NMPRA

airraptor wrote: Now with that I changed out the whole top end on that engine set up with same numbers and didn't run as strong as it did before. Thoughts?

Re visit the liner. If you read back through you'll find where it says to just change the piston and rod of a good running motor that has worn out its piston fit. "Credit-Dub jett many moons ago" The liner was in whole the the secrete to that motors performance. Try using the new piston from the new drop in. Measure where it "bites" if it fits, run it in the old liner. No need to regenerate the surface of the liner. A little breakin as per this thread and You will be pleasantly surprised. If the fit is not acceptable have the manufacturer fit a piston to your liking.
RR

Being an Ole' Information Technology guy, I was wondering if there is a capability to Download this "Wealth of Information", so a guy could print and binder the Doc for reference while in other locations of the home

airplanescotty wrote:Being an Ole' Information Technology guy, I was wondering if there is a capability to Download this "Wealth of Information", so a guy could print and binder the Doc for reference while in other locations of the home

I use this http://www.tensons.com/products/websiterippercopier/ to save things if saving to a page using Chrome will not get the job done.

If I can get permission to turn this thread into a document, I will grab it and save it in Word / PDF format to be shared.

Thanks Don,,,,

I just finished moving all this information to a document! Pictures, of course, included!

After I proof my work I will make it available to whom ever would like a copy

Well,,, Maureen's "Proof Reading" & "Attention to Detail" skills,,,, snatched Victory from the Jaw's Of Defeat!!

Correction time,,, clearly,, exceeded Scotty's Expectations

I deleted salutations and resized the pictures to save space. Current doc is 69 pages and 7.2 MB's

I have asked Rocket to Review the doc to make sure the pictures are not TOO Small to negate the discussion points.

Upon his approval, sharing will commence!

If anyone would like a copy of this Motor Discussion document,,, send me your E-Mail address

My E-Mail address is airplanescotty@gmail.com

I have made the thread summary that "airplanescotty" compiled in pdf format available for download at the main site here:

http://www.nmpra.net/articles/RocketMotorDiscussion.pdf

Was the Head Bold/Back Plate Inch Pound torque setting recommended somewhere in this doc? If Yes, where??

Thank You ~ XXOO

I think it's like 13 in/lbs..

By the way, an old CD works great for sticking a printed degree wheel on.. Just make a plug and drill the 5/16" hole in the middle..

Lee,

It's been a while since I bought my torque wrench but I'm fairly sure that it's in/oz not in/lbs.

Lonnie

LOL, I guess I never looked, just set it to 13 for the head bolts and 30 for the plug..

There seems to be a lot of misinformation about torque screw drivers. For our application it is in fact in. lbs. Typically for a head or backplate 10-12 in. lbs. If you have a Utica tool it's stamped right on it.

Cool Beans & Thank you gentlemen!!

XXOO

Scotty

Ha ha, I bet most of you thought this thread was dead (and maybe some wish it was).

But I wanted a little clarification on this subject and rather than begin a new thread I thought my questions would fit well here:

This may be a simple subject for most to grasp, and I think I’ve got it, but I want to put it in my own words to make sure I am understanding this correctly:

When speaking of TDC (top-dead-center), I understand this is the actual distance measured between the top of the piston (at its highest point - TDC) and the top of the liner (with or without shims). But for our pylon engines, when speaking of TDC, we are actually referring to the timing, or exhaust timing, or in actuality, the point at which the top of the piston eclipses the top of the exhaust port thereby sealing the combustion chamber. In other words, this TDC measurement is really "code" for how high or low the liner is in the case and the anticipated performance characteristics expected due to the "timing" or the closing of the exhaust port, right?

So, an engine with say, a .151” TDC will be “timed” lower than an engine with say, a .154” TDC, right? So again, TDC in this case is really used as a reference to the timing, right?

Of course then too, we do need to know TDC (this time, the actual distance measurement between the top of the piston and the top of the liner) to calculate the head clearance between the top of the piston and the bottom of the head (or head button). (Isn’t this distance also referred to as the squish band?)

Hey, hand me that squish band, will ya!? LOL

Again, I know this is basic, and I think I understand the premise, I’m just putting it in my own words:

When speaking of engine “setup,” we use the figures that describe TDC (referring to timing) and head clearance (a component of which is the TDC measurement).

So, for example, an engine that is set at .151/.015 is timed rather low (or, at least lower than an engine with a TDC of .154”). The .151" engine has its liner set lower in the case and could be said to be timed lower than the engine with TDC of .154”, yes?

Of course, raising or lowering the liner increases or decreases the head clearance (squish band?) accordingly.

I’m not asking how to set an engine, I’m just making sure my understanding and terminology is correct.

Once more to clarify, when we toss out figures such as “.151/.015” we’re speaking of the timing and head clearance.

Thanks!

Tim

I think you'll find that the top of the piston is quite a ways further down the sleeve when it closes the exhaust port than .151, .154, etc.

The numbers that people throw out are measurements of the difference between the top of the piston at top dead center, and the top of the sleeve flange. Yes, larger numbers imply that the sleeve is higher, which raises the edge of the exhaust (and intake) ports with respect to the centerline of the crankshaft, which increases the timing duration in degrees.. so it's a way of getting relative numbers without using a degree wheel. The degree wheel would be the proper way to measure actual port timing.

and the .015 is the distance between the top of the piston at TDC, and the squish band of the head.