Help!!! Carb, timing????

[72 Blaze]

Ok I hope everyone checked out my hidden winch! I'm trying to start out positive. LOL! Ok my dizzy kept hitting the firewall. Witch was screwing up my timing. I thought. So I bought a new MSD with an extern coil. I was going to started from scratch. I found top dead center and the timing mark was on 0. I dropped the dizzy in pointing to the #1 plug. Easy (right) the 350 would only spit and sputter. So I knew I was off. Some how! I then after a couple tries just had a buddy bump the starter until I felt the air blow my thumb off the #1 spark plug hole. I dropped the dizzy right in. Just like the last time a couple off years ago. And she fired right up. But she will only run way off the timing mark. I have carried her to several different guys before and they always set the timing at the same spot!! Its a newer Gm crate moter Edelbrock intake and edelbrock carb(600) about a year old. Taylor wires headers flowmasters and k&n air filter. Small cam and thats about all. I didn't build the motor. It idles fine and you can rev it up and it runs great. You put it in gear and it has a mind of its own. I sometimes sputters at low end and runs fine under full trottle. And then sometime boggs when you are rolling and then punch it. Just set it up with a vac gage and it's pulling around 19-20 at idle. I'm about to pull my hair out. I'm not an motor expert at all and I don't know what else to do. It runs fine on top end but when I slow down and give it a little throttle it stunbles until you give it more gas. Should I go buy a new carb!!? I'M BROKE!!! Any help would be great, yall know a whole lot more about these blazers than I do. I can drive it but I never know if I will make it home

Thanks

 

[bot0611]

What carb does the engine have?? maybe a carb thing

I had a similar experience 2 mechanics put got the timing in the same spot but the engine did not like it, so i got it on my own using a vacuum gauge.

Have you checked the fuel filter?clogged lines???vacuum leak???

 

[djtejas]

I had a problem like this after building a mild motor and used the stock GM HEI.
Turned out it was because the vacuum advance can gave it too much advance; some can be as much as 20 degrees. This doesn't work well with any kind of performance motor.
I made a limit to that keeps the vacuum advance at 8 degrees. Made a huge difference.
I then later experimented with different mechanical advance springs until I got it dialed in just right.
My motor has the Edelbrock Perfomer Plus cam, Edelbrock 1405 carb, Edelbrock Air Gap intake, and headers...averages 14-16 mpg AND performs better than it ever did.

 

[72 Blaze]

Hey thanks for the reply! I set it tonight hooking up to the back of the carb. (using a vacum gage)Where the brake booster was pluged into. And adjusted the screws on the front of the carb until I got good steady vacum. About 19-20... I will give it a test run tomorrow! My folks next door dont like to hear me floating the vales passed 7!! LOL How did you adjust yours?

 

[72 Blaze]

Sounds the same as my motor! I have never played around with the springs sounds like I need to look into that! Thanks

 

[djtejas]

Sounds the same as my motor! I have never played around with the springs sounds like I need to look into that! Thanks

The big thing was limiting the vacuum advance to 8 degrees...made a huge difference...then the springs.

I tried several different combinations of springs and ended up with the strongest ones...that seems to work better with a heavy vehicle...mechanical advance starts around 800rpm and is all in around 3000rpm...this gave me the best performance.

 

[Blazin'4x4]

Funny story, My buds blazer had an aftermarket timing tab bolted in the wrong spot from the po.

Took a little while to figure that one out.