Carburetor upgrade and intake manifold

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Efregoso

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Hi so currently I have a slant 6 with a one barrel carb, I'm looking to put an edelbrock 4 barrel carb on it, and I as wondering if I needed to upgrade my intake manifold as well, or just buy an adapter plate? And if so which ones work best? Anything to point me in the right direction would be appreciated.
 
There is no way to put even a two barrel carb onto the one barrel intake, even if someone made an adapter. You will have to get an intake to accommodate a bigger carb.
Nothing is ever easy.
 
You'll want to go a bit bigger exhaust too. I have a 2bbl setup and a bigger pipe than stock and she runs just fine. You may be overkill with a 4 bbl if you keep things stock.
 
I have a stock 1965, 225 Slant that I installed Clifford intake and headers with a Holley 390 CFM carb. I also had Johnny Dart " on this site" put me together a Dist. for this setup and this little Valiant / 225 runs great!
 
Okay thanks, so now I was wondering what intake would be recommended for the setup? I do want to do the 4 barrel carb. So what intake would be best?
 
Efregoso said:
Okay thanks, so now I was wondering what intake would be recommended for the setup? I do want to do the 4 barrel carb. So what intake would be best?
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Not really many choices. Most common one available is the Clifford intake, I believe.
 
Make an exhaust upgrade prt of your program to help the breathing. 2-1/4" exhaust is not too big.

What year of /6 do you have? The early ones (before '71, I think; corrections welcomed) have a cam that breathes less so if you have an early one, then a cam upgrade is in order.
 
With the Clifford intake, Headers ,Holley, Johnny Dart Dist. I also used 2.5 in. single exhaust with a Flowmaster.
 
I have a 73 /6 I found an offenhauser intake manifold that will do the job, so I'm going with that, and possibly a Holley390. I'll for sure make an exhaust upgrade part of my adjustments. Anything else that I would be recommended?
 
Efregoso said:
Anything else that I would be recommended?
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How about putting a fresh double roller timing chain in it?


The stock chains suck. they stretch too easy.


Napa sells the double roller timing chain and gears for the slant, but they are sold individually, not as a set. I don't have the part numbers, but I bought one a few years back.
 
It is not the easiest mod, but the best single thing to do on a slant is increase compression, by milling the head, or the block. Milling the head is easier/cheaper. Get the CR up to 8.5-9.5 to 1. The more compression the more cam you can run, and would need to run, so figure a package. With a stock cam stay closer to 8.5-1. Increasing the CR also enhances any other mods.
 
Heck, even a fresh stock replacement chain will do a lot for you; getting the cam in time will make the low and mid range response and low end torque better.

If you go to the extent to change the timing chain, then you might as well change cams too since you have the timing cover off. Can be done in the car; getting lifters up is the one hard part, as they tend to get a varnish ridge in the lifter bores. There are some new torque cam grinds out developed by Doug Dutra that emphasize lift and low end torque; it would be a good compliment to the carb and manifold and large exhaust. Uses stock valve springs.

BTW, what year engine is this?
 
The offenhauser 4 barrel intake is a good option. I believe it will allow you to keep your stock manifold if you can't get a hold of headers, which tend to be hard to find and expensive. It seems a lot of people just change the stock 1 7/8" pipe for a 2 1/4" pipe. Can still run dual exhaust with a modified manifold and dutra dual manifold if you want. I think I saw a offenhauser manifold on eBay yesterday.
 
Aspen76 said:
The offenhauser 4 barrel intake is a good option. I believe it will allow you to keep your stock manifold if you can't get a hold of headers, which tend to be hard to find and expensive. It seems a lot of people just change the stock 1 7/8" pipe for a 2 1/4" pipe. Can still run dual exhaust with a modified manifold and dutra dual manifold if you want. I think I saw a offenhauser manifold on eBay yesterday.
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Agreed
 
So if they can't find headers they use a bigger pipe and just straight pipe it?
I was told that would work
 
One large pipe with a good flowing muffler. You won't be able to go with no muffler (like you can with a turbo on the vehicle).
 
So I'm doing the instal right now, was wondering if anyone had a 4 barrel edelbrock on theirs that I could see pictures of? I want to be sure I'm mounting it correctly
 
So I got most of it figured out what only thing I'm stuck at is the rod that connects to the throttle for the butterfly valve has the hook shaped in the wrong direction so I either see myself having to purchase a new one or having toake my own, any thoughts?
 
So I figured all that, and I'm now working on te electric choke the wire isn't long enough to reach the fuse box under the dash. Is there a way to splice it to any of the other hot wires?
Or should I just go buy a longer wire?
 
great conversation. I bought a '73 dart sport in july, slant 6-225. A few weeks later grabbed an offenhauser 4 bbl alum intake for $20, then found a holley 390 that requires me to rebuild it for $150. My plan is to gradually modify the engine( headers, dual exhaust, mild cam, new ignition,shaving the heads and maybe piston work)..I still want to drive her though. Can I add these things one at a time, will the car run with a 4 barrel carb but no exhaust work?..can I shave the heads without changing the cam?...I am not (obviously) making a race car, but want the car as stock as possible, but with a little pep and a nice growl.

if anyone can give me a ball park figure and specs on headers, a cam, how much to shave the heads, ignition and anything else they may have done , or other ideas, it would be greatly appreciated
 
Efregoso said:
So I figured all that, and I'm now working on te electric choke the wire isn't long enough to reach the fuse box under the dash. Is there a way to splice it to any of the other hot wires?
Or should I just go buy a longer wire?
Click to expand...

I am a maintenance /industrial electrician, not an automotive one, but my advice is to replace the wire, a wire with a splice is just one added place something can go wrong.
 
drauhut said:
great conversation. I bought a '73 dart sport in july, slant 6-225. A few weeks later grabbed an offenhauser 4 bbl alum intake for $20, then found a holley 390 that requires me to rebuild it for $150. My plan is to gradually modify the engine( headers, dual exhaust, mild cam, new ignition,shaving the heads and maybe piston work)..I still want to drive her though. Can I add these things one at a time, will the car run with a 4 barrel carb but no exhaust work?..can I shave the heads without changing the cam?...I am not (obviously) making a race car, but want the car as stock as possible, but with a little pep and a nice growl.

if anyone can give me a ball park figure and specs on headers, a cam, how much to shave the heads, ignition and anything else they may have done , or other ideas, it would be greatly appreciated
Click to expand...

You can do pretty much any of those additions 1 at a time. Here is one possible sequence:
I'd do the manifold change and new carb first to get it all settled. You'll burn another manifold gasket when you do the head work. You may have to tweak jetting after cam and other breathing mods.

I'd do the exhaust soon after the cam (and actually as soon as I could), as you will need the added breathing to use the cam, etc.

I would forego the piston work, unless you have low compression right now or excessive oil consumption.

Then go for the head shave and work; don't be surprised if you need to do valve guides and valve work at that time. We just had a good valve job done that included a steep angle grind into the ports to unshroud around the valves with all new guides and a few new valves. $55 for parts (not inlcuding gaskets), $90 for the valve job, $72 to install and size 12 guides, and $45 to shave the head .030. (Engine machine work around here is pretty reasonable for good work so you may pay more.) You can get a whole /6 Felpro gasket set for $65.

Mild torque cam and reground lifters from Doug Dutra cost $250 + shipping from CA. You can probably get cheaper but I would trust Doug's grinds for whatever the application.

I'd absolutely change the timing chain with the cam (or even do it with no cam) due to the wear on the original chains. I corrected about 4 degrees of retarded timing in the cam just with a new chain.
 
thanks very much for the advice. Over the winter I will be rebuilding the carb I found, and will install it when the weather starts to warm up( hard to work out there when it dips below freezing).
 
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