Engine torque plate for boring/honing

[CleverHans]

This may be a loopy idea but I'm thinking about making a engine torque plate by using a redundant head and machining boring holes, more or less, 'up through the combustion chambers'.

Will this work or should I keep taking the little white tablets?

 

[patprimmer]

Taking out the chamber and above severely weakens the head, but even a beefy steel head plate has different distortion characteristics to an intact head, but it goes a lot closed to replicating an actual had.

If you sleeve the holes and fill the head with grout, you might do better. Just a guess on my part.

Regards
pat pprimmer@acay.com.au
eng-tips, by professional engineers for professional engineers
Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[willeng]

Clever Hans

Pat is again right that the steel simulates the head more accurately, but just about anything will do the job if you can simulate the amount of distortion caused by the heads torqued to the correct specs.

If you fit a head to the block & torque it correctly, you can then turn it over & measure the distortion created.

As long as you can simulate this basically anything will do the job!!

Note: The little blue ones work better!!

 

[Tmoose]

In my very limited experience (iron barrel HarleY Sportsters and precision machine tools) the cylinder-wall/bearing-bore bulges about 0.0005 inch locally over the torqued bolt. Slightly used cylinders finished without a torque plate had a shiny stripe (missing the hone pattern) right over each head bolt. Gotta think the rings did not enjoy that.

If the bolts/studs thread into the deck I'd spend the time to duplicate the engaged fastener length.

 

[evelrod]

In my experience with certain four cyl Ford products I have found a one inch steel plate with special studs or bolts to work well. The main problem I encountered years past in some engines, eg, small block V8's was in the choice of fasteners used. If your engine will have studs, use studs in the torque plate, etc. Also, use the same type fastener you intend to use in the final assembly in the main caps and torque them properly. Some engines do not distort the same with bolts as with studs and you can end up creating a problem where, perhaps, one did not exist before.
In addition, you may choose a commercially built plate from one of the contempory head mfgrs. Not cheap, but they do a better job in the long run and you can use stock fasteners.

Sorry for the late post, I hope this helps a bit.

Rod

 

[Majik]

I know this is a late post but I want to correct some misinformation.

Torqueing the head onto the block and then measuring the distortion.

A heavy steel plate will more accuratly represent distortion.


This topic seems to be frequently misrepresented. You can NOT measure distortion with a dial bore gauge! Well you can recieve some distorted numbers but they will not tell you anything about the distortion of the bore. Most distortion is caused by casting shifts and then the head and the main bolt torque on the block. Different head gaskets cause different distortions as well. Most every hot rod magazine around hypes "bored and honed with a torque plate" and most torque plates around are 1/2" to 1" steel headgasket patterns offering no validation in that the simulate anything but a steel plate being bolted to the block. Many race engine manufacturers use inclinometers to plot cylinder distortion with a head on and then can machine a torque plate to fit that style of block. Measuring distortion with a dial bore gauge doesn't tell you if your walls are straight up and down... only that the distance side to side is x inches. When you plot it in 360 degrees you start to see you would have no clue if your cylinder was even close to straight up and down. You would be better served to get a real hone or find one such as a 8 stone or diamond hone if you are looking to eliminate distortion and purchasing an engineered torque plate from a qualified manufacturer instead of attempting to make one yourself. The reason they are expensive is that the tooling to make one properly is expensive. using studs in stud applications and bolts and bolt applications is a basic with torque plates. the ultimate right now is to heat the torque plate and block upto running temperatures and hone. The main difference in distortion you will find is heating the block... and using a quality hone to eliminate out of round holes. (note most holes look like a rounded square in a 4 stone common hone) Your gains will be much higher if you procured quality equipment than attempting to make a torque plate. Even a quality one yields little gains (ex 350chevy iron block 5HP street.. 10HP race) in the fight against distortion compared to a hot block or a quality hone. (together around 5% more output) Hone finishes and ring selection would be a better use of time.

 

[incandescent]

majik, I have heard from a reliable source that hot honing has yielded an average of only 0.5% and a peak of 1% over a standard race level hone.

Could you explain a little more on how race companies develop their torque plates? Your description of "most torque plates around are 1/2" to 1" steel headgasket patterns" is negative, yet all the torque plates I've seen are this way. I do not understand how else they might be developed?

Thanks in advance.

Does anyone have SAE paper 2002-01-3299 "Summary of Results of Development and Validation of Hot- Honing System to Provide Improved Engine Performance" ? What does it say regarding power gains?

 

[willeng]

Majik

Hot block honing is essential & has been common practice for thirty years, not sure any body mentioned reading distortion with a std type dial bore gauge even though you can read distorsion to some degree with these.

Quote "Hone finishes and ring selection would be a better use of time"

It may be suggested you get the holes round before worrying about what type of hone finish or ring type you use. Personally i haven't had much success in buying out of round rings or sealing out of round bores.
Bore alignment is also a different discussion.

Casting issues aside, if the bore distorts when the head is torqued then sorry my friend this is the cause not casting, it is possible to get the bores near perfect until you torque the head so casting would seem to be a non issue & is always flawed. Finding ways to get around the flaws is necessary.

10hp in a race application is a lot when you consider times that come down to thousands of a second & many people spend countless hours for a lot less.