guys i have a .030 over bored 8ba with a 4 inch merc crank offset ground to 4 1/8 for 1940 ford connecting rods. i,ve never assembled a engine with this style of rods,where the bearings free float. do any of you fellas have experience with this setup and can offer any info-tips for me. i have tons of $ in this engine and dont want to mess it up this late in the game. heres my engine spec's. 400 jr cam/kit real johnson adj. lifers ross .030 o/s forged pistons ported and polished ports (both sides over size stainless valves barron street heads edelbrock intake with 1- 97 and 2-81 strombergs n.o.s. crab top points dist truck water pumps truck oil pan n.o.s. sheifer aluminum flywheel h/d clutch assy top loader truck 3 speed trans h/d oil pump (modified oil system " n.o.s. 1940 ford rods. thanks for all help regards old man bob in tn.
Remember this, these engine, stock, were put together by a bunch of workers and they are made easy to put together. Put the short block together, and make sure the cam is set right , and there is no play front to back with the crank, turn the crank and make sure it turns easily after you have assembled everything with lubrication on it. Then put the heads on, with putty on the head to make sure the pistons don't hit the head,or the valve don't hit the head, pull them off and make sure you have the clearances. Llube, lube , lube. Put the heads back on, tighten it all down to specs, and try to crank it with wrench on front pulley, If all is ok and it spins it is probably ok to fire it up. Pretty hard to make a mistake with a flat head. The nuts are not the problem and if you are not going to run fuel everything should be ok
I'm guessing you mean you have 21A style rods with one bearing supporting two rods, as long as the machinist made sure everything is round and clearanced for floating rod bearings it shouldnt go together different than any other engine. the poster above me summed it up pretty much with checking that nothing should be smacking into anything else either, and oiling everything is a must. I did use Isky rev-lube on my 400jr when I installed all the lifters, for break in. Sounds like a sweet little V8, need some pictures and video of it running with that biggish cam in it.
The lifters you are using have an "interference" fit on the threaded portion that helps to maintain the clearances you want to run for your particular cam.it is important to arrive at the proper clearances quickly as the more turns on the lifters will soon eradicate the interference fit and they will no longer maintain the clearance you are wanting to achieve. In other words,they will become loose and sloppy.I have always run a 9 1/2 inch clutch,even at the track,where I ran 15 flats at 90 mph. There is no need for a heavy duty clutch unless you are slipping the clutch or ride the clutch or pull heavy loads.You are defeating the purpose of running an aluminum flywheel by putting a heavier 10 in or 11 in clutch on the flywheel.Your throttle response will be noticeably poorer with a heavy pressure plate than what you need.Full floating bearings out of the box need to be checked for the proper spread to fit the rod properly.Out to out on the rod bearings should be 2.215 to 2.220 inches. Hope this info will give you more insight into the flathead motors.
^^^ John, is the setting of this spread the operation I have heard mention of on FordBarn where they say to use a mallet to achieve the correct fit of the floater bearings. By out to out I assume you mean the outside overall width of the bearing insert at the part line. Correct? I've always had the later type bearings so the floaters are a bit of a mystery to me. Mart.
If your crank has 2 oil galley holes on the big end journal, you will be better of running 8BA rods that take a tanged bearing.
You are CORRECT in your assumption on the bearing spread.If the spread is incorrect in either direction, it does NOT take a heavy blow to make it the proper fit,as they will move either way easily. Flatheadjohn47
I would never advocate the tapping of the bearing to change the diameter of the bearing. Any time you change the diameter at the break of the circle is never true as the bearing is now not a circle anymore. Either the bearing should be changed to a different size or the crank or rod bearing resized. Hell, it makes little difference over all, as if the bearing is over size the rod will squeeze it tight, and if it is undersize the crank will spread it., It is only when the thickness of the bearing is wrong that you will have problems. Feel free to disagree, but that is the way mechanical things work! At least you don't have to blue and scrape them to fit.
Hopefully you have new floater bearings I have found the King brand bearings to be very good quality. First be sure the main bearings have the proper clearance including end play. To work correctly there must be end play in the crankshaft but no more than .006 thousands if you put the crank in with no end play you will spin the rear main bearing causing the motor to lock up. The floater bearing assembly takes a lot of patience to get right its not easy you must use a lot of assembly oil. This being your first attempt you will find it gets very tight as you add more rods and pistons into the block. The motor will loosen up after you spin it over for a while but it is a different feel than an insert rod bearing type of assembly. As for ARP rod nuts if your going to spin this baby up over 6 grand sure spend the money but if you have NOS rod nuts they will work fine for a street motor.
And they frequently do need adjustment to achieve operating clearance on both sides of the bearing. Pop over to Fordbarn...Ol' Ron has posted his excellent instructions, and there is a better version with pics in his book, which is still available over there. Too tight on either side and they will tend to act like locked bearings. Theoretical advantages of the floaters (beyond the fact that they are the only one that will fit your application) are some reduction in drag and near complete immunity to the greatest cause of rod failure from big end stress...all reasons why your 91A and the similar 21A rods were in just about every large displacement racing flathead back then. They may well fall into place without exercising your mallet, but you need to know. This is the kind of thing you just have to know, because there are hardly any mechanics left who have ever seen such a thing! Nowadays, floating bearings are still used in such things as turbochargers that spin at R's beyond the limits of plain or roller bearings.
thanks fellas i,ve built alot of engine in my years but never a flathead V-8 much less a hot one. this is my last redeo hotroddin being a old man now. last question please. I,am 6'1" tall and 250 lbs will I fit in a 3 window 32 with a 2" chop top comfortably ? thanks bob
BOY thats a nice merc. i had a 49 and a 50 about 20 yrs ago. a fella in japan just had to have em both so on the boat they went.
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