as I've mentioned before, zxappeal and I are building the 292 for my '66 Chevy pickup. It will be significantly warmed over from stock form. CR will be raised 2-3 points, much bigger cam, headers, Mallory ignition, performance intake manifold, dual progressive Weber carbs, oversized valves, you name it. None of it is extreme or anything, but pretty much every aspect of it will be a significant step up from stock.

Here's the induction setup: http://www.cliffordperformance.net/Merchant2/merchant.mvc?Screen=PROD&Store_Code=CP&Product_Code=42-4650-K&Category_Code=C250

(I think that's particularly cool).


At any rate, I got pretty much all of the parts from Clifford Performance, who specialize in hot domestic inline-sixes. That's pretty much all they do. Their rebuild kit comes with a set of .010-over main bearings, and they specify cutting the crank by .010". However, my crankshaft is dead-on specs, and zxappeal and I can't quite wrap our brains around why in the hell you'd cut a perfect crankshaft by .010" just to fit .010"-over bearings.

See the following email exchange between Clifford and me:

Larry,

I'm about to finally finish up the build on my Chevy 292, using all Clifford parts (standard rebuild kit, 270 duration cam, and dual Weber induction. We mic'd the crank, and it is absolutely 100%, perfectly, right-on blueprint specs. I know you guys recommend to go with .010-over main bearings, and that's what's in the kit. I can have the crank turned, but it seems a little crazy to me to turn the crank when it's already perfect.

What doesn't make sense to me is that a .010-under crank and .010-over bearings gives the exact same clearance as a blueprint-spec crank and standard bearings. I just don't see how it could make any difference. If it's a matter of wanting very tight tolerances, that would make sense to turn a marginal crank .010" and fit the slightly oversized bearings so as to have a really perfect fit...but I just can't understand doing it when you already have a really perfect fit.

Is there something I'm missing here?

-Josh

_______

Make sure you machine shop grinds .010.



We need 1.005 clearance or we will not have good oil pressure.



Thank you



Larry 6=8

3/10/2011 9:20:13 PM

Sounds like a sweet build....but ol' Larry's response...

[Edited on March 10, 2011 at 9:43 PM. Reason : .]

3/10/2011 9:42:32 PM

You should respond with:

Quote :

"We won't have good oil pressure? WE?! Mother fucker, this is MY damn truck and I'm taking my business elsewhere!"

You know, just upping the crazy ante a little. All kidding aside, sounds like a cool build. What sort of power figures are you expecting vs stock?

[Edited on March 10, 2011 at 10:47 PM. Reason : .]

3/10/2011 10:45:58 PM

Any reason you're sticking with the 6 instead of a V8?

3/11/2011 6:52:34 AM

Keeping it original I'm sure.

3/11/2011 8:48:40 AM

Duke...already took care of this...Brad and I agree that there's no use in grinding a crank that specs perfectly to stock, especially when there's not a crank grinder around here that can really nail the clearances perfectly. It'll have to go to a good race shop, and the cost to do so would be about two or three times what a garden variety grind job would cost. After reading the above note, Duke, I think they're blowing smoke up your ass, especially since a crank that mikes perfectly to spec will have a much tighter clearance than 0.005" which is way too loose to maintain good pressure and oil control when running 5w30 or 10w30. Most generic regrinds I've seen end up Plastigaging at about 0.003" which is still a little looser than one would ideally want to see. But it's hard for your run-of-the-mill shop to hold much tighter end-to-end.

I ordered the bearings last Saturday, just haven't called you to tell you (running short on the time thing).

Brad's gonna mock it up as soon as he gets the stuff. I've had the opportunity to stop by and hang out with him a bit lately.

We got some valve spring issue to sort out as well, but that's not nearly as crucial right now. Gotta get some spring seats to fit the springs. They're out there, just gotta find 'em.

On this build, we're gonna be running a 272 degree duration cam, not sure what the lobe centers are ground at or what the total lift at 0.050" lash will be. Twin Weber 38/38 carbs. I wanted to find propane pistons to run in this one because they don't have nearly as severe a dish, but the guys at Clifford don't do it that way. I don't know if I trust their judgment a whole lot; I think it might have something to do with the fact that traditionally (up until recently) the pistons have been really hard to find, as Federal Mogul stopped producing them for a while.

[Edited on March 11, 2011 at 10:40 AM. Reason : blah blah blah]

3/11/2011 10:33:08 AM

Quote :

". Gotta get some spring seats to fit the springs. They're out there, just gotta find 'em."

my machinist pointed me towards these guys for guides once.. might have what you need..

http://www.precisionengineparts.com/

[Edited on March 11, 2011 at 10:43 AM. Reason : quote]

3/11/2011 10:42:34 AM

I would go with Clifford's advice. Just cause you cant figure it out does not mean there isnt a good reason to do it.

3/11/2011 11:46:13 AM

Joel...his whole argument is that the clearance needs to be proper for good oil pressure. Believe me, the clearances are just lovely. Do YOU understand the oil journal wedge principle? I do.

3/11/2011 12:32:46 PM

sorry, when

Quote :

"What doesn't make sense to me is that a .010-under crank and .010-over bearings gives the exact same clearance as a blueprint-spec crank and standard bearings. I just don't see how it could make any difference. If it's a matter of wanting very tight tolerances, that would make sense to turn a marginal crank .010" and fit the slightly oversized bearings so as to have a really perfect fit...but I just can't understand doing it when you already have a really perfect fit."

yields

Quote :

"Make sure you machine shop grinds .010.We need 1.005 clearance or we will not have good oil pressure."

He didn't thoroughly read the email. He probably gets a bazillion emails and just skimmed through yours. I see this all the time when you try to get tech support.

[Edited on March 11, 2011 at 1:00 PM. Reason : he assumed you were another idiot who didn't read instructions]

3/11/2011 12:59:39 PM

Quote :

"I would go with Clifford's advice. Just cause you cant figure it out does not mean there isnt a good reason to do it. "

That's exactly why I've talked to him a couple of times and then sent that email...it makes no sense to me, but they've built a ton of hot domestic I-6s, and I have built exactly zero. Clifford is pretty much the go-to, top-shelf company for what I'm doing. That said, Dan and I are mechanical engineers and he's an old rodder. I wanted to make sure there wasn't some trick of the trade he knew about that we didn't before disregarding his advice, and wanted to know the "why", not just that he's adamant about the .010".

Now that I know that it's simply an issue of tight, uniform tolerances, I'm confident that we're right and he's...unnecessary at best and likely sub-optimal on this one. What he's saying makes sense for probably the majority of cases where the crank might technically be within specs, but only barely, and with variances all over the place. That is not what we're dealing with, as I told him.

Quote :

"Any reason you're sticking with the 6 instead of a V8? "

Partially to keep it original. My granddad bought the truck new in '66, and I learned to drive on it when I was a kid. Despite the hot motor, I'll be retaining the 3-speed on the column, too.

The other reason is because a hot small-block with a 4-on-the-floor or a 5-speed from an 80s Z28 or something is just kinda boring, expected, and played out. I won't be racing it or anything...it's just for fun and cool factor.

Quote :

"What sort of power figures are you expecting vs stock? "

I don't know, just guesstimating, maybe 260 hp at the crank? Maybe 280? Hell, I don't know. I think they were SAE gross-rated at 170, originally (with a scrawny little 1-bbl, tiny intake and exhaust manifolds, a VERY tame looking cam, and something like 7.5:1 CR).

Quote :

"I ordered the bearings last Saturday, just haven't called you to tell you (running short on the time thing). "

Sweet. How much do I owe you for those?

Quote :

"We got some valve spring issue to sort out as well, but that's not nearly as crucial right now. Gotta get some spring seats to fit the springs. They're out there, just gotta find 'em."

I thought that was sorted out? I seem to remember bringing Brad some valvetrain parts that I'd originally left down in granddad's shop.

Quote :

"On this build, we're gonna be running a 272 degree duration cam, not sure what the lobe centers are ground at or what the total lift at 0.050" lash will be. Twin Weber 38/38 carbs."

I think it's a 270-duration cam, with 32-36 Webers. I won't swear to that, though.

Quote :

"I wanted to find propane pistons to run in this one because they don't have nearly as severe a dish, but the guys at Clifford don't do it that way. I don't know if I trust their judgment a whole lot; I think it might have something to do with the fact that traditionally (up until recently) the pistons have been really hard to find, as Federal Mogul stopped producing them for a while. "

Yeah, that sounds very plausible. They say they zero-deck the block to fix the 292's "swirl problem", but that doesn't account for chopping a shitload off the head yet still using deeply dished pistons. Whatever...they've found something that works, and I didn't want to experiment on that part.

3/11/2011 10:23:31 PM

Do not turn that crank. Mic everything out and size your bearings accordingly. I used about 4 different size main bearings on my last engine build. Use plastigauge as a sanity check. I might lean towards overkill but I dont enjoy pulling heads and dropping oil pans because I got a good deal on one size fits all bearings.

3/12/2011 9:27:01 AM

Quote :

" especially when there's not a crank grinder around here that can really nail the clearances perfectly. "

Boyettets can and will hit the numbers everytime.

3/12/2011 6:45:27 PM

Quote :

"Do not turn that crank. Mic everything out and size your bearings accordingly. I used about 4 different size main bearings on my last engine build. Use plastigauge as a sanity check. I might lean towards overkill but I dont enjoy pulling heads and dropping oil pans because I got a good deal on one size fits all bearings. "

You have that luxury with OEM Honda bearings, which come in 4 different clearance classes for each bearing size. We have a little leeway with rod bearings (available in 0.001" and 0.002" undersize), but not much.

3/13/2011 3:19:43 PM

When it comes to measuring everything to make sure you have the perfect fit, let me know if you guys want me to give you a hand. I may have a brand new FARO Arm shortly.

[Edited on March 13, 2011 at 4:38 PM. Reason : d]

3/13/2011 4:38:18 PM

felt like a lot more than 4 choices when i was doing it!!!!!!!!

i would guess the chevy clearances will be at least 2x a honda spec so youre probably fine with a one size fits all.

3/13/2011 11:43:45 PM

That's because you got a lot of number/letter combinations you can go through.

3/14/2011 1:02:02 AM