Stutters at 2500 rpm

[78cordoba]

I have a 1978 Cordoba with a rebuilt 400 with a very mild cam edelbrock e street heads and a 1407 carb a was trying to break in the cam but I get stuttering at 2500 rpm and it won't rev past it I'm leaning towards distributor or fuel system but unsure where I should start

 

[Geoff 2]

Make sure BOTH needles & seats in the carb are open, one not stuck shut.

 

[78cordoba]

Would that happen on a new carb though?

 

[1967coronet]

Would that happen on a new carb though?

Yes, all these new carbs are put together by people who will never use one.
Edelbrock builds a great carb but it's a crap shoot if they are adjusted to spec when boxed.
Float levels way off are a real issue with them.
On your distributor, if you have a new repop orange box we have seen many threads on those being bad.
What do the plugs look like ?

 

[PurpleBeeper]

My fist guess is your timing is way off (too advanced)

 

[78cordoba]

Just noticed hissing around brake booster when I shut it off I think I have a bad vacuum leak

 

[RemCharger]

They make 450 carbs a day. lots of room for f*€k ups

 

[78cordoba]

Thanks I'll fix the vacuum leak then check out the carb. i know the mixture screw show no change when you run them in. I'm assuming that is from the vacuum leak. I'm 99 % sure them timing is correct.

 

[78cordoba]

I'll pull plugs and look they are new though

 

[78cordoba]

box is blue and silver I'll believe I'll check later

 

[Don Frelier]

My brother had several blue ignition ECUS do something similar.
Try a brand name one from Rock Auto.

 

[78cordoba]

Carb checks out floats were off a little but I adjusted them. Did not see a change

 

[78cordoba]

brake booster it leaking so I plugged line going to it for now

 

[78cordoba]

My brother had several blue ignition ECUS do something similar.
Try a brand name one from Rock Auto.

Would you mind sending me a link to one your suggesting

 

[Don Frelier]

 

[78cordoba]

Pulled all plugs most are black with soot number 6 cylinder spark plug broke when i took it out and I noticed its a lot cleaner

 

[Geoff 2]

#6 plug may have had a cracked insulator before you removed it. That can cause a misfire.

 

[78cordoba]

#6 plug may have had a cracked insulator before you removed it. That can cause a misfire.

Ok yeah I wondered that. I'm gonna replace the plugs and put on a new ecu and dizzy just to rule that out. Just to verify what side of the carb should i hooked vacuum advanced to. Timed vacuum or manifold?

 

[Don Frelier]

If you only change one item at a time and then test you'll know what the problem was.

 

[78cordoba]

I agree but I don't want to run it to much to diagnose because It still hasn't been ran for the 20 min break in