Converting Stromberg Carburetors for Methanol

Converting Stromberg Carburetors for Methanol

Notes courtesy of Clive from in the UK .  He does not vouch for their accuracy.


Now, about the alky conversion. I am no expert, but I have gained a few tips from people over the years, which I have included below.

All the best  - sounds a neat project


Alcohol Notes

These were some notes I picked up from various sources. I cannot verify any of the advice, sadly! They are probably tips from back in the day. I can’t remember now.

It all needs bigger fuel lines – ½”  hose from tank to shutoff valve, and ½” to distribution block. Then 3/8 or 1/4 ID to carbs.

Needs a bigger pump for loads more fuel – and more pressure – 4psi min for pure alky and more for nitrated fuels.

Emulsion tubes are drilled to 0.125

For alky: dump tubes to 0.116 or larger (0.125), power jet to 0.070”, main jets 0.086, chop off idle tubes and drill to 0.040. Drill needle seats (inlet?) to 0.125 or as much as 0.140

Main jets –
Nitro 5%  - jet size 86 – 91

Nitro 10% - jet size 89 – 92

Nitro 15% - jet size 91 – 94

Nitro 20% - jet size 93 – 98

Nitro 25% - jet size 96 – 105

Spark setting is more advanced. 4 degs more for alky total 18-24 before TDC

Clean out your carbs after using the rich fuels, or they will gum up with white powder (alky) or melt (nitro).

Edelbrock Alky-conversion kit

These are some old instructions from Edelbrock for converting Stromberg Carburetors for use with methanol.

 Install parts are supplied. Namely, idle jets, dump tubes, power jet, metering jets and special needle valve and seat. Remove idle adjustment screws from base of carburetor and redrill holes behind idling screws to 0.055”. Approx correct jetting for model 48s is 0.082. For model 97s, 0.076. One half inch fuel lines should be used to the carburetor. Large capacity fuel filter is desirable.

This is a letter from a guy with more advice

Clive: The info on converting to methanol was from a kit that Edelbrock made some years ago.     
             Fuel inlet (needle & seat) enlarge to .125
             Idle pickup tubes are enlarged to .055
             Main jets are .082
             Emulsion tubes are out to .135
             Power valves are .069

       As for nitro I'm still working on the perfect set up and always run a little on the rich side. Nitro can make pretty little silver sparks coming from your headers and this is usually pistons melting.
        The passage sizes varies with the percentage of nitro but a general rule increase everything you did with methanol about 12 to 14% for every 10% nito added.
       I am working on a couple of 48's right now, installing .175  ID emulsion tubes and enlarging passages for 30% nitro. I have made a simple jig to bore the bodies out . 250 to accept the large tubes.
       I have a dragster buddy from Denver CO who has good results on his 286 inch Flathead running four 48's on methanol and runs .072 jets.
       Both of my dragsters run Hilborn injection (shame on me). However I am working on a 60's style nostalgia altered which will run a 357 cu in Buick straight eight with four 48's on 30%.

Wayne Ludington


And thanks to Clive at