Quote:
Originally Posted by JWL
For best results bore near the minimum required to get clean-up and coordinate with pistons available.
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Even though we sell many kits that go directly to the 3.312" o'size I personally am in 100% agreement with John here. For a couple reasons, first, you shorten the life of the block for future builds, second (you may not totally believe this but dyno tests prove it for us on many builds), the "thinner" the walls the more power you lose, and third, there will no "major" power difference whether you go .030" over or .125" over. We are ONLY talking bore size here NOT stroke. You WILL pick up much with the upstroke but not so much from the add'l o'bore increase?
With respect to your build recommendations, when we do any Flatheads over here, there are 2 procedures that are NEVER open for debate, my customer's are made aware of this going in and I haven't had a single one "walk".
First one is the "block-plate" is used to finish the bore's, this is mandatory, and second one, they must agree to the bronze guide option. Everything else is "open to debate".
The only other item in the build strongly recommended here is the use of some type "moly" ring and preferably a newer style "metric" pack. We have them on the shelf for a smaller o'bore, but ONLY in +.040" (3.228"). We keep the Ross pistons on the shelf for this setup also but only for the 4.000" (stock-Merc) stroke. None of this is mandatory, only recommended, especially if you are "chasing" HP though.
For the 3.312" bore we have 6 kits on the shelf now at all times. Most are 3.312" x 4.250", very popular seller's! These straight-forward builds average 150+ HP and 250+ Torque easily.
(Add) The build in my signature below here I believe has close to 30,000 on it now. It is a very comfortable "driver" according to my friend, the owner. It was built a while back.
Thanks, Gary in N.Y.
P.S. We've learned over the years the value of block-plate honing and about valves "sticking/hanging" during storage periods. The bronze-line guides solve this particular issue. If your original guides are in decent shape you don't need to purchase new ones, simply line those originals,we do this all the time!