Subject.... boring with a torque plate-

>A .... engine reborer will have the required "False Head"..A block of
>thick steel, prebored to clear the bar..that he can torque down on the
>block to bring it to its actual running configuration while it is being
>bored and honed..All in less time than it will take you to bolt it down
>on your mill table so it don't move..too much!

No he won't ! - only once in a blue moon and only for very common blocks do you
find anyone with a "torque plate" to bore and hone them with. In the USA you
certainly have plates for standard V8s cos there are **** loads of em about.
Over here I have never seen a block bored with a torque plate in 20 years of
building engines. 1 or 2 firms have plates for certain types of race engine if
you think the extra cost is worth while. There are too many types of engine and
not enough of each one for it to be cost effective to make the plates up.

For road use, (and most race engines) torque plates are a complete waste of
time anyway. For some thin walled engines taken to flat out drag race spec they
allow you to gap the rings a tad tighter but it's debatable if any extra real
power shows up at the end of the day.


Dave Baker at Puma Race Engines (London - England) - specialist flow
development and engine work. .

**************************************** *********************************

>I have to wonder if the distortion form the head being bolted on
>isn't less than the normal thermal distortion form the engine
>being at operating temperature. Maybe they should bore engines at
>operating temperature too (:-)


Some people do that too - I only know of one company over here though who
advertises boring a block at running temperature. Another waste of time in my
opinion. Blocks don't run at an even temperature over the length of the bore
and the bore walls go all over the place as soon as they have high speed piston
thrust and vibration acting on them anyway.

I look at it this way. Bore wear takes place mainly in a very limited area at
the top of the ring travel. You can strip a newish engine down and find 1 thou
of wear over just a quarter of an inch of bore length but the power and
cranking pressure won't yet be much affected. That means the rings can cope
with moving in and out over that 1 thou in such a short distance. Even at 3
thou wear you see little drop in power. I stripped an engine recently with 8
thou wear and that certainly was smoking a bit but power was not too bad still.
Maybe 95% of original output.

So does even less than 1 thou of ovality or taper over the whole length of the
bore cause the rings any problems? I doubt it somehow.

I don't dispute that in theory the perfect bore should be round and straight at
operating temperature and with the stresses of the head and mains caps bolted
on. Whether the few tenths error you end up with by not boring with these
stresses in place makes the slightest difference is open to opinion. My
opinion, after seeing what engines can cope with in terms of machining error
and still run at peak power is as I say above. Also most engine reconditioners
don't get a bore anyway near round and straight at the best of times. 1 thou
taper or ovality is par for the course when I check other people's work. That 1
thou is still going to be there if they bored with a torque plate on - just in
a different part of the bore I suspect. Call me a cynic.


Dave Baker at Puma Race Engines (London - England) - specialist flow
development and engine work. .

 

I've seen my engine builder use torq plates when boring at times when I was visiting his shop, so I know that he uses them. I recall reading somewhere a long time ago that it's better to start with a seasoned (used) block than a new one when building a race engine because the block has gone thru all it's heat cycling already and will distort less after subsequent machine work is done.

My builder wasn't able to finish hone my new Dart block to size in his shop because of the hardness (high nickle content) of the block, so he had to send it out to have it honed on a Sunnen hone at another shop before he could continue.

 

Unless this guy has done it with and without a plate then how will he know? You can't say something is a waste or not unless you have actually tested it. You also can't build maximum power if you actually are losing some by not doing this procedure, assuming hes never done it for a comparision.

Most of the engine builders I've heard about have done the wrong stuff to find out for themselves. They not only learn but place themself in a competive position. If you get the same results with step saving procedures you save time, time is money. If a procedure they do seems to produce something, life or power, they get the business.
They don't get this rep from guessing though.

Over here how many engine types are being rebuilt? He even mentions this.

 

Doing Hi-Perf engines for near 40 years now we've done "tons" of blocks. Boring a block (with a plate) is a waste of time, unless your only leaving a couple of thousandth's to finish hone, in this case you'll never achieve a good base finish anyway. We have found certain blocks don't respond to the plate, in other words, the bores are the same with or without it after final honing. We do them all with plates, but as I said, some don't need it. If you get in a position where you want to "stress" up a block and no plate is available, simply take some "grade-8" hardware and some "hardened" flat washers and
"torque 'em up" in the head bolt holes. We just did 2 old "nailhead" Buick's and pair of 409's with this method. Works great! We've done it this way for years. The only area that's affected by the plate is around the (head) bolts. Back aways, Jenkins and a few other "bigtime" builders actually honed the blocks with 180 degree water circulating through the casting. Don't know if it made a difference or not. Being it's not done this way now, I would figure they were "beatin' a dead horse".
Thanks, Gary in N.Y.

 

Now if they give a sticker that says 'Block Plate Honed' then it would be worth some horsepower. Seems I saw a show like '2 guys garage' or 'hp TV' where they toured a rebuilder and the owner said they stopped doing it since it made no difference.

 

...
Well... that sounds like a good reason to use it to me.

Whatever helps him sleep at night since he can't get his hands on them. Sure if you have to pay $xxx to get one made or shipped to you for every engine you build, it's not worth that. But if you're balancing and blueprinting and quench-ing anyway (and in the US) it certainly shouldn't be neglected. I agree that the operating temperature method isn't worth it, if you've seen an IR picture of a running engine, the temps are all over the place.

-Chris

 

Machine shops will give you 2 prices for boring and honing, with or without torque plates, hows the ordinary gearhead like myself supposed to know it's a waste of money ?

 

Trying to learn something here.......when a shop bores a block...how much stock are they leaving for the finish hone? ....or another way of putting it.....how close to finish do they bore? Would it vary depending on what kind of machine finish they get?
Thanks

 

The block plate (hone) is good investment due to the fact that it MAY help, but it will definitely NOT hurt. Now, as to amount of "stock" removal, this we feel is of the utmost importance. We find in order to achieve an "excellent" base finish, that you have to hone no less than .005". Anything less than that number won't have the finish that's needed for the rings to function. We leave between .006" and .007" to end up with the hone. A little more effort, but worth it. Thanks, Gary in N.Y.
P.S. One more important piece here, ALL blocks should be "hand-washed". No cleaning tank alone is good enough. Hot, soapy, water, period!

 

Good info....thanks very much. 6 or 7 is more than I expected.....actually 5 sounds like a chore. Do you start with rough stones.....then change to a finer set as you get closer to size?

 

One of the better machine shops in this area is located in Conway SC ... does a lot of race stuff ... from iron production for hobby class to aluminum Donovan mountain motors. Lately, Dennis has been getting about $12/hole without plate ... $15/hole with plate.

 

Well put.

 

I've had experience this summer with 2 shops, one very good the other a complete jerk who did lousy work. One block was ready to assemble after we washed it down with soap and water then ATF. The other block is almost wrecked and will need to be bored to .040 plus they stole my rods!
Be sure you check all the dimensions before building your engine. I had the plate used on both and they get about $22- $35 per hole to do this around CT.
Gary

 

Gary,
What was the name of the good one!
Bob

 

East Coast in North Haven. If you want to know the bad one, let me know.
Gary

 

I can tell you with experience that deck plate honing will not do anything to improve power. It WILL improve oil economy-- For some engines significantly!!

When the head bolts are torqued in place they pull on the upper threads of the engine block which tend to distort the bore in a clover leaf shape. For most engines with four bolts/bore this would be a 4 leaf clover shape. For Chevys, imagine a 5 leaf clover because of the 5 head bolts. In fact, bore distortion can be broken down as to order: 2nd order-oval, 3rd order-3 lobes, 4th--4 lobes (clover leaf), etc. When these components are added together they describe the total level of bore distortion. The ability of a piston ring to take the shape of the bore (conformability) decreases with the order of the type of distortion by the 4th power. This means oval distortions can be handled relatively well by the ring, but as the predominant order of the distortion increases, it's ability to conform to those distortions is drastically reduced. By deck plate honing, you are intentionally stressing the cylinder bore to induce this distortion while honing so that with the cylinder head assembled to the block, the bore does not have these higher order, hard to seal, distortions present; essentially this makes the bore round with the engine in the assembled state.

I have seen numerous examples of production engines baselined with radio-metric oil consumption measurement* equipment that have then had the bores deck plate honed and re-tested with the result being that the oil consumption drops by 4-8 times.

Look at modern engine designs. The head bolts are longer so that the thread engagement is made further down the bore where it is less detrimental to ring seal, or the deck of the block is open so that the stresses of keeping the head clamped on the block are isolated from the bores.

A side benefit to round bores is that the ring tensions can be decreased because the conformability requirements of the rings are reduced. This in turn reduces friction losses due to the rings and this will improve engine power (albeit indirectly).

This data is indisputable and I have seen it time and time again on many different engine designs. I have seen the comparisons of the distortion differences between deck plate honing vs. standard honing measured to the micron by million dollar CMM's and have seen the improvements correlate by engine testing. Deck plate honing works!!!!!!

*radiometric oil consumption testing is performed by some of the OE's to measure oil burned due to escaping past the rings. It's performed by spiking the oil in the crankcase with a small amount of radio-isotope(on the order of the radio activity used to make a watch dial luminous). The presence of the isotope is then measured in the exhaust. It is extremely sensitive and can detect less than a gram of oil burned by an engine in an hour!!

 

I would think these are one and the same. Burning oil hurts power, as would leakage across the rings the other way of course.

Great info by the way

-Chris

 

Excellent! You've explained deck plate honing concisely & w/ benefit of hands-on observation of precision data ... what some of us already knew; albeit from only intuition & anecdotal evidence. Thanks!

I'd be very interested to know a bit of GM history with deck plate honing: when did GM begin this with serial production? ... ? which chevy V8? ... did it coincide with introduction of thinner radial wall rings for serial production? ... before or after? ... anything you'd care to share!