The Ford Barn

drolston · 09-25-2016, 09:51 PM

Pretty much stock '41 Coupe, except for full dress flathead; - so please don't send me to the H.A.M.B!

Carburetor return/close springs plus accelerator pump springs on the 3x2 setup add up to a total force that stretches the stock throttle linkage caps and prevents reaching full open throttle. I am fabricating a replacement linkage that uses Speedway screw-in end attachments. That should solve the linkage spring-stretching problem, but I am afraid three times the force to full open throttle will bend the firewall mounted throttle pull, and worse, twist the throttle shaft on the primary carb.

I was wondering if it is safe to remove the return springs on the accelerator pumps (or maybe just the secondaries). That is a substantial fraction of the throttle return force. There is little slack in accelerator pump linkage, so the accelerator pump piston is going to be retracted, with or without the accelerator pump spring.

Every time I think I am smarter than Ford, (like converting to tube shocks) I find myself regretting it. So where am I going wrong on this idea.

Ol' Ron · 09-26-2016, 08:21 AM

First get some block off plates for the end carbs, install each carb on the engine and fire them up, take it for a ride around the block or so. This will eliminate the "Bad carb". Now install the progressive so the center carb opens at leas 2/3, before the end carbs start to open. (they will only open 1/2 way. Now all this should operate with out any bind. add the spring for the center carb and the spring for the end carbs and fir them up. with 94's close the idle jets, on 97 just crack them. Idle should be set with the center carb. This is the basic way I do it. now if the engine is 49-53 change the distributor to MSD or modified SBC with vacuum. # carbs look great on an engine, however a stock engine doesn't need them and mileage will suffer. I'd just put block off offl pates under the end carbs.

51 MERC-CT · 09-26-2016, 10:04 AM

Quote:

Originally Posted by Ol' Ron

I'd just put block off offl pates under the end carbs.

I second that.

drolston · 09-26-2016, 04:30 PM

Sorry to mislead. Car is stock, but in addition to three 97's, the engine has headers, Offy 425 heads, and is getting a stroker kit to 286, and a Scnneider 248F cam. The secondaries were built without chokes and idle circuits, and I do want to open them up from time to time, just to hear the music and recall ancient hot rod days.

I spent days on the bench getting the progressive linkage (the expensive variety) set up perfectly; there is no binding, just a lot of spring force opposing throttle opening. So, can I take the accelerator pump springs off, or not? At least on the secondaries?

Regarding the progressive linkage. The way I have it rigged now, the secondaries start to open when the center carb is about half way open, and they all reach full open together. As you suggest, I could adjust the linkage so that the secondaries do not get to full open. What would you recommend with 286 cubic inches and a pretty mild street cam?

Ol' Ron · 09-26-2016, 05:51 PM

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The only way to answer that is to drive it, At present I have a friends 294, L-100, etc running 3 of uncle max 97's. He sets them up and that's the way I run them. I used an AF meter to jet for cruise and changed the mains to what he recommended. now as for the center carb, 95% of your driving will be local and in cruise , so WOT is just for "Passing??". Now if you feel you need more just take out a screwdriver and move the stop. You just don't need all that gas in the engine. Do Not remove the carb spring just use a lighter spring on the center carb. You'll have to putz with it to get it the way you like it.

09-25-2016, 09:51 PM	#1
drolston Senior Member Join Date: Jun 2014 Location: Williamsburg, VA Posts: 1,627	Throttle pull on Offy 3x2 Carbs Pretty much stock '41 Coupe, except for full dress flathead; - so please don't send me to the H.A.M.B! Carburetor return/close springs plus accelerator pump springs on the 3x2 setup add up to a total force that stretches the stock throttle linkage caps and prevents reaching full open throttle. I am fabricating a replacement linkage that uses Speedway screw-in end attachments. That should solve the linkage spring-stretching problem, but I am afraid three times the force to full open throttle will bend the firewall mounted throttle pull, and worse, twist the throttle shaft on the primary carb. I was wondering if it is safe to remove the return springs on the accelerator pumps (or maybe just the secondaries). That is a substantial fraction of the throttle return force. There is little slack in accelerator pump linkage, so the accelerator pump piston is going to be retracted, with or without the accelerator pump spring. Every time I think I am smarter than Ford, (like converting to tube shocks) I find myself regretting it. So where am I going wrong on this idea.

09-26-2016, 08:21 AM	#2
Ol' Ron Senior Member Join Date: May 2010 Location: Chester Vt Posts: 8,859	Re: Throttle pull on Offy 3x2 Carbs First get some block off plates for the end carbs, install each carb on the engine and fire them up, take it for a ride around the block or so. This will eliminate the "Bad carb". Now install the progressive so the center carb opens at leas 2/3, before the end carbs start to open. (they will only open 1/2 way. Now all this should operate with out any bind. add the spring for the center carb and the spring for the end carbs and fir them up. with 94's close the idle jets, on 97 just crack them. Idle should be set with the center carb. This is the basic way I do it. now if the engine is 49-53 change the distributor to MSD or modified SBC with vacuum. # carbs look great on an engine, however a stock engine doesn't need them and mileage will suffer. I'd just put block off offl pates under the end carbs.

09-26-2016, 04:30 PM	#4
drolston Senior Member Join Date: Jun 2014 Location: Williamsburg, VA Posts: 1,627	Re: Throttle pull on Offy 3x2 Carbs Sorry to mislead. Car is stock, but in addition to three 97's, the engine has headers, Offy 425 heads, and is getting a stroker kit to 286, and a Scnneider 248F cam. The secondaries were built without chokes and idle circuits, and I do want to open them up from time to time, just to hear the music and recall ancient hot rod days. I spent days on the bench getting the progressive linkage (the expensive variety) set up perfectly; there is no binding, just a lot of spring force opposing throttle opening. So, can I take the accelerator pump springs off, or not? At least on the secondaries? Regarding the progressive linkage. The way I have it rigged now, the secondaries start to open when the center carb is about half way open, and they all reach full open together. As you suggest, I could adjust the linkage so that the secondaries do not get to full open. What would you recommend with 286 cubic inches and a pretty mild street cam?

09-26-2016, 05:51 PM	#5
Ol' Ron Senior Member Join Date: May 2010 Location: Chester Vt Posts: 8,859	Re: Throttle pull on Offy 3x2 Carbs Sponsored Links (Register now to hide all advertisements) The only way to answer that is to drive it, At present I have a friends 294, L-100, etc running 3 of uncle max 97's. He sets them up and that's the way I run them. I used an AF meter to jet for cruise and changed the mains to what he recommended. now as for the center carb, 95% of your driving will be local and in cruise , so WOT is just for "Passing??". Now if you feel you need more just take out a screwdriver and move the stop. You just don't need all that gas in the engine. Do Not remove the carb spring just use a lighter spring on the center carb. You'll have to putz with it to get it the way you like it.