Slant 6 4 barrel carb

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drauhut

drauhut

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I am swithing my '73 dart sport slant 6 from a 2 barrel to a 4 barrel carb. Already have an offenhauser 4 bll intake manifold, looking to buy a used holley 390 and rebuild it. There are 2 different types available for me locally, one has vaccuum operated secondaries the other is mechanically operated secondaries. Any idea which one i need..or can either be used?

Thanks
 
Fro driveability, a vacuum secondary would be the best choice for a smaller displacement engine; the engine will draw what it needs, not what the driver tries to force it to use. I assume this is for the street? Any cam upgrade? Other things being done, like new timing chain and bigger exhaust? If you don't riase the breathing power of the einge, you are very likely to be dissappointed.
 
I would look into see if it can run an electric choke on it. When properly hooked up and adjusted, they work great, much better than the stock style thermostat chokes.


I used an electric choke on a 318 daily driver in Detroit with no problem. When properly installed/hooked up and adjusted; I would come out on a cold winter morning and pump the gas pedal twice, crank the engine over, and when it started wait until the oil pressure gauge came to pressure, then put it in gear and drive away - no stumble even in 20° F and below...


The electric choke makes for good driveablility....
 
thanks for the response..yes it is for street use,and I intend to replace the cam, timing chain, dual exhaust and headers,coil.. but due to budget(my wife imposed on me .LOL) I can only do a few things at a time. Are there 2 different types of carbs, or just 2 ways of controlling the secondary's on the same carb?...



I do have an electric choke, though I will have to test it to make sure it works. I have put the car away for the winter and it wont see the road till the salt trucks are gone and the roads salt free.On cold mornings in Oct she didn't want to stay running until she got warm, so I suspect this may be the issue.

thanks for the help
 
vacuum is easier to manage with a diaphragm spring change.
 
Is it advisable to replace the ignition coil with a stronger output voltage?...I have read someone installed a 45,000 v coil and increased spark plug gap...if this is done, does any other item need to be replaced ie..ballast resister, electronic ignition, plugs, dist components etc etc?

After rebuilding and re-installing my single barrel holley carb, she starts and runs in cold weather, the choke and high idle finally work, it feels good to rebuild something the first time and have immediate success doing so. For all you guys who've done this for years, it will seem like a small deal, but I now feel ready to take on the 4 barrel. I have read that the camshaft can be replaced WITHOUT removing the block, is this true?
 
I normally love a Holley, but I hate them for this application. I think you would much better success with a small AVS. JMO.
 
i have a 390 holley with elec choke on my slant. it works well.
 

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cam can be pulled but eyeball your exit path, you may end up hitting a valence or bumper or worse. No wiggle room with a cam pull intil the last journal is clear. Imagine about right in the center of the left side of the timing cover.
 
drauhut said:
I have read that the camshaft can be replaced WITHOUT removing the block, is this true?
Click to expand...
Your biggest challene (besides a straight out path as Pishta mentioned; be ready to jack up one side of the engine for that) is getting the lifters pulled up. You have the the mechanical cam and lifters and the lifters are 'dumb-bell' shaped with a narrowed 'waist' in the middle. If there is a lot of varnish built up in the engine, then the lifters can be very difficult to pull up; varnish will form in a ring inside the lifter bores in the area of the narrowed waist, and the lower part of the lifter will not want to slip past that easily.

Be prepared with some very long needle nosed vise-grips or surgical forceps to grab the lip and work them out (like a 10" reach), as well as some Gum-out to work down around the lifters to try to soften any varnish ring. (Change the oil afterwards.) If your engine is pretty clean on the inside, then no issue. (I was the lucky guy with the old sooooper-varnished engine, and had to drive the lifters out from the bottom with a hammer and a maple dowel when I tore down the engine!)
 
drauhut said:
Is it advisable to replace the ignition coil with a stronger output voltage?...I have read someone installed a 45,000 v coil and increased spark plug gap...if this is done, does any other item need to be replaced ie..ballast resister, electronic ignition, plugs, dist components etc etc?

After rebuilding and re-installing my single barrel holley carb, she starts and runs in cold weather, the choke and high idle finally work, it feels good to rebuild something the first time and have immediate success doing so. For all you guys who've done this for years, it will seem like a small deal, but I now feel ready to take on the 4 barrel. I have read that the camshaft can be replaced WITHOUT removing the block, is this true?
Click to expand...

Go to www.slantsix/org and look up HEI conversions; it will have all you need to now.

Any reason to not go to a 2 BBL conversion rather than 4 BBL?
 
I guess , since I found a 4 brl offenhauser alum intake for dirt cheap at a garage sale, I just sort of went with the 4 brl idea. I found a holley 390 cfm carb for $75 and that's where I sit now. Not a lot invested in the thought yet, but a few others have mentioned they have had success with this set up. So I'll give her a shot. Hopefully, after increasing exhaust size(still unsure whether to go with single or dual exhaust) and headers along with cam replacement, maybe it'll work fine for me...
 
Check back in the threads here in the last couple of weeks for a discussion the exhaust; dual vs. single. Just be careful with the cam selection and look for moderate lift over duration.
 
thanks for your help...I am taking things slowly and tend to ask a crapload of questions before I go ahead..Happy New Year to all.
 
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