340 running like a lame duck

[Rdchallenger]

Me and the 340 just don't seem to like each other. It has no low end torque (wouldn't even break the tires loose in first while trying to power break). Loses speed going up hills, I pulled out of the slow lane into the passing lane going to a car show, pushed down on the gas and almost got rear ended by a '68 mustang that has a stock 302 who pulled out the same time I did. Was told it smelled like it was running rich by said Mustang driver when we got to the show.

Specs are to best of my knowledge.
Zeroed out 340 rebuild with internals of a '68 340.
Air gap intake
2.02 U heads
New FBO ignition box and coil
3.91 gears
27 inch tires
Comp Cams Xtreme Energy 20-223-3
2.5 inch exhaust with X pipe
1970 Manifolds
750 vacuum secondary Proform Carb (going to reject it probably)
904 transmission with stock converter (part of my problem I think)
Approx 140 (if I remember correctly on the compression test) all cylinders within a few pounds of each other.
36* total and 16* initial I think if I remember correctly.

Any other info I'd be happy to answer. I'm just at wits end, I know the engine wouldn't compare to new cars today but damn at least break the rear loose and have some pulling power going up slight hills.

Please help! Y'all are my only hope.

[torredcuda]

140 lbs seems a bit low, stock converter will hold you back a bit but it should get up and go better than that. Check all the usual - be sure you getting full throttle, kickdown adjusted and working properly,  initial timing and curve up the rpm range, pull plugs and read them. What are specs on the carb - jet sizes etc.?

[DeathProofCuda]

First place to start is tuning/making sure the carb is running well.  Wideband O2 would be a good investment, unless you have lots of time on your hands.  You already have the feedback from the Mustang driver telling you that the car is running rich.  Running too rich kills power.  Start with the easy stuff before questioning your entire set up.   Good luck with it.  Report back with if you get it figured out.

[Bullitt-]

 I would suspect issues with cam timing or wiped cam... Get a vacuum gauge.... rather have this than a timing light


https://www.amazon.com/Bosch-FIX-7803-Vacuum-Pressure/dp/B084DBYLCL

[torredcuda]

What Proform carb, some of them have some large jet sizes? "Primary Main Jet Si 86 / 93"

https://www.proformparts.com/carburetors?attr%5B1000154%5D%5B%5D=12303&attr%5B1000091%5D%5B%5D=8198

[Rdchallenger]

What Proform carb, some of them have some large jet sizes? "Primary Main Jet Si 86 / 93"

https://www.proformparts.com/carburetors?attr%5B1000154%5D%5B%5D=12303&attr%5B1000091%5D%5B%5D=8198

The street series
https://www.proformparts.com/product-detail/67208/engine-carburetor-street-series-model-750-cfm-vacuum-secondaries-type

I do have a rejet kit coming.

[torredcuda]

What Proform carb, some of them have some large jet sizes? "Primary Main Jet Si 86 / 93"

https://www.proformparts.com/carburetors?attr%5B1000154%5D%5B%5D=12303&attr%5B1000091%5D%5B%5D=8198

The street series
https://www.proformparts.com/product-detail/67208/engine-carburetor-street-series-model-750-cfm-vacuum-secondaries-type

I do have a rejet kit coming.

Just as a guess you probably want to be 70-78 for main jets, you also want to check vacuum and adjust power valve to match.

[Rdchallenger]

What Proform carb, some of them have some large jet sizes? "Primary Main Jet Si 86 / 93"

https://www.proformparts.com/carburetors?attr%5B1000154%5D%5B%5D=12303&attr%5B1000091%5D%5B%5D=8198

The street series
https://www.proformparts.com/product-detail/67208/engine-carburetor-street-series-model-750-cfm-vacuum-secondaries-type

I do have a rejet kit coming.

Just as a guess you probably want to be 70-78 for main jets, you also want to check vacuum and adjust power valve to match.

Yikes! That much?  I better order the other jetting kit. The one I bought was the 80-90

[Brads70]

https://www.jegs.com/i/JEGS/555/15019/10002/-1


This is what I use? Cheap enough, much cheaper than buying them in pairs.

[Rdchallenger]

https://www.jegs.com/i/JEGS/555/15019/10002/-1


This is what I use? Cheap enough, much cheaper than buying them in pairs.

I went ahead and found a 70-80 set on Amazon since it showed these not shipping until November.

[Brads70]

https://www.jegs.com/i/JEGS/555/15019/10002/-1


This is what I use? Cheap enough, much cheaper than buying them in pairs.

I went ahead and found a 70-80 set on Amazon since it showed these not shipping until November.

Opps ya I didn't notice that.
These I have and found useful as well. Lots of manufacturers and vendors. ...
https://www.jegs.com/i/Quick-Fuel/793/41-100QFT/10002/-1

For the air bleeds I just buy the smallest or blanks and drill my own. Try different squirters too. 
It takes awhile to tune them but when you do it's runs much better!

[jimynick]

Someone mentioned the cam and you should check that it was degreed in correctly when the engine went back together. One keyway notch out and things don't work properly. Good luck 

[Chryco Psycho]

2 of the main problems I see with this are the cam choice , Comp cams for Mopars perform poorly & degreeing them is a must , the compression is too low & the cam could likely be the problem .
I have swapped out FBO junk with generic cheap parts & seen substantial power gains , every system I installed ended up in the trash .
Tuning is essential , timing & carb tuning can make a a massive difference alone , the Proform carbs work extremely well when tuned .

[blown motor]

My 340 with X heads, Lunati cam, 650 Edelbrock, TTI headers with 2.5" exhaust with X pipe and 904 with stock converter will break the tires free easily. Compression, when checked a few years ago, was about 155. A 750 carb on a 340 seems a little big too me. I thought rule of thumb was about 2 cfm/cubic inch.

[Rdchallenger]

Thank you all for the suggestions. I haven't been able to change out the jets yet. I'm getting a degree wheel for the cam.
Also, apologies! I forgot to mention in my initial post that I followed this article on hot rod in regards to my engine build. The only difference is I did not use headers. Also Rereading the article though it seems I missed the part where they degreed the cam  as I just lined it up.

Would that kill my engine power that badly?

https://www.motortrend.com/how-to/mopp-0102-1970-340-high-performance-mill-dyno/