I'm having engine rebuild stress and need some advice!

[MaxFarmer]

We're dealing with my 2001 LB7. I had a set of Crower Rods from Socaldiesel (Trippin) put in while I was waiting on my heads. New bearings and piston rings, stock LB7 pistons went back in. The heads showed up today but they ran into a BIG problem.
Normal piston PROTRUSION above the block on full stroke is supposed to be between .008 to .012". I think I was in the .010 range stock b/c they ordered the "B" gaskets for the rebuild.
Today, going back together they measured my PROTRUSION to be .019-.022!!
They want to know what I want to do....I have no idea! I guess they called Guy (Trippin) and he said the only thing he knew was to mill the pistons. Isnt that going to make my already weak LB7 piston even weaker? Has anyone else just plain milled pistons before? Wont that cause the dreaded sharp edges in the bowl?
WHAT SHOULD I DO?!? This really sucks!

 

[MaxFarmer]

P.S. The only thing I can think of that caused this is that the Crower rods are not the same length as my stockers....It shouldnt be this way, should it?

The other option that the dealer gave me was to put a head gasket on for an LB7 that has been overbored .030. I guess they are thicker, but this moves my fire-ring out that much further and they dont think that it will work.

I'm open to any and all ideas! :help:

 

[TNRGreene]

Call Eric

 

[MaxFarmer]

I just sent him a PM. The shitty part is I was going to take it to him a month ago but the 11 hour drive pussed me out (with a blown headgasket).

 

[MaxFarmer]

I'm suprised I havnt gotten more input here! I have to make a decision today wether to start all over or put the thick gaskets on and forget about it. I dont know enough to know if the .005" over spec is enough to screw up my compression ratio or cause any contact or if it will be just fine.
The shop is wanting it done and out of there b/c they are also a John Deere Dealership and this is their busiest time of the year (spring planting season!).

I ALMOST think it would be OK, I havnt heard of anyone else with problems like this. Does everyone else check all the clearances before putting the heads on?

 

[McRat]

You need to find out what the crush thickness is on the 3rd size of headgaskets. Check all pistons at TDC next to the wristpin for height. If you do it on the top or bottom, piston rocking might give a bad number.

 

[MaxFarmer]

Pat, they checked them right over the wrist pin. The crush thickness of the thickest gasket was what left me .005" over GM spec yet. On top of that, I know Guy had to deck a SMALL amount (I dont know how much though) off of the heads to take care of the fire-ring groove off the old gasket.

I decided to have them send the motor to a machine shop in another town. I guess they were voted #1 machine shop of the year last year in Vegas. I dont know why it happened in Vegas when we're in Nebraska, but that's another story.
So, that takes care of my balancing issue also. They are going to make all the pistons have the same clearance and then balance everything.

Pat, what are you going to for Compression Ratio on your new build? I know Nasty Girl was 15:1 or 15.5:1 but I dont think I need to go that low. With the GT 4094 and 75hp injectors, how low should I go with my CR? I was guessing 16:1.
Suggestions?
Man, my simple head-gasket change has sure ballooned into a $20K project! Definately NOT what I had planned on!

 

[McRat]

Nothing is ever as easy at looks, and Casper still ain't running!

I'm going 15:1. How low you go depends on boost. There is very little data on differences in compression, but I'd think 16:1 would be fine. They won't take off that much.

 

[dieselson]

I say 15:1

 

[02freighttrain]

I say 14:1 and stoke it with fuel and air. At least that's what I'm gonna try.
Ain't no bending at this point. It's break'in.
So, Pat what are you taking off your pistons. .040?

 

[Kat]

So, Pat what are you taking off your pistons. .040?

He doesn't know Guy did them. He will let you know though

 

[02freighttrain]

He doesn't know Guy did them. He will let you know though

Guy is a good Guy:hail: to know, who knows a scary amount when it comes to these matters. I think it's great that we are going to have a lot of different combo's to find out what works and makes power. Unfortunately I'm stuck with my CR decision and I feel good about it. I hope it will start on those cold 50 degree Fla mornings.

 

[Mike L.]

Unfortunately there is no set of guide rules on how to build one of these engines. You guys are writing the book right now. There will be pain I'm sure. I commend all of you guys for doing this. You have heart. :grd:

 

[sweetdiesel]

You guys are writing the book right now. There will be pain I'm sure. I commend all of you guys for doing this. You have heart.

:werd:
i also think its great to have 3 different builds you guys rock

 

[MaxFarmer]

:werd:
i also think its great to have 3 different builds you guys rock

Thanks Guys!

02, I like the sounds of what you're doing! I dont have the nads to go that low! Plus, I know I wouldnt start in the winter here in Nebraska being that low!

Pat/Kat, you said Guy is doing your pistons for you. Will they have to be modified again after you get the assembly together to get your clearances right or do you know yet?

http://www.dieselplace.com/forum/showthread.php?t=142821
Heres a link to the same opening post on the place for those of you who want to read the 3 pages so far---those of you who arent BANNED!

 

[Kat]

Pat/Kat, you said Guy is doing your pistons for you. Will they have to be modified again after you get the assembly together to get your clearances right or do you know yet?

Pat says ours should be good to go. We took ours off the top of the piston for more clearance.

 

[MaxFarmer]

Well, the machine shop FINALLY is starting to look at the motor. He ran an interesting thought by me today and I wanted to get your guys' input. Sorry if this has been discuessed before, but it seems new to me.
He claims that on some of the V8 gassers he does that they can/are able to shorten the Crower rods and then make counter bearings. At first it sounded like it might work, but now I dont know. From what I have heard, if you shorten rods (bend them) that the piston skirts will hit the crank. I suppose this is what he meant by the counter bearings. He said this may weaken the rods some, but not a whole lot.
I'm still thinking the best way is to just take some off the top of the pistons, I only want to go down to around 15.5-16:1 CR. I dont have Excel on this computer or I would run Guy's table ( http://dieselplace.com/forum/showthread.php?t=137033&highlight=piston+compression )(Post #2) and see how much I would have to take off to get down to there with my .020" protrusion.

Any thoughts on this shortening the rod idea?

 

[02freighttrain]

Shortening rod's will require machine work that I am not familiar with. (nearly impossible). If you want to lower CR by 1 point, then take around .030 off the deck of the piston. Balancing is a good idea after the surgery. We are going to high rpm in the furture Keeping the harmonics out of the scene will be important.

 

[MaxFarmer]

Thanks for chiming in Freighttrain. I've been doing a hell of a lot of reading again and it sounds a lot simpler to me to take back some of the lip of the bowl and then deck the top of the piston. I'm going to stay away from coatings, I dont run hard enough to justify that at this time.
The whole shortening the rod idea scares me! I think it will end up in a lot more work that I really dont want to have to pay for!