Question-------------------------
Followup To
Question -
Hi Dick,
Last year I bought a 1973 Superior motorhome that was built by Chrysler on a Chrysler frame and drivetrain.It has been refurbished inside and nicely painted on the outside.It has a 413 Industral engine that sounds fairly good. The guy that did this said it ran good when he bought it but it sucked trash up from the tank while driving it home.The motor started easily and idled well till it warmed up and then would die or stall when accelerating and "spit back". Supposedly he rebuilt the carburetor but I'm not sure because the base plate was worn out and had a vacume leak around the shaft.
I have so far:
1. Replaced the gas tank with a used clean one.
2. Replaced the carburetor with a new Holly 600
and all fuel filters.
3. Tested the electric fuel pump (12 lbs)and
replaced the fuel regulator.
4. I then tested the intake manifold with a carb
cleaner for a vacume leak and found no
noticable difference in idleing.
The motor then idled great and smooth even when warmed up but still was rough on acceleration.
I then:
5. Replaced the plugs, wireing,rotor,capacitor
and distributor cap. The distributor
looked to be in good shape. Also replaced
the PVC valve and ignition coil.
6. I ran a compression test and found it to
be close to each clyinder. 120 to 125. I
don't know what it should be but I don't
suspect a valve problem and I have good oil
pressure so the cam isn't a real suspect.
I haven't pulled the valve covers and measured the lift on the cam lobes and really don't have a way to measure them.
In Summary, The motor idles great, accelerates poorly when a load is placed on it and runs good after a good speed is reached.
Any Ideas or suggestions will be greatly appricated.
Thx..JD
Answer -
These are very good engines, with lots of power. I don't know what the weight of your motorhome is, but a 413 will pull like a freight train, normally.
I doubt you have a serious valve problem - your compression is a bit low, but since they are even, I would leave that to the last to worry about. I don't know what altitude you live at, but 130 isn't terribly low even at sea level. If the engine hasn't been used much in recent years, you could also have some stuck rings - so switch to very high detergent oil - buy Diesel rated oil, and change it and the filter often for a while. But neither stuck rings or valve leakage is going to cause the symptoms you are having - I suspect carburetor problems remain a big part of the problem.
You've done all the right things so far, but I'd check the timing chain for stretch, and investigate the exhaust system for debris.
You don't say how many miles are on the engine - usually motorhomes don't acccumlate much mileage, but maybe this is an exception. Unless you are certain that it is under about 75,000 miles, check for timing chain slop the easy way:
Take off the distributor cap, and manually, with a socket and breaker bar on the crank bolt, pull the engine to the TDC mark on the timing indicator slowly, smoothly, and in a clockwise direction, stopping exactly on TDC. Now, with your third hand, put some rotation pressure on the rotor to take all the slop out of the centrifugal advance mechanism in the distributor, and then with your other two hands, back up the crankshaft counterclockwise until you just perceive motion in the distributor rotor shaft. Read the timing indicator. This will give you a very rough idea of the condition of the timing chain and gears. The factory wear limit is one link, or about 3/8" on the chain, which translates to about 6 degrees on the timing indicator. If it is anywhere near that limit, you could be flirting with jumping time.
If it isn't, forget that possibility, and do the next test:
Find a country road where no one will call the cops, and drop the headers off the manifolds, then see how much power you have. If there is a noticeable increase in power, you've found it!
The Holley 4160, by the way, is a terrible carburetor. When you say "a new 600", I assume you're referring to the CFM. That seems a little high for a 413, but probably isn't going to do anything but increase your fuel consumption. If by "new" you mean professionally rebuilt, I'm sorry to tell you that unless it was done by a carburetor expert like Jon Hargrove of Eldon MO, it is probably still a long way from right. I've had very poor results from "rebuilt" carburetors, unless I've done it myself or had it done by Jon. If it is truly brand new, then I'm probably wrong about this, assuming no one has tried to "adjust" it.
If it is rebuilt, or has been "fiddled with", then I strongly advise you to get the modern Edlebrock reproduction of the famous AFB Carter. This will cost you about $300, and will remove any concerns about carburetor problems for the rest of your life! Summit Racing and P.A.W. both stock these, and will tell you which model you need for a 413 which came with a Holley. Be sure to tell them if you have an RV cam. You'll have to dope out the linkage yourself, but they probably will be able to help there also. It will come with an electrically assisted choke, which you just hook up to the Ignition circuit.
Your 12 PSI fuel pressure bothers me - but since you have a regulator (I assume it is set to 3-5 PSI?), I guess that's OK.
It is also possible that you have a worn out camshaft, particularly if this engine has been rebuilt and an aftermarket camshaft was installed without replacing the lifters, causing rapid wear. Good oil pressure doesn't change that picture - oil pressure depends mostly on oil pump and bearing condition, not cam lobes. (Of course worn camshaft bearings will cause low oil pressure too, but that is very rare unless the engine has over 300K miles.)
Anyway, that's all I can think of at the moment - let me know what you find out, please.
Dick
Thanks Dick,
Welcome back from vacation.
The weight of my RV is a 9000 lbs 20' class A.
My altitude is 3241 ft. I don't suspect stuck rings but will follow your advise to make sure. I too think I still have mainly carb troubles.
The motor is high mileage, above 100,000, orignal cam,and I'm sure some stretch and gear wear in the timing chain.
I havent checked it as you suggested due to the tight access area but mayhave too soon...Just as soon as my old worn body is up to it...lol
I live in the country and have 10 acres of land to roar around in to check the exhaust for debris but haven't as yet due to same reason above. I know that the exhaust is very strong and burns the eyes while standing behind it.
I misstated the fuel pressure. I think it was rated at 12 lbs but producing around 8 lbs and regulated to 3 and a half.
Dick, I have tinkered under the ole shadetree on cars since I was a boy in the early '50's but never mastered carburation. I took the MH to a young but good mechanic to rebuild the carb and he was the one that replaced it. I don't know that it is a factory rebuilt Holly but a 4160 or not? But the number was something like a 80547 or something to that extent.
It also as you know has vacuum assisted secondaries and I'm not so sure they are operating. After the engine had warmed up, I placed the tranny in drive and watched the vacuum diaphragm for operation while driving and chain throttle linkage went slack. I traced the vacuum line back to a unit that has a tranny cable and the line back to the base of the carb.
They seemed to be ok. Also the only way the engine will
rev up smoothly is a slow pressure on the trottle. Fast accleration will cause a backfire through carb.
Now as for the Edlebrock reproduction Carter, the only thing I see listed on Summit Racing is a Holly rebuilt Carter AFB that I don't think it's what you recommended. Do you recommend a Edlebrock Carb from Edlebrock?
What about a Carter AFB from Jon Hargrove? Do you think
it had an RV cam as I have no way to verify that?
In a summarization, I know that eventually the engine will have to be rebuilt but I was hoping to wait awhile. Any new parts like Carbs added now is not a waste as they will be used later. I would like the best trouble free and fuel efficiency Carb I can get.
Thx...Up a (shade)tree...JD
AnswerI'm trying to juggle too many balls here - I missed something else too! I see your engine is supposed to be an "industrial" engine. I have no idea what that is - and it might indeed be a 413, I suppose - who knows what Chrysler was doing in those years.
We did indeed have a short vacation - we drove up the California coast to a car show in Solvang (about 260 miles north of home) for 3 days, driving another of our old cars (a 1967 Imperial, in this case - also with a 440).
Let me know any progress you make, please.
Dick
