Thread: hesitation on a 350

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well first off the setup is 350, bored .030 over, performer rpm intake, 2.02 heads, mild comp cam 224/ 230 @ .050", 650 edelbrock thunderseries carb, msd 6al ignition, msd pro bil distributor with blaster 2 coil. The problem I am having is that when I mash on it, the car hesitates/stalls till it gets a little above 2k then takes off like a bat out of hell. Im runnin 12 initial timing and 36 total. I recently took off my flow master cross over muffler and replaced it with 2 forty series and notice that the hesitation grew a bit worse and I feel like im not getting the same kick when I open up the secondaries cruisin around 30-40. so I figured it was runnin too lean, checked the 3 6 2 4 plugs and they were white tipped. so I started playing with the idle mixture and noticed when I richened it and revved it i would either get a loud pop or full back fire through the carb. Any thoughts to help me out would be great, could it be the springs on my rods or the rods them self? I have checked the floats on the carb as well as the seats/needle. Floats were a little off so corrected it, not the problem, Choke does open fully when car is warmed.

Are you sure you don't have any vacuum leaks anywhere? Also are you getting true time from the marks on the harmonic balancer? the outer ring has been known to slide around on teh inner part throwing off the timing mark alignment.

Still sounds more like a vacuum issue or a problem with the carb itself.

if it was running lean it sure wouldnt run better after 2000 rpm. (more rpm's = more gas) sounds like to me if it gas its to rich. sounds like the secondary are dumping to soon, id lean them out somehow and try it.

well guys i have been through and through it, carb apart and back together. floats adjusted, tried diff accelartoin nozzles, on the phone with tech for 2 hours runnin through carb. They said to mail it back because they have no clue what could be the problem sense we ran through everything. I adjusted and readjust my lifters. tried many diff timing settings, all ignition parts r working well. but it Just kind of came to mind that when i installed the 2.02 heads roller rocker arms and cam that I used the supplied springs supplied with the heads and not from comp cam which is where the rockers and cam cam from. Could this be causing my problem?

Eh, I doubt it. Where those springs may fail is when you start twisting the higher RPMs, then you may see something. It's always best to keep the springs as matched as possible with the cam manufacturer's suggested ratings be it with their springs or some other manufacturer.

Do you have a vacuum gauge? If not, get one. One that's used for tuning. I believe Sears-Craftman still makes theirs and that's the ones I've been using. This gauge can really aid in tuning and troubleshooting. Might be able to tell us what's going on.

I'd still check out those springs and make sure they will work with your cam, or switch them out, either way it eliminates any probability. Just watch for coil bind if any is suspected and make sure the installed height is correct.

I do have a vacuum gauge and tune the carb to the point that i get the most vacuum at idle wich sits at about 13.

I got a 350, in a built rig, my van, that has an Edelbrock Carb on it. I chased the same symptoms you have described for almost a year. I even called Edelbrock and they e-mailed me an off the wall schedule for adjusting the IMS. They told me to go 2 1/2 turns from bottom to begin adjusting. I later tore the carb down and found a crack from casting through the carb.
With all fairness to Edelbrock, I did find some vaccum leaks throughout. Their manifold was machined with a very larg gap that wouldn't seal with a gasket. I got it machined. The vaccum port by the distributor was very sloppy. Even with the fitting tight, it would wobble. I had to drill it out and retap.
I found, the gasket surface to the carb was not true. Heavy vaccum leaks.
The rear vaccum tap was very loose.
The intake planes were off.
Everybody has their off day. Edelbrock is one of the first after market sources I turned to untill now. Even their tech had an hair day on this. They would not accept a return as I had taken a year to find the faults. It was in my shop show van and was in daily service.
I had to get another shop vehicle. I just got burned out on it. I also had a machine shop do the rebuild, and should have done it myself. The things I found are things I check. Finding these things, I now doubt the rebuild.
I chased the exhaust, the timing, valve adjustment. I had to replace a lifter, brand new Edelbrock. I was in the engine daily to just get to the shop.
It sounds like vaccum, and I hope it is easier to find than mine was.

Ditto on the quality of Edelbrocks stuff. I am certainly NOT impressed with the quality of any of their products. I'd say ten years back was about the end of their reign of making quality stuff. I too had to fight tooth and nail just to get an RPM cam exchanged because the lobe/lifter wasn't properly hardened/machined and that didn't count all the money out of MY pocket to teardown and clean up all the metal that was left behind after a 20 minute break-in. I just won't deal with new Edelbrock stuff anymore, not worth the headaches.

Anyways- I'm assuming that the needle is fairly steady at 13 inches? What's it do when you throttle it? Or when you hold it at 2000 or in drive under a load?

If nothing else at all, and they are willing to do so, exchange the carb. If it still acts the same with a new carb, obvious the problem may be elsewhere. You do have all the vacuum ports pluged and routed correctly right? How bout that pcv valve?

Check you float's in you carb. Your rear float is overflowing.

what is the lift of the cam. if it is over .500 you should have ysed there springs.

well guys i have been through and through it, carb apart and back together. floats adjusted, tried diff accelartoin nozzles, on the phone with tech for 2 hours runnin through carb. They said to mail it back because they have no clue what could be the problem sense we ran through everything. I adjusted and readjust my lifters. tried many diff timing settings, all ignition parts r working well. but it Just kind of came to mind that when i installed the 2.02 heads roller rocker arms and cam that I used the supplied springs supplied with the heads and not from comp cam which is where the rockers and cam cam from. Could this be causing my problem?

Could I possibly just need a stall converter? Im runnin the comp cam 12-242-2 wich is supposed to be the biggest cam for a stock converter but Im bigging to feel that it just might not be getting it done.

I'm begining to wonder 'what' kinda hesitation you're having here. Throws me for a loop when you start thinking that the converter could be it. In MY opinion, the converter shouldn't be part of the problem, however this doesn't mean you won't benefit from a little extra stall on the converter.

Still think the problem is in or related to the carb by way of a vaccum leak or such.

I actually took it to my local speed shop today and he adjusted the carb and timing, wich greatly limited the hesitation but did not eliminate it. Turns out while my timing light was showing 14 degrees, but actually i was at about 8 or 9. I guess I will be getting a single wire timing light. He also told me that He thinks my cam needs at least a 1800 stall and rec a 2k stall. So I think im going to give it a shot. He also could not find a vacuum leak

How would i pick the right timing curve for my car?

Should be a suggested range on your cam's card. The fella at the speed shop would also have a pretty good idea too, since he knows a little more about your setup and how well it's taking tune.

No, vac leaks, eh? Good. They can be a pain to chase down. Proper timing will definately make change to the car's performance, and could very possibly eliminate that hesitation completely. Sorry, I took it for granted that you had already set-up the distributor once that upgrades were installed.