1973 340 Cam advice

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trigger_andy

trigger_andy

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Hey all,

Ive stumbled on a 1973 340 from the North of Scotland of all places and was in a van? :/

Anyway the guy I bought it off of was not particular wanting to sell it but needed funds. He says its running etc but I've not see it do so. I can turn the Torque Converter over by hand.

The weirdest thing is there is a 2 Barrel Maifold on there. No idea why someone would want to do that but there it is. Numbers check out ok on the block and the Heads as being a '73 340.

Im planning on running it in my Aussie Charger (A Body) behind a 4 speed and Im hoping someone can advice me what cam to get and what Carb too.

I have a Weiand Action+Plus Manifoldfor it and as Im needing that fitted Im as well getting a Cam as well.

Any assistance is much appreciated.

Andy
 
Well. A few more details about what YOU want out of the car and what trans, size rear end you have as well as gear ratio would be a huge help. Tire size is also help.
 
Thee stock 340 cam is a GREAT piece. If it's in good shape, there's no need to change it.
 
RustyRatRod said:
Thee stock 340 cam is a GREAT piece. If it's in good shape, there's no need to change it.
Click to expand...

I thought the 340 cam was revised/down graded for the low compression engines? If this is not the case then I'd most likely keep the cam. :)
 
What do you plan to use the car for? Street cruising? Full road race? The missus hauling groceries? The cam depends on the use.
 
trigger_andy said:
I thought the 340 cam was revised/down graded for the low compression engines? If this is not the case then I'd most likely keep the cam. :)
Click to expand...

Nope, the 340 and 360 4 bbls all took the 268/276 cam....
 
trigger_andy said:
Hey all,

Ive stumbled on a 1973 340 from the North of Scotland of all places and was in a van? :/

Anyway the guy I bought it off of was not particular wanting to sell it but needed funds. He says its running etc but I've not see it do so. I can turn the Torque Converter over by hand.

The weirdest thing is there is a 2 Barrel Maifold on there. No idea why someone would want to do that but there it is.

Andy
Click to expand...

They most likely put the intake and carb from the original van engine so they didn't have to get new linkages and kick down for it... Same air cleaner etc...
 
rumblefish360 said:
Well. A few more details about what YOU want out of the car and what trans, size rear end you have as well as gear ratio would be a huge help. Tire size is also help.
Click to expand...

Hey,

On the back there is 235/60/15"s

It has 2.92:1 gears at the back which may or may not go to 3.23:1 if that would make a difference?

The 4 speed is not the early and sought after close ratio boxes but a later more open ratio box that was mated to 318's in Australia. I've been advised that I should keep the 2.92:1 in the diff.

I'm really after a bit of fun. I don't do more than 500 miles a year and don't care about motorway RPMs and just wanna mess around in the roads.

Hope that helps?

Thanks,

Andy
 
krazykuda said:
They most likely put the intake and carb from the original van engine so they didn't have to get new linkages and kick down for it... Same air cleaner etc...
Click to expand...
Ah, makes sense! :D was meant to still fry the tyres! :D

I noted the valve springs where duals so there might be other changes?
 
trigger_andy said:
Hey,

On the back there is 235/60/15"s

It has 2.92:1 gears at the back which may or may not go to 3.23:1 if that would make a difference?

The 4 speed is not the early and sought after close ratio boxes but a later more open ratio box that was mated to 318's in Australia. I've been advised that I should keep the 2.92:1 in the diff.

I'm really after a bit of fun. I don't do more than 500 miles a year and don't care about motorway RPMs and just wanna mess around in the roads.

Hope that helps?

Thanks,

Andy
Click to expand...


If you want to keep the highway gears, I would upgrade the cam to 276 - 284 max duration with a set of Rhoades lifters to tame it out... It will still have some low end and mid range grunt to get off the line, without sacrificing top end....

Rhoads Lifters

Articles


The action plus intake is a spread bore intake, so a spread bore holley or carter thermoquad would bolt directly on - go with whichever you are more comfortable with... Both have their following... I've run the Holley List # 6711 spread bore carb for a good spread bore... It doesn't come with electric choke, so you have to use a stock style spread bore thermostat choke which aren't as accurate....

Changing to a 3.23 will help acceleration and still have good highway manners, but will drop top end and MPG...
 
I think the OP wants torque and if he does not increase the rear gear, then he is going to need it in the cam. Without hesitation, I would go the other way on duration - shorter- and work on a faster ramp cam, advance the cam timing a few degrees, and see if I could up the lift some. The older cams have been eclipsed by some of the later cams designs. Shorter duration with that '73 low compression engine will help torque.... more duration will tend to make it boggy.

I really would go up in the rear gearing and look at the 3.55; it is hard to go wrong with that if you don't care if the RPM's are a bit high on the open road and don't mind burning a bit more fuel. If you did that, then I would look at the cam a bit differently.

I'd look at the Lunati VooDoo series of cams and similar faster ramp cams, and put in some better valve springs. Once you go up beyond about .450-.460" of lift, you need to be looking at the retainers so that they do not hit the seals and tops of the guides. But pushing the lift up into the upper 400 range is a good step up. It will expand the upper RPM range.
 
I'm not really a fan of any gear below 3.55 AND your current tire size as I would consider that the absolute minimum. And only because you have the 4spd manual behind it.

IF that is going to be the running gear, I myself would wait until you see how it is with the stock cam inside the engine.

As a point of flexable intake and carb to use for now and later that would cover all the bases, I would ether keep the OE intake and carb IF you have it for the 340 or make a move to a RPM & a 750 Holley DP as a base min.
 
Wow, thank you so much for the replies guys! :D I've just had a 6 hour drive and have 4 hours sleep now before catching a flight so I'll digest all that great input on the flight. :)

As a point of interest I have another '73 340 that will be getting built over the next year with 1970 stock 340 rotating parts and heads so my money will be going into that project.

The 340 I've just got only has the 2bbl manifold and all the other bits and bobs, Dizzy etc. (Can that be used in a 4bbl?) I'm not wanting to spend more than I have to get it running in the Charger. The Weiand was thrown in with the deal so I'd prefer to just use that and put a second hand carb on. I'd be happy changing the cam if it made a noticeable difference and the rear gears too as they will stay when the other 340 is ready.

I'll get the heads cleaned up as there is a lot of deposits and get the valves lapped in. Going off topic would getting the heads slimmed and running a thinner set of head gaskets be worth the time? Or should I just dump it in?

Many thanks,

Andy
 
Oh, I'll assume the Edelbrock Performer intake and 600cfm carb on the 318 in the Charger just now would be useless on a 340?
 
trigger_andy said:
Oh, I'll assume the Edelbrock Performer intake and 600cfm carb on the 318 in the Charger just now would be useless on a 340?
Click to expand...

The wiand dual plane intakes (Action plus and Stealth) are better than the edelbrock performer...
 
Stock cam, with the gears you mention, dual plane intake, 600 eddy or 700 dbl pump holley carb would fit great.
 
trigger_andy said:
I thought the 340 cam was revised/down graded for the low compression engines? If this is not the case then I'd most likely keep the cam. :)
Click to expand...

The 340 cam was the same from 1968 to 1973 with the exception of the 1968 340 4 speed cam. Other than that, they are all the same.
 
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Click to expand
I'm really after a bit of fun.
I don't do more than 500 miles a year
and don't care about motorway RPMs and
just wanna mess around in the roads.
As a point of interest I have another '73 340 that will be getting built over the next year with 1970 stock 340 rotating parts and heads so
my money will be going into that project.

The 340 I've just got only has the 2bbl manifold and all the other bits and bobs, Dizzy etc. (Can that be used in a 4bbl?) Yes
I'm not wanting to spend more than I have to get it running in the Charger. The Weiand was thrown in with the deal so I'd prefer to just use that and put a second hand carb on.
I'd be happy changing (the cam if it made a noticeable difference and) the rear gears too
as they will stay when the other 340 is ready.
Click to expand...

3.91s and drop the 340 in exactly as it is, 2bbl and at all
Hit 62mph @6000,in second gear, badaboom!
If you score, in your price range, a suitable: 4bbl,cable bracket,and air filter house, then add that, since you have a manifold.
 
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trigger_andy said:
Oh, I'll assume the Edelbrock Performer intake and 600cfm carb on the 318 in the Charger just now would be useless on a 340?
Click to expand...
You can use the distributor, intake, etc... no problem because there the same for any small block engine. Of course the rate of which the distributor will advance will change for the application.
The 2bbl. will swap on. The Edelbrock Performer is equal to the stock 4bbl. intake. The Weiands are better. The 600 carb is fine.
 
trigger_andy said:
I'll get the heads cleaned up as there is a lot of deposits and get the valves lapped in. Going off topic would getting the heads slimmed and running a thinner set of head gaskets be worth the time? Or should I just dump it in?
Click to expand...
If you are asking about the '73 340, IMHO the answer is absolutely. These had lower compression pistons (4 valve reliefs on the piston tops), and if you mill the heads (slimmed?) and use thinner gaskets, it will improve your low RPM torque, and widen the torque band. Milling .030" off the heads will remove about 5 cc from the head chamber volume.
 
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If you really want to swap out that cam, I gotta tell you I'm no fan of 114* LSA cams
Using the OEM 268/276 cam specs, the DCR in an 8.4SCR engine goes from 6.74@128 psi to 7.03@135psi by simply closing up the LSA from the OEM of 114 to a custom at 108LSa.
The compression distance increases from 116* to 122*, and the
time spent in power extraction also increases by 6* from 104* to 110*,while
overlap increases from 44* to 56*
The powerband will become narrower, but the specific horsepower will become greater, and you get a few more yards travelled on a gallon of gas. Who knew 6*could do all that!
This may not be the cat's meow for a TF-automatic with a 59% 1-2 shift split. But it can be dynomite with a 4-speed. And that includes a city-car with something like 3.91s,lol.

A similar effect can be created by advancing the 114*LSA cam from the 110* factory setting to 104*, but this really messes up the exhaust cycle. This will reduce the power extraction to 98* and POOF! goes any fuel economy you mighta had. It also messes up the overlap cycle,by opening up the intake while there is still a lot of energy in the exhaust. With headers, a lot of fresh fuel charge can go straight across the piston and out into the header. With log-manifolds some of that exhaust can end up in the intake. So that's like a triple whammy to fuel economy. Quadruple if you include the 3.91s,lol.
But then if you are only gonna drive it 500 miles a year, then who cares.


But then, if you are only gonna drive it 500 miles a year, then why spend any money on it at all? The 2bbl will be running at it's WOT-rated capacity at about 2600rpm @ 100% VE. With an 8.4Scr engine running (guessing) up to 60%VE at say 3700 and with the 2.92s and a 2.66 low,this might be 37mph.
So this 2bbl might actually not top out until 3700rpm/37mph,still in first gear. Of course the engine won't stop revving or blow up or anything stupid like that when it tops out the 2bbl. No it will rev all the way to redline,just fine, and pull more than it's rated capacity while doing so.. It will just be missing maybe 20 or 30 hp up there. When you hit second gear (1.91), it will again pull strong all the way to about 52mph/3700again.
Of course a 500 or more cfm on that included manifold will pump up the 3700 to 5500 zone, at the top of first, taking first gear (2.66)all the way to 55 mph.

Order your 4bbl throttle cable bracket today,lol.
 
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RustyRatRod said:
The 340 cam was the same from 1968 to 1973 with the exception of the 1968 340 4 speed cam. Other than that, they are all the same.
Click to expand...

Wasn't that also used in the 78-79 Lil Red Express and factory 4 bbl 360's (ie, 73-76 duster/dart)...
 
a couple of thoughts...your valve springs are probably stock pieces having a damper inside the single wound spring.Your intake is fine and any 600 cfm carb will be good.
With 2.94 or 3.23 i'd select a 204 / 214 .429 / .444 cam.(Nearly every company makes one) and you will break the tires loose easily from a dead stop and pull hard from 1200 rpm to about 4800.You'll have a ball on the street to well past legal speeds with this combination.
 
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