Murphy Posted August 27, 2011 Share Posted August 27, 2011 Have been reading up on Q-jets & have a question, why is there a different part # for automatics vs manual tranny? I have a 7041208 DN. The last number (8) denotes auto.... Quote Link to comment Share on other sites More sharing options...
stangeba Posted August 27, 2011 Share Posted August 27, 2011 This may help: Pre-76 7028219 DG 1938 70 - Prefix code. "70" will appear on all late '60's Rochester Carburetors. 2 - Decade produced. 2 - 1960's 3 - 1060's with A.I.R. 4 - 1970-1975 8 - Year produced. 8 = 1968 2 - Model 0 - Monojet (1 bbl) Federal standards 1 - Two jet (2 bbl) Federal standards 2 - Quadrajet (4 bbl) Federal standards 3 - Monojet (1 bbl) California standards 4 - Two jet (2 bbl) California standards 5 - Quadrajet (4 bbl) California standards 6 - VariJet (2 bbl) Fed 1 - Division. 0, 1, and 2 all indicate Chevrolet. 4 - Buick 5 - Olds 6,7 - Pontiac 9 - Transmission Even numbers - Automatic Transmission Odd numbers - Manual Transmission DG - Customer code. 1938 - Date Code 193 - 193 rd Day of the year 8 - Year MY CARB 7041202 DG 1938 70 - Prefix code. "70" will appear on all late '60's Rochester Carburetors. 2 - Decade produced. 2 - 1960's 3 - 1060's with A.I.R. 4 - 1970-1975 1 - Year produced. 1 = 1971 2 - Model 0 - Monojet (1 bbl) Federal standards 1 - Two jet (2 bbl) Federal standards 2 - Quadrajet (4 bbl) Federal standards 3 - Monojet (1 bbl) California standards 4 - Two jet (2 bbl) California standards 5 - Quadrajet (4 bbl) California standards 6 - VariJet (2 bbl) Fed 1 - Division. 0, 1, and 2 all indicate Chevrolet. 4 - Buick 5 - Olds 6,7 - Pontiac 9 - Transmission “2 = Automatic” Even numbers - Automatic Transmission Odd numbers - Manual Transmission DG - Customer code. 0681 - Date Code 068 - 68 th. Day of the year (March 9th) 1 – Year (1971) Quote Link to comment Share on other sites More sharing options...
Murphy Posted August 27, 2011 Author Share Posted August 27, 2011 THX, I understand that...but whats different between the auto/manual style carb? Quote Link to comment Share on other sites More sharing options...
Mr70Monte Posted August 27, 2011 Share Posted August 27, 2011 the throttle arm would be different, no need for kickdown linkage on a manual trans. Quote Link to comment Share on other sites More sharing options...
RichG Posted August 28, 2011 Share Posted August 28, 2011 the throttle arm would be different, no need for kickdown linkage on a manual trans. I'm not sure that is entirely correct because the TH-400 has an electric kickdown switch mounted on the accelerator pedal bracket. My guess would be the quantity of vacuum ports because a manual trans doesn't have a modulator. Just a guess. Quote Link to comment Share on other sites More sharing options...
Mr70Monte Posted August 29, 2011 Share Posted August 29, 2011 Originally Posted By: Mr70Monte the throttle arm would be different, no need for kickdown linkage on a manual trans. My guess would be the quantity of vacuum ports because a manual trans doesn't have a modulator. Just a guess. The transmission modulator hooks up to the intake manifold on an automatic transmission. so, what is the correct answer? Quote Link to comment Share on other sites More sharing options...
RichG Posted August 29, 2011 Share Posted August 29, 2011 I tried doing some research. Closest answer I could find said that manual trans carbs have a vacuum pull off for idle when you take your foot off the gas. Sort of keeps the rpm's up a little. Seems that most rebuilders leave them off. Seems like a MT carb will work fine in an Automatic car. I swapped my Q-Jet out in the early 80's for a Carter. Should have kept the Q-Jet but who knew? Quote Link to comment Share on other sites More sharing options...
lastss Posted August 29, 2011 Share Posted August 29, 2011 The difference is at the rear of the base it has no threaded hole for vac fitting for brake booster Quote Link to comment Share on other sites More sharing options...
stangeba Posted August 29, 2011 Share Posted August 29, 2011 Couldn't you get power brakes on a 4 speed car? Bruce Quote Link to comment Share on other sites More sharing options...
Murphy Posted August 29, 2011 Author Share Posted August 29, 2011 In the future, I'm planning on pulling the TH350 & installing a manual (possibly a Keisler 5-speed)so that's why I asked the question.........bottom line is that I will need to close a vaccuum port on carb? Quote Link to comment Share on other sites More sharing options...
Mr70Monte Posted August 29, 2011 Share Posted August 29, 2011 The difference is at the rear of the base it has no threaded hole for vac fitting for brake booster My 7040202 carb has no port on the back of the base, I have a hard steel line coming off the vacuum tee on the intake manifold, then a rubber hose going to the booster. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.