crank tolorance
- Thread starter 4ford
- Start date
If the 8BA crank is ready to go, get some 8BA rods and bearings.
Technically the 8BA crank plus floating bearings is probably superior to all 8BA stuff, would you see the benefits? Doubt it. This is a regular street driven engine?
If you need to change bearings on the crank in the future, for whatever reason, you'll be glad you went for 8BA bearings. The cost difference is large. The chance of screw ups is much smaller.
This is my opinion.
Martin.
Technically the 8BA crank plus floating bearings is probably superior to all 8BA stuff, would you see the benefits? Doubt it. This is a regular street driven engine?
If you need to change bearings on the crank in the future, for whatever reason, you'll be glad you went for 8BA bearings. The cost difference is large. The chance of screw ups is much smaller.
This is my opinion.
Martin.
Bored&Stroked
Well-known member
I agree with Scooder - for what you're doing, I wouldn't screw around with the full-floater rods and/or bearings. (And this is from a guy that just spent 8 hours setting up 1940 21A full-floaters for a 284 cube race engine - so I know them well).
Heck, I'd just go to eBay and find a set of 8BA rods (probably $40 - $60), have them rebuilt and run the late insert bearings and the 8BA crank. You'll save money, the setup is 'modern/easy' and you'll be very happy.
PS: If you need any technical help, just PM me - be glad to help validate anything you're hearing from any machine shop.
Posts 21-23 suggest this thread has taken a turn. I thought the goal was 500 mi per year, and possibly a budget build, based on 500 / yr. If you're going to start screwing around, mixing parts with a different crank, rods from another unknown source, probably not matched from the same engine, then you are starting down the path of a really nice build, but budget-be-damned. For one thing, now you have to add the balancing cost. I've done two engines this way in the last few years, one with a Merc crank, one with a Ford crank, and both were expensive because of the extra machine-shop costs, and extra new parts. I might add, in the case of the build with the Ford crank, I'm still able to source these cranks for free, but the end total still comes out $$$. I would re-evaluate the goal, and think carefully if the goal is 500 mi/yr. If the goal is to build a nice engine for your heirs to use and abuse, then budget be damned.
JMO
JMO
I really appreciate all the things that were talked about on here, I just cant put it back together with old bearings and then when I fire it up and hear something then say to myself you should have done it right dumb -ss so I will see about the floaters and if this guy comes thru with what he says, he seems to think its not that more expensive??? will see
thanks again!!
thanks again!!
Bored&Stroked
Well-known member
It isn't just cost, somebody has to know how to use a rubber mallet and size them correctly to fit the rods and journals. You can't just throw them into the engine . . . need to spend some time on them. You might want to buy Ol' Ron's book - he gets into it.
Just wanted to make sure you/he know there is more than just sizing the crank and rods correctly - one has to spend time on the bearings.
B&S
Bored&Stroked
Well-known member
Cool - I think you'll be very happy with your decision. One last question, you really should have the reciprocating assembly balanced. Is he is a real machine shop, then he'll have the equipment.
He'll need the following:
Crank, Rods, Pistons/Pins, Rings, Bearings, Flywheel, Clutch, Crank Pulley.
You can't believe what a difference having the whole assembly balanced makes. If I had any of these engines all apart, I would always do this, you'll be glad you did. It is probably a couple hundred dollar expense - but well worth it in my book.
GOSFAST
Well-known member
I would make a recommendation with respect to "building-in" the bearing clearance NOW, this is such an important issue when you are finally finished. It could be the difference between having 5# oil pressure idling or 20#.
If you are starting from scratch, BEFORE machining the crank to any undersize, you should place ALL the brgs in their respective positions, the 3 mains and the 8 rods, and using the correct tools determine to what the final crank sizes will/should be ground. This procedure elimates ANY questions concerning "low" oil pressure as a brg issue after the fact! We want .002" clearance on both, give or take a couple tenths! We also like .002" between the cam and the cam journals, but there aren't too many options about this final number!
With all brg clearances it comes down to "tolerances", if they are "stacked" against you it will be costly, if they come out in your favor it'll be a "home-run". We don't like "gambling" with these numbers, we want them built-in. This is simply part of "blueprinting" a build. It is the ONLY correct way to get it done! And this is relatively easy when "sizing" the cranks!
(Add) With repect to the rods I would want new pin bushings installed also, or it would be "no-sale" here! We run 2 engine balancers here, this is no issue!
Thanks, Gary in N.Y.
P.S. Any build that has "loose" mains, "loose" rods, or "loose" cam brgs will be a "pain-in-the-butt" to deal with afterwards! It will take ALL the fun out of using/enjoying the ride!