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Rebuild for mileage and emissions
https://slantsix.org/forum/viewtopic.php?t=64507		 Page 3 of 12
Author:  slantzilla [ Fri Mar 06, 2020 1:52 pm ]
Post subject:  Re: Rebuild for mileage and emissions
Stock deck height can vary but is normally right at -.180".
Author:  Dart270 [ Fri Mar 06, 2020 2:56 pm ]
Post subject:  Re: Rebuild for mileage and emissions
Yep, I almost always get 0.180" or right around there for mid 60s to mid 70s motors. Have seen 0.220" on an early Slant and 0.150 on an 80s cast cranker...

Lou
Author:  rich006 [ Sun Mar 08, 2020 4:38 pm ]
Post subject:  Re: Rebuild for mileage and emissions
Before machining, the head part of the combustion chamber has 59 cc plus or minus one. That does not include all the crust on the valves. :-)
Author:  rich006 [ Mon Mar 09, 2020 4:26 am ]
Post subject:  Re: Rebuild for mileage and emissions
I estimated my original static compression ratio at 8.2 based on the numbers I've measured.

Head volume 59 cc, 3.60 ci
Deck height 0.155" on average
Bore 3.40"
Stroke 4.125" (not measured)
Gasket thickness 0.021"

Static compression ratio 8.2

If the deck height is .180 instead of what I measured, then I'm off by two tenths. Also, if my head cc measurement is off by 1 cc, that could add or subtract a tenth.

If I shave a combined 0.050 off the block and head, I should increase compression by about 4.5 tenths.
Author:  Dart270 [ Mon Mar 09, 2020 5:45 am ]
Post subject:  Re: Rebuild for mileage and emissions
Your numbers appear to be correct. You will be using an aftermarket head gasket, which will be between 0.034" (Felpro) and 0.048" (most others) in compressed thickness, as opposed to 0.021" for the stock steel gasket.

You may want to re-measure the piston-deck ht at TDC and make sure there is no significant carbon on the piston top and your caliper is checked/calibrated. I have never seen an early-mid 70s motor with that small of a deck height.

In any case, if you shave 0.050 - 0.080" off, you should be in the right range. Personally, I would probably take 0.060" off and you almost certainly will not need shorter pushrods. More than that and you might need them, although probably not until about a 0.100" cut.

Lou
Author:  rich006 [ Mon Mar 09, 2020 7:14 pm ]
Post subject:  Re: Rebuild for mileage and emissions
I'm looking for recommendations on parts suppliers or brands for the following.

- Timing set
- Radiator
- Engine paint - Also, do I need a primer?
- Oil additive for break-in
- Motor mounts (just the inserts? the whole thing?)
Author:  DusterIdiot [ Mon Mar 09, 2020 9:02 pm ]
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Author:  Dart270 [ Tue Mar 10, 2020 4:05 am ]
Post subject:  Re: Rebuild for mileage and emissions
I agree with about everything Dusteridiot said. Here are a few other considerations:

The Cloyes single link-belt (stock replacement) chain and gears should work fine for your application. The last one I used was not stamped/degreed accurately. The Rollmaster chain and gears (ebay - Campbell enterprises?) is excellent and the last 2-3 I used were dead on.

I like Duplicolor engine paint and I do not use primer. If there is any surface rust, then I brush it with Jasco metal prep first.

If your radiator is in good shape, reusing is fine. I would get it boiled/rodded out by a shop that has good recommendations. Otherwise, Dusteridiot has it. No real downside to a larger radiator. Perhaps some here will have ideas about brands that don't suck these days?

Lou
Author:  coconuteater64 [ Tue Mar 10, 2020 6:36 am ]
Post subject:  Re: Rebuild for mileage and emissions
I use Rustoleum (Tremclad in Canada) oil based paint on the engines, or Ace Hardware farm implement paint. The red is very close to the original slant paint and no primer required.
Author:  rich006 [ Thu Mar 26, 2020 6:38 am ]
Post subject:  Re: Rebuild for mileage and emissions
I got the initial report from the machine shop. On initial inspection the pistons look fine, but he's going to clean them more thoroughly and check again. The exhaust valve guides are worn to the point of needing replacement, but the intake guides are OK. I think the valves themselves will be replaced.

The cylinders are worn 4 to 5 thousandths. He says for my application I can keep the stock pistons, but I don't mind spending a couple hundred dollars on a new set of pistons if it will make a difference. What do you all think?
Author:  ProCycle [ Thu Mar 26, 2020 10:23 am ]
Post subject:  Re: Rebuild for mileage and emissions
For me 4-5 thousandths wear in the cylinders would automatically mean boring it to 0.020" over with new oversized pistons.
Author:  drgonzo [ Thu Mar 26, 2020 11:49 am ]
Post subject:  Re: Rebuild for mileage and emissions
If I bought new pistons I would go oversize and bore it.
Author:  Dart270 [ Thu Mar 26, 2020 12:34 pm ]
Post subject:  Re: Rebuild for mileage and emissions
Given all the time and effort you are spending, it is probably best to find a good set of oversize pistons and bore the cylinders. Oversize 0.020" or 0.30" pistons and rings are getting harder to find, although you still can. 0.040" and 0.060" are more common, and that is not a big overbore for a Slant 6.

If you are going to stay with stock bore and just hone it, then you should probably just stay with the original pistons. Even with new stock replacement pistons, they will not seal as well as doing an overbore. Again, if getting new pistons anyway, you want to overbore the block and have fresh surfaces with the proper clearances newly machined.

Lou
Author:  rich006 [ Thu Mar 26, 2020 1:33 pm ]
Post subject:  Piston source?
RockAuto offers EngineTech and Sealed Power in a range of overbore sizes, both for under $20 each. Given that I'm not building for high RPM, are these brands acceptable?
Author:  DusterIdiot [ Thu Mar 26, 2020 7:19 pm ]
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