I have basicly rebuilt the whole top end. Here's the spec's: Edlebrock Intake 2101 Performer, Edlebrock 1406 carb(previously on stock manafold with adapter plate), stock cam, push rods, lifters, head gaskets, new valve seals, valves lapped, new valve covers(Edlebrock),Edlebrock air breather,fuel pump, flex lines going to pump, fuel filter, new braided spark plug wire, new plugs. Now the fun starts. Took off the CAT, replaced with straight pipe. New mufflers. All welded up. PRETTY!! So far! Fired it up, NO PROBLEM. Had the vaccuum advanced plugged, set timing and all was good. Ran at 850 RPMS for an hour after the initial 2500 RPM break in for the Cam for a few minutes. Now it I start it up, and it's fine. Let it get to operating temp., take the RPM up to about 1500-1700 or so and it does this SURGE stuff...Goes to 1500 drops to like it wants to stall and just keeps repeating over and over again. I actually blew 2 brand new mufflers all to *&^%$ from when it back-fired so loud and shot some serious FLAME! I have never seen this happen. It will run like a champ as long as I don't hold the RPM steady. It keeps going into this cycle. I replaced the fuel pum, fuel filter, and flex lines...Same thing. No changes to the carb were ever done. I'm open here.....

 

sounds like your timing is slipping.

 

Forgot to mention that. New timing chain, cam & crank gears. Doubles at that.

 

OPS! Forgot one more thing.. Added a chrome Alternator. Previously I had this: Red wire to Bat terminal, ground wire to geound hole on back of alternator, and a 2 wire that clipped in. NOW: red wire to BATT on AlT. and ground to the hole on ALT. No place to plug in the 2 wire clip, just tucked it away.

 

Hello,
I looked at a couple of other forum websites, and several had similar topics. The commonality on most of these was intake manifold vacuum related.

So my uneducated guess would be to look for a source of vacuum leak, or unplugged hose somewhere from your intake manifold swap. Or maybe you have a bad seal someplace when you put the intake manifold, or new carb on.

kdf

 

What is your timing set at? Hopefully not stock since you have pulled the EGR and other emissions stuff.

Try setting the timing pers Lars' specs. Max centrifugal 36 degrees at 2500 rpm. Use a vacuum can that pulls about 16 more for a total of 52. Don't worry about advance at idle (after all, how often do you drive there).

Once you get the timing sorted out, you may need to tweak the jetting on the carb.

Tuning just takes patience and only change one thing at a time. Good luck.

 

It could be a vacuum leak. At times it can be hard to pin point the leak. If you have a spray can or starting fluid you can spray it at the place where you think the leak is. There will be an evident increase in rpms if there is a leak.

 

This is quick and DIRTY. Go around the intake maniflod and use a TRUCKLOAD of silicon and apply it all the way around the edges. This is a TEMPORARY fix only. See if this remedies the surge problem. If so then set your timing again and see how it runs. If it OK then you need to remove all the silicon and re-install your manifold. Install the vaccum accessories one by one and see if they contribute to leaks also.

A smoke test (where you pump low pressure smoke into the intake through a vaccum source) is a great way to find leaks but the average person doesn't have a smoke generator at home.

Bummer about the mufflers. I did the same thing to a pair of Stainless Mufflers if it makes you feel any better.

Good luck.

 

Sounds familiar. And I vote for a vacuum leak at the carb base. When I installed the #1406 I was very careful not to over-tighten the carb hold-down nuts so as not to damage the flanges. I fired up and got the same condition you are describing.

I used a soapy water spray to check for vacuum leaks. None at intake manifold but yes at carb base on 3/8" phenolic spacer. I tightened the carb nuts down gently and evenly until the condition disappeared.

 

Thanks for all the replys. I have found the problem! Finally. It was not vacuum. It's electrical. I had a brand new dist. and I put it in and the problem is gone. So I looked at the old one and the 2 wires in the bottom looked a little strange. In fact, one was flat for about 1/2 inch. I pried it up and I could see bare wire. So, it's time to rebuild that puppy. Sorry about starting another thread on this but I thought it was something related to the fuel getting to hot.

 

hey Paul i think i see a spec of dirt on that manifold , what are you slacking off up there?...just kidding ..it looks good as always

 

I looking at your vacuum line going to your dist. adv., I noticed it's on the right side port of you carb. I thought the ported side was on the passenger side?

 

That is the correct position for non-emission controlled vehicles.