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so i'm working on a 1957 235 which is in my 51 panel.

the motor is brand new rebuild with a mild cam, dual zeniths and fenton dual exhaust. the distributor is stock with a petronix modual.

the motor has about2 or 3 miles on it and i really have only just completed the build. today, after syncing the carbs, i thought i'd check the timing to see if i could smooth it out a bit. wish i had left it alone because after loosening the distributor and moving it just a bit clockwise, the engine was running great but than started knocking pretty loudly and before i could shut it down, it died and now i can't get it started.

i'm kinda freaking out now, i'm new to this and i'm worried that i may have done some serious damage. any suggestions on what could be going on? somebody set my mind at ease and tell me it is something simple. is it possible that i forgot to tighten the distributor nut and it jumped a tooth? if thats the case, is it possiable i did some serious harm?

HELP!

You don’t say if you rotated the dizzy back to its beginning spot and tried to start it?

Does the engine spin freely with the starter and just won't fire up and run, or does it crank slowly or not at all? It's possible the distributor slipped upward in the clamp a little and disengaged the oil pump drive. If that's the case, you could have some major bearing and/or crankshaft damage. If it spins freely, I'd suggest removing the distributor and running the oil pump with a straight screwdriver bit in a drill motor to see if it has normal oil pressure before trying to start the engine again. If it's hard to crank, or won't turn at all, you'll need to drop the oil pan and inspect some bearings.
Jerry

ok, so i did try to rotate the dizzy back but it still didn't start. the other thing is i know i didn't loosen the nut that much, just enough to move it but when it started knocking i lost my mind and ran back to shut it down but it died before i got there.

the engine is spinning freely but, it won't start.
is it really possible that such a small amount of movement could cause the shaft to come out of the pump? i mean, its only engaged that little bit?

so if i pull the dizzy and try to get the pressure up, how much pressure should i be able to get with a drill motor?

A common mistake people make when installing distributors is to fail to get the housing deep enough into the block to engage the oil pump drive slot. There's about 1/4" of engagement between the tang on the end of the distributor shaft and the slot in the pump drive shaft. The engine will start and run with the dizzy that far up- - -it just won't have any oil pressure. "Knocking" is sort of like the chest pain a heart attack victim experiences- - - - -it's an absolute necessity to find out why it's happening, while there might be a possibility of corrective surgery instead of a funeral. Do whatever it takes to be absolutely sure you've found and fixed the problem. I'd expect to see a minimum of 30 PSI on a cold engine while spinning the pump with a 1/2" drill motor. If it's showing pressure with the drill, then figure out why it's not starting, and do a short test run to see if it still knocks. If so, tear it down and start over.
Jerry

so, i've got a bent push rod. strange thing it that there seems to be a oil tube coming from the center of the head connected to the rocker assembly. this tube seems to be closed, squeezed shut.

now that seems a bit too crazy to have been done so i have to think there is a reason or the guy who rebuilt my motor has a [censored] off guy workin for him....right?

That tube is the oil supply to the rocker arms- - - -it comes from an oil gallery drilled into the rear cam bearing area under the pushrod cover. Depending on the year of the rocker assembly, that tube might have been squeezed shut at the factory. Some of the earlier ones were open ended, and dumped excess oil back into the valve valley.

Pushrods don't bend for no reason. Either the valve guide was fitted too tight, gum from stale gasoline in the fuel tank caused a valve to seize in the guide, or somebody adjusted an intake valve too tight and caused it to hit the top of a piston.
Jerry

The 57 235 tube was crimped shut...sort of wrapped around like a question mark and where it went over the top of the center connector piece it was crimped. Go to Google and search for 235 rocker arm tube or something like that and I'll bet you'll find some images of it.

Jerry is right by the way. My experience is most bent pushrods in these occur from stuck valve stems.

Sounds like your oil supply tube is fine. Here is Pre '68 Dave's blog that shows the variations in the oil supply tube. Rocker Oiling The style of tube should be matched to the rockers you are running. The blog describes it better than i could...


The bent pushrod is from something else, as Jerry and Jon said.

ok, thanks for the info. so here is the deal.

the motor is a complete rebuild. its only been ran by the builder on a stand and then by me as stated before. so i can assume, (jokes aside) that this was due to a builder error?

also, i was able to remove the side inspection cover and can see the bent rod off the lifter. i was also able to peak in the cylinder with my buddies snap-on camera and it looks intact. so what else should i be looking for? if a stuck valve was the problem that bent the rod, can i just replace the rod? the rocker is also pushed some what off the valve.does the motor need to come out and start over? if i can leave it in, do i need to pull the head? what else could be damaged?

thanks for all the help

Did the problem happen after the engine was installed in your truck? If so, did you clean or replace the fuel tank before running the engine? Sticky valves are most commonly caused by gunk from a dirty fuel tank getting dissolved by fresh gasoline and getting deposited in the valve guides. It usually happens after a couple of warmup/cool down cycles that allow the guides to tighten up. Then shortly after the next startup a valve seizes in the guide and a pushrod bends. You might be able to use penetrating oil and a pry bar between the rocker arms and the shaft to see if all the valves move freely, but the most effective fix is to remove the cylinder head and find the source of the problem. It will either be too-tight valve stem to guide clearance, or more likely, residue from contaminated fuel.
Jerry

thanks jerry,

i forgot to say that the tank was removed, cleaned, and given the 3 step por 15 tank treatment. it had well over 2 mts to dry/cure before new fuel was put in.

In that case, I'm going to guess that your machinist fitted the valve stems a little too close in the guides. What we used to consider to be "normal" clearances on valve guides, pistons, bearings, etc. are called "worn out" these days. Machinists who are accustomed to working on today's rice rockets are prone to tighten things up too much on the old stovebolt engines. Stem-to-guide clearance of around .0015" or so is just about right for stovebolts.
Jerry

ok jerry, once again this forum has been very helpful.

Just too add a little to the conversation, the stock original GM supplied push rods were solid type push rods and somewhat prone to bending. The after market replacements from sealed power, TRW and others are tube type push rods and are significantly stronger and thus less prone to bending. So if you bent a push rod, for whatever reason, replace them all with after market. Its one of those instances in which the after market parts are actually better then GM.

thats good advice. the current ones are solid.

now that i've pulled the head, i noticed that the front 3 cylinders have quite a lot of carbon on them in spite of the fact that the engine has ran for less than 30 mins total while the back 3 are clean. what could this be caused by?

also, the stuck valve, it is a stuck intake valve on the 4th cylinder, left a bit of what i'd call "tattooing" on the piston top. it really looks ok to me but should i be worried about that?

and last, i have been told by a few people that the dual carb set up looks great but forget it and go with a single two barrel. i'm sure there are may options and opinions. i'd like to hear if anyone is inclined.

thanks again.

Any piston/valve contact is too much. The fact that the valve is stuck in the guide probably means the stem is bent. Replace it. Stovebolt intakes are virtually vertical in relation to the piston, but don't rely on that to mean the piston will simply punch the valve straight back up into the guide.

On the carbon fouling- - - - -you've got one carburetor too many. Dual carbs on a stovebolt are eye candy. Unless you've done some extensive modifications to make the engine need that much carburetion, and you only plan to run wide open throttle most of the time, trash the dual carb setup, buy a 3-carb manifold, and make the two outboard carbs non-functional dummies with a solid plate between the carbs and the manifold. You'll get much better performance and the ignorant mouth-breathers at car shows will drool all over your fancy engine compartment!

The only 2 barrel I'd consider would be a small-bore Rochester for a 265 V8, with enough modification of a stock intake manifold to make it fit, and flow enough volume to accommodate the extra capacity. I'm working on that project, boring the hole under the carb out about 1/4" larger, and fabricating an aluminum adapter block to allow the carb to bolt on the manifold securely. The progressive-linkage 2 barrels some of the resto-ripoff people sell is a solution to a nonexistent problem unless some intake manifold modifications are done in the process of the carb conversion.
Jerry

ok, so i'm replacing the valve and guide. i guess i was more concerned with the piston.

as for the carbs, the motor was rebuilt with a mild cam and a eye at "hoping" it up.

so given that, is an single 2 barrel the way to go? or are we talking 4 barrel or a bigger one barrel?

If you see valve marks on the tops of the pistons, you may very well have bent a valve. Any contact will do that. Since you have the head off, flip it up so the intake/Exhaust ports are facing straight up. Pour some solvent, mineral spirits or the like into each of the intake ports and see if you have any leaking into the combustion chamber. If you do, the head of he valve is tweaked. But you could also have a bent stem.

As for dual carbs, as Patrick Swaize said in the movie Roadhouse, "opinions vary". I love them and have run them for close to 40 years. All kinds. Some run better then others. I like the 1974 Ford pinto holley weber 5200 progressive two bbl for a 2X2 set up. You can use adapters on a vintage intake, that set up runs really well, out of the box. I think the smaller carter/webers that Tom Langdon sells are also a decent choice for a 235. If you want new carbs, not rebuild, then use the weber 32/36 carbs instead of the pinto carbs.

I ran the dual pinto set up on an old Weiand manifold on a 235 for 20 years. Put it on a 261 motor and it ran equally well. I recently switched over to a Clifford 2X2 and that intake is a pretty nice piece. Give me a moment and I will post a photo of the Weiand pinto carb set up.

Couple of photos when I was refreshing this set up in 2015. My adapters were put together using transdapt adapters for a VW. I originally did this conversion back in the later 80s at the suggestion of Tom Langdon and those adapters were all I could locate at the local speed shop so I used them and some aluminum plate to get the carbs adapted and oriented correctly. With the webers, you need the fuel lines toward the fender, not toward the motor. Toward the moter makes doing the linkage easier but leaves the main jets in the carb toward the front of the motor. So if you accelerate sort of hard, you run the risk of the fuel uncovering the main jets and getting a stumble. Orienting the carbs the other way puts the main jets toward the rear of the motor and fuel moves toward the main jets on acceleration.

An inline six needs one carb- - - -or three. Two carbs don't make good nonsense, and with the cylinder head design of a stovebolt Chevy engine, it doesn't matter how many carbs you install, the port design won't let it perform more than a minuscule amount better than it does with a one-barrel carb. Even extensive porting and polishing doesn't make the 1920's engine design any better. Running dual carbs on a stovebolt is like putting g lipstick on a pig. Ditto for dual exhausts. The ports and the combustion chamber design in between the two "improvements" are a choke point you can't avoid. If you tie two pieces of anchor chain for a battleship together with baling wire, how well do you think it's going to do at holding the ship in place?
Jerry

Like I said, opinions vary.

hey thanks for the replies again, all info is helpful.

regardless of how it improves performance, you have to admit, that weiand intake is a beautiful piece.

I agree. I have owned a couple of other brands of 2X1 intakes. A couple of weiands, Offy, cyclone, a McGurk, tattersfield and a thicksun dog bone. Out of all of those that I ran, I liked the weiand, tattersfield and dog bone the best. The weiand and tattersfield were the better runners. The dog bone was the coolest looking hands down. I like the weiand intakes. Nice castings, they polish up really nice, and I like the linkage set up better. Also, many of them came set up for the smaller 216 size carbs (Carter YF for example) which was a better carb to use then the slightly larger 235 carbs on a street 2x1, at least in my opinion.

so what do you think about the zenith 228s and edelbrock manifold? i also have a new fenton intake i could use.

the engine is a 1957 235. the cam is a comp f66 260h-10 with .447 lift and 212 dur.

I would run the edlebrock. You don't see many of them around. I don't know much about the Zenith carbs except to say that those who do rave about them. Charlie Baker (the late 12 Port Charlie - Vintage Design and Development) and I talked about them once in a while but I was never able to find a decent reasonably priced matched pair here on the east coast and the carter YFs were easier to find and cheaper to use. Then, Tom Langdon turned me on to using the pinto carbs and truth be told, they ran so good that I never looked back. I am sure someone with knowledge will come along here and walk you through the use of a Zeneith, at least I hope so as I would love to learn a little more about them myself. On the other hand, I would imagine they are still somewhat scarce.

An adjustable jet is available for some/most/all Zenith 228 carburetors. Maybe someone with knowledge will come along here and also comment on this?

https://totco.auctivacommerce.com/Product.aspx?ProductId=1087878

What i don't understand about the (2) 1-barrel setups that I have encountered before is, if you get the same performance out of (1) 1-barrel carb than with (2) 1-barrel carbs, what is the point? Seems like double the cost and maintenance for the same performance.

You would have to first accept the presumption that a 2X1 runs only as good as a single carb. Not everyone agrees with that sort of presumption, including myself.