LMM: Engine Assembly Questions

[CRAWLEN]

Hi guys,



About to assemble my fresh build lmm and have a few questions.
First one might sound a bit stupid, not sure if im missing something or doing something wrong or what.


I am a bit puzzled on why my piston protrusion is around .152mm so the block was decked not by much just to ensure its flat, and over bored by .020
it was fitted with a callies crank, Carrillo rods and mahle race cast, valve relived pistons with a 16.5 CR



before the machine work im pretty sure it was running b grade head gaskets and was siting between the min max of B.



would like some advice on this if possible. i did expect the piston protrusion to be lower due to the 16.5 pistons but not that much. considering its now out of the min max for grade a gaskets. thinking just fitting grade a or b would be fine but welcome to any suggestions.


Second question is piston rings, have seen a few things about a set of mahle rings that are no good a wear out. but cant tell if the rings i have are ok or not the only PN: i have is 4075MDK-D and from my googling that doesn't bring up anything. again any suggestion or advice would be great

 

[DAVe3283]

You could always go back to your machine shop and ask them what they did. Did they move the crank centerline when boring the mains? It could just be the new pistons, but mine are the same CR and didn't drop the protrusion out of spec like that.

Have you triple-checked your measurements? All your bearings are installed correctly, and there is assembly lube on the crank/rods bearings? The mains & rod caps are all torqued to spec? (Making sure things are all centered how they will be during operation.)

Can you post up the measurements for all 8 pistons?

 

[Chevy1925]

i would be calling up the machine shop and asking quite a few questions. honestly, if you are not working with the machine shop on this build and you are assembling it, you are kind of going at this blind. They are the ones that have speced the engine out for you and have alot of info. what ever we will tell you is a best guess.

that said, most shops will take .005 off the top of the block but if they took off less, this could be why you are only getting .006 protrusion. im not 100% sure race cast pistons are .010 shorter than stock pistons, i believe its an option.

How are you measuring protrusion?

as for being "out of spec".... well your not building a stock engine. at this point, i would run an A gasket. that puts p to h clearance at about .031-.035 but i always error to the tight side since you will be running head studs with much more torque load on them. This isnt a bad area to be quench wise for performance.

btw, your CR wont really affect your piston to head clearance. its mainly bowl parameters that do

 

[CRAWLEN]

i haven't done all cylinders yet, just 1 and 6 and thought something wasn't right, or i was doing something wrong.
the machine shop assembled the short block i am just doing everything else it was assembled with assembly lube. block was line honed also.


the way im measuring at this stage is with a straight edge and feeler gauges. going to try buy a piston protrusion gauge today to get a better reading.
i was thinking about this yesterday and i might be wrong saying it was B Grade to begin with and it might of been A. but im guessing there is no real way to find out what was in it before now since the gaskets are binned.


i will also try measuring with the block upside down just to see if the crank drops due to the oil clearance.



Chevy1925, when working out quench and best piston to head clearance what shuld i aim for. and this is with the arp 625 studs.

 

[Chevy1925]

What’s your power level? How much fuel/pulse width you gunna run? Since you don’t have forged pistons, you can run the piston to head clearance tight, I wouldn’t go under .025. .030 is a good area and safe. Your valve reliefs won’t help for fuel Econ where a tighter piston to head clearance would help due to quench so trying to tighten it up won’t give you much benefit.

If the machine shop did the work on assembelinf the bottom end, they should have verified all the things down there. Flipping the block upside down won’t do you any good as that’s not how things should be measured and will be skewed.

Get a better way to measure protrusion, using a bridge with a dial indicator zeroed to the block and then measuring on the piston over the wrist pin is the best way. Turn the engine over slow as the piston comes to its complete tdc and record that measurment. You could be off a good bit as you may not be at true tdc

 

[CRAWLEN]

power level we have been looking at going for 800hp. that side on the tuning for pulse width im not sure about as we haven't got there yet as mark is going to be looking after tuning. but i have a set of 100% sticks.


yeah after posting that comment about upside down sounded a bit stupid and realized that wouldn't do a thing.



yeah plan is today try and get a bridge as im in Australia. and go that way, i did also notice the way i measured it was wrong i wasn't going over the top of the pin more to the top and bottom of the pistons. so i wouldn't be surprised if i caused a bad measurement when pushing the straight edge down

 

[S Phinney]

Using a straight edge and feeler gauge is useless on checking piston protrusion. 25-30 thou is were you would want to be. I prefer 30 because you may want to step up the power level and turn it a little harder.


Sent from my iPhone using Tapatalk

 

[CRAWLEN]

so managed to get better readings. off all pistons as follows. with a dial indicator over the pin and using the highest reading from front and back of the piston. ( think i wrote 7 down wrong looking at the value )



1 2

0.0045 0.0045
3 4

0.0045 0.0055
5 6

0.0035 0.0050
7 8

0.0025 0.0045


going of cylinder 4 with a 0.0055 protrusion i would say grade A would suit well to have a nice piston to head clearance with the big studs. i did want to run the wave stoppers but i seen they only come in C grade. but everywhere says they are fine to use in place of A or B grade.


also noticed there isn't really any A grade gaskets on the internet.
i do have a set of brand new genuine C grade head gaskets here though.
open to any suggestions on what gasket to go guessing its either going to be a grade b or the grade c wave stoppers.

 

[DAVe3283]

also noticed there isn't really any A grade gaskets on the internet.
i do have a set of brand new genuine C grade head gaskets here though.
open to any suggestions on what gasket to go guessing its either going to be a grade b or the grade c wave stoppers.

RockAuto has both ACDelco (factory) gaskets and Mahle gaskets in Grade A. They may list them as 0.95mm instead of Grade A, but that's the same thing. If they don't ship to Australia, see if there are any local Mahle / Victor Reinz dealers. I usually buy my gaskets through Henry @ Creatures of the Night Performance, he may ship to Australia for you.

I have had good luck running Mahle head gaskets at 660 HP (tow tune) and occasionally 700+ WHP (track tune), so not too far off your goal. I have heard mixed things about the new gold colored ACDelco gaskets, they seem prone to breaking, which is why I run the Mahle.

 

[Chevy1925]

the regular mahle or the wave stoppers will do what you need. you can go with a C gasket, its not going to hurt anything mechanically. Alot of people on the net like to say "just go with a C gasket" because they dont have a clue on how to measure protrusion and then setup a gasket for that. the A's would be the way i go though

i ran the gold AC Delco's in my truck. Im still waiting to hear back from the machine shop if my head/s cracked before one of those let go or if they are in fact good and it was the gold gaskets that let loose. Either way, im not testing my luck with them again. Granted i was very hard on them (240*+ coolant temp towing/pulling hills in the middle of summer, lots of rpm at that time and more power than i should have probably been using).

as for the low number 7, id look into that. if you put used rods in, you might have a short one or a miscut piston.

 

[CRAWLEN]

The c's I have are the mahle genuine c's. But was keen to run wave stopers on this build just to help as we didn't oring the block. I do like some extra insurance.

But I feel like c's are just going to be way to big or is there slight thickness difference not that bad ? Especially having a valve reliefs ?


If it's going to cause issues I might aswell go tighter but happy to hear some thoughts and suggestions

 

[Bdsankey]

The c's I have are the mahle genuine c's. But was keen to run wave stopers on this build just to help as we didn't oring the block. I do like some extra insurance.

But I feel like c's are just going to be way to big or is there slight thickness difference not that bad ? Especially having a valve reliefs ?


If it's going to cause issues I might aswell go tighter but happy to hear some thoughts and suggestions

A grade "A" is proper thickness, that said if you've got brand new grade "C" gaskets I personally would run them because I'm cheap and don't like to throw away good parts.

 

[CRAWLEN]

so i went with A's just bought a set from summit as i needed some other bits and just makes it easier. went with the Genuine Mahle just like the C's i had. so hopefully all goes well and i don't smash a piston in to the head :roflmao:
but all the measurements are correct so should be fine fingers crossed.


so does anyone have anything to add about piston rings in my first post i was asking about if they are ok as i seen some people having issues