I've been searching for a couple of days on the board and the internet in general and have not found what I need so I'm going to go ahead and post some questions: I have a fresh 235 with a mild cam and dual 1 barrel Rochester auto-choke carbs on a Fenton intake and a set of tube split 6 headers. I ran the heat tubes for the auto-choke to the bungs that are on the headers (not drilled) and cut a groove in the fitting to allow the vacuum from the auto-choke pull-off to draw the heat to the choke spring, does the vacuum supply to the auto-choke pull off draw a continuous stream of air or does it just "pull" on one side? If it just "pulls" on one side how does the heat get to the spring? If I run this set up, and it does continuously draw a heated vacuum stream from the "stove" on the headers to the base of the carbs, do I need to install a "Heat Plate" to the intake manifold? Do I need a heat plate anyway since the pipe headers get fairly hot and run so close to the intake? If I run a heat plate from one of the bungs, does it need to be drilled to provide a positive pressure? I have done a couple of preliminary starts with the 235 before I cut the groove in the fitting for the chokes (the heat tubes never even got warm), it runs but seems to run rich, does anyone have a good starting point for the mixture screws on a dual carb set-up? What I found for stock was 1 1/2 turns from closed. If all this stuff has been gone over before I do apologize, if you have some links that would be great.
I see your in Florida I am up north of Washington state and a friend has a similar setup as yours and dosen't have the stove setup either but only drives it in the summer . It runs good now after I made some new linkage and rebuilt both carbs, I know it is a a little rich but dosen't foul plugs. I believe I set the carbs about the same amout as you have, I can't remember since it was last spring. We may try Langdons(on link below) description this spring. Link>>> http://www.inliners.org/tech/info.html
Thanks JohnE for the info and 22rdstr for the link! I don't know if I'll need to do the carb rebuild, maybe down the road a bit once I get it back on the road, I'll be interested to see of the set-up I now have on the auto-choke will lean it out a bit since it was completely capped off before, at least I'll have a little more air directly to the mixture.
The auto-chokes are working great now, they pull off just fine as it gets warmer. It still does not idle well and it pops and sputters a lot. I think I may have a problem with the rear carb, the 5 and 6 plugs do not look the same as the rest of the plugs, much more sooty black around the outside but the center is white, the other plugs are more of a brown and they are evenly colored. I may have some timing issues I need to sort out as well.
Thanks fellas! I messed around with it tonight and I think I got the timing set reasonably close now, I had it too far advanced. Now it takes a little bump of the key and it fires right up when it is warm. Still runs a little rough, but better than before. I'm going to throw a new set of plugs at it this weekend and do some more tweeking to see if I can dial it in.
Still was not running well so I decided to tear apart what I thought was the bad Carb (never judge a book by its cover), didn't find anything so cleaned it real good and put it back together. I figured I might as well take a look at the "good" Carb, good thing I did because who ever built it put the base gasket on upside down, you think they would check that stuff better before they sell them. It also has a very rough power valve, and some other not so good issues, but I flipped the gasket, cleaned the hell out of it, tried my best to smooth out the power valve and put it back together. Started it up and it runs 100% better, it will idle now and when I adjust the mixture screws it actually makes a difference! Still need to play with the timing but at least I'm heading in the right direction. I also found out that the carbs have different jets in them, one has a 58, the other a 57.
Worked on it this weekend and the more I do the more I find. Got the timing about as good as it is going to get, and it idles fairly smooth but has a rythmic "almost miss", and the vac guage fluctuates in time with it, so we decided to readjust the valves. All was going well until we found one that was pumped up, and would not release. It would visably slightly open the valve if adjusted to spec. So I pulled out the lifter and took it apart, it had a bunch of goop in it (I'm thinking assembly lube), cleaned it out, put it back together reinstalled it and still have the fluctuation, but the lifter is working correctly now. I think that I need to drop and match the jets because it still run rich, I might just redo both carbs, match all the parts and do the procedure outlined in the link provided by 22rdstrguy, could probably do everything in about an hour, these carbs are so simple. I need to get some exhaust on it before I mess with it any more, it is loud and the neighbors (and wife) have mentioned it. I might run a compression test on it just to rule out any mechanical issues with any cyl. Other than that, its nice that it starts right up, that it idles and the chokes work right!
Well I got a couple of rebuild kits, two matching jets (50 down from a 57 and a 58), and a hardware kit from Mike's Carburetors. Rebuilt the carbs again, put them back on and started it up. It cranked right up and idled great but could not accelerate, it would not run well at all "off idle", it pops, sputters, etc. It is much leaner at ldle...maybe too lean. So I bit the bullet, ripped them back off and tore them apart again. I am getting some fatter jets (52s), and I'm going to try to open up the air bleed to see if that will help. I did find one of the accelerator pumps return spring was very weak so it got replaced. I'll take some photos of the progress and keep you posted on the results.
Run some heat to the bottom of the intake - exhaust or water. It REALLY helps on off-idle. Here in San Diego, I ran without it for years and always had a slight flat-spot. Used a water heat kit from Langdon, made a BIG difference. With a manual choke, I can open it up fully within 3-4 blocks of driving. Get a vacuum gauge and learn how to use it - really helps to nail the timing and idle mixture, sort out engine issues. On my '57 block with 848 head and 3/4 cam (260 dur./.450" lift), I run 10 degrees advance on 87 gas. Do a compression test - high and low readings should be no more than 10% apart. Good Luck, Tim
Thanks Tim, I'm installing the heat plate before the carbs go back on. I do have the vac gauge hooked up to the manifold and I get about 16 to 18 in. of vac at idle, I used that and my ear to set the timing, it is about as good as I can get it. I think I will have to get the exhaust put on and take it out on the road to see how it performs before I know if it is good or not. I really don't know how a straight 6 with a big cam is supposed to sound, it idles pretty smooth, but has a rhythmic fluctuation that could be the cam or a weak cylinder, it is not a miss, in fact it might just be nothing at all. The vac gauge also fluctuates in time with the sound of the motor (stands to reason), about an in. or two continuously at idle. Compression check is in the works.
Well I took the carbs apart again put in the fatter jets (52) and drilled out the air bleed, I also replaced the accelerator pump on the front Carb...again! It still does not squirt as consistantly as I think it should, I really don't know why unless there is a problem with the casting, it just doesn't seem tight in the hole, the other Carb squirts very consistantly and seems a bit tighter so I guess my next move there is to replace the Carb body, not going to happen any time soon. I also added the heat plate. Got everything back together and it runs pretty good, still a little lean so I think I need to bump up the jets some more. It accelerates good some of the time, other times it takes a little double pump (accelerator pump issue I hope). I finally did the cam break in, ran it at about 1500 rpm for 20 min. ran very smooth at that rpm until about min. 12, then it would pop out the exhaust every once in a while.
Just some updated pics. I've been trying to locate some larger jets for the carbs, no luck yet, my next option...drill them out!
how much fuel pressure are you running? cut an in line adjustable fuel valve in... available thru speedway motors or summit or your local oreillys / pepboys stores the cheap one $35 will work fine! if it has too much fuel pressure it willl blow fuel right thru the seats and run rough u also need a water heated intake on that motor not exhaust heated those get too hot
what size jets? When i played with my 3x1 setup i got a pile of them. I'll see what i have here and see if i can find the place i got mine from too
I don't know how much fuel psi it currently has, it is the same fuel pump that was installed when I purchased the car and it ran great for months (aside from the oil leaks, excessive blow-by, wore out motor mounts and clutch chatter) with the single carb set up. What would be the proper psi to run? The heat plate is what came with the manifold, it is designed to work on the Fenton Manifold with Fenton headers, I dont have Fenton headers so I had to do a little custom work. I drilled out one of the bungs on the pipe headers I have with a relatively small hole, also I'm using a smaller dia. tubing to route it to the intake than what the kit came with. I have seen many others with this similar set up that are using two tubes to the heat plate (one from each of the split headers), I'm just using the one from the front header. After 20 min. at 1500 rpm the manifold was just warm to the touch, in fact I thought it should be warmer but I was going to wait till I get it on the road before I make any changes. I currently have 52's installed. The original jets that were installed were a 57 in one of the carbs and a 58 in the other, it ran OK but really rich! I was thinking I could split the difference and install 55's in each to see how that would work. The first time I rebuilt the carbs I installed 50's, well that was waaayyy to lean, the 52's are better but still pretty far on the lean side. I think 54's or 55's would cut it just right.
That was before the 3x1. I had a Ellis with W1's on it, really disliked the W1's and got my 3x1 Offy with Rochester B's on it setup progressive. That will come off this summer and I'll put my Ellis back on with Holley 894's. this is where i got my spare jets.... http://www.carburetion.com/r1.asp I got a handful of the small ones so i can drill them out and step them up till i it got rich. I then drilled another set to the size before it got rich. I can't find my notes as to what size I setteled on, but you seem to have it under control sizewise.
Thanks for the link! You'll have to let me know how the Holley's work out. I went with the Rochester's cuz they are cheap and simple...a good place to start but I'm always open to improvement.
I determined that my distributor is bad and needs to be replaced. It appears that the shaft is not straight and it worbles so it has chewed up the contacts on one side of the cap and wore the brand new rotor down. I think that now it is not always making contact with some of the contacts and is slicing into the others. I found this when I took the cap off while adjusting the valves, it had shavings in it! I'm hoping this is where my problem is, but now its more money on a distributor...ARGG!
I was looking at the adapter from Langdons since I am about to put headers on my 235. I guess you just swaped out the fittings to run a hardline to the mainfold?? I will be keeping the stock intake for a little while right now. For those using water to heat the intake, what approach did you take to plumb it? ( for future reference)
The headers that I have are standard steel pipe type, not cast iron, they have bungs welded to them. The Fenton intake is designed to use a heat plate in the same general area as the stock manifold, I'm not sure but I think it will bolt directly to the stock exhaust manifold if not using headers. It came with a heat plate kit that runs a copper tube from one of those bungs (some use 2 tubes, one from each header) to the cavity that the heat plate covers. It does a pretty good job, before I installed the heat plate the intake was ice cold while running, seriously you could keep your beer cold on it, now with the heat plate installed it is warm to the touch. I'm pretty sure that heat plate will bolt up to the stock manifold, you could call Chev's of the 40's to check for sure. I looked at running water to warm the manifold but it would be significantly more plumbing and some modifications to the manifold (since it is designed to use exhaust heat) that I didn't want to get into.
I have preety much the same set up you have, but with mechanical lifters. And an HEI dist. When I was drag racing with it, I needed to be up there in the 58-60 jet to get good high RPM looking plugs. I just looked at my notes and see that I have 52's in there now, And for mileage and smoothness It's real happy there. I also have the floats level set a little low (1/8 in.)to help with the splash over from the accelerator pump linkage. Sounds like you are on the right track with what you are doing. I did find that leaner running caused mid range pinging and had to take a little timing out compared to what it would stand with the richer jets. Now I don't run carb heat and have a manual choke, just on the rear carb. We have cold weather here and also high humidity most of the time. After a few minutes of warm up and than driving, icing is not a problem. After running for a while, the intake manifold gets so hot that you can't touch it. I don't have a carb boil problem, or vapor lock issues in warm weather. The manifold gets hot just from heat radiating from the exhaust, I guess. Stock fuel pump. frank
Some valuable tech articles on 235/261 multiple carb applications. http://www.inliners.org/tech/tech4.html http://www.inliners.org/tech/why_you_need_heat_to_your_inlet_.htm
That's a great article because it mentions making restriction jet adjustments on the hi speed and off idle . Guys have a flat spot or hesitation at low speed and start changing the main jets.Engines in a moderate state of tune operate from the off idle transition until about 1800 rpm at light engine loads . Going down the road in high gear at 45 mph the main jets may not be online yet.
Thanks for the info, it always helps to get some actual data from someone that has done it and knows whats what. I'm still using the 6v system so I'm limited to the stock dist. (with the Petronics upgrade) and I'm sure I'm not getting the full potential, but I want to keep the 6v (at least for now). The 57-58 jet combo I had was really too rich, the 52's I have in there now might be OK, it just seems lean to me. I really need to get the new dist. on it, get that timed in, then get some exhaust on it, put in new plugs, drive it and see where its at then. My headers are pipe, not cast and they get HOT so I originally thought they would keep the manifold hot enough, but it does perform much better with the heat plate. Of course this is only what I've seen in the garage, it might be much different with the hood on it out on the road!
These are great articles and I did the procedure in the first one that opens up the off idle/high speed passage, I may need to open the restriction a bit more, it does still have a bit of a hesitation, but I want to get everything else right before I do that.
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