Poorman's Torque Plate

[CZLN6]

Howdy All:

Did anyone else notice the photo in the article entitled, "Build Your First Performance Engine", in the July 2006 issue of CAR CRAFT?

The photo is on page 53. Rather than a one piece torque plate, JMS Racing Engines has come up with an alternative to the expensive-to-build-to-use-rarely torque plate. The caption says,

"The machine shop you use should apply head-bolt torque to the block when it is being bored. Since the procedure is about the torque on the bolt- not the torque on the plate itself, JMS came up with torque bushings that simulate the stress head bolts put on the block. If you don't do this, the cylinder will distort and the rings will wear causing a shiny spot to appear on the cylinder wall near the bolt location. This is especially troublesome on the 400, where the bolt hole is so close to the cylinder wall."

I'm particularly interested in this method because of torque distortion on the thin wall casting on our sixes, the cost of making a torque plate and the outcome of more accurate machining.

The shims JMS is using appear to be a piece of steel pipe about an inch and a half long. The length will have to replicate the thickness of the head at each bolt hole. THe inner diameter is unknown, but the OD appears to be about an inch. I will be contacting JMS to see what pipe material they are using to make the shims. I hope they are good at sharing info.

Anyone about to build a short block should certainly take a look at this idea.

Adios, David

 

[addo]

Sounds like 1" bar stock would do fine. A clever and easy fix for #1 cylinder!

 

[drag-200stang]

Hi David,

The experiences I've had with our 6's using torque plates and inspecting the wear pattern on stock engines with bolts shows about 1/2" down from the deck, the walls by the bolt holes are pulled away from the piston. Using studs doesn't seem to change this effect. I personally don't think the bushing set up will simulate the distortion properly. It's more like the cylinder is being pulled on by the bolt boss and the case is stretching outward. I don't think compressing the bolt boss will duplicate the stresses in the same manner to make it worthwhile. Their method may work on a small block Chevy. Maybe you could devise some kind of test to verify their set up works on our small 6.

 

[MandarinaRacing]

What about the length of the head? Would that also come into play?

Alex

 

[Anonymous]

My local machine shop told me about using old discarded wrist pins, cut to size. They said it worked pretty well on some older antique blocks.

 

[6bangerbill]

I sawed a damaged 300 block apart and was amazed to find that the head bolt bosses are cast attached to the outside surface of the of the block, the bolts dont pull on the cylinder liner casting. This is is news to me and should reduce destortion of cylinder blocks allot ( those crafty engineers). Ive made up a honing plate out of 1 1/4 6061 t6 plate to use anyway. It only covers three cylinders but was assured by my machinest it would work well for honing three cylinders at a time. I could not find any thick aluminum plate that was 29" long at the surplus yard . The 300 is actually two three cylinder engines made together anyway. Im a beliver in using the plate after measuring .005" distortion with and without it on a 400 cheby block. By the way, the cylinder walls measured .200" on the sectioned block with my mikes.

 

[Thad]

FWIW
The head bolt when torqued, for lack of a better term, squeezes the metal against the head, much like pressing down on a rubber ball, causing it to deform to the unsupported side.

With torque plate on and torqued, for a BSF and SBF this can be as much as 0.002" when measuring bore +/- 1" down between two oposite bolt positions.

JMS sells torque plate and has a good rep so I don't see them selling a product that would hurt their name.

I would say the hole in the bushing is th same as the bolt hole in the head;
length, equal to or greater the the lenghth of the hthickness of the head.

Should work, maybe not as well as a true torque plate but definitely better than nothing.

 

[drag-200stang]

Alex,
I'm sure the length of the cylinder head has an effect. Anything you can do to replicate the torqued cylinder head will give you the best results. I still believe a proper torque plate is the right way to hone a performance engine. Maybe AZ coupe can work out a rental program from a few areas in the country when he's not so busy. I tried running 180 deg water through the block while honing - was not worth the effort.