Sorry bout the double post.Already in Tech/General

I'll start with what I got --

Everything is new-

350 HO crate,performer intake,performer 1406 carb,mallory with adjustable vac advance dist,GM wires...
the only thing not new is the power steering pump and trans.

OK, at about 1500rpm I have a slight miss/vibration(while driving and park) I took it to the dealer just to make sure it wasn't a mechanical problem. They said all was good, Just needed to be "tuned".

So,I put a new O2 in to see whats going on. In park,as I open up to 1300-1500 area,the voltage drops way low .00x range(lean) right?

Next I ran a wire into the car to monitor the meter while driving,once I get to the same range ( cruising at 40ish 4th gear) I get a .7 to .9 reading,but still feel the miss/vibration whatever.

I'v changed springs,jets rods,timing 8* to 12*,right now the jets are 107-rods 65/47 pink springs. "Seems" better but not good enough.

I know most are gonna say ditch the carb and get a holley.

Any Ideas????

I sprayed starting fluid everywhere. Didn't find anything.

Could timing advance have anything to do with it?

i've got another set of rods on the way (.58/.42) might go to .113 on the jets.

Am I going the right direction????

 

i don't have a miss, but i've been messing with that same carb on my HO for a while now...

at 104/107 jets, purple springs, .43 nozzle, and letter 4 on the chart rods.

seems better, but no hard evidence.

one of these days i'll get the crate demon...

 

Tobias05,thanks for the reply,What is yours doing?

Mine feels like a vibration when I hit about 1500 rpm through 2000rpm,then seems fine after 2k.Idles fine too.After 2K pulls hard.

We can't be the only 2 here with this combo.There has to be an Edelbrock expert here somewhere.

Gonna mess with mine saturday,if I can't get it soon I might go to a Qjet and put my dual snork back on.

 

I've been fighting the same problem with my 350HO. I've tried a 1406 and Quadrajet carb, same problem, tried two different distributors/coils and different advance springs, same problem, replaced all the plugs, wires, and battery cables, same problem, replaced intake manifold gaskets, same problem, cranked up the fuel pressure (electric pump) to insane amounts for a carb, same problem, advanced the timing, pings like crazy, retard the timing, acts lazy.....currently have it at 10 degrees and it runs fine except for the part throttle surge/flat spot.

Idles great and runs like a bat out of hell at WOT, but at throttle tip in with a load it surges a bit.....and going down that highway at 60mph when you give a little throttle to speed up, it wants to surge/fall on its face....until you put it to the floor and then it takes off.

I'm almost to the point of tearing down this new crate motor. I'm sure I'll get to that point as there is nothing left to do.

 

Hoover87--I don't know what the answer is but there has to be one.
Seems others have this motor and run great.WTF is wrong...

When did you buy your H.O ??

thanks for the reply!!

 

Any luck yet??? I saw another post out there somewhere that suggested that the 1406 just wasn't enough carb and to switch to something like a holley that had a bigger accelerator squirt. I don't get it though, I built an egine similar to the 350ho with darn near the same came, but minus the vortec heads and didn't have any trouble like this at all. It ran great with a Q-jet and an old Carter AFB.

Anyway, my 350ho was new in April 2002. Still doesn't have very many miles on it....it's never ran right

 

No,not yet. I did find my plug wires(new gmpp) arcing.Not big SNAP arcs,but lots of small ones and glowing around the plug boots.So I bought some MSD 8.5s and cap/rotor. No change. MSDs are arcing just like the GMPPs.
Might change the ignition module?

The 1406 may be jetted too lean but not to small for it.The primaries are smaller on the Q-jet.I had the ccQ-jet on a 350 roller motor non-vortec,with a bigger cam (.480/.480) no problems though.

Not sure,but maybe the smaller primary boosters are helpful???

I'll keep ya posted on any findings.

 

I wonder if these Vortec heads are part of the problem????

Maybe they have different flow charateristics or something...I'm grasping obviously.

Maybe I'll swap a pair of old 350 heads on there and see what happens.

Might be cheaper to grab a set out of a buddy's barn to test with than it is to have the Vortecs checked out or to buy a new carb just to try.

 

I picked up a reman q-jet. Got it on but have not had time to play with it.I did start it up though and it's running waaayyy rich. Thats one thing I could't get the Edelbrock to do no matter what I did.Gonna play with it this weekend. I think i'm gonna pull the valve covers and maybe check the valve lash and springs. I almost swear it feels like a balance issue but the dealer said it wasn't,so i don't know. We'll see.

Later

 

Let us know what you find. I'm gonna fight with mine a little today too. I'm going to stick a different fuel pressure guage on it and see what it does.

 

Update--new plugs gap.040,replaced power piston spring,was kinda bent and crusty.I was having an issue with the secondarys drawing fuel for some reason so I lowered the float.Seems to have stopped. I've got very little idle mix control.Still rich,not as bad though.I can screw them all the wat in and turn the curb idle all the way out and it still runs,a little rough but does not die?So it's gotta be getting fuel from somewhere else.?

Still missing,better, but not gone.Seems I am getting closer,I think?Looked for spark arc when it got dark,didn't see any.

Maybe someone out there can help us ?????

 

177 views.

 

I increased the accelerator pump shot a bit and it helped, but stil not right.

Have you confirmed your fuel pressure...at idle and while your driving???

My buddies dad has been having the same issue with his New 440 and it turned out that the new fuel pump he put on was bad. Would idle around 6 or so, but would jump up to 20+ pounds as soon as he hit the throttle. He replaced the fuel pump and it runs great now. It was forcing too much fuel through the carb.

I found an old truck with a 350 in it in my dad's back yard, so I'm going to try and get him to give me the heads to test with and we'll see from there.

Good luck!!

 

I checked my fuel pressure with a different guage and the reading was totally different than the first guage. The pressure was way low. I cranked it up and seems to run a lot better, but still not perfect! Now it almost acts like the pressure is a bit TOO high, but the part throttle surging is mostly gone. It is hard to tell for sure.

I did this first with the 1406 carb and it responded to the fuel pressure increase pretty well. I swapped back to the Q-jet carb and it was very finicky about pressure possibly being too high. Shoot, it started to seap fuel out of the gaskets of the carb and then the truck died. So, with that said, I don't know what guage to believe now.

I'm still not even 100% sure that it is a fuel issue....it might just be masking a problem somewhere else.

 

Fuel pressure is 6psi steady. I did back the rockers off a quarter turn. Took it for a ride seemed better but then the upper rad hose blew off and had to get it home before meltdown Cheap a$$ clamps stipped. Gonna try again this weekend after I clean the mess that made.

 

try this, rev it to about 3000 & turn the key off & see if you feel the same vibration as it comes down through the RPM range.

 

I'll try anything,and if I do/Don't feel a vib/miss????

 

if you do feel the same vibration, then its not an ignition problem, its a balance problem.

 

Ahhh,I see. Well, I did it once and did'nt seem to feel it. Going to do it a few times in a row just to make sure. Thanks for the info.

 

Well, good luck! I'll keep checking in to see if you are making any progress. I've had it with mine and am going to pull the 350HO out and drop in a rebuilt 454 I just picked up. The deal was too sweet to pass up.

I did find a few issues, or what appeared to be issues with my fuel pressure. I cranked it up a bit and it seemed to run better, but I think more fuel was just masking the problem.

I'm still skeptical of the heads at this point, but because I know I got mine hot a few times when it first went in.

Another thing I've been reading about is the possibility of internal vacuum leaks. Seal the PCV openings in the valve covers and put a vacuum guage on one and see if it builds vacuum. I don't believe it should build any vacuum in the crankcase, but do some research to confirm that.

I hope you get 'er dialed in!

 

Tried the 3000rpm thing again and it seems fine. Going to play with yhe advance curve and see if that helps.
Let us know how the big block goes.

I've done other engines and never had issues like this,musta been lucky.

 

A quick update.... my mechanic friend and the machinist at VanSenus say its a balance problem.Where the dealership said its a tuning issue.Now the problem is they say I have the correct balancer and flex plate,I have 2 people saying a balance issue and the dealer who sold me the engine saying different??????

I'm going to let my friend the mechanic dig in and see what he can find.

 

Id say balance issue also based on what your saying it feels like. Did this only havppen when the 350HO motor went in?

 

Yes. I didn't notice it during break-in,but afterwards when I was doin the fine tuning it was there and is still.

All part numbers for the balancer and flex plate check out,whether they are the right parts though?????

 

whats your timing currently set at? What has changed since break in? Anything major or just jets/timing etc?

You can usually pinpoint what caused something by thinking back to the changes that were made and what led up to it.

if your absolutely positive it did not do this during break in, Im not sure it would be a balance issue unless maybe your balancer was damaged somehow.

 

timing is currently set at 12*,i've had it from 8-16 with no apparent differance.

I really don't notice it above 2000 rpm,during break-in it was above that(2500+)so after 25 min. or so I shut it down and let the oil drain,changed the filter and filled it up. Set timing at 10* like the manual said,set the high and curb idle and A/F mix.

After I all other fluids and connections,I took it for a ride,and there it was.So strairht home I went,checking flex plate ,converter bolts, pretty much anything and everything,vacuum leaks.....after a few weekends of finding nothing, I took it to the dealer who told me mechanicly it was fine just needed "tuning",suggested a dyno tuning.

Thats when I started playing with rod and jets,differant timing ,plug gaps.Still there.Recently I tried a differant distributor ,cap ,rotor ,wires,coil,still the same.So i put every thing back the way it was when i started.

Thats when I gave in and took it to my mechanic who said a balance issue,then he sent me to the machine shop for his opinion and he said the same thing.

Now do I take it back to the dealer or do the mechanic and I try to figure it out?