W@nker machinist didnt mark piston to bore

[BMGTZ]

So I have finally got round to assembling my stroker engine after having got it back from the machining shop.

problem one.....pistons not marked to which bore the should be in. machinist is a turd!!

problem two .... dont have access to an internal mic so cant check bore size of big end when the bearings are installed. "well use plastiguage you say" great Idea...off to repco ...buys plastiguage. figures out how to stop the crank moving. installs rod with piston{no rings} to stop rod turning. torque it down. great cant get the F&*^$%(* cap off!!

get cap off by tapping piston down......stuffs plastigauge reading due to impact.


drop nice new piston on floor because i didn't put the cir-clips in.......{don't know which bore it will be in yet}

Gave up drinking ..... a month before Christmas. Got three bottles of bourbon for Christmas.....now getting pissed.

is there another way to get these caps off without hitting them......or do I need to go buy an internal mic

 

[bazeng]

That sucks!

Hmmm maybe try and put the plasti gauge on the piston side of the rod bearing so when you hit the rod bolt, it won't crush.

I always use micrometres and bore gauges. time consuming but better to be sure.

 

[DOUGMO]

is it just the big ends you need to check brian?
or the mains aswell?

 

[BMGTZ]

That sucks!

Hmmm maybe try and put the plasti gauge on the piston side of the rod bearing so when you hit the rod bolt, it won't crush.

I always use micrometers and bore gauges. time consuming but better to be sure.

much more relaxed now.....{several red wine late, didnt like bourbon r} I have to build three engines so I am going to buy the right gear. plastigauge just isn't doing the job for me and I cant afford to be wrong on three engines!!

take this as example.......K1 technologies crank std bearing size....polished due to being used for a very short time, so expected to be loose or at least very slightly loose. arp main studs and line bored block thru mains...fresh by same w@nker. damn thing spins with one finger and feels beautiful.......removed all oil......plastigage says too tight. extremely tight!!

I have used this stuff before in my 52 years on the planet and it went ok......bit that was std manufacturer stuff not after market performance gear.

must be doing something different....so I am just going to get the right stuff

 

[BMGTZ]

is it just the big ends you need to check brian?
or the mains aswell?

both mate but ......not having a good day. and plastigage lies!! so Ive called it quits and will do it when I have the right stuff

 

[DOUGMO]

I can tell you how to check the mains with a dial indicator if you have one? - still very acccurate.

I dont think(but I could be wrong) you can do the big ends the same way though

 

[BMGTZ]

I can tell you how to check the mains with a dial indicator if you have one? - still very acccurate.

I dont think(but I could be wrong) you can do the big ends the same way though

I have a very good dial indicator...so fire away mate!!

 

[Smutt]

Brian, I am/ was a Fitter Machinist, I have a set of telescopic gauges (up to 150mm I.D) and outside mics up to 50mm (not big enough i know) also a good set of verniers...

And some left over plastiguage.. you have my number... sucks when shit goes wrong..

 

[BMGTZ]

Brian, I am/ was a Fitter Machinist, I have a set of telescopic gauges (up to 150mm I.D) and outside mics up to 50mm (not big enough i know) also a good set of verniers...

And some left over plastiguage.. you have my number... sucks when shit goes wrong..

hey Sam,

I will give you a call to organise things re the telescopic gauges......I will buy what ever else i need.

I still have 300mm of plastiguage but cant seem to get it to make sense......whereas Mics and verniers etc dont lie!!

 

[Smutt]

I have always tapped the piston and conrod upwards from underneath to separate from the big end, then the cap comes off easy...

Maybe the pistons are all the same size (to 0.01 of a mm), measure them. If they are all within 0.01 of a mm, it wont matter what bore they go in.

Measure the bores as you intend.

Did the shop supply you with the bearings (and pistons/ rings) for each engine? or machine to suit (yes... they should've), then all the machining should be spot on for the bearings as supplied!

All the measuring/ machining and tolerances should be sorted at the machine shop THATS THEIR JOB, I see your frustration, you shouldnt have to double check their workmanship.

Plastigauge should be an assembly tolerance check to confirm machining tolerances..

 

[trq-str]

For the big ends I tap the rod bolts also, same as baz.

Plastigauge should be an assembly tolerance check to confirm machining tolerances..

Agreed^^

I usually clearance my bearings to .002 or .0025 inches when using forged rods (unless specified otherwise). Using both plastigage green and red to confirm machining, to date it has worked for me every time.

Having said this, I don't like using the stuff, but I’ve never had a problem with it either.

 

[BMGTZ]

the bore to piston thing is ok I can sort that pretty easy......the rod caps on manley rods are located buy the two tubluar tangs that surround the rod bolts. These tangs have a crush fit into thier respective bores.....it is this that is causing the issues! they CANT just be wriggled off. so the impact that is required to separate them is causing the plastigage to squash further. I may try what Baz suggested and put the plastigage into the rod ...not the rod cap. that way knocking down the piston wont squash it more than it was.

as far as the bearing and machining goes.....well they had the bearings.....but they say the crank is very good quality and just needs a polish so the bearings stayed in their packets!! It is my inability to accept their say so that it will be "fine" that brings me to want to check it myself. If it was a standard road motor...different story. I would whack it together and "hope"

 

[DOUGMO]

pretty big bearing clearances trq-str for a performance engine.

Its still inside factory specs but pretty large still.

I think factory spec is 0.0008 - 0.0030?

Brian Ill pm you my number if you like and I can explain how to use the dial indicator? dont think I can
explain it too well on here.

 

[trq-str]

pretty big bearing clearances trq-str for a performance engine.

Its still inside factory specs but pretty large

Manley calls for .002 inches minimum with their forged rods, I'm more than happy to use the clearance they recommend.
With stock rods I aim for much less.

 

[BMGTZ]

Brian Ill pm you my number if you like and I can explain how to use the dial indicator? dont think I can
explain it too well on here.

yes please mate...gave up on it today and did chassis work instead. braced up the the rear cross member and seam welded the rear across the body above the cross member. should take launches nicely now.

 

[Smutt]

I have this week off work, yell out, if you want me to drop off my measuring gear, I too am savvy with a dial indicator B)

 

[blackvr]

When I have sticky caps, sit the engine up on the stand, put the conrod bolts half way in the threads and tap the heads of the bolts lightly with a platic hammer or a piece of hardwood.... works every time for me. gently from side to side wiggles them off with out too much load. I would have been happy with .002" clearance, even a bit more.

Remember in competition engines, more clearance equals more oil flow equals more heat removed. That goes for side clearance of the big end of the conrod in the crank as well. I wouldnt worry about what bore the piston goes in.... They would have too be pretty garbage pistons to have that much variation... and the same goes for the bore size.... would have to be a pretty crap machinist to have that much bore variation !! Mind you I ALWAYS check the machinists work ...

 

[DOUGMO]

I have to disagree on the clearances being better when bigger on a competition engine.

If the clearance is big, when the conrod is pushed onto the big end on the crank if the gap is large the conrod
can move further and push the oil out away from the bearing alot more easily.
If the clearance is tight it can more easily keep the oil in there, but people do have different ideas on this.

I personally would go as close as possible to the minimum recommended factory clearance.

 

[bazeng]

Pros and cons for both tight and loose.
Just make sure you use the oil to suite.

1 thou (0-30)
2 thou (20-50)

Loose equals more power (less friction), tight equals greater life span (as George described). But we have to keep in mind materials used and heat expansion. Too right and things can seize. Too loose and things will wear from excessive movement.

I've pulled down my motor with tight clearances after 5000kms any everything looked new except for a cracked cylinder wall and excessive piston sidewall wear (5 thou piston to bore).

My opinion anyway.

 

[BMGTZ]

.0035 in / 0.0889 millimeters piston to wall clearance is the recommended clearance from CP pistons. after checking it seems I have .06mm/0.00236in the wanker machinist decided to make it tighter instead of to the piston manufacturers spec!!

that puts it just outside the highest spec for a standard piston in the engine manual......is it a bit tight for a forged piston?

I wont be using a lot of boost....23/24 on a FP68HTA. that has a max rating of 47lbs min....not huge