Torque plate

[03GC]

I have been talking to a local top notch builder/machinist in my area (mid Michigan) and he told me he would not bore and hone my block without a plate. He said that on a weak block(not saying a 4.0 block is) you can distort a bore enough to bind up a piston (like a .002 clearance cast piston). Maybe a jeep block is a good one that doesn't distort much.

He told me if I was to make one, make it 1" thick if steel, or 1.5 "if out of cast iron. I would probably surface grind it after I bored the holes ,just to make sure it is flat.

He also said that he puts the same type of head gasket between the block and plate while machining. This allows the block to distort more closely to how it is when the head is on.

Maybe it is not even an issue on a 4.0 block. Does anyone have a finished block they can can put a head on and measure how out of round the bores are? I would guess that if all 6 bores ended up round within .001-.0015 with a head torqued up that would be good(just my opinion).

I may end up making a plate if it seems to make a difference on the 4.0 block, but it will take me quite a few lunch breaks to bore 6 4" holes in a 1" thick plate.

By the way , this guy has never done a jeep 4.0 block. He does v8s and small 4 cyls(drag ,circle track and hot street stuff).

Paul

[03GC]

Just looked at Hesco's site and it shows a block getting honed without a tq plate on it . Not that they are gods over there but they sure seem to have alot of experience.

Maybe the jeep block does't distort enough to make it worth the hassle.

Paul

[SilverXJ]

I asked Hesco about selling me a torque plate. They said it cost to produce them became prohibitive to sell them ($800) they only have the one they use left. The last few posts here concern a torque plate: viewtopic.php?f=5&t=530&start=45 TurboTom said he will measure the bores to see how they are effected by the head and bolts.

[1bolt]

I was just reading up on this on Eng-tips I haven't found any real consensus that the overall stiffness of the plate is actually important. And several suggestions that the localized "pull" of the bolts around each cylinder is the overriding factor (creates most of the bore distortion) also read about some setups that actually heat the block to normal oil temps before the final hone is done.

Interesting stuff at some point I was struck with the idea to just saw 4" holes in a stock head. Also the thought occurred to use head bolts and simple spacer sleeves, but further reading suggested that these would cause the distortion to be too localized... Not spread out enough.

So far I get the distinct impression that Torque plates are neither an exact science nor capable of accurately simulating ALL the bore distortion effects that are possible (such as combustion and coolant/oil heat, crankshaft stress' on the block webbing etc. etc.) Basically it's just a tool to get the bores a little closer to what they might be and call it good enough.

[03GC]

1 bolt, you bring up a good point. Say we get the bores within .001 of being round at room temp. What are they at 250 deg block temp with 1600deg combustion happening 2500 times a minute?

The late great (in my opinion) Smokey Yunick played around with pumping 250 deg oil in the block while honing. He tried bored out cyl heads ,torque plates,differnt dia bolts and studs, you name it. His conclusion in his book was it is a huge pain in the ass to get bores round with the heads bolted down. Most of the info in his books is about 1955-1975 SBC but I would think it is probably be similar in all engines.

Most likely, for a 260hp 300 ft lb 4.6l the difference between a tq.plate and not a tq. plate machined block isn't worth sweating about.

Does anyone know what the factory did? I kinda doubt they used one in a production line but maybe.

Paul

[SilverXJ]

Does anyone know what the factory did? I kinda doubt they used one in a production line but maybe.

Paul

That what has been bugging me. I doubt the factory used torque plates. No Jeep FSM I have ever read has mentioned anything about a torque plate, in rebuilding or otherwise, nor have I ever heard of any mass produced engine using them. The only difference over ours and a stock engine in this case would be the at the lower end of the stroke where the piston pulls out of the bore more. But at that depth how much does a torque plate help? A good running 4.0L goes for 200k+ miles before needing a rebuild. I understand we are throwing a bunch of extra variables into the mix, but I don't see how they will effect the piston to bore relationship. We use a stock head, with the exception of Hesco's aluminum head. However, I know Hesco used torque plates because they have access to one.. however, do they change out a steel for aluminum one based on the head they are running? If I had easy access to a torque plate i would use it, just because I am anal like that.

Question, would there be any benefit to using an aluminum torque plate at all? I have access to a router at work and I think a few of us to get together the funds to but a piece of aluminum if it would be a benefit to us.

[SIXPAK]

The torque plate that TT is using came from me. At the UPS store it weighed in at 71lbs and from Ohio to VA it was 55.30 to ship one way. I'm thinking off the top of my head it is 1.5" inches thick steel. As far as turning this TQ plate into a travel the country loaner I'm a bit up in the air about that. I have sent it to several people but it is usually to people I know directly or have a good idea of who they are. Some of the questions I was throwing out in the other tread was just to get info on what people think would be a reasonable way to handle a "loaner" senario. I personally feel guilty asking for a deposit for roughly $870 bucks but how else do I protect my investment? BTW 1bolt, i did read the entire thread but was trying to get a concensus of others on the forum.

If someone else would like to make a plate like 03GC mentioned or has the facilities to make a TQ plate that would be fine. No one will be stepping on any toes here in Ohio. Besides, looks like mine may be a poor choice to ship around as it may be a bit thick.

[SilverXJ]

I personally feel guilty asking for a deposit for roughly $870 bucks but how else do I protect my investment? BTW 1bolt, i did read the entire thread but was trying to get a concensus of others on the forum.

You really shouldn't feel guilty about that. It is only there to protect yourself against loss or theft. You should also insure it for the full value when shipping. I know the shipping companies, UPS, FEDEX, etc, can be quite harsh on items as I have had a solid tie rod damaged by them. If you can I would get the current amount that it would take to remake it or buy it as a deposit as I know steel prices fluctuate.

[1bolt]

Well I'd like to keep the discussion on the hypothetical side for a bit, when I posted I wasn't thinking about Sixpak's $900 71 pound plate. So it's not really fair to post something discouraging based on that. Sixpak you may very well be right but I think there's grist for the mill.

Aluminum plates are made and generally for alu heads, but even in a number of Engineer filled discussions I read so far; I wasn't able to find anything concrete with respects to exact stiffness or material properties. I think most torque plates are not actually engineered to mimic the specific engine's head in anything but bore size and bolt locations.

Think of it this way, we know a cast iron head is pretty rigid stuff (at least going by old roller cam discussions), and it's also probably a lot thicker in aggregate than a 1" thick steel plate... When you account for the fact that there's 3d structure to a head. Steel is not that similar to iron. So we're already talking about torque plates being another material, and more easy to flex, yet locally probably less easy to compress where the bolts pull the block up. Than an actual cylinder head. Steel might be a pretty poor choice.

What I'm getting at is if the torque plate is an approximation that's "good enough" and just serves to get us "a little closer" to lower bore friction (I think that's a fair assesment). Then torquing with a 2" thick piece of aluminum is better than not doing it at all. I also thought of aluminum which is what got me googling. It's probably more compressible than iron, but iron is more compressible than steel, and they are both likely more rigid than steel.

Then again what about using a piece of boxed tubing, then have it decked? quarter wall tubing is going to be WAY more rigid than 1/2 inch steel plate, and I'd bet with some sleeves in the bore holes and bolt holes it would maybe even be more rigid than a 1" thick steel plate. and a hell of a lot lighter.

Probably we should worry about the details after we talk about the plate itself but. We'd want a blow molded plastic shipping case (like transmissions and engines ship in) so box cost is one time (or occasional) and defrayed just like material cost. The plate should be passed around... NOT shipped A to B B to A A to C C to A. Rather A to B B to C C to D. One shipping charge per use not two, and shipped USPS not United Package Smashers assuming we can get it under 70 pounds (it wont happen if its that heavy) USPS is just far kinder to packages in my experience.

One last unrelated thought, UPS stores are a great way to spend from 10 to 20 dollars more than you have to. Can't beat printing a shipping label off with paypal IMHO. Course you need a scale.

[SilverXJ]

To save on weight what about a 1" thick piece of aluminum followed by box tube frame on top that the head bolts go through? Maybe a 1/8" piece of steel under the aluminum to protect the soft aluminum.

[Alex22]

The shop I work at has over 20 torque plates, most of them are from BHJ and are between 1.75 to 2 inches thick and have steel spacers to take up the room between the plate and the stock bolt to allow for the correct amount of stretch.
The thinner the deck surface, thinner the bore and the larger the water holes are on the deck the more benefit there will be from a torque plate. Which is why its a bad idea to hone a SB chevy 400 without a plate. The 4.0 block on the other hand has thicker cylinder walls a dicent deck thickness and the water holes arent too big.
I have been meaning to bolt my head back to the block and get a bore gauge in there to see how much deformation is present. I'm not sure where i put the old head bolts but I'll start digging through the piles.

[SIXPAK]

TT should be posting some results of his bore dia before and after the plate was installed. I think it will end up pretty interesting. Maybe we can get him to post the results in this thread also.

[TurboTom]

I should finish the valve job tomorrow, that will free up the mill so I can modify the T/P as Sixpak requested. I will post the results of any bore changes as soon as I can.

[5-90]

A torque plate is typically used with maximum effort engines, where every little detail is critical and usually contributes to wringing a few extra HP/pound-feet out of the combination.

Are they used on production engines? I'd be surprised. Do you need them for OEM overhauls? Probably not. Performance buildups? The more performance you want, the more you might need one.

If you're going to balls-out performance, running on 120LL AvGas, trying to get things as close to the low end of tolerance as possible, and making damned sure they /stay/ that way, it becomes critical.

Still, I'd like to know the difference in cylinder dimensions with/without the torque plate - more for academic interest. I've never compared results...

[TurboTom]

Here is a picture of the plate. The shop is closed until next Tuesday ( gone to the races), so the numbers will have to wait until then.
But I will give a detailed review.