xafalcongs
Well-known member
Can you safely bore a latemodel X-flow .060" over? That would take it to 3.74" or 95mm.
--J
--J
Max safe overbore for a 4.1 X-flow
- Thread starter xafalcongs
- Start date
An x-flow will take 60 thou over. My 228 has 56 thou over 305 Chevy pistons.
As Mike at FSPP and others say, bore the minimum amount to get the cross hatch , ovalarity and tapper within limits. In most cases, 30 thou does the trick.
Since most US engines went to modern thin wall (120-180 thou) green sand castings in 1963, any I6 or small block Ford made after 1963 prefers 30 thou over. That way, you've got a chance of a 50 year run out of a block With a lack of corriosion inhibitor typical of most backyard serviced Falcons, the wall thickness that was perhaps 120 around the cylinders in 1985 may be only 90 thou in 2005.
The text book rule is to check with a sonar ray or cover meter, and if you go to less than 10:1 compression , you need about 120 thou wall thickness against the thrust face of the piston.
As Mike at FSPP and others say, bore the minimum amount to get the cross hatch , ovalarity and tapper within limits. In most cases, 30 thou does the trick.
Since most US engines went to modern thin wall (120-180 thou) green sand castings in 1963, any I6 or small block Ford made after 1963 prefers 30 thou over. That way, you've got a chance of a 50 year run out of a block With a lack of corriosion inhibitor typical of most backyard serviced Falcons, the wall thickness that was perhaps 120 around the cylinders in 1985 may be only 90 thou in 2005.
The text book rule is to check with a sonar ray or cover meter, and if you go to less than 10:1 compression , you need about 120 thou wall thickness against the thrust face of the piston.
xafalcongs
Well-known member
xecute®™© he he":1oisxodf said:
Thanks for the replies. Yes, I would sonic check before I bored the block. I actually am only planning on a .045 overbore to bring the cylinders in at 3.725". From there, I'm looking at destroking the motor to 3.75" to achieve a 245ci (4.0ltr) final displacement. I still need to spec the crank to see if it can be ground down to use a 1.88" rod bearing. I'd like to use a 6" rod but may go up to a 6.25" rod depending on what piston blanks I can have milled by Ross. I want a compact, re light, piston on a long-ish rod as I want to get this thing to rev a little easier. I'd like to see a 6500rpm redline with hp all in by 5500.....plus a 10:1 compression.....this may be a very expensive experiment!
xafalcongs
Well-known member
DYNOED250":3gtcs1qe said:
Hey that's great news. Don't know how I've missed those as I'm on their site quite often looking at vee-eight part numbers. I'll check them out as that would save me a good bit of money. Ross slugs will set you back around US$200 each for a custom job.
A
Anonymous
Guest
Sorry to res an old post, but I have bored a 250 out 120 before, going from 3.680 to 3.8 It took three blocks before I found one that would take it, but it can be done.
