cam advice for 340 street motor

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krenzy_84

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Hi I'm looking at cams for a 340 I'm building for my 72 duster. Will have 323 gears and I'm willing to put a 2500 or so stall in when the motor is out. I don't want a crazy race car idle but i would like a nice lope to it but something still drivable. Does not have power brakes i put Kelsey hayes 4 pistons in the front. Motor is a 69 340 bored 40 over and i have 1970 U heads with 2.02 intakes just gonna have gone through maybe port match the intake. Suggestions?
 
[email protected]/2800TC/ AirGap. This favors midrange and top-end. Some lope but only at very low rpm.
[email protected]/2500 if you need to keep the cylinder pressure up. This favors midrange and lower rpms. It has a barely perceptible lope.
[email protected] if you want a tire-fryer and spend a lotta time on the hiway. But the Scr may have to be adjusted to run this puppy.

I highly recommend to not order a cam until you know what the absolute Cr will be, otherwise you might be setting yourself up for disappointment........ or additional machining costs.
or
you can decide today where you want the power to be, and then do the machining to optimize it.
 
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agree with AJ
carb and manifold
header and pipe size
what pistons and gasket and have you ccd the heads do all four end chambers and report back
as AJ implies it makes a big difference
did you bowl blend below the valve job, how many angles on the 2.02s
is the short block together
do you already have valve springs
stock rockers or???
 
The short block is together and it has sealed power pistons part number L2316. Just looking on the net the factory U heads should be around 72 cc I'm not sure if my heads have been milled or not I'm gonna take them in to get valve job done and straightened. But if they are around 72 that puts it at 9.5 to 1. I do not have valve springs as i will buy them to match the cam i choose. not sure on rockers from what ive been reading roller would be the way to go.
 
If hydraulic flat tappet, 2500T.C., 9.5:1, it sounds like a Comp XE268H would be about right. That's 224/230° @ .050, lift is .477"/.480"

Of course there are dozens of other similar cams on the market, just using Comp as an example.
 
i have built and run the xe 268 in a near identical 340.It needs a converter (i used a dynamic 9 1/2" that stalled 3200) From midrange up it ran extremely hard and the power seemed limitless.For the street i think i'd use the smaller XE 262 or something similar and bet it would outperform the 268.
Actually it's hard to beat the stock cam in a 340 A body as an all round performer
so don't go too much bigger for the street.
 
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get your head ccs b 4 doing any more than thinking about a cam
when you have the heads off measure the piston to deck clerance
we can then nail this puppy
3.23 gears IMHO 368 is too much
take what ir333 said seriously
re-read what AJ said
 
I'm with ir3333 on converter. 2500 is barely more than a stock 340 converter. Even a stock 340 car could stand to have more converter. Converter is one of the biggest performance upgrades you can make. With an ex 268, the difference between a 10.75 inch 2500 stall and a good 9.5 or 10 inch 3500 would be significant.
 
Wyrmrider said:
get your head ccs b 4 doing any more than thinking about a cam
when you have the heads off measure the piston to deck clerance
we can then nail this puppy
3.23 gears IMHO 368 is too much
take what ir333 said seriously
re-read what AJ said
Click to expand...
At least with a tire of 26 inches or smaller, there it will be OK if the stall is indeed at least 2300/2400.

Another 500 rpm would be good & max IMO for a true streeter.
 
A 2500 is NOT more than a stock 340 high stall.

That said, go with one of the Thumpr cams or the Hughes Whiplash.
 
Rusty- whiplash with a real 9.5 and iron heads?
he may not have a real 9.5- I'm going to wait and see
I can see rolling your own whiplash style cam using Howard's lobes (for Hyd)
the bigger the intake lobe the more you squeeze the lca- just keep an eye on the overlap and the other events
 
krenzy_84 said:
Hi I'm looking at cams for a 340 I'm building for my 72 duster. Will have 323 gears and I'm willing to put a 2500 or so stall in when the motor is out. I don't want a crazy race car idle but i would like a nice lope to it but something still drivable. Does not have power brakes i put Kelsey hayes 4 pistons in the front. Motor is a 69 340 bored 40 over and i have 1970 U heads with 2.02 intakes just gonna have gone through maybe port match the intake. Suggestions?
Click to expand...

I think we are losing sight of the OPs request;
It will have 3.23s.
Willing to put a 2500 or so stall
Krenzy wants to run 3.23s and a regular TC, common, stay on target

>The later your ICA is the more compression you need to run to keep the low-rpm torque up. Failing that you will need to get a TC ever higher, and the 3.23s will be long gone, as will be fuel economy.
>The more overlap you have the lopier the idle, and the more fuel goes out the tailpipe around town
Those are big sacrifices just to hear the big-cam lope.

But sure; long period cams with lots of overlap,release the engines ability to operate at higher rpms, and that is how they make more power...... always at the sacrifice of low-rpm power. It's always a trade. But to get to those higher rpms where the power is...... for a streeter, requires ever bigger rear gears and ever higher stalls.
A cam that peaks at 5200, using 3.23s comes to the peak at about 50mph in first gear. It doesn't even get on the pipe until about 35/40 mph.
Krenzy wants to run 3.23s and a regular TC
Krenzy needs torque to get him up there, cuz he only has a 7.91 starter gear.
Back to post #2

The factory 1969 340 727 TC was rated at 2350 +/-100,behind the factory stock 340, per my FSM. I cannot say further cuz all my 340s have been in stickcar As.
 
I had a CC268H for years behind my 340, stock X heads, with performer RPM. I had somewhere @ 32-3500 Stall (been awhile). When I had 4.10 gears it was fun stoplight to stoplight & around town, but then I got a job that required a longer highway travel. I went to an available set of 3.23, it was slow from a start, but if I was already at 35 or so & downshifted, it was ok because I could wind it up pretty far to keep it in the zone for the shift.
Listen to the above & don't go too big. I wouldn't pick a cam on how it sounds, the burble of any V8 through the right mufflers sounds way better than most anything on the road anyway.
 
Stock cam, 2800 converter is my opinion...
Then put some ultrflos or some other straight through design mufflers, dial the advance curve for 10 degree mechanical advance and start with 22 initial and go from there.
 
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FWIW.... my sons' 10:1 340 in a '65 'Cuda and 3.55 rear gears has a 268-ish range cam and a 2200 stall converter. We went low on the stall speed for 2 reasons:
- A bit better economy
- We do a lot of road race style driving on the local mountain roads and high stall converters make it harder to modulate the throttle in all RPM ranges; most/all TC's tend to 'mush' around the lockup RPM with part throttle and putting that lockup speed higher just takes away from your usable RPM range for torque steering the car.

With that, it is a tire fryer with that rear gear and the lighter car. With the OP's 3.23 and a bit heavier car, then a 2500 (maybe 2800) would make better sense for what we do. For drag racing, then going higher makes sense. IMHO there is no 1 'right' answer; it is all in how you use the car.

And 100% agreed on the cam sound. I think RRR said it right once: If it is a good engine, it will sound right without any messing with the cam to make it sound lopey.
 
Thanks for all the replies i think i will go just over stock or even stock. Would using a mopar purple cam be a good idea and what part number would be close to stock and work for me?
 
krenzy_84 said:
Thanks for all the replies i think i will go just over stock or even stock. Would using a mopar purple cam be a good idea and what part number would be close to stock and work for me?
Click to expand...
im not as knowledgeable as alot of the members on here but FWIW with your stock(ish) heads the older purple shaft designs are a good match for their flow as they were designed for - I have used the 268/272 .450/.455 camshaft which worked well - ( different beast though when i swapped for modern rhs heads)
 
268 is bigger than he needs to go with discussed converter and gears
268 Mopar is bigger than 268 aftermarket
and 268 aftermarket is too big
Factory hp cam is only 209 @.050 but you can get cams with shorter than HP cam seat durations but more at .050 and more lift
did you come up with an accurate compression ratio?
here's a voodoo
VD 475/494 262/[email protected] 220/226 112lsa #60302
Hughes 495/503 216/220 I do not know what the seat timing is
or as Rusty suggested a whiplash style if your compression comes out lower
 
Wym, FWIW, his SCR should be around 9.2, 9.4, or 9.6 with his listed components and 73 cc chambers, depending on whether he used the .051", .039", or .028" thick head gaskets respectively.
 
figure .050 below deck for the piston and what do you get- so far not measured but that's what others get
I'd be squeezing the lobe centers down with compression drooping if keeping the same lobe

what would be your plan of attack
 
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For stock late '72-73 pistons, yes. But he says he has L2316 Speed Pros and those should sit at the same height out of the block at the early ones, at around .018" above deck. (Compression height is 1.840".) I used 6 cc's in the eyebrows and now I see they are 7.5 cc's so that drops CR another 0.1 or so.

Just trying to provide some info to help answer the CR question. With the CR in the low-mid 9's range, then the cam can be bigger, and IMHO it is tweaking around the application to go 262 or 268 or thereabouts. But the 262 intake range is probably best with a lower stall TC in a general street cruiser. As in post #12, you're trading low RPM torque for high RPM HP, so it kinda depends now on what the OP wants to be doing with the car: Street cruise? Drag Race? Road race?

Getting the lift up is a worthwhile goal IMHO, and that points to maybe 1.6 rockers if that can be afforded (since the OP asked about rockers...). Another can o' worms; if one goes that route, then valvetrain stresses go up somewhat. (As Crackedback recently stated, it is easy to spend other people's $$ LOL)
 
Right nm9 I had brain fade on the CH
323 gears and use a stock HP converter which I hope he already has
post 12 and/or post 2
We we tested for Chrysler the DC 268 cam was ok in that combination (no gain in 60 ft some gain in the 8th) one size larger and the bottom end went soft loss in 60 ft bout the same in the 8th gain in the 1/4 The DC 268 has faster ramps than the HP 268 (better check my notes - that memory may be for a BBM)
 
nm9stheham said:
And 100% agreed on the cam sound. I think RRR said it right once: If it is a good engine, it will sound right without any messing with the cam to make it sound lopey.
Click to expand...

Yeah but people don't wanna hear that so I just recommend the Thumpr or the Whiplash since that sounds like a cooler recommendation.
 
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