Building an Engine "Tight"

[HeWhoOvercomes]

Hi all! I just dropped off my 7M at the machine shop, with a complete list of tolerances from the TSRM. I've read most of the guides on here regarding machining and rebuilding these things, so I brought it to the machinist's attention that I want to build the engine "tight". But then I got to wondering what "tight" actually means. Is it anything within the prescribed tolerances in the TSRM, or should I lean toward the smaller clearance. BTW, I'm mostly talking about oil clearance.

To those of you with experience building 7M's, what advise can you give me on setting crank, rod, and cam oil clearances?

Thanks!

 

[IndigoMKII]

paging ij..

 

[HeWhoOvercomes]

paging ij..

I agree. What do you think IJ? :1zhelp:

 

[IJ.]

What is the expected power output?

 

[HeWhoOvercomes]

Realistically, about 450 WHP for now, but I'd like to be able to make up to 600 reliably. What effect does power level have on clearance?

 

[IJ.]

A huge effect, Tight is fine for a standard rebuild, ignore all the "it's not a Chevy so needs to be built tight" BULLSHIT that people spout, I stupidly ignore my better instincts when I built my first 7M and had nothing but problems with it, went back to tried and true clearances I'd used in just about every engine I'd ever built and guess what no problems...

Low to mid 2's for your 450ish, I'd be going high 2's for 600, any tighter you're going to see funky wear patterns on the bearings as the block wet noodles all over the place..

 

[HeWhoOvercomes]

Thanks for the reply. Pardon my ignorance, but when you say mid-2's or high-2's, what's the unit you're using? It's my first rebuild.

 

[Insidious Surmiser]

that would be .0020" (inches)

 

[HeWhoOvercomes]

Is it thousandths of an inch?

 

[HeWhoOvercomes]

that would be .0020" (inches)

Cool. Haha, it looks like you beat me to it.

 

[IJ.]

<nods> yep inches
(I'm old)

 

[HeWhoOvercomes]

So, it looks like that puts me a bit above the TSRM tolerance. Is there any trade-up in longevity when you make the clearances larger? I mean, obviously if you run a 700 hp motor with stock oil clearance you'll kill the motor a lot faster, but if you only run 300 hp with 600 hp clearances, is that extra space going to have consequences?

 

[IJ.]

Just need to select an Oil weight that gives you good hot idle pressures, Who were you before you were overcoming shit?

 

[HeWhoOvercomes]

Just need to select an Oil weight that gives you good hot idle pressures, Who were you before you were overcoming shit?

Haha! HeWhoDoesn'tOvercome, I guess? It's a bible verse.

 

[super51fan]

The loose set up may be true. But then how can a stock block MKIV make 650 rwhp all day long on stock clearances?

The factory engine is what most people would call "blueprinted". Select fit bearings that are .0001 difference.

And select fit pistons to bore.

 

[hvyman]

Because 2jzgte.

 

[Insidious Surmiser]

The loose set up may be true. But then how can a stock block MKIV make 650 rwhp all day long on stock clearances?

The factory engine is what most people would call "blueprinted". Select fit bearings that are .0001 difference.

And select fit pistons to bore.

stock block 7m's will make more than that, and stock block 2jz's will make a lot more than that (both reliably for thousands of miles) ::dead horse:: A lot of factors come into play as to why engines fail. If Ian's had as much success as he has assembling the engine the way he did... that's that.

 

[IJ.]

The loose set up may be true. But then how can a stock block MKIV make 650 rwhp all day long on stock clearances?

The factory engine is what most people would call "blueprinted". Select fit bearings that are .0001 difference.

And select fit pistons to bore.

Aren't too many Factory Fresh engines making that sort of power....