No need to notch pistons. On a B, the exhaust valve can contact the block
at extreme lifts. 18V blocks are flycut to prevent this, and with the
deeper combustion chambers on the pre 18V head, you need to really take a
whole lot off the head, and have a hairy cam to make this a concern.
Regards,
Chris Delling
At 02:11 PM 2/22/98 -0900, Baker, G. wrote:
>Scott,
> I would imagine you could shave more than .060 if you notched the pistons
>for valve clearances. This is done often on "regular" engines and I'd be
>interested in hearing from a guru if this shouldn't be done with an LBC.
> On another topic......The head on my 56 A is cracked across the "tit"
>separating the intake and exhaust. I believe the shape of this combustion
>chamber is similar to another earlier F*** head and when this occurred in
them
>they were just machined off......slightly and evenly. It's the only flaw
after
>magnifluxing and I think I've read these "tits" just get hot and cause
>detonation
>anyway so I don't see any reason not to proceed and then measure the CC
>afterwards
>to make them all the same.
>Any input would be appreciated.
>Thanks,
>Gregg Baker
>
>
>At 05:02 PM 2/22/98 +0000, you wrote:
>>I have a 1965 cylinder head with the large combustion chambers on my
>>1972 18V engine. As a result, my compression numbers are in the
>>cellar. This also causes me new problems when I'm looking at
>>pistons, because if I order the pistons for a 1972 engine, they're
>>expecting the smaller combustion chambers, so I get a low
>>compression ratio. If I order the older pistons that will work with
>>the head, I have the wrong connecting rods. Since I just got the
>>engine rebuilt in November, I'd like to fix my CR woes without buying
>>new pistons or rods at all.
>> Is it possible to shave enough material off of the old large-chamber
>>heads to reduce the chamber size to that of a newer head? If I can
>>do this, I can just order the newer 18V pistons, and the compression
>>ratios will be as advertised in the catalog. If not, can I use the
>>older rods and pistons with the old head in a 18V engine?
>> I know I can order custom pistons from Venolia, but would prefer
>>using a standard part. I could also just break down and buy a 18V
>>head, but my old head is straight, uncracked, and recently completely
>>rebuilt, so I'd like to hold onto it.
>> Does anyone know how much I'd have to shave the head to make the
>>chamber volume equivalent to a 18V head? I know I can take off .060,
>>based on the recommendations of some of the list members, but I don't
>>know what this reduces the chamber volume to.
>>Thanks,
>>Scott
>>
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