Issues after swap. Intake/carb

[RegMan79]

Hello everyone.

So I swapped my intake and carb last week (first time). I finally got it running, but not well. It's hard to keep running and it back fires at half throttle also I'm seeing some smoke out the valve covers. It ran good before the swap and only smoked for a second on start ups out the tail pipe. The idle screw & mixture screws don't seem to have much of an effect when turned. On a cold start it will run for about 20-30 seconds and die, then it's hard to get running again.

It's 79 Monte 267 SBC. I swapped the stock 2 barrel/intake for a edelbrock performer and holly 4160 600cfm vac secondarys and electric choke. I set the timing at 12 degrees and made sure the firing order was correct.

The carb is used and might need a rebuild, I want to rule anything else out first. I replaced the accelerator pump dia. and fuel bowl gaskets. I cleaned the bowls, needle & seats up and sprayed some passages out. Also removed jets and made sure they were clear. I've been trying to adjust the choke now.

I set timing while idle was a little high but that was I only time I could get it to stay running. So timing might be off a little. I used a vacuum gauge and it read about 21in. But once again the idle was a little high, might not be correct.

Vacuums: I have the brake booster plugged into the intake, Trans vac is on the front base port, vac advance is on the timed port by metering block, pcv is on the other big port on left base. Missing something?

I'm thinking:

1. Vacuum leak (intake)
2. Choke adjustment
3. Timing not correct
4. ?
Please help lol

 

[olds307 and 403]

I believe that 267 has tiny ports like the Olds 260, late 307 and Ford 255 V8. You probably have a port mismatch which may be adding to your issues. Make sure your timing is where it needs to be and check for vacuum leaks. Use carb cleaner or WD-40 and spray around the carb and intake. There is a good chance that carb needs rejected for that little 267.

 

[79 USA 1]

Sounds like a vacuum leak. The manifold you installed allows you to run both a spread bore (Q-jet) and a square bore (Holley, Edelbrock, etc) correct? I had a similar issue when I changed to a 750 Holley on my 406 with a Weiand Action Plus intake. I found you must run a base plate adapter when going to a square bore carb. Thin metal plate with an extra gasket.
https://www.summitracing.com/parts/edl-2732

This past fall I did a 4 bbl intake/ Q-jet carb swap on my new 79 Monte Carlo with the 267 engine and was surprised how much it perked this little engine up.
Hope this helps!
Bob S.

 

[Bar50]

Power valve blown in the Holley carb....?

These are pretty nice to add to the top of the plate he mentioned.

https://www.summitracing.com/parts/edl-9266/overview/

 

[Hutch949]

I just had my cousin put a edelbrock 2701 intake and a holly 1850s carb which is 600cfm on my 79 Monte Carlo 305. He took all the smog crap off also. It runs like a different car.It had 2 barrel carb on it from factory.Feels like it picked up 50 horses.The intake and carb was new,he said all he had to do was adjust the idle.It is does make a lot more noise under the hood now,it's like you can hear the air going into the carb now. I guess because I put a open element breather on it.

 

[79 USA 1]

I just had my cousin put a edelbrock 2701 intake and a holly 1850s carb which is 600cfm on my 79 Monte Carlo 305. He took all the smog crap off also. It runs like a different car.It had 2 barrel carb on it from factory.Feels like it picked up 50 horses.The intake and carb was new,he said all he had to do was adjust the idle.It is does make a lot more noise under the hood now,it's like you can hear the air going into the carb now. I guess because I put a open element breather on it.

Hutch949,
305 in a 79 Monte Carlo should have had the Q-Jet carb from the factory.
If your 5th digit in the VIN is a 'J' then its a 267 with the 2 barrel carb and 5 miles of vacuum hoses for the emission crap.
An 'H' in the 5th digit is the 305.

The new 79 Monte Carlo I picked up had headers and true dual exhaust put on by the previous owner, the 4bbl swap really made this little engine get out of its own way.

 

[RegMan79]

Summit was cool. They sent me a new intake gasket just in case I did give my self an intake vacuum leak. This was my first swap so I may have knocked rtv off the front/back walls when adjusting it.

My uncle had given me this car about 6 months ago. He's had it for 10 plus years and thought it was at 305 the whole time he had it. I ran the VIN number and its a crappy 267. I think a lot of people think they have a 305 when it's really crappy 267.

If I could get it to run long enough for me to properly spray everything with carb cleaner I could rule out the vacuum leak. I used all new vacuum hoses, so I don't think it's a hose. Either something with the used carb, timing (set it while it was kinda idling high), or vacuum leak. Frustration. ..

 

[79 USA 1]

RegMan79,

Take your time and retrace your steps.
Might be worth putting a rebuild kit into the carb or at least remove the float bowls and dry check your float settings.
(This link may help http://documents.holley.com/techlibrary_adjusting_your_carburetor.pdf)
Check for torn float bowl gaskets, be sure all ports on carb are either hooked up to something or plugged. Base line the mixture screws- lightly seat each screw then back out 1 1/4 to 1 1/2 turns.
If you remove the intake to reseal it, pick up a can of "gasgacinch" to tack the intake gaskets to the heads. (Keeps the gaskets from moving) I use it on every intake I've done and never had one fail ....Yet!

Take your time and don't let frustration take over. In the end that "Crappy 267" might just run well enough to allow you to save money to build a 350, 383 or bigger displacement engine to replace it!
Good Luck!
Bob S.

 

[pontiacgp]

if you start the engine you can use carb cleaner to find vacuum leaks. I think it's best to know what the problem is before you try to fix it

 

[Hutch949]

My 79 did have a 267 v8 that went to 100,000 miles, I took that out and put a new gm 305 crate motor that they put in the 1980 or 81 corvette and I just reused my 2 barrel carb and manifold with all 5 miles of vaccuum lines,still had to pass emissions back then. That motor now has around 125,000 miles on it but it still runs good so I decided to put the new carb and intake on it.I have owned the car for 35 years but was parked the last 8 years,I just decided to start playing with it again.I found my old paper work on the crate motor and did a little research, one website said that was the worst corvette motor ever made and I do believe that.It has been dependable though,just not a lot of power.