Hypothetical build questions…

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vntned

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So, I kinda ended up with a ‘67 Valiant two door in a trade, which I probably don’t need, but I might keep it anyways.

So if I keep it, it will be a super low buck driver. Something that I can drive anytime and anywhere on pump gas, highway cruising would be a must, and I would have to put it together with stuff I already have laying around.

So the Valiant was a slant six, three on the tree car originally. No option car. It currently has a v8 crossmember with BBP disc brakes that my buddy and I swapped in, as well as super stock springs out back with a ‘67 B-body 8.75” rear housing and axles. The car also comes with a pair of Hooker headers, a motor plate, passenger floor pan, 4spd floor hump, 15x8 Rallyes on the back and 14s up front. maybe a few other small things that I’m not thinking of right now.

To be driveable, the car needs an engine, trans, rear chunk, radiator, under hood wiring, gas tank and rear brakes.

What I have laying around:

Complete 340 short block with a steel crank, rods, TRW 10.5:1 forged pistons, windage tray, etc.

Jheads with 2.02/1.60 valves, springs and retainers, heads have a nice port job but nothing crazy.

Trans I have is an iron A833 overdrive.

Rear chunk with highway gears.

I have tons of the small stuff needed as far as mounts, distributor, electric ignition conversion, carb, coil, flywheel, drum brake stuff, etc..

I also have some cams, but they are large mechanicals, except for one old Mopar grind, might be ok, just gotta check.

Hard parts I would need would be a bellhousing, clutch, gas tank, radiator, and rear chunk with a decent gear.

The question is, with what I have, what would be suggested for a cam and rear gear?


Oh, and I would have to put stock springs back under it in the rear.

4C16136E-B94A-4C5A-A446-8CA2F0C00D36.jpeg
 
Cam wise you could go in many directions it depends on you, sounds like you know **** what range you thinking ? maybe we could help narrow it down, i'd say intake 215 to 225 @ fifty .480 to .525 lift. possibly more depends what your looking for and gears the OD has a deep 1st so 3.23-3.73
 
So looking through my cam stash, aside from a few big mechanicals, I have:

An oldskool Mopar Purple cam
#P4452761AE
Lift is .450/.455
Dur. Adv. is 268/272
@0.050 228/231
110 Lsa
1500-5800rpm

Or a Comp Cams Nostalgia Plus
#CL20-671-4
Lift is .484/.484
Dur. Adv. 284/291
@0.050 239/246
108Lsa
2500-6400rpm

Not gonna lie, that Comp will make 30hp over that old MP, and that is tempting…
 
You say you want to drive it "anytime anywhere", your words. That sounds like you want to drive it a lot. To that end, I would look for something with non modern style lobes. Something with "slow and lazy" ramps compared to modern grinds. In the end, you'll be happier and so will the valve train. Maybe an NOS grind from Erson, or like what I have in Gladys, my Ford truck, a Crane Fireball. Maybe one of the old Crower Hydraulic Hauler grinds or one of their Ultra Beast cams. Maybe an old Isky grind. If you go flat tappet, whether solid or hydraulic, I would sure try to find something old and NOS.
 
i think cam selection is going to be critical here. you're working with somewhat diametrically opposed forces: a big valve, high(ish) compression motor that wants to spin and make power uptown; and an OD crash box that has kinda crappy ratios to stay in what could be a narrow power band that also is going to eat into that rpm where you make power while at cruise.

i think anything less than 3.55 you're going to have a dog at highway speed. with OD you'll only be clicking about 2200 and that's where that type of motor just starts to get cooking.

i'm with RRR here, a smaller cam without a radical profile would probably do better for what you're trying to achieve. carb as well, small and vacuum secondaries.

also, keep in mind that the OD boxes don't like a ton of power put to them without some upgrades they won't last.

edited, i didn't see that the OD box was an iron unit. disregard and carry on.
 
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vntned said:
So looking through my cam stash, aside from a few big mechanicals, I have:

An oldskool Mopar Purple cam
#P4452761AE
Lift is .450/.455
Dur. Adv. is 268/272
@0.050 228/231
110 Lsa
1500-5800rpm

Or a Comp Cams Nostalgia Plus
#CL20-671-4
Lift is .484/.484
Dur. Adv. 284/291
@0.050 239/246
108Lsa
2500-6400rpm

Not gonna lie, that Comp will make 30hp over that old MP, and that is tempting…
Click to expand...
While the Comp may make more HP, the drive anywhere aspect you’re looking for is ether the MP cam or a new cam all together. The low first gear trans will like 3.23’s (IMO) at the most. In overdrive, the ratio drops to the low 2.xx. If you use 3.55’s, use a tall tire. In OD, it’ll be a hair above 2.50 final drive.

The OD gear boxes are best used as intended. In drivers. AKA small cam cars traveling far. Not to big of a camshaft since there operating ranges can quickly be in a range above the final drives cruise range. You’re going to have to work out your final gear ratio drive and tire size for the cruise rpm for a camshaft duration that will work well. If the cam is to large rod the final cruise rpm between the tire size and gear ratio, the engine will become less efficient and may use more fuel than intended.

Do you know what the head flows?

Nice car, always wanted one of those.
 
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If I was picking between the 2 cams you listed, I would hands down pick the MP '761' cam. I have that cam in a much heavier 71 Challenger with a mild 360/727/3.23's, and it will get 20 mpg on the highway. Either run a regular 833 four speed with 3.23 gears, or the 833OD with 3.55 gears. You will have to baby the OD trans probably, if the 340 has at least stock amount or higher HP.
 
I don’t think he will have to “Baby” it but I wouldn’t go slamming gears @ 7K. Gears 1,2,3, ought to be just fine getting on it. 4th place s the one everyone worries about. Perhaps it’s valid under high HP, rpm and torque.
 
JDMopar said:
Yeah, the slam-bang is what ends them....
Click to expand...
Pretty much! I don’t know why New Process did what they did.
I have a long tail shaft iron OD in the garage I want to make use of in my ‘79 Magnum for those long cruises from Fl. back up to N.Y. It has 3.55’s out back. It will equal 2.52 in OD with a 245/60/15 tire.
JDMopar said:
and more so the aluminum case ones than the iron ones like he has.
Click to expand...
He stated he has the iron unit.
 
JDMopar said:
Yeah, the slam-bang is what ends them....and more so the aluminum case ones than the iron ones like he has.
Click to expand...


Junk clutches kill parts. Good clutches don’t. The OD box will take close to what a non OD box will if the clutch isn’t garbage. 99.9% of them are straight garbage
 
JDMopar said:
If I was picking between the 2 cams you listed, I would hands down pick the MP '761' cam. I have that cam in a much heavier 71 Challenger with a mild 360/727/3.23's, and it will get 20 mpg on the highway. Either run a regular 833 four speed with 3.23 gears, or the 833OD with 3.55 gears. You will have to baby the OD trans probably, if the 340 has at least stock amount or higher HP.
Click to expand...
Noted in other posts, any real power on 75-76 alum od trans, will shred the OD gear while in od
 
I've done this swap a time or two.
I have used the stock 340 short
with 318 heads, and I have used both
a stock 318 cam, or a stock 360 2bbl cam; installed straight up.
I used a Factory cast-iron dual-plane Small-port, spreadbore intake with a Thermoquad.
This makes your 340 basically, a big-bore 318, with a magnificent bottom- end. It will pull any gears. But
If you have the A833od then you can run a lot more starter gear than what you think might be right.

I suggest a cruising rpm of not less than 2200, (because that is already pushing the ability of the factory type distributor to provide adequate cruise-timing) and with a .73 overdrive, and 26.5" rear tires, that points to 3.73s; for 2200=64mph.
However, this makes the starter gear to be; 3.73 x 3.09=11.53 which is way more than this combo needs, but it will be a lotta fun. But more importantly;
Second gear will be 3.73 x 1.67=6.23 which is perfect.

Now, there is one caveat. The CCP with the Tall pistons in there,
may be much too high to use the 318 cam; too high probably for WOT detonation-free operation, no matter what gas is in it. So you are gonna have to carefully measure the Scr, and adjust it as may be required, to get the CCP into the required window with the Ica of whatever cam you stick in there, so as to make it streetable.
But, I would try to keep the CCP as high as is possible to run the cam of your choice.
There are two or three reasons for this;
1) when the bug bites for a bigger cam, you won't have to throw away as much CCP, which, with a manual-trans, you usually don't want to do.
2) Big CCP helps make Big Fuel-economy.
3) Big CCP will increase the Low-rpm Torque, so yo don't have to slip the clutch out so long, and you can still burn ribber whenever you want to......

You may ask;
1) Why the 318 small-port heads? Answer, with 3.73s and a 1.67 Second gear ratio, 65mph will be about 5100 rpm, and the 318 heads will easily be enough.
2) Why the 318 cam? Answer, cuz it's the right cam to go 5100 rpm with, for starters, but more importantly; the specs are;
240/248/112 @.008 But that is only half the story,
in at split overlap, the specs are;
240 intake/130 compression/122 power /248 exh/20*overlap.
With this information we can figure out a few things;
1) Because the overlap is so very small, this tells us that the Headers are overkill, but you already got them, they won't hurt anything, and the inertial-tuning will still work.
2) with 130* of compression, she is gonna make a lotta cylinder-pressure in those very modest sized chambers, with pop-up pistons.
3) Normally 122* of extraction is ridiculously large. But in this case, combined with the other specs, this is gonna extract about as much energy out of the expanding gasses as will ever be possible. This means "massive" low-rpm torque, for an SBM, which makes for the possibility of extracting modern-day 4-banger type Fuel-Economy.
4) So since the CCP with the 318 cam is gonna be so huge, I have found the 360 cam to be acceptable. The new specs, in straight up, are;
252intake/123 compression/119 power/256 exh/30* overlap.
This does several things for us; notably;
The pressure will be down about 12 psi or more, helping shed some of that excess pressure. Power extraction is only 3* less, but really, it was excessive with the 318 cam anyway.
This 360 cam is almost 2 sizes bigger than the 318 cam, so the power-peak is gonna go up some 300 rpm. This wont't make much of a power increase with the 318 heads, but it will extend the operating range, at least the same 300 rpm, which will get you 70 mph@5500 in Second gear; so that's a good trade.
5) the overlap is now 30 degrees, so not a lot but I bet the headers will find it.
6) the hardest part of this marriage, IMO, is gonna be setting up the timing curves. You will need to mod every moving part in the distributor, and yur gonna need a lotta Vacuum advance, and
I highly recommend you find a dash-mounted, adjustable, timing module. or an electronically programmable distributor.

The first time I did this was in about 1975. The engine went into a 1965 V100 station wagon, with an A904. It didn't corner very well, but in a straight line, it was "btchng. Oh and, she was my DD for 2 years, and made fantastic fuel economy. I still have that engine/trans, as I sold the car without it. To this day, I still have fond memories of it; and wish I still had it, cuz with what I have learned since then, I think she would corner a lot better today.
This post, is of course, a reflection of what I might do, and in no way is it a "you-just-gotta-do-it my way, lol.

This combo with a 360 top-end, and cam that has more than 44* of overlap, will be just as much fun, but will never achieve the mpgs of either of the factory 2bbl cams. The cost of gas will never go down again, but will steadily march upwards until it becomes unafford for most of us, so I have to look ahead to buying the cheapest gas out there and have to make it work. To that end, I would target CCP of 155psi or perhaps a little less.
 
Brooks James said:
Noted in other posts, any real power on 75-76 alum od trans, will shred the OD gear while in od
Click to expand...
This is correct, but can be mitigated by paying attention before you let the clutch out on that last shift. Oh and don't put an atomic clutch into it.
I have never shredded one during passing.
It's always been by shocking it on the 3-4 shift, my fault.
I now run a factory 340 disc in my CenterForce PP, and
The PP has a reduced static pressure.
It now takes off at low-rpm with just a hint of slippage, so it's kindof a dump-it-and-go deal. I depend on the flyweights for performance.
 
The Mopar cam you listed or something along the lines of an Isky 280 Mega.
 
The Isky 280 Mega is a good size street cam. Not for mileage.
(LOL)
If the OP was looking for mileage, I’d pretty much second AJ’s post and use the 360 cam with stock heads. We don’t know the level of porting his heads have. That’s why I wouldn’t use that cam.

Personally, I, myself would use a stock 340 camshaft with 1.6 rockers on his ported heads and a 3.55 gear set (Max) over the 3.73’s AJ said to use, or suggested to use. Ether way, it’ll reduce the cruise rpm a tad, have a 10.96 first gear or a 3.23 gear and have a nicer 9.98 first gear, which is closer to ideal, but the other gears are a little off. The gear spread keeps things off balance and interesting.

There’s no real right or wrong to it. Just what you want from a less than ideal gear set up. Everyone has there point of view and taste.

@vntned , are you looking for a cruising machine?
What’s the typical speed you’re traveling at?
Is interstate traveling going to be in the future with this car?
Because, the limit is 70 mph in most places, but that is mostly right lane speeds.
 
Rat Bastid said:
Junk clutches kill parts. Good clutches don’t. The OD box will take close to what a non OD box will if the clutch isn’t garbage. 99.9% of them are straight garbage
Click to expand...
So, with a regular ol driver type street car with moderate power and an aluminum 833OD.....exactly what kind of clutch would help it survive if one drove it like they had some sense?
 
Stuff the MP cam in it since you already have it and find some 3.73 or 3.91 gears. 3.91s are a blast with a 4 speed. JMHO
 
JDMopar said:
So, with a regular ol driver type street car with moderate power and an aluminum 833OD.....exactly what kind of clutch would help it survive if one drove it like they had some sense?
Click to expand...

You need a Soft Lock clutch. Or at least a clutch tamer.
 
The intent for the car would not be fuel mileage. I don’t care what anybody here says, you are not gonna get good fuel mileage with a modified smallblock. 12-14mpg around town is fine by me.

The intent for the car would be able to drive at modern interstate speeds, 70+mph, without screaming at 3000+rpm’s.

I just took my old D100 on the PowerTour and with 3.23s, an A727 and 28” tall tires out back, it was turning 3000+rpm the entire time.

Not that I will be on the interstate everyday, but I want the capability.


I’m really thinking 3.23s with the overdrive are gonna get me what I want as far as hwy mph/rpm.

The question left to answer is what cam would provide a broad enough power band to cover that 3000rpm drop from 1st-2nd with the overdrive?
 
I don’t think it’s that much of a RPM drop and no cam covers that range in a way you could call good. Also, 3K isn’t screaming. You’re just used to new rides that cruise at 70 mph @ 1500 rpm. That’s todays rpm. Yesteryears rpm was an easy 2500 - 3000.

If you’re thinking 3.23’s, your (yet unknown) tire size has a play in a camshaft selection. You said you don’t care about mileage but do not want to travel at 3K rpm. OK….

Your first gear, 3.09 X 3.23 = 9.98 (Excellent for hot rods)
In overdrive, .73 (?) X 3.23 = 2.35 (Not so good for hot rods)
The problem here is a hot rod cam takes advantage and feels best with the first gear final ratio while the OD ratio is so high it’s stifling power and mileage. And the flip side of a small cam….
You get the idea.

If I suggest a cam to try and bridge both the ability to help provide power on take off and be reasonable enough for decent mileage, it can not really be done very well. I know you said you don’t care but here’s the rub, mileage will tank with to large of a cam, a small cam cuts power turning the first gear take off power to a crappy level. A cam between 210 - 218 @050 is what I’d look at myself.


With the Purple cam you have now, I’d use that and tune that carb to be a lean runner on cruise. Fatten the secondary side as needed. Just send it. It’ll be fine enough.

The thing with the OD transmission is the 1-2 & the 3-OD shift has a big drop. You’ll have to rev the engine a bit higher and call it normal. That is just simply how it is going to be. IMO, you can try really hard from here to get the perfect set up with one of the most difficult transmissions and be upset or just not worry about it. You’ll never get to a modern day level, the car lacks all of the equipment that makes it possible except cubic inches and probably a very reasonable car weight.

The old tech is limited. Even if you try and band aid the cam with Rhodes lifters, grab more lift with 1.6 rockers, use new heads custom ported to take advantage of the cam and in the direction you want, it’ll never get to the new car point where you have great power and a double OD for great V8 mileage. Just do the best you can and enjoy it.
 
vntned said:
The intent for the car would not be fuel mileage. I don’t care what anybody here says, you are not gonna get good fuel mileage with a modified smallblock. 12-14mpg around town is fine by me.

The intent for the car would be able to drive at modern interstate speeds, 70+mph, without screaming at 3000+rpm’s.

I just took my old D100 on the PowerTour and with 3.23s, an A727 and 28” tall tires out back, it was turning 3000+rpm the entire time.

Not that I will be on the interstate everyday, but I want the capability.


I’m really thinking 3.23s with the overdrive are gonna get me what I want as far as hwy mph/rpm.

The question left to answer is what cam would provide a broad enough power band to cover that 3000rpm drop from 1st-2nd with the overdrive?
Click to expand...
I would run the Purple Shaft, but the 10.5:1 slugs may be a bit much, even with the thicker Fel-Pro type of gasket. Get an actual cc for it and determine the real SCR 1st.
That Comp is just a dual pattern version of the 284°/.484" Purple shaft, certainly liveable on the street, and a better fit w/an actual 10.5:1 SCR.....comes with a nice "rumpityrumpityrump" idle...:p
 
For what it’s worth, though expensive, Cometic will make nearly any gasket thickness and diameter you want to adjust the compression ratio.
 
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