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Old 20-01-2019, 05:18 PM   #1
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2.4 shaved heads on 2.0?

Hi folks,

can i mount shaved 28cc heads from a Merc 2.4 on my 2.0? And if, with what kind of gasket?


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Old 22-01-2019, 07:34 PM   #2
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Anyone has an idea?


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Old 05-02-2019, 03:23 PM   #3
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If the questions are about how compression you should get using different cylinder head CC, and of course knowing the thickness of the headgasket, better to read this before, these infos cover different engines size, but the advises you can find in are pretty good, (from biggerhammer)

Cylinder Heads
Pending Research

You can drop the cc's in the 200 heads to 31 cc's and still run 93 pump gas. It will do a lot for all around performance. (14)

Difference between 2.4 and 2.5 head gaskets: They are different. The cylinder holes are bigger on the 2.5 and the 2.5 has dowel pins. I would get the right gasket. There will be a very poor seal around the cylinders. (15)

I have cut 2.4 as tight as 28CC and folks are happy on pump gas.....Our suggestion on 91 octane on the 2.5 is no tighter than 34CC with thin head gaskets. (16)

The rule of thumb is anything over 145 cranking PSI with a good strong battery is beyond pump gas. (17)
Stock heads on a 200 fishing motor and hi-po motor, where typically 38cc. The first 245/260 motors were even as generous as 42cc, but this was later reduced. (19)

Performance heads and stock heads share the same casting. Primary difference is CC's and the fact that stock heads have black paint, while performance heads are "natural".

As far as just taking the time and added expence to convert to a thin head gaskets VS thick, it is not measurable, some of the heads we cut have to have A LOT of material removed to achieve the desired pump gas top compatable compression. ( 145 ) This amount as I have atested to MANY times vary from head to head , and combustion chamber configuration to combustion chamber configurations. Going from the absolute thickest ( .061 ) to absolute thinnest ( .041 ) ( Hi Per gaskets ) would NOT raise compression enough to even fool with. Maybe 3 to 6 lbs at best and when one is trying to get the max out of a pump gas motor this amount is not measurable. (29)

"MOST loss foam embrelled 1 piece heads that are stock and NOT A DRAG or F1 motor the formula for cutting is as follows :

For every .010" that is removed from the head surface the cc 's will be deminished by .7 cc's
Example: .040" removed will diminish the CC's by 2.8

This is ballpark and not exact but I have found after cutting a zillion heads this to be the norm ! My max that I will cut a pump gas motor with the thin head gaskets is 35 cc's , I will go 34 cc's with the thicker ( drag motor gaskets) and 33 cc's with the very thick fishing motor gaskest! My target is 145 max lbs anything higher your asking for a problem and will end up at the sleeving shop with your wallet a bunch lighter ! " (37)
2.5L Pro Max : "32 cc's is to tight for pump gas especially on a Pro max. I have found 35.5 cc's will live but that as tight as I have the experience that will live on pump gas on that motor !" (36) When more compression is added more BTU's are created, which along with more power comes more heat - with more compression being generated more fuel must be added to slow or stop detonation and make a safe HP gain..(39)

To CC your heads, follow the following procedure from Jay Smith

"I don't know but one way to CC a head and that is with a 100cc buret , a flat pulg ( to screw into the plug hole ), a piece of 1/4"thick plexiglas ( with a filler hole drilled in it ) some heavy grease to smear on the sealing surface to prevent the liquid from OZZING out the edges and I use methonol with some red food color mixed in so my blind ass can see the levels. The rest aint rocket science."

There is also a pictorial on how to CC the motor at HydroStream History & Performance Home Page
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Old 14-02-2019, 01:18 PM   #4
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I think he is more concerned about a possible difference in chamber width. I cannot answer your question, but I'm sure the guys over at can. I would post your question there.
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Old 14-02-2019, 04:21 PM   #5
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Doesn't it depend on whether the 2.0 is based on a 2.4 or 2.5 block. Two types of 2.0 no?
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