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Yet another 1725 rebuild

Discussion in '"Stock" Alpine' started by spmdr, Nov 26, 2020.

  1. spmdr

    spmdr Donation Time

    Yesterday I started the rebuild on the Street SV Alpine.

    Lovingly known as Marie's Alpine...


    It looks like the short block is original, unmolested.

    I can't say the same for the rest.

    The head has clearly been off, by evidence of the head gasket being on Up side down!

    The engine ran OK, but it had blue smoke out the exhaust and a fair amount of blow-by.

    The oil pressure was Great!

    I have not finished a close inspection of the Bores, but I am considering rebuilding it with STD Bore.

    The pistons are USED UP, with more ring side clearance than I can remember ever seeing,

    and still having the rings in one piece!


    Has anyone regretted NOT boring to an oversize?

    DW
     
  2. bernd_st

    bernd_st Bronze Level Sponsor

    Question is whether your bores are still within measured tolerances and whether they actually still carry the honing cross hatch patterns. If not and if the bores are shiny, then better to go for a rebore...
     
  3. spmdr

    spmdr Donation Time

    So far, I just pulled out the #1 piston to check the ring grooves. I'm surprised how little top ridge/ware is in the cylinder.

    No cross hatch to be seen in the ring travel, but very consistent good looking bores.

    I have not looked at the "specs" of the Alpine engine in a long time, but when I read them, I was thinking they were quite loose.

    Based on the looks ONLY (lack of top ridge), I would be surprised if the bores are out of "spec".

    It may come down to what parts are out there. I won't put it together with cast iron top rings.
     
    Last edited: Nov 27, 2020
  4. sunalp

    sunalp Platinum Level Sponsor

    I've seen 1725 bores with very little ridge on top, but they were ovaled pretty
    badly. Couldn't see it with the naked eye. That's one reason to overbore the cylinders.
    Depends on how well you know the engine and what and how it was used.
     
  5. bernd_st

    bernd_st Bronze Level Sponsor

    If in doubt bring the block to good engine machine shop. They'll measure the bores and tell you - at least mine is doing so...
     
  6. husky drvr

    husky drvr Gold Level Sponsor

    DW,

    Considering your description of the pistons, and knowing wear is rarely unilateral, I'll second Bernd's suggestion to have the block measured.

    At least you'll know what you're dealing with at that point.
     
  7. RootesRooter

    RootesRooter Platinum Level Sponsor

    I wonder if the ridges were reamed when the head was off?
     
  8. spmdr

    spmdr Donation Time

    I DID lay a dial caliper across the bore to check the size, it IS STD at the top.

    It never ceases to amaze me how much ware is found in Alpine ring grooves!

    The rest of the engine is NOT worn as much.

    And I have seen SBFs with a LOT of overall ware, and the ring groves are not that bad.

    DW
     
  9. spmdr

    spmdr Donation Time

    The jury is in on the cylinder ware.

    The max I measured is +.003" in the #1 bore.

    So far, with just one Rootes Book I consulted, it looks like .0022 is the limit,

    And that number is suspect. The numbers seemed to be just production variation numbers.


    It still blows me away how much clearance is in the ring grooves.

    With the top groove coming in at .090" and the top ring warn down to about .060" on the inside,

    and the top ring end gap is in excess of .062"

    It's no wonder it used some oil!


    I think it's fair to say this engine NEEDS a rebuild.

    However, IF you look at the crank and bearings, you would wonder why I took it apart.

    They are like brand NEW!


    I talked to Rick at SS, he only has Low compression pistons (assumed to be 15cc dish?) in +.020 oversized.

    Hmmm, what to do?
     
    Last edited: Dec 2, 2020
  10. Mike O'D

    Mike O'D Gold Level Sponsor

    You need a bore gauge to measure the cylinders - calipers will not be accurate at all. The pistons that Rick sells are not low compression, they are standard dish top pistons just like the originals. Have it bored and get oversized pistons.
     
  11. spmdr

    spmdr Donation Time

    I just used the Dial calipers for a quick check of the bore.

    All the bores were checked with a Dial bore gauge that has .0005 resolution.


    Rick doesn't have all the types of pistons in ALL the sizes, at this time.
     
  12. Mike O'D

    Mike O'D Gold Level Sponsor

    Great - you never know someone's experience level.
     
  13. spmdr

    spmdr Donation Time

    After a casual look for Alpine engine parts, some are not easy to come by,

    Like original replacement Pistons and rings.

    Sure, if I JUST wanted pistons and rings, no problem.

    But they would not be "as original", in the sizes I'm looking for.


    Fortunately, I found a set of used pistons, very near the top of my Alpine parts pile,

    that are STD AND have very little ring groove ware.

    I'm thinking now may be as good a chance as any to reuse them.

    I just need some new "as original" STD rings.


    SS is a strike out.

    Hastings no longer lists them for an Alpine, however Grant still does.

    So far, the web is not as helpful as it could be.
     
  14. alpine_64

    alpine_64 Donation Time

    Dan i sold Jeff Keyzer on this site a set of NOS std hepolite pistons and rings a while back, but believe he ended up over boring... He may have them still
     
  15. Shannon Boal

    Shannon Boal Bronze Level Sponsor

    Your bores sound OK at 0.003" max taper. Rings will seal fine with more than that (how are other bores?).... Ring groove wear: rings seal well as measured with cylinder leak-down gauge up to ring to groove clearance of 0.004", with the seal going rapidly downhill at 0.005" and greater.... So, new pistons. Standard pistons will work fine in a slightly worn cylinder with loose (0.0025"-0.0035") skirt clearance, although the ring end gaps are gonna be larger than spec....if you can find a first class machinist, not a bad idea to consult. I was an engine builder, ASE certified machinist. I like Moly filled top rings, iron second rings, three piece oil rings for used bores. I think that Alpine engines normally consume a bit of oil. They also seem to be tough on ring grooves!
     
    Last edited: Dec 20, 2020

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