Big RPM drop when put in gear

On my 41 Chevy, small block Chevy 406/ turbo 350 combo I'm experiencing a 500 RPM ( or more depending on where I set the idle at ) drop when I put it in gear. I currently have the idle at 1050 rmp's and it drops to 550 rpm's and wants to die. No matter where I set the rpm's at idle ( even higher ) it drops to the same 550 rpm's. I have a couple different 1406 Edelbrock carbs, and it does the same thing with any one I put on. Car has been sitting many years and got it back up and running last year again with minimum miles put on it, everything worked well then. My first thought is the torque convertor took a dump. Only other changes made were new intake gaskets and the addition of a 1/2" carb spacer. Checked for vacuum leaks and none to be found. Any idea's ?

 

what is the initial timing?

does it have vacuum advance, and is it connected to full time vacuum or ported?

Is the cam pretty big and the converter is the wrong one for it?

 

Vacuum advance is locked out (HEI) on a Sun machine, total timing is 35 degree's, Comp. Cam, very mild .268/ .465 ish. Combo has run just fine for 3500 miles, now the engine is being pulled down in gear.

 

put in a stick shift trans. problem solved.

 

Take the spacer off, they can make drastic or minor changes in both directions.

 

Funny Guy !

 

That was my next move. Did not think a 1/2" spacer would be a drastic difference.

 

I'll be damned, at 65 years old still learning. Removing the spacer gained me 200 rpm's and back where it was. Thanks for the help fellas ! Now I get to clean for four hours for a car show tomorrow, weather permitting.

 

spacers can do some odd things, affecting the atomozation ? of the fuel or the vacuum signal. My experience has always been trial and error. Glad you got it sorted out.

 

If your spacer was an open one rather than 4 hole that could do it. Less signal to the idle circuits.

 

Yep, it was open.

 

Well it was short lived, converter indeed took a dump and turned into a direct drive and couldn't keep the rpm's up to keep the engine running. Should be back together sometime this week. Had a buddy go through the transmission just to be on the safe side and make this a one and done deal. All looked good inside the transmission.

 

I just have to ask...what is under the tarp in the background of the photo of your car's underside? Looks like an interesting profile.

Lynn

 

Glad you got it sorted, sad it was the TC.
That was my first thought also .... last week someone was having similar issues with a chebby truck in a different forum. Basically had to put it in neutral at a stop light just so it would stay running.
Turned into a direct drive. ..... I suggested TC.

Nobody wants to hear they have a expensive transmission problem when their asking about a simple tune issue

 

I thought it was his avatar ?
Looks like the correct shape !

Tommy

 

New B&M converter was the most expensive thing, helps to have a buddy that builds performance Turbo 400's that would do a lowly Turbo 350. All the wear parts were like new with some still having the numbers visible on the clutch's. Basically just new seals, bushings and gaskets other than that. Got away pretty cheap all things considered.

 

Will get to the Avatar car after I finish the current 62 Bel Air wagon project, but I sure ain't getting any faster !

 

Sounds good, if it is on the H.A.M.B. often this is just considered as a opportunity to step up our game.
Just a bunch of gear heads over here .... your cars look spectacular.
The photo of your TC looked to be some stock ho hum TC. .... you stepped up and made it better.

I was over on the Silverado (chebby truck) forum. And there was a really old post about the issue that had been revived a couple of times and never really solved.
People were coming back and asking if anyone has fixed this yet? .... I spent X$ at the shop to fix it and it still does it.
One poster nailed it and said sounds like TC, check it ..... Thats all he said and nobody took him serious.
So the thread continued.

So I simply made a post about how a TC works and when it fails what could happen, and describes their symptoms perfectly. .... Just sad they spend hundreds of $$ at a mechanic to fix it and nothing gets fixed. They simply fix codes shown on their scanner .... I wonder if a TC would ever show on a scanner?
Anyways that ended the thread.

These people are driving their 15 year old hoopty that runs and drives fine .... just at a stop light is a problem. .... They are not happy to hear a transmission issue.