The power on my 1970 etype OTS dropped. I thought maybe carb adjustment. During carb cleaning I noticed main butterfly throttle valves only open about 25%. Checked the linkage and followed it back to the secondary butterflies in the intake manifold…which are stuck and will not move. Anybody had this happen? Thoughts?
Thoughts?
Disable them: either disconnect, and prop wide open, or remove them altogether.
The gain in performance is remarkable.
I was wondering if there was any reason to keep them? To remove, can it be done from the carb side of the manifold? Or do I need to remove the entire manifold?
Thanks
“Working on mysteries without any clues”
I removed the butterfly’s and shafts on our 69 some 40 year’s ago, I still have the car, and I don’t remember much, if any, noticeable increase in performance.
Micheal,
Well you can do Pete’s way…that is to disconnect the linkage that runs between the inner and outer butterflys and reverse it and jam it against the manifold (except you say the inners are stuck,thing is if so then the outer butterfly’s will not work as this linkage ties them together…so how can this be so?)
Or, take the whole intake manifold off and take it apart and you will soon see how you can remove the inner brass butterfly’s…in essence leaves 2 holes that the shaft went thru…can use jb weld and seal them up or tig weld aluminium…if your in Phoenix…we have a great “puddle pusher”…er welder…Tony
Mitch
ps you can call me and I will"talk you thru it…970 779 0456
Neither did I Robert…until I got rid of the distributor (adv. curve).
Every one i did i noticed an immediate increase in throttle responsiveness: to complete it, yes,recurving the distributor completed the transformation.
I had a Sun machine, back then!
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Michael,
The following thread describes what is often referred to as “the 5 minute Strangleberg fix”. Clearly you need to find out why your secondary butterflies are stuck, but hopefully at that point you can apply the “fix”.
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I was able to free the forward secondary butterfly, cleaned everything and reassembled…to see what ‘stock’ is like…wow, really quick!! Likely at some later date I will disconnect both secondaries and secure them in ‘open’ position to check the difference. The car just turned 34,000 mi so initially I am trying to understand the car in stock/original configuration and then begin modification. The 3 on the top of the list are 1) secondary butterflies and 2) switching the 3.54 fir a 2.88 differential (which I already have) and 3) electronic ignition…although the original points/consensus/coil seem to work fine.
Thanks to all for the help.
Michael
1970 Jaguar etype OTS
1908 REO Model G
1914 Ford Model T
From the photo is seems that with the secondary butterflies removed, the intake passage has been bored to a larger diameter. In theory this increases air flow in or ‘breathing’. But the air flow limiting diameter is still likely the carb. Why would this procedure make a difference?
I pulled both carbs as a unit so I could un-do the screws that secure each secondary butterfly plate to the shafts in the secondary manifold. I left every thing else intact so that from the outside you cannot tell anything has been altered and I could easily take back to original if I did not like the result. Throttle response for me was a HUGE improvement. Fifteen plus years later the plates and screws still ride around in a zip lock back in the glove box. One day in the near future I hope to try the sleeving option Bill and others suggest to make it a truly direct path from the carbs to cylinders.
David
68 E-type FHC
Trust us: when you get a electronic ignition, like a Pertronix or, the best, an EDIS, you will be thricely amazed at the improvement.
I switched to 2" carbs instead of the 1.75" Stranglebergs. The pipe ID is 2". So everything is smooth.
The secondaries have a delayed opening to the mains. I wonder if the insertion of a spacer/block to open both simultaneously would be an improvement?
I like the option of just removing the plates from the secondaries and leaving the shafts and linkage so it looks original…but I believe the screws hiding the plates are accessed from the engine side of the intake manifold.
The disconnected shafts are held from sliding out by the plates. Taking the plates out leaves the shafts loose. More to the point, the big payoff, instantly available, is holding/jamming the secondaries always open, not removing them.
The additional gains in power and pick-up that may come from removing secondary parts completely, or even sleeving the throats, are a) minor by comparison and b) only effective at WOT, since at anything less than full throttle the partially closed main carb plates are what restricts airflow in the normal way ( not the jammed-open secondaries left in place).
Peter,
I agree that the biggest return from the least invasive effort would be to secure the secondary butterflies in the wide open position, most especially if it can be done without removing either the carbs or the manifold(s). Can you or someone here post a clear diagram or picture as to how to go about it. The added benefit, of course, is that it would be fully reversible should some future owner so prefer.
It has all been done before, more than once I believe. One (my original?) thread was supplemented with excellent photos by another lister to visualize my carefully worded verbal description. One sentence covers it:
Unclip the secondary link rods at the primary (carburettor) end and swing them towards the head to jam each secondary after you twist them open against spring tension.
Takes the same time to do as to type, once you find a screwdriver or pick to undo the rod clip.
Edit: The original ‘Strangleberg’ thread seems to be ‘live’ again on this list right now…
I tried to find the link to the thread you referenced, with the photos, but couldn’t. If someone can it would be much appreciated. I realize I’m being overly cautious but don’t want “to fix” what presently is working on my car–just want to make it work better.
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