MaxPF's 6.2 build

[smalltruckbigcid]

Some pro engine builders claim that during the torqueing a stud can "mole" into whatever they are screwed into. To stop this many builders drop a bb into the bottom of the hole and loctite the stud screwed down against the bb.

This problem can be very noticeable if you run a tap through all the bolt holes during cleanup. The reason is that many taps are slightly larger than the stud threads and that gives you a slightly looser thread fit. I really think thats why GM built so many sbc in the late 70's and 80's that the head bolts were installed with some sort of thread sealant on even the blind holes.
George

 

[imiceman44]

Some pro engine builders claim that during the torqueing a stud can "mole" into whatever they are screwed into. To stop this many builders drop a bb into the bottom of the hole and loctite the stud screwed down against the bb.

This problem can be very noticeable if you run a tap through all the bolt holes during cleanup. The reason is that many taps are slightly larger than the stud threads and that gives you a slightly looser thread fit. I really think thats why GM built so many sbc in the late 70's and 80's that the head bolts were installed with some sort of thread sealant on even the blind holes.
George

Interesting, and it seems logical too, hmmm.
I miss reading technical info in magazines, but these past few months, I don't no stinkin magazines, I've had my share of tech to keep me alive.
Keep em comin'

 

[tRustyK5]

The advantage of the stud is that it doesn't put radial stress on the threaded hole in the block. When you tighten a bolt in a threaded hole the camming action of the threads sliding over one another tries to push the threads in the hole away from the bolt. This puts tensile stress on the threaded hole. With a stud, you thread it all the way into the hole and torque the nut on the other end. Since the threads don't rotate in the block during torqueing, there is no camming action. The threads are locked together by friction, and the forces on the threads in the hole are mainly shear, as the stud tries to pull them straight up out of the hole. Why is this important? Well, cracks in 6.2 and 6.5 blocks start at the outer bolt holes on the intermediate webs. It is a region of highly localized stress, partially from the static stress caused by torquing the bolt, and partly from bending loads as the caps are rocked fore and aft during firing events. By eliminating the static stress caused by the torquing of a bolt, it leaves a much greater yield strength margin to resist fatigue and cracking due to cap loading. The stud girdle should control any fore and aft movement of the cap, minimizing any side loading of the hole. All that should be left is shear loading of the threads, which is what they are designed fore. In theory, this should eliminate block cracking under high loading. We'll see Oh, also the stock outer bolts only engage half of the threads in the block (only about .330"). The fewer threads that you engage, the more stress is created. The studs engage ALL of the threads in the block.

There are other advantages with studs, like minimizing wear on threaded holes (important for racing motors that are frequently torn down - not so important for non-racing apps), more reliable torquing due to lack of twisting, and the fact that the studs are made of stronger material to allow more preload. Is it worth it? I'll let you know in 500k miles

What is the recomended torque value on the head studs? I'm guessing it'd be a fair bit more than the TTY values meaning better and more reliable clamping?

Rene

 

[MaxPF]

IIRC it is around 90-95 ft-lbs when using ARP's moly lube on the threads (which is reccomended over motor oil). The studs do not yield - the torque value preloads them to about 75% of their yield strength. This means that the preload is consistent, and the studs are reuseable

 

[tRustyK5]

Cool deal, although I'm kinda surprised it's not higher. I guess once you get the correct clamping force enough torque is enough. Are those vales from the ARP torque table?

Rene

 

[smalltruckbigcid]

Arp's table read 95 ftlbs with their lube. And their lube is the good stuff. I know of a couple of pro engine builders that use that stuff as assembly lube. I really like ARP's parts just hate the price tag...
George

 

[tRustyK5]

I dunno, $155 for 34 studs, nuts, washers isn't bad in my books. Assuming nuts and washers are 50 cents each that makes each stud worth $3.55. Seems cheap to me...especially for centerless ground 200ksi studs.

I do plan on having this truck for a long time, so it's worth the added expense, also even if the engine needs rebuilding later these studs are re-usable where the TTY head bolts aren't.

Rene

 

[MaxPF]

Cool deal, although I'm kinda surprised it's not higher. I guess once you get the correct clamping force enough torque is enough. Are those vales from the ARP torque table?

Rene

The lube makes a big difference. If you use motor oil you would have to torque them to 122 ft-lbs. I would use their moly lube because it it's much lower friction will give more accurate torqueing. IIRC the torque on the studs may be a bit different from what their chart says, probably due to the fact the block threads on the stud are 12mm. The studs include a sheet which lists the torque spec for the studs.

 

[MaxPF]

Reality Check

Today I started adding up how much it would cost to finish the motor the way I would like. In short, it ain't gonna happen that way

So, I have pared things down to a more realistic build. The important parts have already been taken care of: Mahle pistons, a new crank, main girdle, main studs, and head studs. I will be springing for a gear drive. Hot tip: you don't have to spend a ridiculous $400 that Kennedy and DSG charges for this item. It turns out that Pete Jackson makes one (it may be the one that Kennedy and DSG sell): http://store.summitracing.com/partdetail.asp?autofilter=1∂=PJJ%2D6%2D2%2DD&N=700+4294925232+400293+115&autoview=sku For now I will use a new GM harmonic damper. In a year or two I will change it out for a Fluidampr. Right now the extra $300 a Fluidampr costs can be used elsewhere. On the top end I will have new exhaust seats installed, but I will reuse the precups. Matt at Peninsular said even though the cracks exceed GM's limit they will be fine. He said he has never seen one fail. Good enough for me. I will port match and smooth the casting flash in the runners on the heads and intake. I won't enlarge the ports or mess with the flow directors on the intake ports, just a general cleanup since it costs nothing except time. This is known to add power to an NA motor.

The IP and injectors will definitely get a rebuild. I will retain the v-belt setup since all the parts are in good shape and a swap to serp belts would be $$$. Finally, there will be no turbo for now. For a turbo setup I would need not only the turbo, but also I would have to build the exhaust manifolds, intake adapter, and put a complete (stainless steel) exhaust system under the truck. By staying NA I simply have to change the head pipes and ditch the cats. This means a lot less time and money. Besides, Lee Swanger over at the Diesel Page is making as much HP with his NA motor as a stock turbo 6.5. This motor was already making 165HP stock, so I figure I will play with it and see how much hot-rodded NA HP I can make.

In short, I want to get the motor built and in before mid-October. Then I can start enjoying the fuel savings before I go Elk hunting at the end of October. Otherwise I won't get this thing done until the end of winter

 

[tRustyK5]

Reality checks suck, but we all have them on our projects. It sounds like you made some smart choices that'll get on back on the road without too much being compromised. All the difficult parts to beef up you already have. The rest of your wish list seems to be peripheral stuff that could be done later.

Are you gonna port match the intake as well? I did mine on my K5 and my right foot dyno noticed a good improvement. The intake casting I had was pretty poor with most runners needing almost .250" of material removed. This was just to get the ports sized and aligned with the gasket. On a 1" x 2" port that is a significant amount of material removed...

Rene

 

[MaxPF]

Reality checks suck, but we all have them on our projects. It sounds like you made some smart choices that'll get on back on the road without too much being compromised. All the difficult parts to beef up you already have. The rest of your wish list seems to be peripheral stuff that could be done later.Are you gonna port match the intake as well? I did mine on my K5 and my right foot dyno noticed a good improvement. The intake casting I had was pretty poor with most runners needing almost .250" of material removed. This was just to get the ports sized and aligned with the gasket. On a 1" x 2" port that is a significant amount of material removed...

Rene

Yup. These mods are known to make significant improvements. I haven't checked the (mis)match of my ports yet, but I am sure they are terrible, like most stock motors. Nothing a little won't fix

 

[colbystephens]

how do you see if the ports are mismatched? seems like it would be hard to tell because the one face meets the other.

 

[MaxPF]

how do you see if the ports are mismatched? seems like it would be hard to tell because the one face meets the other.

Simple. You use a gasket as a template

 

[tRustyK5]

Yup, that's what I did...plus used some dowel stock that fit the intake bolt holes snugly to ensure I had the gasket located as accurately as possible. I did find the intake port casting accuracy on the heads to be vastly better. Pretty much on size and on location...unlike the intake manifold.

Rene

 

[colbystephens]

so you put the gasket on, then look where the indentations are? makes sense i guess!

 

[tRustyK5]

First, turn the intake manifold upside down. Stick the gaskets on the intake centered up on the bolt holes. I seem to recall there is a locating nub on the gasket itself, but I used some snug fitting dowels through the bolt holes to hold it in place as exactly as possible.

Now compare the gasket's opening to the actual intake port openings. The openings are meant to be the same size. I used a steel scribe to trace the areas on the intake that were inside of the gaskets port opening. I then used a brandy new carbide burr made for aluminum on my air die grinder to enlarge the opening to the new scribed lines. For most of my intake, this required getting 2-2.5" into each port to properly blend and open the port enough. I occassionally dropped the gasket on to check my work...

All told I spent less than 3 hours hogging my intake ports out and blending it all. I used an 80 grit flap wheel to do my finish work.

Simple and nearly free mod that makes a noticable improvement in power. FWIW I'll be doing this again when I do head gaskets on the '83. i'll likely gut the 'C' code intake and remove the EGR stuff while I'm at it.

Rene

 

[MaxPF]

The crank is almost ready to go!

Well, I finally got to use the manual lathe at my friend's shop. It has been tied up with paying jobs for the last couple of months, so I haven't been able to machine my crank to fit my block.

For those who haven't read the whole thread, I bought a brand new GM 6.5 crank for my engine project. The problem? 6.5's all have one-piece rear main seals, whereas my 6.2 block uses a 2-piece seal. I bought it hoping I could make it fit, and when I measured it after I got it I confirmed that it would work with the proper modifications. Why not simply buy a new 6.2 s-pice seal crank? Simple - there aren't any to be had. All the NOS GM cranks have dried up, and all current production, whether AMG/GEP or Chinese (

) are one-piece seal types. So, if you want a new crank for your 2-piece seal 6.2, this is the only way to get one.

Here's what a stock 6.5 crank looks like (this is a pic of some Chinese POS on Ebay - I never got a good pic of mine before I machined it ):

You see that the seal surface is slightly larger than the flywheel hub.

Now, let's see what a 6.2 2-pice seal crank looks like:

Here's a closer look at the seal area:

You notice that next to the rear main journal is an oil-slinger flange, and then the seal surface, followed by the flywheel flange. The seal surface has a bit smaller diameter than the main journals. The distance between the counterweight cheek and the seal surface cheek is greater on the 6.5 crank vs the distance from the counterweight cheek to the oil slinger cheek on the 6.2 crank. This means that I could not duplicate the entire oil slinger. Instead, I ended up with a "mini-slinger" that comes very close to the block at it's outer edge. This should make a decent dynamic seal and give good oil control. Here's what it looks like in the block:

Here's a closer look:

You can see where the original radius started on the main journal side. I made the diameter of the mini-slinger such that it approaches quite close to the angled groove in the block. The pics don't show just how close it really is. For those who wonder if the mini-slinger will be enough, remember that the 2-piece seal motors originally used a rope seal, which were little more than dirt wipers. The modern neoprene seals work quite well as long as they are properly installed (and the CDR valve isn't plugged). With it's close distance to the block and tapered edge I doubt much oil will migrate past it.

Here's what I did. First, I mounted the crank in the 3-jaw chuck and supported the snout end with a live center. Then an indicator was used to check runout on both ends, and adjustments were made until runout was less than .001". Then, I checked the runout of the center main journal to check for warpage. You can imagine my dismay when the indicator read .0045 . The spec is .0025 or less, and ideally you want less than .001". We had the ends indicated in to only a few tenths runout, so if the crank was straight it should have read less than .0025". After some rechecking and coming up with the same reading over and over, I figured the crank was junk. Then my friend had a realization. He relaxed pressure on the live center and we spun the crank again. The indicator read .0004"!!! Less than half a thou of runout . The pressure of the live center flexed the crank that much. So, with the crank confirmed to be straight, I started hacking away.

The rough machining was done with a diamond-shaped carbide insert. Once I got down to the diameter of the mini-slinger, I switched to a .160" wide carbide grooving insert and snuck up to within .010" of the finished diameter, I also left steps in each corner for radii. The final cuts were made with another carbide insert which my friend ground into a .093" radius. I removed the steps and .008" of the remaining material, leaving me with .002 material and nice radii in the corners. Finally, I polished the seal surface in stages. I started with 80 grit cloth sanding tape, and then after I got it as smooth as possible (and .0005" smaller) I went to 400, then to 800, and finally for grins finished up with 1200 grit. The surface is mirror smooth, although it doesn't look like it in the pics since it is coated with oil and a few dust particles.

Here's some more pics of the crank in the block. BTW, the "bearings" are pieces of cardboard. I haven't got the actual bearings yet:

I also deburred and radiused bolt holes and the edges of the bulkheads. Basically, anyplace a stress riser could form:

The final bit of good news is that my machinist friend has also started CNCing my stud girdles Right now only one is partially roughed. The roughing end mill he was using was already in poor shape when he started, and it gasped its last after an hour of noisy cutting, so he decided to call it a day (that was Friday evening). He should be able to resume carving on them Monday afternoon, and hopefully they will be done by the end of the week. Then I can send the block off to the machine shop for boring and honing. I will also have the line bore rechecked and honed if it is needed.

Yup, piece by piece it is coming together

 

[pauly383]

WOW

 

[colbystephens]

:drool:

 

[4x4_76]

So, how much did that new crank cost? I've been looking in my garage and searching crank that was removed from the block that's under the worktable. So far no luck finding it. I remember it having one bad journal, so wouldn't been any good to use.

Also that block has cracked webs. Don't remember how badly. But after reading this thread couple of times, I started to wonder that if I buy main stud kit and fab full main girdle, could I use that block? What I've heard, crack free blocks are hard to find in here.