plastigage infos

[giorgio67 182]

HI,

I was reading my manual to see the specifications of the crankshaft/bearings clearance as i need to buy some plastigage to check my engine main bearings.

The manual says: Bearings clearance 0.013-0.056 mm (0.0005-0.0022 inch) but there are not these measures in the plastigage range, they start with 0.018-0.045 mm so no good for the minimum and no good for the maximum clearance.

Regarding the inches it's the same so 0.001-0.007 as a starting choice.

Anyone have an advice regarding this?

Thanks in advance.

Giorgio

Edited September 3, 2008 by ghe67

[USAndretti42 308]

Get the bearing inner diameter measured with a bore micrometer and the journals with a regular micrometer and calulate the difference. I don'tr think Plastigage would be accurate at those small clearances anyway. In fact, there are those who think that Plastigage isn't accurate ever as the results are too open to interpretation.

[giorgio67 182]

Trevor,

this is another question.

I know that maybe Plastigage will be not so accurate even if Lotus Cars advise to use it to calculate the clearance...and I know that micrometer it'smore precise for the job but i will try anyway to see the differences.

Cheers

Giorgio

[Buddsy 1,619]

Hi Giorgio

Thats a tricky one!! I measured my crankshaft with a micrometer and as it was the right size I bought new bearings standard size so didnt bother trying to measure the clearance. Measuring bores is often a bit of a bitch to be honest. If you measure the bearing bore you will have to do it while they are still in the block with the bearing housing casting together. If you dont have a bore gauge and you know a local engineer you could get them to grind or turn up a bit of bar your crank size +0.04mm that shouldn't quite go in. If it does you bearing are oversize. You will be able to judge how bad they are too. You could get a bit made same size as your crank but theres not much point as you will put your crank in and give it a spin when you are doing the assembly.

That would be my plan

Buddsy

[giorgio67 182]

Ciao Buddsy,

thanks for your point of view.

I have not still measured my crankshaft but I hope that everything will be in the tolerances so I can buy standard main saving the crank grinding job.

By the way, any news about the alloy radiator for your (my) car?

I have just wrote to a UK sellers to see if he's able to supply Esprit 3 fans rad, the rad for other cars are very good made and incredible cheap.

Let me know.

Thanks

Giorgio

[Buddsy 1,619]

I have just started to think about that, my engine is just about done so am looking at these other bits, are you comming over for the sale?

[giorgio67 182]

Buddsy,

I'm not in hurry for that.....sadly I need to do so much work....but I'd like to see the options and the prices for this part.

As I have told you I have two options:

first, buying directly from England from specialist with your help...

second, I need to find the right meaures to see if I can have my rad made here in Italy, but I have not received any answer about that.

anyone can help me ? (measures and drawings)

Cheers

Giorgio

Edited September 3, 2008 by ghe67

[DanR 69]

I regularly use plastigage and found it reliable even when I used to build racing engines.

Giorgio buy the size that covers the clearance you have specified. Cut small lengths and lay it across your journals. Fit the caps and tension to spec. That way it allows for bearing crush. DO NOT TURN THE ENGINE or you'll have to start again. Remove the caps and use the scale that comes with the plastigage to see how wide it has been flattened. The wider it is the tighter the clearance.

It's a good indicator and the final arbiter of how accurate all your micrometer measurements and machining work (if done) has been.

Just buy the size you mentioned. I doubt you will have any clearances at .0005mm and the plastigage would be flattened beyond the scale so you'd still know. Anyway I think that's way too tight and I'd have the part machined to open it a little.

Edited September 4, 2008 by DanR

[USAndretti42 308]

Giorgio,

I just did a Google search for Plastigage and found that it is available to measure 0.001" to 0.003" (0.025mm to 0.075mm)

[Esprit Aviation 2]

Plastige always worked for me. You can even do both side of the bearing at once to check for any abnormalities, or in my case, if you are paranoid!