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Thread: Learning webers on a 1700 supersprint

  1. #1
    Join Date
    Nov 2020
    Location
    SE Wisconsin
    Posts
    25

    Default Learning webers on a 1700 supersprint

    My 1996 7 supersprint is new to me so it is getting a very thorough once over. New carb kits from Peagsus installed save for the needles since they are aftermarket pieces and not viton tipped. Likely work fine, but so should my current viton.

    I wrote down my baseline for all jets in both carbs. Both float heights were VERY incorrect and not consistent side to side. Now set to AEAP (as exact as possible!) by eyeball and calipers to 12.5mm and 25mm with gasket.

    All jets are as suggested for the supersprint save for the large idle jets. I have read that stock should be 45 and most switch to 50's. Mine currently has 65's. Upon startup with fresh gaskets and float levels the car seems to already be running better and settles into a smoother lower idle than was possible before the new bits and float reset. I made sure the independent 'idle' screws were all closed and I will go through a full balance and airscrew reset this weekend. My question is.. are there ANY other Supersprint owners out there with idle jets this big on a stock 135hp? At idle it smells rich and stumbles at the 1/4 throttle mark and sounds like it is trying to clear up. Once past say 3k it is nice and clean sounding.

    What say you general public? Is this a common change or was a previous owner trying to counteract some other issue with big idles?

    Worst case i will grab some smaller from pegasus and give it a whirl but wanted to check in with the knowledge base beforehand.
    Thanks for any and all...useful...input!

    Ryan

  2. #2
    Join Date
    Dec 2020
    Posts
    8

    Default

    I'd put 50's in it and see what happens, it's really difficult to go off what others are doing, there area so many variables that will influence idle and low speed operation.

    Spark timing, cam timing, exhaust designs.

    You have done good by taking them apart, cleaning, and making everything match will give you a good baseline to tune from.
    If you cant dial it back with the mixture screws, It's likely that the low speed jet is too big.

    I think the Viton tipped fuel needle will provide better service and low speed operation. (a more consistent float level)

  3. #3
    Join Date
    Feb 2020
    Location
    Redondo Beach, CA
    Posts
    15

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    My 2 cents after playing with a wideband on my crossflow- I started with 45F9 and that was running too lean at part throttle low engine speeds. 50F9 was running a bit rich, sometimes below 12:1. I’m running 50F8 now and I think that is helping to split the difference. 65’s sound like they would be too large.

  4. #4
    Join Date
    Nov 2020
    Location
    SE Wisconsin
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    25

    Default

    Quote Originally Posted by Elise111 View Post
    My 2 cents after playing with a wideband on my crossflow- I started with 45F9 and that was running too lean at part throttle low engine speeds. 50F9 was running a bit rich, sometimes below 12:1. I’m running 50F8 now and I think that is helping to split the difference. 65’s sound like they would be too large.
    The 65s sound rich to my yet untrained crossflow ear. The not crisp running seems to be about 5 to 25-ish % throttle. I'll see what Pegasus has for me. (quick looks shows f8 and f9 in stock sizes by 5's...sweet)
    Last edited by rdhunt1; 12-18-2020 at 05:14 PM.

  5. #5
    Join Date
    Jan 2020
    Posts
    197

    Default

    Pegasus will sell you several sizes of idle jets and reimburse you for the ones you don't need. I would go down to 50s and see how it runs. My car had too narrow jets and had hesitation for the first 33 years of its life. I had bigger idle jets installed and its like night and day. Pulls nicely through the whole rev range.
    1987 Caterham 1700 Supersprint
    2002 Porsche Boxster
    2004 Porsche Boxster S
    1941 Dodge Luxury Liner
    2009 Mercedes CLK 350 Cabriolet
    2017 Chevrolet Volt

  6. #6
    Join Date
    Apr 2013
    Posts
    159

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    Anker - I thought you had them tuned last year and all was good now?
    1997 Caterham, BDA
    1991 Miata, supercharged
    2017 VW GTI
    1977 13' Boston Whaler

  7. #7
    Join Date
    Jan 2020
    Posts
    197

    Default

    I did, just giving some advice!
    4
    1987 Caterham 1700 Supersprint
    2002 Porsche Boxster
    2004 Porsche Boxster S
    1941 Dodge Luxury Liner
    2009 Mercedes CLK 350 Cabriolet
    2017 Chevrolet Volt

  8. #8
    Join Date
    Nov 2020
    Location
    SE Wisconsin
    Posts
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    Default

    Keep it coming...please! Exactly the experience/advice i'm looking for. I did grab both 50 f8 and 50 f9 on saturday. The switch from 65 f8 to 50 f8 was drastic!! The crap 1/4 throttle response is 100% gone and the intake is beginning to sound nice and crisp! I think it may even be a bit lean now. I get hiccups through the intake when the car is cold. Interestingly, the hiccups seem to be through the two forward venturies on each carb. I will likely try the 50 f9 since Elise111 said they were a touch richer based on afr. Huge improvement already!

    I did find that i am not getting very good response from the #3 cylinder mixture screw. I took it and the #2 out to compare and didn't see anything of significance. No damage or bends. No length or diameter changes between the two checking with good calipers. Possibly plugged?? Investigation on this will continue. You can definitely alter idle speed with the other three. #3 cylinder, not that much.

    Next question for those still willing to share... best source for distributor cap/rotor? Lucas dizzy, with Aldon sticker and Pertronix ignitor inside. Do I need to get serial/model ##? I have read the Aldon modded dist may not have the best curve for the Supersprint. Thoughts ?

  9. #9
    Join Date
    Dec 2020
    Posts
    8

    Default

    A problem with a single runner would not be timing related.
    I'd look at the valve train and a compression check.
    Plug and wire/coil check.
    Check carb for a plugged low speed jet or passage.

  10. #10
    Join Date
    Oct 2019
    Location
    SE NC
    Posts
    127

    Default

    Agree with @Bent Wrench - chased a similar issue on my pre-crossflow through HT leads, dizzy and cap, etc. before finding weak valve springs on 3 while doing leakdown testing and checking valve tappet clearances.
    Henry
    1965 Seven S2
    1969 Elan S4

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