Measuring Crankshaft end-float questions?

[Bruce_B]

Well I just bolted down the crankshaft in my 1275 block and it rotates smoothly--a good thing.

Now to measure end-float, I have standard thrust-washers. The instructions say to 'lever' the crankshaft to one end and measure the difference by the thrust washer.

I' tried moving the crank with a large screwdriver between the
block (Front of engine) and the crank web. Nothing much seems to move, and I can't measure any float with feeler gauges.

So:
(1) Do I need to move push harder to get the crank to move?
(2) Since everything rotates smoothly can I assume I have adequate end-float? (probably not a good idea.
(3) What if I have zero end-float?

Thanks....

 

[Bugeye58]

Bruce, check it with a dial indicator.
Jeff

 

[Hap Waldrop]

Do what Jeff said, if you had zero end float the crank wouldn't turn, or it would be real hard to turn

 

[Bruce_B]

Just finished with the dial indicator. Just about .001 of endfloat. On to the pistons!!


thanks all

 

[DrEntropy]

If ya could see it/feel it WITHOUT the dial indicator, chances are it'd be excessive.

For your rod/ main bearings: Plasti-gauge! Ideally the green flavor. /bcforum/images/%%GRAEMLIN_URL%%/jester.gif

 

[Trevor Jessie]

Is that mint?

 

[Bugeye58]

For your rod/ main bearings: Plasti-gauge! Ideally the green flavor. /bcforum/images/%%GRAEMLIN_URL%%/jester.gif

Bah! I use a bore gauge, a micrometer, and a calculator for bearing clearances, rather than trust the vagaries of plastigage interpretation. /bcforum/images/%%GRAEMLIN_URL%%/grin.gif
But, most aren't as anal as I.
Jeff

 

[DrEntropy]

Too true. The mint stuff will indicate well enuff for us mere mortals. /bcforum/images/%%GRAEMLIN_URL%%/devilgrin.gif

Yeah, Trev. But it gets kinda 'chewy' pretty quick. /bcforum/images/%%GRAEMLIN_URL%%/jester.gif

 

[piman]

Hallo Bruce,

what is the end float supposed to be on a 1275?, 0.001" seems on the tight side, and what will happen as the engine warms up, will the clearance change? Specifications are there for a reason.

Alec

 

[Hap Waldrop]

Spec crank end float is .002-.003". One of the biggest mistake most make when rebuilding a A-series engine is to buy new thrust washers, A ,and B series engines's thrust washers could last for a handful of rebuilds. Most long time racers normally save used thrust washers instead of using new, I have a whole plastic baggie full of them. I normally check end float whan I'm disassembling the engine, if in spec and 99.9% of time it is, then I put the used thrust washers up for reusing on the engine assembly. Most of the time you end up buying new thrust washer thinking you are doing the right thing, then they are too thick by a thousand or two and you end up sanding them down to get back to thickness of the one you took out of the block to start with.

Burce, pry the crank in both directions, don't assume you already all the way on one side, you could very well have a .001" in the other direction as well.

OK, here's the disclaimer guys, if you have Triumph engined 1500 MIdget, then everything I said is above is useless, these engine eat thrust washers and it one of it's (1500) major downfalls.

 

[Hap Waldrop]

On clearance I rather see a novice engine builder use plastigauge, just because using and reading a mic or bore gauge is a skill that needs to be practiced. One of the first things I always do with apprentices is put a crankshaft in the lathe for holding it, then give them a piece of paper, a pen and the mics needed to measure a journal and tell them to get me 25 measurements on each journal, it's a exercise to show them how the numbers will be all over the place until they learn the "feel" of using a mic.

If you are building a engine, and it's getting all the machine work done crank-wise, line boring, rod resizing, crank grinding, then you can spec out your clearence on paper with a bearing book before it all go to machine shop to get the exact clearence you want. I built all my street engines to .0015" on both rods and mains.

Here's a formula for clearence

housing bore - bearing shell thickness x2 - journal diameter = clearence

To get main bearing clearence, I would have the main housing bore torqued down with no bearings in the housing bore and then measure with a bore gauge.

Then measure the bearings shell thickness with ball end mic

Then measure the crankshaft journal with a normal outside mic.

On a rod clearence I do the same thing except since I have a Sunnen rod honing machine and gauge, I use my Sunnen AG-300 rod gauge, but everybody doesn't have a $2000 rod gauge lying around so, a bore guage or inside mic can be used here.

Having a good bearing book is key, it will give you all the specs a factory manual does not.

 

[DrEntropy]

On clearance I rather see a novice engine builder use plastigauge, just because using and reading a mic or bore gauge is a skill that needs to be practiced.

's why I said it. Micrometer "feel" is as much a skill as about anything else: with practice it comes to you... but plastigauge will fit the "go/no go" bill for a street engine without the necessity of bore gauges 'n mic's with different anvils, bearing books, et al.

I'm surprised it hasn't been mentioned that a hammer handle or a piece of hardwood is a better tool for prising the crank back-and-forth than a metal implement.

I drool'd over that Sunnen rod gauge comment, BTW. /bcforum/images/%%GRAEMLIN_URL%%/wink.gif

~good~ machinists and shops are becoming more rare around here. How 'bout a move to Sunny Florida, Hap?!? /bcforum/images/%%GRAEMLIN_URL%%/devilgrin.gif

 

[Bruce_B]

OK..went back and tried again. With the lever in place and placing pressure on it. I have .002 clearance.

I have have some specs that say the minimum amount of clearance is .001 and that the thrust washers will soon wear with normal use.

But with the sage advice of this board. the .002 is good..now It's time to check the piston rings. They came premounted on the pistons so I'll be checking them one at a time as I press the piston in from the top.

Thanks...

 

[Hap Waldrop]

Bruce, it sounds like you're probably ok on side thrust clearence, the main thing is that the crankshaft turns in the block easy with assembly lube on the bearings and the thrust washers in place and everything torqued down. If it does that, then you're ready for the next step.

 

[jlaird]

Rings premounted on the pistons, what will they think of next?

 

[Hap Waldrop]

Rings premounted on the pistons, what will they think of next?

Yep, but they still to be removed and checked for ring gap.

 

[jlaird]

Rings premounted on the pistons, what will they think of next?

/bcforum/images/%%GRAEMLIN_URL%%/wall.gif why would they even bother. Seems like a waste of time.

 

[piman]

Hello Hap,

you mention a book for bearings? Have a look at Aston Martin 6 cylinder (57ish to late 60's. Each main bearing size comes in three grades, so critical is the clearance on that engine.

Alec

 

[JerryB]

Bruce......

It's always nice to see someone who wants to do a decent job assembling an engine and wants to see some good numbers instead of just throwing things together and hoping it wont explode.

I'll add coupla things that werent mentioned.....

the crank trust is taken by the center main. The top half in the case (block) and the bottom in the main cap.

What you want to do is torque the 1 and 3 main. Then just SNUG the #2 (center) main...then lever the crank front and rear a few times to SET the #2 cap...then lever the crank to the rear and torque the center main.

That way you have aligned the cap thrust faces to the case thrust faces. Rotate the crank (two finger should move it easily and observe that the thrust washers "float" and are free. THEN measure your end float of the crank. It can be done easily on these motors with a feeler guage if you dont have a dial indicator and mag base.

Ring end gap......top ring & second ring .004" per inch of bore is a general rule. ....but sometimes stock type iron ring sets are on the very high side.......and so you have to find the largest ring gap ring and work backwards to get the other 4 the same or very close. You should always check with the piston mfgr for the correct gap. For a 2.800" bore your numbers posted on another thread are good for street use.

 

[SilentUnicorn]

https://www.britishcarforum.com/bcforum/u.../gonew/1#UNREAD

link to "other thread"