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Thread: Rev range

  1. #31
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    Quote Originally Posted by 78HZSBC View Post
    Its not so much as keeping my foot into it but just reading the memory on the tacho, 6500rpm would have been only brief at first/ second gear as im still trying to keep the revs down for the run in period.
    I have a manual gearbox with 3.9 diff ratio so 6500 comes pretty quick.


    Yes Hydraulic flat tappet


    Are rev limiters available? My ignition is Mallory HEI
    What do you recommend?

    Heads are DRP alloy 196cc/ 64cc 23 deg
    Intake is Performer RPM dual plane
    i would say 6500rpm would be quite safe if valve springs are correct for the application and if it actually makes power at that rpm

  2. #32
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    hi
    Torque would be falling off a cliff at 6500rpm

  3. #33
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    Quote Originally Posted by GtoGeoff View Post
    Yup, rev limiter essential if manual & a good idea if auto. Building a 455 Pontiac at the moment, owner on a budget, cannot afford better rods. Factory rods are 'cast' steel & are known to grenade around 5700 in a 455. So using the Summit HEI module in the HEI, has an adj built in rev limiter.
    Hopefully an auto with highway gears

  4. #34
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    Quote Originally Posted by swampy View Post
    hi
    Torque would be falling off a cliff at 6500rpm
    doesent matter if the horsepower is still holding there

  5. #35
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    Does anyone know if MSD and Mallory Hei distributors are similar or the same manufacture?
    Apparently the 75 series Mallory has an inbuilt rev limiter but i have the 85 series one that doesnt.
    Im looking to buy the MSD 83647 rev limiter internal module (https://www.summitracing.com/parts/msd-83647) but not sure if it will work with the Mallory... looks very similar.

    Would anyone know if its safe to order this module?

  6. #36
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    HEI dist are HEI, no mater what brand. Modules will interchange. I have used the MSD 83547 a couple of times. Do not like it for two reasons:

    [1] Never had much luck getting the rev limiter set as per instructions.

    [2] Setting limiter relies on accuracy of the tach being used.

    I am waiting on the Summit HEI module to arrive, which has a 5000-9000 rpm adj limiter, which you set with dip switches. Also cheaper, SUM- 850730

  7. #37
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    Quote Originally Posted by GtoGeoff View Post
    HEI dist are HEI, no mater what brand. Modules will interchange. I have used the MSD 83547 a couple of times. Do not like it for two reasons:

    [1] Never had much luck getting the rev limiter set as per instructions.

    [2] Setting limiter relies on accuracy of the tach being used.

    I am waiting on the Summit HEI module to arrive, which has a 5000-9000 rpm adj limiter, which you set with dip switches. Also cheaper, SUM- 850730
    Oh ok, i read your previous post and assumed you were talking about the MSD 83547.
    Well ill take your advice on that as ive never used one so appreciate the recommendation, will order one soon.
    Cheers
    Last edited by 78HZSBC; 09-10-2021 at 09:21 PM.

  8. #38
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    Ah looks like ive found the problem, when i recall the memory on my tacho it reads 6500rpm but really its only around 5000-5500rpm so the memory function is obviously faulty.
    Normally dont look at the tach too much when driving and have been trying to keep the revs down as i mentioned still running the engine in so pretty sure i haven't pushed it past 5500.
    Anyway the tach reading seems to be fairly accurate as i checked it against my timing light that has rev reading on it so all good.
    Shame the memory function doesnt work

  9. #39
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    78,
    I quoted the wrong # in post 36. Correct is 83647. The first MSD iteration was simply #8364; it adjusted the rev limiter with dip switches. Then came the 83645, which from memory was labelled as 'digital'; it had an inbuilt traction control system & the rev limiter was set with a small dial [ potentiometer ] . Third & current version is 83647 HEAT digital.

  10. #40
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    Quote Originally Posted by GtoGeoff View Post
    78,
    I quoted the wrong # in post 36. Correct is 83647. The first MSD iteration was simply #8364; it adjusted the rev limiter with dip switches. Then came the 83645, which from memory was labelled as 'digital'; it had an inbuilt traction control system & the rev limiter was set with a small dial [ potentiometer ] . Third & current version is 83647 HEAT digital.
    So will the SUM-850730 work?
    And what the difference with that and the 83647?
    I just ordered the 850730 today from Summit and dont know if i can cancel it
    Last edited by 78HZSBC; 10-10-2021 at 08:29 PM.

  11. #41
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    78,
    Either will work in a GM HEI dist. Direct replacement. You can see pics of both on the Summit website, both look similar. I like the Summit rev limiter setting better, which is why I will be using it. Difference is in how rev limiter is set & I explained how they both work in the posts above.

  12. #42
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    Sorry GTO i miss read the post, all good.

    One thing i guess a rev limiter would be good for is you could set it low when leaving the car at a garage to be worked on, no spirited test drives lol

  13. #43
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    By the way im looking to buy a new carbi for this 350 as i have a 600vac at the moment, i was looking at the Holley Street HP 750 Vac but i notice the search link says discontinued product.

    https://www.holley.com/products/discontinued_product/parts/0-82750

    Im sure i could still find one but got me thinking why would they discontinue it.
    Is there something new they might have brought out to be its replacement or this one shown to have problems?

    Any thoughts on should i still be looking to buy this Carbi?

  14. #44
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    Quote Originally Posted by 78HZSBC View Post
    By the way im looking to buy a new carbi for this 350 as i have a 600vac at the moment, i was looking at the Holley Street HP 750 Vac but i notice the search link says discontinued product.

    https://www.holley.com/products/discontinued_product/parts/0-82750

    Im sure i could still find one but got me thinking why would they discontinue it.
    Is there something new they might have brought out to be its replacement or this one shown to have problems?

    Any thoughts on should i still be looking to buy this Carbi?
    Add ‘SA’ on the end of the p/n

    https://www.holley.com/products/fuel_systems/carburetors/street_strip/parts/0-82750SA

    It wouldn’t be the wrong carby, but would be handy to book a dyno tune the day you fit it if it has 77 primary jets as per specs

    Sent from my iPad using Tapatalk
    Last edited by BasicQ; 12-10-2021 at 07:16 PM. Reason: To add words

  15. #45
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    Would 77 likely be too big for my application? Reading the specs on the one i have now from memory is around 63.
    Obviously jets can be changed.
    Couple of reasons why i like this one is it doesnt have a choke system i dont need but mainly i like the idea of adjustable air bleeds as thats a problem i have now.
    I have to adjust the idle screw too far allowing the throttle plates to be held open a little too much, think this effects my throttle response from idle. Not a big issue but be nice to adjust this instead of drilling holes in the plates.
    Oh yeah also like the quick change vac spring set up also

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