Stretch Bolt Help Rqd, Built Drag engine

[StuartW]

Ok finally a year later got around to finishing the build on the cooking motor

 

The Big end bolts are 3/8WMC carillo and i am attempting for the first time a bolt stretch torque!

 

The specs are .0050-.0070" and/or 45ft/lb with a torque wrench, I wanted to be perfect on this so going for the stretch method.

 

Just need a lil clarification on the DTI as i dont want to get it wrong

 

From what i can see the DTI shows every little increment in .001" so am i correct in assuming that if the dial was zeroe'd with no stretching torque on the bolt, I would need to see 5-7 on the dial? the alternative would be 50 but that seems far too high.

 

If i had a metric DTI i would be fine lol

 

Just want some clarification

 

Edited December 11, 2010 by StuartW (see edit history)

[jagman]

Correct, each increment is 1 thou , and the guage goes round 2 and a half times ,ie 0-250 thou - the smaller inner indicator shows 100thou ,200thou , and add the large pointer for the 100 or 200 for the amount in between

[StuartW]

Thanks Jagman, I was never brilliant with Decimal places!

 

So you defo agree 0.0070 seventy thou? would simply read 7 increments only?

[Terminator]

That is how I would read it! 7 X 1000 = 7 thou

[jagman]

Thanks Jagman, I was never brilliant with Decimal places!

 

So you defo agree 0.0070 seventy thou? would simply read 7 increments only?

 

Nope your not good with decimals!! LOL

 

7.000 = 7 thousand thou ie 7 inch

0.7 = 7 hundred thou

0.07 = 70 thou

0.007 = 7 thou

0.001 = 1 thou

 

0.0070 is actually 0.007 - not 70 thou but 7 thou or seven markings on the guage - the whole gauge movement is 1/4 inch or 250/1000 or 250 thou

[Terminator]

One rotation of the large pointer is 100 thou. 2 and 1/2 rotations is 250 thou . 70 thou would be 70 of the 1000 markings or 70 on the gauge. You only want 7 individual markings as you said in your post.

[StuartW]

phew cheers guys ;-0)

[Chris Wilson]

As below, just seven graduations longer for the bolts.

Edited December 13, 2010 by Chris Wilson (see edit history)

[TLicense]

If you tell me what the weight of the pistons after they were balanced, what rev limit you're aiming to run at, and what the original "un-fitted" bolt length was I can work out the exact bolt stretch you need. 0.005 - 0.007 is a reasonably large tolerance and you can target a particular stretch that will make the engine as strong as possible within that range.

[Digsy]

Can you really measure bolt stretch like that?

 

*Edit* Just looked at the larger pic. I assume the other end of the dti holder is registering on the end of the bolt.

Edited December 14, 2010 by Digsy (see edit history)

[Chris Wilson]

Yes and yes.

[Lude]

what language is this lol

[Chris Wilson]

DTI = dial test indicator = accurate means of measuring small distances / movements

[StuartW]

If you tell me what the weight of the pistons after they were balanced, what rev limit you're aiming to run at, and what the original "un-fitted" bolt length was I can work out the exact bolt stretch you need. 0.005 - 0.007 is a reasonably large tolerance and you can target a particular stretch that will make the engine as strong as possible within that range.

 

Sorry for late reply only just saw the replies...I aim to progressively run up to 9800 rpm.

The WMC bolt un stretched is 49.48mm from tip to tail.

 

piston weights

1. (Towards front of car) 342.5

2. 341.6

3. 341.6

4. 342.3

5. 341.7

6. 341.1

 

I could at this stage re-arrange the pistons if you think that will be to any advantage?

Many Thanks for the repiles.

[Chris Wilson]

9800 RPM? I'd be wearing a hard hat if I was near it at that RPM That's a LOT of revs for a big floppy in line six.