Pics of flipped 60 series intake, downdraft conversion.

Today I started my downdraft conversion, Looked like it would be real easy with the marvel carb base having 3 mounting holes like a stromberg 97 and some of the Holley 94s.

Well after I got it all apart I found the marvel base to be about half again larger than the 97 or 94s and with the heat riser still attached it leaves little room for a good air cleaner.

Tomorrow I will be taking the heat riser off and start making an adaptor plate to mount three bolt base holley 94 on, Once the heat riser section is off there will be a lot of room for an old oil bath air cleaner.

I will post more pics as I go through this. But here are a few for now.

So far I have the intake turned upside down and bolted back on, Heat riser is still in place and carb is just sitting on top to show clearence.

Will tackle the throttle linkage or cable once I get the carb and intake sorted.

Will probably build my own 2x2 or 3x2 intake later, but first want to see what improvements just switching to a downdraft will be, I am sure there will be a lot, biggest is no more gas leaking on the exhaust.

Looks good.

I will be starting mine in a few days.

I am going to make an adapter plate like this one only with the holes 45 degrees apart not 90 degrees

Here's a 2-bolt to 3-bolt adapter

http://www.secretsofspeed.com/ADAPTER-23.htm

Here are some photos of the engine in my (former) 1932 Buick 97 where it had what appeared to be a 1940-ish Carter carburetor retrofitted. Perhaps they'll help you out as you modify yours. Sadly, I have no basis of comparison between the original setup and the downdraft carburetor, but I will say that it drove superbly and always felt very strong. If I didn't already have my 1929 Cadillac (which is a nicer car overall), I would have kept that Buick, it was a fantastic runner that was a joy to drive. A friend of mine who is a '32 Buick expert (he owns 4 or 5 of them) drove it and said it felt like any other of his cars, so I don't think it added much horsepower, but perhaps driveability was improved. As I said, it was a great runner.

If you'd like some hi-res shots of these, E-mail me and I'd be happy to send you the large size files. Good luck!

Thanks Matt.

The carburetors we are using are a lot smaller,but

The pics did answer a few questions I had:

1. He was able to use the original gas pedal setup including the throttle rod .

2. He pulled a vacuum for the windshield wipers of a bolt hole in the top (now bottom) of the intake manifold.

3. He replaced the exhaust heat valve with a straight pipe with flanges.

Does anyone have a suggestion on how to run the fuel line? It looks a little awkward.

I am real happy to hear it ran well!

Thanks again Matt.

Dwight

Thanks Matt. That looks like what I am doing, I just bought the aluminum plate today to make the mount, all the 60,80 and 90 series have a dual carb and matching base on the intake so its a little more involded than the smaller engines, It doesnt help that I just moved into a smaller house and most of my tools are impossible to get to right now, Mine will look kind of crude for awhile.

The throttle looks easy and pics make it look very easy along with the heat cross over pipe. I wish I could get to my lathe.

I ordered a carb conversion adapter from speedway motors,( its 4 bolt base on one side and 3 bolt base on other) It fits almost perfect on the Buick intake when flipped over, carb will sit a little crooked but not enough that most people will even notice, So now to fix the throttle shafts on my carbs and get everything mounted.

Mock up of rochester for chevy 292 on the flipped manifold of my 1930 model 47.

I am looking for suggestions for the throttle linkage:

When the accelerator is depressed the rod moves out.

The throttle on the carb opens as it is pushed up.

Thanks for any ideas.

Dwight

dwight here is what i done to my 1930 using a 94 holley,made an adaptor and chamfered the inside to port up with the carby,then added the phenolic spacer to stop the freezing of the bottom of the carby and then made the airfilter assy to suit,took a little bit of trial and error but it seems to run good.

scott

Thanks Scott.

Very nice job. It looks like it grew there!

The spacer looks good as does the fuel line.

I am not quite sure how you connected the accelerator rod to the gas pedal or the carb. I will have to study it more closely. I do like the way it sneaks between the intake and exhaust manifolds!

Thanks again,

Dwight

P.S. You also solved my, "How do I mount the horn question!"

I forgot your accelerator pedal is on the other side! DUH

For BEST results, when migrating one O.E. carburetor to a different application; the donor engine should be within plus or minus three (3) percent of the donee engine in displacement.

So if you have a 1933 60 series, my references show 273 CID.

Three percent of 273 is approximately 8.

Thus, for the very best results, the donor engine should be about 265 to 281 CID.

Since an adapter is necessary, better to choose for the best carb, and then cut the adapter to fit.

Jon.

I designed an built the linkage today. I operates very smoothly through the whole range. I will trim off the end off the bellcrank and make the verticle rod into a "Z" bend to neaten things up.

I plan to hang the horn a little higher than Scott did in front of the bell crank to hide it.

I have miy 66s up and running with the holley 94 downdraft, I had to advance the distributor about 20 degrees with the old leaky Marvel and forgot about that when I went to start it, Got a lot of backfire, after readjusting the timing it runs smoother and stronger.

This should be a fun driving car now that I dont have to worry about gas dripping on the exhaust.

Congrats on getting the 66's running!

My wife commented immediately on the lack of a gasoline smell in the garage!

Mine starts and runs fine, except it runs a little rough, and the air/fuel mixture screw has no affect.

My neighbor asked if I covered up the hole that supplies air to the mixture screw.

My response was the usual one for me: "What hole?"

Looks like I have a little more machining to do! I never would have figured that one out on my own!

(Hole is in right bottom corner)

I machined a small trough in the aluminum adapter. The idle screw makes a difference now.

I bought a vacuum gauge today. It was very easy to fine tune the timing, just like everyone has been telling me! Oh, btw it holds steady at 17 throughout the speed range.

It runs much smoother now, but only with the choke halfway closed. If I open it all the way, the engine stumbles and dies.

Could the trough I cut in the adapter be too small?

Thanks,

Dwight

I machined a small trough in the aluminum adapter. The idle screw makes a difference now.

I bought a vacuum gauge today. It was very easy to fine tune the timing, just like everyone has been telling me! Oh, btw it holds steady at 17 throughout the speed range.

It runs much smoother now, but only with the choke halfway closed. If I open it all the way, the engine stumbles and dies.

Could the trough I cut in the adapter be too small?

Thanks,

Dwight

SOUND LIKE ITS TOO LEAN,SO YOU NEED TO EXPERIMENT WITH THE MIXTURE AND RICHEN IT UP LITTLE BIT AT A TIME BY ADJUSTING OR REPLACING THE MAIN JET.

SCOTT

DWIGHT COULD YOU SEND ME SOME MORE COLOUR PICTURES OF YOUR PLEASE ALSO WHAT IS THE COLOUR YOU CHOISE.

I HAVE STARTED TO PAINT MINE 1930 THIS WEEK.

MY EMAIL barkwood@iinet.net.au

SCOTT

when I put a down draft on my 25x25 I found you could use a carb off a smaller engine (cubic inch) because most of the carbs we are using came off engines which revved out to a higher rpm we put a carb of a 186 cubic inch onto the buick which is 191 from memory it came down to air flow though the carb to perform at its best and its still on the car and goes great starts good no petrol leaks and I got a little bit better miles per gallon

I finally got my 32 out for a drive, it was like a whole new engine, starts much easier and runs like a new car, twice as fast picking up speed over the marvel. best thing I have done for this car.

Excellent!!!!!