Glad for your success.  For me, still learning is a wonderful and rewarding thing.  I’m helping some club members with their mid-fifties Mercury and Thunderbird.  And I’ve found the internet can provide a lot of information. 

Definitely good timing.

My winter daily driver started running bad.

Whether at idle or while driving, rpms drop 200-300 randomly and for unknown reason to me.

I drove to work and on way home yesterday, noticed this weird behavior.

I truly dislike having to have a scanner/computer to diagnose issues.

So, I just drove the truck to work and had no problems.

Carb may still need minor adjustments for choke and fast idle, besides that…runs great again!

Will be adding a 1” 4 hole spacer to mount permanently when it arrives.

Plan to remove the plastic air cleaner spacer on top if there is enough clearance to valve cover.
I believe the choke hangs up occasionally on it.

Added a heat shield to deflect heat from exhaust manifold below the primary bowl.

Last edited by Nos681 (9/10/2026 3:56 PM)

The general theory on carb spacers is that an open spacer effectively adds plenum volume to the intake, which should help the engine breathe at higher RPM.  The taller the spacer the greater the volume increase, the better it helps at higher RPM.  If you look at most engine tests done on dynos where pesky things like hood clearance don't matter those engines are almost always fitted with a 1" or taller open spacer, because it adds top end power and makes the builder look that much better.

A 4 hole spacer by comparison acts as an extension of the carb's throttle bores and tends to improve low end torque.   

Nos681 wrote:

I ordered and installed a 4 hole spacer 1” tall.

RV6…should I do a “Sally” mod and add more 4 hole spacers until it touches the hood? 😁

Keep adding spacers till you get a tunnel ram effect. 300 more HP that way.

I did the same thing.   I had purchased a new Edelbrock carburetor in the spring thinking it was going to be bolt on and go.  It wasn't. The cold and warm starts were horrible. I sent it back.   I also went to the Thunderhead289 for help on how to make my old Summit Racing carburetor work better.  I got the timing dialed in and installed larger idle jets and that helped out with the warm starts.  Figured out one press of the pedal for cold start if it sat less than a week.  More than a week a couple of presses of the gas pedal.   Warm starts 1/4 pedal while cranking.  If the car was warm and sat for at least 4 hours one push of the pedal to set the choke.  This helped quite of bit knowing what works best for my own starting procedures.   Steve69