340Help!!

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calgee

calgee

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Hi guys I need some help/recommendations. I recently was told by a local MOPAR guy I wiped a lobe off my cam although I haven’t pulled it to confirm. I built the motor a few years ago and from what he is telling me, I set it up wrong and since a new cam is in order there may be other changes I need to make. The motor is bored .30 over with forged pistons, a comp xtreme energy Comp cam 268 intake 280 exhaust with the recommended 901-16 springs,800 cfm Edelbrock Performer carb and An Air Gap intake. The heads are stock X heads and if I recall theonly thing one to them was a valve job. I am running a 2300-2500 converter with 3.55 gears. It seems like from talking to him the entire set up is wrong. The car just doesn’t drive like I expected and I think its over carbed over cammed. What type of cam would be good for a mild street application. Will I need to change springs? Is there a way to tone down the carb or will I need to buy something smaller? I was also told that and MSD ignition would be much better than the Mopar Electronic “orange box” I am running now. I just want the car to be a lot more driver friendly than it is now. This is the first rebuild I have ever done so forgive me for my ignorance!
 
If you did wipe that cam you will need to pull that engine and clean out all the metal. Take the oil pump apart too and make sure it did not get chewed up. Pop that intake manifold off and take a look at the cam.
 
Sounds like a perfect time to switch to a Roller Cam!
 
roller isn't all crack up like some make it. If the valve springs get weak on a roller cam and you float the valves it pounds the heck out of the pin on the rollers and you ruin a expensive set of roller lifters--hopefully that is all.

A flat tapped cam broken in right and using a oil high in zinc--which is also better for the bearings and pistons--will last as long as a roller cam and cost less and needs less valve spring pressure to run over 6,000 rpm's . For max racing roller cams can make more HP but for your everyday street engine its not needed, IMO

That 800 carb is too big--even the 750 on the afb-eddy doesn't pull over the boosters rightly. 500 and 600-650 carbs are the way to go. One 600 or 650 avs carb would work better and two 500 carbs on an older dual quad intake is perfect--again,IMO

But those intakes are hard to find and then you gotta buy 2 carbs--so get a 650 avs, it work better.

Lets hope the cam isn't wiped, it should be an OK combo with a smaller carb--if you really want a 750--800 carb get a Holley
 
First verify if indeed the cam has a wiped lobe on it or why it's running poorly. Pull valve covers and watch the the retainer to see if you have one that isn't moving.

If it idles badly, pull one spark plug wire at a time to see if the engine changes tone. If it doesn't when you pull the wire, you've found your dead hole. Ice cube on the header tube could help identify a dead hole as well. If it melts slower than the rest = dead hole

That cam you have is a good street cam for a 340. Not too crazy, gives some idle lope, decent power. The 901 springs are fine. May be some interference with retainer to valve seal/guide, but, I doubt it.
 
Pull the valve covers, crank the engine over by hand and see if all the valves are opening and closing like they should. You might have dropped a pushrod, wiped the cam or something else. What are the symptoms now?

What exactly were you expecting and what isn't it doing?

What does your timing curve look like and where is your jetting?

Like crackedback said, this is a decent combo and the car should run well with a proper tune.
 
The only thing I see wrong with the combo is the carb is too big. A 650 is plenty and will most likely give better low speed drivability. That cam isn't all that big. Like the others mentioned verify the cam is indeed wiped and as Bill said if it is you need to disassemble the entire engine and clean all the metal flakes out.

BTW: Did you recurve the distributor advance for a quicker advance and less initial timing when you did it? If not you should have as that'll help low end response. If your Mopar ignition is working correctly you'll see very little difference switching to a MSD.
 
Thanks for the input. After backing out of the driveway one day i accelerated and the engine made a loud pop. It got louder as you gave it more gas. I immediately backed it into the drive way and after pulling the valve covers noticed the rockers and push rod on the #2 cylinder werent moving. It doesnt look like the rid is bent either.As far as timing I just timed it to top dead center at zero degrees on the marks on the timing chain cover (probably stupid i know). The car just seems like a bear to drive. It just hasnt ever run smooth. If you accelerate to quickly it loses power and will act like its going to die or it seems like the fuel gets cut off. Any help is very appreciated. Thanks!
 
Actually it sounds like it might have a bad valve too now due to the cam not opening it all the way and burning it.
Over carbed and under advanced also.
 
Valves not moving is a bad sign that the cam has gone south. One reason it never ran good was probably the timing. With a performance cam you need to give it more initial timing and you did the opposite. If the dist. had been set up properly I bet it would have ran pretty good. As for losing power when you accelerated quickly, that could have been a lack of fuel. Maybe a bad fuel pump, clogged filter, or possibly dirt in the carbs main jets. Sorry to say but it sounds like it's time to yank it back out and completely go through it again because as mentioned earlier when a cam goes bad it fills the engine full of trash and needs cleaned out. And don't be too hard on yourself about not getting the timing right and a carb that was too big. We all had to learn. I give you credit for doing it yourself.
 
fishy68 said:
Valves not moving is a bad sign that the cam has gone south. One reason it never ran good was probably the timing. With a performance cam you need to give it more initial timing and you did the opposite. If the dist. had been set up properly I bet it would have ran pretty good. As for losing power when you accelerated quickly, that could have been a lack of fuel. Maybe a bad fuel pump, clogged filter, or possibly dirt in the carbs main jets. Sorry to say but it sounds like it's time to yank it back out and completely go through it again because as mentioned earlier when a cam goes bad it fills the engine full of trash and needs cleaned out. And don't be too hard on yourself about not getting the timing right and a carb that was too big. We all had to learn. I give you credit for doing it yourself.
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I agree, that is how we all learn. Sounds like a good combo, just to much carb. It is hard to beat a 600 Edelbrock for a street ride. But it looks as if you did wipe out a cam lobe or two. When you rebuild it use an oil high in zinc, especially on first start up and engine break in.
 
So I think I am going to pull the motor this week and get to work. In your opinion(s) will it need an entire rebuild? Should I order the 600 or 650 carb? Any recommendations for camshaft? When you say trash in the motor, crankshaft,rods,pistons,cylinders etc will all need attention? Thanks again for everyones input. I just dont want to make the same mistake twice!
 
Main thing is you want to clean,clean clean everything. And then you want to go to step two, clean clean clean! 600 or 650 AFB either one is good. I use Hughes cams only. I have their HEH2328AL in my 360 Dart.
 
Check the compression first, then the plugs(not firing, which one?) then to lift. Probably valve and cam.

Read up on setting timing, and too big a carb.
 
calgee said:
So I think I am going to pull the motor this week and get to work. In your opinion(s) will it need an entire rebuild? Should I order the 600 or 650 carb? Any recommendations for camshaft? When you say trash in the motor, crankshaft,rods,pistons,cylinders etc will all need attention? Thanks again for everyones input. I just dont want to make the same mistake twice!
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Yep, as SG said you have to clean it super good so unfortunately it'll need to come completely apart and be hot tanked cause when a cam goes it generally sends small metal particles all throughout the entire engine and you can't get them cleaned out of the oil galley's without hot tanking. And when you get it back from hot tanking scrub the heck out of it with a set of engine cleaning round wire brushes (you can get a set at Summit or Jegs) and soapy water and as soon as your done blow it out real good with compressed air to dry it good and oil it so it doesn't rust. They'll rust in a matter of minutes. You can scrub everything else up with soapy water or pay the machine shop to hot tank it all. Inspect the pistons closely to see if metal particles have been imbedded in them. If so they'll need replaced. SG's right that either a 600 or 650 is fine. I've ran Lunati cams, Racer Brown cams, and Ultradyne's with real good success. Most any of those are ground to take advantage of Mopar's larger diameter lifter and will make more power. Lately I've been calling Jim @ Racer brown cams and having them custom ground and they have all worked great. If you don't want to change anything else keep it about the size (duration) that's in your engine now but pay attention to the lift cause if your heads haven't had the valve guides trimmed down they won't take much more than .450~,475 lift without interference.
 
I noticed after looking at the spec sheet on the comp cam I had in the car, it showed .480 gross lift. Could this be the reason why I wiped the cam?
 
There could be several reasons why the cam went, if it did. The first one that comes to mind is did it fire instantly when you went to start it the first time? Or did you turn it over and over to get fuel and oil pressure? It's critical that the engine fire the instant you turn the key, and that you have the systems ready for it to run for 20 minutes over 1800rpm to break the cam in. So, did you? There is also the possibility that the lifter bores are not in alignment, or that the oil you're using wasn't enough, or the springs aren't set up properly and there's not enough pressure. That cam is fairly mild, and I run it and it's smaller brothers on standard oil (no additives). Also, on it being doggy, yes, the carb is big, but if the timing is set at zero, that's why it's a dog. You need to learn how to properly set up the ignition curve, and add about 16° of initial timing. You'd be amazed what that will do...
 
calgee said:
I noticed after looking at the spec sheet on the comp cam I had in the car, it showed .480 gross lift. Could this be the reason why I wiped the cam?
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That is extremly high, was this cam broke in at all? Was the timing set at all, after the first drive? You may be able to get away with a teardown, if your compression is down in one or more clyinders, Just swap cam, liffters, pushrods. Hopefully all is good with your valves, and other things money spent on.
 
Before you pull it, have you verified, in fact, you have a dead lobe?

Most of the low end response/carb stuff I run into is ignition related. No way, no how will it run properly with initial timing at TDC. If it doesn't have sufficient initial timing, you get rotten performance. Start turning timing into it, start at 10* and reset the idle speed (turning the set screw counter-clockwise), keep going until it stops picking up RPM. Or grab a vacuum gauge and twist it in keeping idle speed same until you hit highest vacuum, then dial it back 1" to desired RPM. If the car still starts when warm, no starter kickback/bad dragging you're good. Then you need to set up the total number.

It will run like a completely different car with more/proper initial.
 
Hi guys just to answer a few your questions or responses, the engine has about 2500k miles on it. I did the rebuild a few years ago and have driven it long distances 200 plus miles or so many times. When the car made the loud bang or pop it was just after I had driven it for about a half hour or so. When it happened I took the air cleaner off and the popping and banging sounded like it was coming back through the carb. Definitely a different sound than a back fire though. I then started one by one pulling the spark plugs off while the car was running and when I pulled the #2 plug wire off the popping/banging went away. I pulled the valve cover and started the car without the #2 plug wire connected and the rocker or push rod was not moving. I did break in the cam but have only been using standard 10w30 (again stupid I know). I talked to MOPAR guy in town and described what it did and was doing and he said the cam is wiped. To correct an earlier statement I made on timing, I set it to whatever it showed in the Chilton manual for timing(I know I know) but I can remember exactly.
 
64val67gtx said:
That is extremly high, was this cam broke in at all? Was the timing set at all, after the first drive? You may be able to get away with a teardown, if your compression is down in one or more clyinders, Just swap cam, liffters, pushrods. Hopefully all is good with your valves, and other things money spent on.
Click to expand...

No, .480 gross lift is pretty mild. Gross lift is what the valve sees. Net lift is lobe lift. If it had .480 net lift, that'd be pretty big.
 
A shaft bolt snap once, was at the end and the shaft bent up and last valves barely moved. Got the broken bolt out and put studs in, had to buy a new shaft also
 
Normally if the cam goes flat it's not sudden like that. If you havent takent the intake off, do that... It sounds to me like it's a bent pushrod, or a lifter came apart. Normal oil should be fine for that cam, and you had more thna enough miles to break it in. I wouldnt get too crazy until you peak into the valley.
 
you can remove the lifters without taking the intake off. Use a magnet flex rod, long as the too long stock intake bolts are gone it can be done, if not you might have to back one bolt out a ways. The head openings are just large enough for the lifters to slip on pass
 
You could've popped a pushrod out, try to aim a flashlight down into the lifter valley and see if anything looks out of place.
 
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