340 with no power

[Chryco Psycho]

a tight or damaged torque converter can drag the rpm down a ton even if the engine is running perfectly

[SwedeFish]

You can experiment to see which bushing works best with your combo of parts but make sure you have 35/36* max at 2,500/3,000 rpm with your timing light. If you just set the initial without checking the total, then you are just guessing.

If you have a high reving 340 with good heads and cam and it's short shifting at 4,500 and then falling below that on the shift it will be a slug
much like many bikes that need RPM to run good. 340's don't have a lot of low rpm TQ but theylove RPM and make their HP upstairs. It's a short stroke big bore motor and it should be shifted at 6,000rpm and maybe even higher. That should be determined at the race track with a shifting loop test. I.E. - make a few runs shifting at different RPM's to see where it ET's the best. If it shifts too quick when it's in drive you probably need to adjust your kickdown linkage. It also should be all the way back on the tranny lever @ full throttle. If it still shifts too quick just shift it manually at 6K. I think you'll see a big difference when you keep the motor in it's power band   

Thanks for your thoroughly reply.

I have adjusted my kickdown linkage so it is all the way back on the tranny at full throttle, at least when I push the throttle back by hand. I need to get someone in the car pushing the gas pedal to check if I really have full throttle when the gas pedal is pushed down to the floor.
Any other reason the tranny shift gear too early? The tranny is rebuilt by a Chrysler tranny expert here in Stockholm, Sweden, that has a good reputation. The converter is also new.
Unfortunately we do not have any local race track here anymore...

You write that I should have 35/36 at 2500/3000 rpm, that early? I need to change my springs again to softer ones.

BR
Kristoffer

[SwedeFish]

a tight or damaged torque converter can drag the rpm down a ton even if the engine is running perfectly

I hope it is not damaged because it is new. Might be too tight though. I need to adjust my carb and timing first and then if it still stalls too low (below 2500 rpm) I will have to talk to the builder of the tranny and converter.

BR
Kristoffer

[Chryco Psycho]

basically you want as much timing as possible without detonation , if you can get 16-20* at idle & a 16* curve in by 2000 rpm without detonation the engine shoudl run better
 if the converter is new it is not damaged & if it is a true 2500 rpm stall it should not be loading the engine at idle

[SwedeFish]

Thanks to all for all the inputs.

As soon as I have the time to do the adjustements I will let you know the result. I hope it will positive

[SwedeFish]

Thanks for all the replies and information.


I have now set the initial timing to 20 degrees. By doing that I was able to decreas the throttle blade opening to 0.02-0.025". I thought that it would help cause I was reading in my Holley book that the throttle blades shouldn't be open more than 0.04-0.06" and I think my throttle blades were open more than that and I couldn't get any change in idle rpm by turning the mixing screws. Accordning to my book this problem can be caused by too much throttle opening at idle. But still no increase in idle rpm when turning the mix screws...? I have now opened the mixing screws 1-1.5 turns.

The car now idles ok at 1100 rpm but when I change it to D the idle drops to 800 rpm and the idle becomes rough.

Still no low end power. The converter (2500 stall) doesn't stall more than 1500 rpm when I try to stall it using the brakes.

The spark plugs looks ok (as far as I can tell). I took the carb apart and everthing looks like it should according to Edelbrock instructions. How should I tune the carburator? Edelbrock Perf. 600 cfm.

Might there be another problem that I have over looked?

Thanks again.

BR
Kristoffer

[422STROKER]

Maybe they need more than 1.5 turns out?

A 600 will probably be lean for that motor, I had one of those on my 318 and it was a bit lean OOTB.

Tom

You should be able to get it to idle nice though.

What kind off vacuum are you getting?

[Chryco Psycho]

typically with low vacuum engines this si the wqorst carb to run , you need to drill holes in the throttle plates to create an air leak so yiou can cklose down the throttle blade to try to get some sensitivity , start around 1/16 of an inch , you may need 1/8" or more though , the other issue is to rstrict the idle air bleed circuit , they only way to do this on an eddy carb is to insert a piece of mig welding wire into the bleed hole to restrict it , this requires removing the top of the carb & jamming the wire in place

[SwedeFish]

Maybe they need more than 1.5 turns out?

A 600 will probably be lean for that motor, I had one of those on my 318 and it was a bit lean OOTB.

Tom

You should be able to get it to idle nice though.

What kind off vacuum are you getting?

Even if I turn them out more than 1.5 turns nothing happens. I tried 3 turns and still no increase i rpm...

When I calculated (cubic inch x rpm  divided by a number I can't remember) the result was apprx. 600 cfm. But maybe it is a bit small, but like you said, it should be able to idle and itshould also be good in the low end, where velocity is important.

I haven't checked my vacuum yet, still have no vacuum gauge...  

[Chryco Psycho]

the math doesn`t work , it never has
 I do not know if the carbs do not flow as much as they are rated for or fi the engine do go past 100% efficiency which si possible even without a supercharger or turbo , but start ith 2x the CI as a rule of thumb , one way top check vacuum without a guage is to loosen the covers over the metering rods & see if they stay down at idle in gear , keep changing springs until they stay down & you will know approx what the vacuum is 

[SwedeFish]

typically with low vacuum engines this si the wqorst carb to run , you need to drill holes in the throttle plates to create an air leak so yiou can cklose down the throttle blade to try to get some sensitivity , start around 1/16 of an inch , you may need 1/8" or more though , the other issue is to rstrict the idle air bleed circuit , they only way to do this on an eddy carb is to insert a piece of mig welding wire into the bleed hole to restrict it , this requires removing the top of the carb & jamming the wire in place

So you think my throttle plates are still not closed enough?
The top is already off, maybe I should try what you are suggesting. It just doesn't feel good to drill in a new carb....

I have a Holley 700 DP sitting in my garage, maybe that would be a better alternative? It is kind of old and I'm not sure about its status. I did a small overhaul on it, changing all the gaskets etc. I had it in my car the first couple of weeks with the new engine but it wouldn't work when the engine was hot. I never tried any hard accelaration with it on since I was still breaking in the engine. And I never did any serious tuning.

[SwedeFish]

the math doesn`t work , it never has
 I do not know if the carbs do not flow as much as they are rated for or fi the engine do go past 100% efficiency which si possible even without a supercharger or turbo , but start ith 2x the CI as a rule of thumb , one way top check vacuum without a guage is to loosen the covers over the metering rods & see if they stay down at idle in gear , keep changing springs until they stay down & you will know approx what the vacuum is 

That is exactly what I tried to tell my teacher - math doesn't work ...

Too bad I just bought the 600 cfm ...

Thanks for the tip on the vacuum check.

[Bullitt-]

Swede, Did you check the float level when the carburetor was apart? Raising the float level will enrich the air/fuel ratio.    Also if the cam has a lot of overlap, which decreases engine vacuum, you may need lighter springs on the metering rods to allow them to be pulled down at idle like CP is suggesting in his last post.

[71chally416]

I saw a recent dyno test where substituting a 800cfm Thunder AVS got an easy 35 hp over the stock 600 carb on a stock 340 rebuild. Do ya still think the 600 is big enough? 

[Supercuda]

I just read the specs for the Edelbrock RPM camshaft. That's a pretty rowdy cam for a small engine like the 340. It should idle at about 900 RPM in neutral, with a drop to about 700-750 and choppy in gear. Chryco's advice for modifying the carb is spot-on, and a little reading on the tuning of carburetors for "non-stock" applications is a good idea. Given that all the distributor information is correct (as an MSD, it should be), an initial timing setting of 16-20 degrees, with between 16-24 degrees of advance, is about right. The advance should be "all in" at between 2500-2700 RPM, and the thing that seems to be forgotten here, is that the heads are aluminum. Aluminum heads not only tolerate more ignition advance, they require it. The double-pumper can be made to work, but I am not fond of this style of carb on a street-driven car. The transmission is doing exactly what it should,, as the stock governor in the trans will shift the gears at about 4,500 RPM in this application. Your options are basically two: change to a high-rpm governor, or shift it yourself when you are serious. I like option two, and use it often. I think that this could be a fun and awesome car, but it will always be soft at the bottom end.