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Spitfire & GT6 Forum

1500 dual carbs

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chris Avatar
chris Platinum Member Chris Roop
Pendleton, OR, USA   USA
Can you use twin SUs from the earlier engines, or do you need to bump up to HS4 carbs? And would an early intake manifold fit up or do you need to get something else?



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TinDrum Herald Ma
cologne, NRW, Germany   DEU
Yes, Mk3 carbs and manifold can be used.
Not ideal but OK.

In fact, Jim Coan from Triumph's west Coast Competition did an engine tuning test of his own 1500 in a Road&Track August 1973 with an Mk3 manifold and twin SU 1 1/4".

Herald

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Tonyfixit Avatar
Tonyfixit Tony M
Duncan, British Columbia, Canada   CAN
In reply to # 1464394 by TinDrum Yes, Mk3 carbs and manifold can be used.
Not ideal but OK.

In fact, Jim Coan from Triumph's west Coast Competition did an engine tuning test of his own 1500 in a Road&Track August 1973 with an Mk3 manifold and twin SU 1 1/4".

Herald

That would be an interesting read :-)

Born Loser Avatar
Born Loser Silver Member Matthew Taylor
Land O Lake, Florida, USA   USA
Think we have covered the Su2's vs Su4's before. On a stock motor, only the very top end (WOT max rpm's) suffers. Start changing cams, pumping up compression...different story.



Matthew
1960 Triumph TR3a
1970 Triumph Spitfire MK 3
2012 Mini Cooper SS Convertible

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chris Avatar
chris Platinum Member Chris Roop
Pendleton, OR, USA   USA
In reply to # 1464446 by Born Loser Think we have covered the Su2's vs Su4's before. On a stock motor, only the very top end (WOT max rpm's) suffers. Start changing cams, pumping up compression...different story.

Sorry, I must not have had the set on to catch it.



Used parts are negotiable; they look better on your car than in my shop.


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69Mk3Spit Avatar
69Mk3Spit Silver Member Dino Finelli
Oakville, ontario, Canada   CAN
For a 1500 unless your hanging out at 4500 rpm plus the hs2 will work perfectly.

74Spit Avatar
74Spit Rick Ladd
Brooklyn, New York, USA   USA
I recently installed a set of HS4 on my 1500. I was running HS2s for years and they worked fine. I installed a 421 header and have a hotter cam. The HS4s gave me more power in the low to mid range than I had with HS2s. It was a nice upgrade for me.


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chris Avatar
chris Platinum Member Chris Roop
Pendleton, OR, USA   USA
What intake manifold did you use? Something from England?



Used parts are negotiable; they look better on your car than in my shop.


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74Spit Avatar
74Spit Rick Ladd
Brooklyn, New York, USA   USA
Yes, stock ero manifold for 1500

Spit driver Avatar
Spit driver David C
Concord vicinity, NH, USA   USA
Did you change the header at the same time as your carb change? If so that may have contributed to your improvement in the low range as well. I would like to se a dyno comparison of several different carb changes, (ie) HS2 vs HS4 vs Weber, so on...

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Spitfire1 Jack Voller
Mt. Dora, Florida, USA   USA
Hey Rick;

David had a good point. Did you do all the work at once or just now add the H4's? I am in the same situation and even went further on my engine running twin H2's.
Please let us know.

74Spit Avatar
74Spit Rick Ladd
Brooklyn, New York, USA   USA
I installed the header last year and just now added the HS4 carbs manifold and airbox. The car ran well with HS2s no complaints. It just has a little more pep with HS4s . I think I have done everything possible for maximum gain with this engine. More power low to mid rage is nice. Highway speeds are great too. Plenty of power for passing . Overdrive makes high speed much more comfortable too.

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Spitfire1 Jack Voller
Mt. Dora, Florida, USA   USA
I guess last question is what size needles are you running?

74Spit Avatar
74Spit Rick Ladd
Brooklyn, New York, USA   USA
Stock needles for ero 1500

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