Uncategorized Archives - John Austin Motorworks https://www.johnaustinmotorworks.com/category/uncategorized/ Building restomods, customs, and other cool stuff Fri, 19 May 2023 20:58:57 +0000 en-US hourly 1 https://wordpress.org/?v=6.8.3 https://www.johnaustinmotorworks.com/wp-content/uploads/2017/01/cropped-jamlogoicon-1-150x150.png Uncategorized Archives - John Austin Motorworks https://www.johnaustinmotorworks.com/category/uncategorized/ 32 32 If Old Trucks Could Talk… https://www.johnaustinmotorworks.com/if-old-trucks-could-talk/ Fri, 19 May 2023 20:55:46 +0000 http://www.johnaustinmotorworks.com/?p=2278 If this old '50 Chevy truck could talk it would just laugh - mock me, really. I'll explain later. Two Rochester 'B' carburetor kits showed up from Mikes Carburetor Parts located right here in Washington. He sells parts for all the old stuff. Rochester carburetor parts ready for reassembly Pretty routine stuff. What was key…

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If this old '50 Chevy truck could talk it would just laugh - mock me, really. I'll explain later.

Two Rochester 'B' carburetor kits showed up from Mikes Carburetor Parts located right here in Washington. He sells parts for all the old stuff.

Carb kits for Rochester B's
Rochester carburetor parts ready for reassembly
Rochester carburetor parts ready for reassembly

Pretty routine stuff. What was key in this case were the new bowl gaskets and accelerator pumps. But the carbs got all the new bits they would accept.

One potential issue noticed and overlooked by previous tinkerers is an important vacuum passage on these carburetors. It's located on the base and is supposed to send a vacuum signal to the 'power' circuit inside the carburetor to add extra fuel under acceleration.

If this port is blocked (no vacuum) then extra fuel will added all the time for an overly rich mixture when you don't need it. Not good.

The carburetor to intake gasket (right) was blocking an important vacuum port on both carbs
The carburetor to intake gasket (right) was blocking an important vacuum port on both carbs

Originally, these old engines had a insulator/spacer between the carb and intake. The spacer had a divot built into it so that engine intake vacuum could reach the port. If you look closely at the photo below it even has the word 'TOP' cast into it.

This old carburetor heat insulator had a small divot built-in to allow engine vacuum to reach the port at the base of the carb..
This old carburetor heat insulator had a small divot built-in to allow engine vacuum to reach the port at the base of the carb..

Without two of these spacers, the workaround is to add a cutout to the base gaskets. Mike's actually sells these carb base gaskets with the extra vacuum ports.

I took a hole punch and created them.

Hole punched carb to intake gaskets to open up the vacuum port
Hole punched carb to intake gaskets to open up the vacuum port
Engine intake manifold vacuum can now reach this port so that the carb can work properly
Engine intake manifold vacuum can now reach this port so that the carb can work properly

With the rebuilt carbs back in place atop the intake we had new leaks at some of the fittings. I switched out a couple of the compression style fittings for proper inverted flare fittings - which, in turn, required some plumbing gymnastics. So, more mods ensued and we ended up with two fabricated aluminum hard lines.

Old carb plumbing modified to accomodate flare fittings at the carb inlets
Old carb plumbing modified to accomodate flare fittings at the carb inlets

Unfortunately, at least one of the carbs still leaks fuel like crazy between the bowl and the air horn. My earlier attempts to straighten it, at least in that area FAILED. The new gasket alone is not enough. It's disappointing and frustrating, to say the least.

Will the truck fire and run though? Right on cue, the truck begins to mock me. The ignition is dead. Ugh...

We had spark before. The engine fired. It wanted to run. Now, nothing. We have voltage to the coil. The coil tests good. The pickup inside the distributor still works but the ignition control module seems to have taken a dump.

An original GM ignition control module. Circa 1980 something...
An original GM ignition control module. Circa 1980 something...
Small cap HEI distributor with external coil
Small cap HEI distributor with external coil

After a lot of digging to identify it, it appears to have been used through the '80's on a number of vehicles. But for the money and availability..? I don't know. I think we'll retire the system for a newer style HEI ignition.

Our progress is thwarted again.

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