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Restoring a series3 with a racing engine?

Discussion in 'Modified Alpine' started by Knightowl61, May 6, 2022.

  1. Knightowl61

    Knightowl61 Gold Level Sponsor

    I posted this under Rootes Racing with little views and no replies, so a repost here.

    A long story - back in the early '70s I put an overdrive transmission from a Hillman into my series 2, shortly afterwards the main shaft broke and I never found another overdrive main shaft. In the mid 80s (early internet) I found a guy that wanted the overdrive unit and we traded for a 1725 engine. He said the engine was built for racing but I never pursued that fact. I eventually put a Toyota engine and 5 speed overdrive in the series 2 and am now restoring a series 3.
    I finally looked at that racing engine after sitting over 35 years and yes it is built for racing.
    I would like more power but a smooth running drivable engine. I don't know how this engine would work as a "driver" car and not a race car. I'm new to the race forum and would like input as to what I should do. Will I have too much compression with the pictured parts and the engine loping and getting power only at high RPM's? The head has the vizard modification but is shaved close to the depth marks.
    [​IMG] [​IMG] [​IMG] [​IMG] [​IMG] [​IMG]
  2. DanR

    DanR Diamond Level Sponsor

    Nice pictures, John. They sure explain better than words.

    I am unfamiliar with these racing engines. Hope you get some explanations,
  3. RootesRooter

    RootesRooter Platinum Level Sponsor

    If you have a standard Vizardization, combined with head skimming that's used up most of your wear markers, and stock pistons, then your compression ratio will be roughly stock. But those high compression pistons will send the C/R soaring. Undoubtedly rougher running on the street, and requiring nothing less than Supreme. I'd stick with the stock pistons and send your stock cam to Delta Cam for the KB grind.

    You could possibly finance your rebuild by selling those high-c/r pistons. I don't know anything about the 11-tooth Isky cam. Maybe meant for a 1592?
  4. husky drvr

    husky drvr Platinum Level Sponsor


    I'm not sure why you think the cam you have labeled as a "standard 1725" because it isn't. Which cam was in the race engine?

    The Isky cam with eleven teeth is the correct tooth count for a 1725. The twelve tooth cam is for a three main engine and pump. They do not interchange without changing the oil pump drive gear to match.

    The thing to remember is the oil pump drive gear MUST have the same number of gear teeth as the camshaft. Lots of things have been changed on these cars through the years, some of which can be a bit subtle. Trying to mesh an 11 and 12 tooth will probably result in something broken. If it turns, the distributor will not stay in time with the cam firing positions.

    Hope this helps,
    Last edited: May 6, 2022
  5. alpine_64

    alpine_64 Donation Time

    The jahns pistons are 12:1 pop ups.
    The isky SB-2 cam was quite aggressive.. I have specs somewhere.
    Check if it has the hollow chromolly isky pushrods too.

    The chambers in the head have to me measured... But likely the motor will need full race gas with the pistons and shaved head.. The jahn pop up pistons were usually .060 over bore.
  6. Knightowl61

    Knightowl61 Gold Level Sponsor

    What I thought was the 1724 cam is a 1592, I didn't know the difference in the unmarked cams. The Jahns pistons are stock size.
    Thanks for the input here, I think the engine will be too aggressive. I'll see if I can trade the Isky cam for a Delta and the Jahns pistons for flat tops.
    I will keep the Vizard head.
  7. husky drvr

    husky drvr Platinum Level Sponsor


    A couple of thoughts, you might consider taking your pistons to a reputable automotive machinist to have the thickness of the piston crowns measured in consideration of having part, to all of the pop up machined from the piston. If possible, it might be more cost effective than finding new pistons. The key is to know, by measurement, exactly what compression ratio you want to have in the engine.

    Next, if you compare the stock 1725 cam specs to the SB-2 specs, the SB-2 seems to be more of a "3/4 race" or fast street, than full race profile and is less aggressive than the Holbay H120 cam. The SB-2 doesn't seem to have the built in cam advance and probably no "quieting ramps" for less noisy operation.

    If your race engine also came with a lightened flywheel, I think I would try to find an offset key to advance the cam like the O/E cam, reassemble the engine, run premium fuel, and run it as is. I've a feeling I'm a bit more tolerant of "uncivilized" engines than you might be, though.

    Hope this helps,

    Jan's chart from "Alpine Marque" #7:

  8. Jay Laifman

    Jay Laifman Gold Level Sponsor

    Any thoughts on the hatch marks on the sides of the pistons? I have an old race engine (not Sunbeam) that we got, and it has those same marks on the side. I was told that that was an "old trick" to get more life out of worn pistons.
  9. husky drvr

    husky drvr Platinum Level Sponsor


    Knurling the piston thrust faces does the same thing as knurling valve guides allowing the machinist to renew proper tolerances with worn parts. In most cases the procedure is just a temporary bandaid. Depends on future expectations. Probably depends on how long a future you see for an engine.

    In the case of "old" race engines, I'm guessing the piston knurling allows slightly looser tolerances for less friction. IIRC, I think I recall most supporters of knurling also felt the knurling carried more oil for better thrust face lubrication.

    I think the knurling fell out of favor as power outputs and RPM's rose due to less ring control and formed stress risers.

    Just a thought,
  10. Jay Laifman

    Jay Laifman Gold Level Sponsor

    Are you saying that for older race engines, it might have been done on new pistons for the reasons you stated? Or, even then, it would only be done on a used piston?

    FWIW, this is on a 1950s Coventry Climax Lola racing engine.
  11. husky drvr

    husky drvr Platinum Level Sponsor

    I suppose it would depend on the builder and budget. Might have depended on rules limiting engine mods like bore size and available high performance parts - or lack thereof. In a low expense "get-er-done" situation, knurling new pistons to fit a worn born would not be a surprise.
  12. Bill Blue

    Bill Blue Platinum Level Sponsor

    Jay, I recall seeing descriptions of hot engine builds that included knurling the new, high performance pistons. But I would imagine that for every knurled new piston, there were hundreds of old pistons knurled. This was back in the day that an engine with 50,000 miles on it was due to a "refreshening" in order to get another 25,000 miles out of the old heap.
  13. Knightowl61

    Knightowl61 Gold Level Sponsor

    Back to the cams, The above chart shows the 1725 and Iski as not being too different. I took apart a 1724 engine (sitting under a tarp outside) and compared the cams diameters. Using a Harbor Freight caliper, both bearing journals = 1.755 and the cam lobes were measured narrow and wide +/- a few thousandths.
    Iski numbers left & 1724 numbers right. posting eliminates all extra spacing.

    Iski 1724
    1.125 Intake 1.147
    1.395 1.435
    .270 difference .288

    1.118 Exhaust 1.144
    1.398 1.430
    .280 difference .286

    I would have thought the difference measurement would be the same as the Valve Lift @clearance but not even close. Any ideas?
    Last edited: May 13, 2022
  14. husky drvr

    husky drvr Platinum Level Sponsor

    Valve lift numbers should have the rocker arm ratio included as opposed to lobe lift numbers.

    The stock ratio is about 1.4:1. Try multiplying your "difference" numbers to see if your closer to your valve lift expectations.

    The other issue I see is Jan's chart implies the SB-2 cam is a single pattern cam with no machined in advance. This means the lift and timing on both lobes should be the same. The 0.10" difference between the I and E lifts you show leads me to wonder if Jan's chart is not showing all data for the SB-2 or if your cam has been reground since leaving Isky, because it's not showing anywhere near Jan's chart's valve lift. It's also possible Isky's listed valve lift is calculated with a rocker ratio different than the stock 1.4. Using Chevy's 1.52 ratio would make the lift number almost match Jan's chart lift number, but still a bit light.

    Just a few thoughts,

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