What is stopping me from offfset grinding my crank say .030 under and offsetting the journal to increase my displacement and raise my compression. how far would I need to offset grind to raise my compression from 8 to 1 up to 9 to 1 compression? I am new to fords and I don't know the numbers yet, so can somebody crunch the numbers for me and send back a reply,or send me the numbers and I will do my best to get the info posted. Any idea how much displacement this will add?Thanx.

P.S. anybody try this before?

 

Go to the search area and type in stroking.......

 

That won't effect the compression very much, about 1%. But that could be an effective way to create quench if you have quench type heads. All 351M/400 engines have open chamber heads so they don't have quench. The 351C - 4bbl has closed chamber heads. Aussie heads are closed chamber heads.

 

There are a lot of different ways to go. Off set grinding a crank will cost about $200. You may get a .030 off set if the crank starts out with near perfect, standard journals. .030 is about max. for stock rods.

Play around with an online calculator like this one.
http://www.kb-silvolite.com/calc.phtml

The increase in displacement won't change compression that much, but having the piston .030 closer to the deck will reduce over all chamber size by 6.3cc. About .5 of a point compression increase.

 

Thanx, I have been reading all I can on this forum for the last three weeks. I have read alot about the stroking and I'am thinking of the 240 i-6 route, but trying to fiqure out the pistons and stroke for a 9-1 compression. I have copied some stuff off the forum wonder if this is a good way to go?

That is our number, the3434H.That piston is for a stroke of 3.500, comp. height of 1.415, 4.00 bore std.,ring pack of 2-5/64 1-3/16. The pin dia. is .9122, rod length 6.025 and piston weight is 489, and pin 103g. The cc to head volumes are as follows for comp. ratios, 62cc-11.1,66cc-10.6,76-9.5. I hope this what you were looking for.
Thanks Tech Dept."
It's a flat top "claimer series" piston. $375 AU (about $207 US).
Take a 400 crank and off set grind the journals to a 4.17" stroke with the 2.123" 240 I-6 rod journal. The 240 rod is 6.795 long, 912" pin. Rods are $80 a set. They have to be narrowed.
10.297
-2.085 (half stroke)
-6.795 rod
-1.415 piston
.
I think this would make about 10.8:1 with a 76cc chamber. I need to figure out how far to offset grind my stroke to get a 9:1 with 76cc heads. I figure a stroke of 4.1 will get me about 9.2:1 with about 418ci, is this about right?Any thoughts?

Well thanx for all the replys. Alot of people on this forum have alot of knowledge and are tons of help when it comes to making these engines come alive.

 

You'll need different rods if you offset grind the crank to 4.1". The journal diameter will be too small.