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Motor Build on a Budget

 
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motormouth  



Joined: 28 Feb 2010
Posts: 113
Location: Canton

PostPosted: Wed Aug 15, 2018 1:03 pm    Post subject: Motor Build on a Budget Reply with quote

Originally, I was planning on building a stroker engine using Ideola's long rod idea here:

http://924board.org/viewtopic.php?t=36293

I spec'ed and ordered a set of Crower Rods, had my crank reground and balanced by a local hotrod shop, ordered some bearings, and then stalled out when looking for pistons. While I still plan to finish that project, I figured I'd use some of these left over parts first, then move onto the high dollar engine.

The engine came out a car that was in a crash where the timing belt broke. Upon tearing apart the engine, it looked like someone had recently rebuilt it, there is still the inked part numbers on the main bearings and the rod bolts are aftermarket. I plan to reuse the bearings, rods, and pistons and put in new rings and gaskets. I'd also like to balance everything and am thinking of lightweighting the rods a bit.

I want to use an NA head with the Turbo pistons to get somewhere around 11.5:1 compression.

I filled the piston with water and found the difference in mass to approximate the volume in the dish at about 35cc.




Here is the damage done to the piston from the valves.






I cleaned it up with a dremel here. I am thinking that the sharp edges left alone would create hot spots and stress risers causing a potential failure mode if ignored.







Then I wet sanded everything by hand to smooth it out.






Weighing the rods and caps







Is anyone familiar with Kamax hardware? I am hoping it is reusable. They look like a German hardware manufacturer. I am going to look for a US based distributor and see what they say.
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MikeJinCO  



Joined: 08 Jun 2010
Posts: 733
Location: Maysville, Colorado

PostPosted: Wed Aug 22, 2018 11:47 pm    Post subject: Reply with quote

I'll send another caution to you. My motor has all 931 internals, block, crank rods, S-2 pistons. We milled the block .020" to flatten it and did a pre assembly with the #1 piston and found the piston to be flush to the top of the block. As I recall the block appeared to have the original milling pattern in it, a much bigger Blanchard grinder type of mark than a smaller aftermarket mill will make. After cutting valve pockets in the pistons for the overlap condition I got a .040 Cometic head gasket to give an ideal quench with the maximum compression to get about 10.4. Now at final assembly the 4 piston is sticking up out of the block .016" I can't believe there is that much variation between pistons, but the two others stick out a bit less. I have now ordered a Cometic .056 gasket to get me back to the .040 quench. My machinist's minimum for clearance is .035". I would go back to using a stock head gasket of about .062 except I need to eliminate the cabin heating water circuit and the Cometic rearranges the water flow to get water to the back of the head whereas the standard gasket will allow the water to short circuit from the #1 piston area back to the head outlet.

I have an old school AMC head gasket of about .066 and am going to do a complete reassembly with clay in the pistons and roll it over.to make sure everything is ok. if this all works then I'll have to see if detonation is a problem and start investigating spark plug options.

As I've said before make it easy and measure the block height first then just go get some JE or Diamond piston. Rebalancing will be required.
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Mike
Poco a Poco, '80 future track car
'77 924
cricketdesigns.com
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