when you ran the block previously?
I do hope its those little things
When I purchased the car and decided to increase the engines capacity and fit new cylinder head's and a much better camshaft etc, it had a standard 4.125" bore and .053" gasket. On recent inspection that gasket did have red sealant around the water way's and stud base's and of course we now know for very good reason. My engine builder made a mistake plain and simple, he maintains he was just following Cometic's instructions, which is also correct, so its a no win situation.
Kiwi, funnily enough im running the cometics in my newly rebuilt 383 for my jet boat and they are leaking oil, installed dry as per instructions, gonna pull the heads and use new gaskets and sealant.
Kiwi, funnily enough im running the cometics in my newly rebuilt 383 for my jet boat and they are leaking oil, installed dry as per instructions, gonna pull the heads and use new gaskets and sealant.
06-05-2015, 10:39 PM
