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Charrlie_S
65 Valiant 100 2dr post 170 turbo
66 Valiant Signet 170 nitrous
64 Valiant Signet
64 Valiant 4dr 170
64 Valiant 4dr 225

Doc thanks for the camshaft worksheet.
By your SWAG analyses, this RV 15/295 cam is most likely going to come in on the hot side of the sweet spot DCR for a street car.

Dose this cam have any lope at idle? What kind of idle vacuum readings should I expect? What rpm dose usable torque start at, and when dose it peter-out?

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Using the 50 degree ICP this cam would give you, DCR is 8.37... that's a little on the "hot" side for the street, but not by much.

This cam has a pretty smooth idle, gets right into the power, "off-idle" and will rev to 5000... may-be a bit more if lashed on the tight side.
Manifold vacuum is in the 15 to 17 range in my 66 Dart wagon w/ a 4 1/2 inch stroker engine. It is actually a pinch to much cam for that engine. (8.5 static CR)
DD

Torque comes on just off idle.
No lope. It presents a very crisp throttle response down low, though that's a combination of factors. My build loves a bone stock Edelbrock/Carter 500 AFB. Had to back off the pump shot a bit is all.

CJ

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Part of Tyrde-Browne Racing

That is not really much above a stock cam. It will be smooth.

Lou

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Home of Slant6-powered fun machines since 1988

I don’t want to come off as an ungrateful wretch for all the advice, belive me it is all very much appreciated. This topic of camshaft profile is in an area that I understand in theory, but have no hands on (pants on) experience with. Please bear with me while I try to get a real world perspective as to how various cam profiles will change the character of my ride.

What I’m saying is, there are no slant six cars within hundreds of miles of here, that run non stock cams that I can jump into for a test ride. I have to rely on your expertise in matching up engine & drive train combinations that will perform to my, perhaps unobtainable, levels of expected performance from one of these little engines.

Doc’s special grind RV 15, that we have been discussing, appears to be a good compromise between wild & mild, where, if I can read between the lines, behaves like a stock cam in vacuum signal, but moves the engine output up several notches from stock, while retaining good drivability throughout the lower to mid portion of a slant’s total rpm band. Say 1200 to 4000 rpm, and not the 3000 to 5300 rpm range I’m presently living with. Doc reported that it is good to 5000 rpm, so it has legs…

[quote]Manifold vacuum is in the 15 to 17 range in my 66 Dart wagon w/ a 4 1/2 inch stroker engine. It is actually a pinch to much cam for that engine. (8.5 static CR)[/quote]

I’m not sure what you are saying here Doc, is that idle or cruise vacuum? And, why too much for that engine, not enough compression, or head flow? Dose this translate to my engine?

Lou:

[quote]That is not really much above a stock cam. It will be smooth.[/quote]


Question to self: How much above stock do I want? A little is good a lot like I have now is too much, so where is the trade-off point. With no seat of the pants experience with any of these cams, stock included, how can I evaluate this other than using your collective experience expressed in “New Times Romanâ€￾.

Another camshaft I read about frequently on these pages is Erson’s 280/270 grind. Folks appear to like this stick, but never is there any description of its characteristics. Is this more of a race cam where torque output is up the rpm band?

I have a copy, of a list of 35 different slant six cams in little itty-bitty print, from different camshaft producers, listing their specifications by catalog number. I know Doc’s is not listed, and I’m not sure which Erson cam would be the “toutedâ€￾ 280/270 stick, on that list.

Mission at hand: Get Bill’s heap to grow some nads; to put a little more “goâ€￾ with the “showâ€￾; and tame the beast…

What you all are saying is I need to move the power output down the rpm band, so it becomes usable on the street, and not at the far high end of the band where it presently resides. Having driven this car for almost 9,000 miles in various states of tune, I’m ready for a change. It is now time to make it my car, a cruiser not a drag queen, and perhaps a bit more socially acceptable as well with quieter exhaust note. Neighbors are voting for the latter, I’m sure…

To complete my cam shopping experience, are there other sticks I should look at for consideration? Keeping in mind that 60 mph is 2950+/- rpm, and shift point is a stock 904’s 4000 rpm.

Enough of what is buzzing around in my head this morning. I just want to get this right the first time around. Thanks for all your patients while I slowly get a handle on this change.

Now it’s off to the scraper with the first of several 100 pound buckets of key blanks & some copper to finance this little project.

Bill

[img]http://i294.photobucket.com/albums/mm87/wjajr/House/100_1317.jpg[/img]

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Something to keep in mind here, the folks back east tend toward more radical cam profiles in street cars than the west coast. Probably because of our primary information providers.

The RV15M RDP is a Mild cam. It provides a built up engine with a pretty good flow, while keeping valve train loads in check. A compromise, if you will. Considering my build, it get's pretty good economy when I'm not fully matted out in the enrichment circuit.

It definitely is going to deliver more with a modified engine than a stock cam will, but it's not going to provide an evil cackle at the stop light.

You could carry more duration and lift. Like one of the other RDP setups to good effect. 280/270 or something similar. Your vacuum will not be as good as the 15M. I get somewhere around 17" HG in gear at idle.

Another 2¢



CJ

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Part of Tyrde-Browne Racing

Lou and I have always been on opposite side of the cam choice debate, I tend to give-up some higher RPM HP for lower RPM torque... Lou wants that extra HP and adjusts his set-up with more converter and rear gearing... it is just a "personal taste" kind of thing.

Another thing to realize is that both the "street performance" RDPs grinds I developed (RV10/295 & RV15/295) are exactly that... designed for street use, in stock to mild performance engines. These designs are the result of years of testing cams in Slant Six engines and working with cam grinders... the goal has been to fill a need or "gap" I see between stock SL6 cams and all the "high performance" profiles.

Here is a interesting story, a few weeks back I am at the local Slant Six Club car show and talk w/ Tom Condrin writer of Mopar suspension book. Tom said he spent a bunch of head flow & computer time to work-out the best cam for his street performance SL6 car. He took the numbers to Dema Elgin to see if he could grind it. Dema took one look, went into his files and pulled out a cam design I had worked out with him 10 years back... the two designs were almost identical. (The design Elgin and I came-up with is between the RV10 & RV15/295... a 258 degree intake lobe combined with the MP 244 exhaust profile)

To be honest, your situation is the "classic" one I have seen many times in the past... a SL6 owner decides to put a "better" cam into his engines, calls-up one of the 'usual suspects' gets a "performance cam", installs it and ends-up dissapointed with the results. (granted, you got your "big cam" with the engine but it is still too much cam for what you are doing with the vehicle)

Is the RV15/295 the "best" cam for your combo... likely not but I bet it is pretty darn close to what you are after for your current driving habits. I will say that it is a lot closer to where you should be, then the current cam you are running.

As for my statement about too much cam for my 66 Dart, that is because that engine has lower compression so I can detect a little "reversion" as the the intake charge reverses, right before the intake valve closes. We adjusted by lashing the intake as loose as possible (.022) but still see a little vacuum guage pulsing at idle. (hence my 15 to 17 reading) the DCR on that engine is at 7.5

Compare to CJ w/ basically the same stroker combo at 10.7 static CR, solid, smooth idle, steady vacuum, crisp off idle response. His DCR has to be around 9 to 1... he can use more cam in that engine

Running the number on your set-up, you are right in-between but with less stroke and CID.
DD

Hey CJ,

[quote]You could carry more duration and lift. Like one of the other RDP setups to good effect. 280/270 or something similar. Your vacuum will not be as good as the 15M. I get somewhere around 17" HG in gear at idle.[/quote]

Presently I have in gear idle fluttering needle vacuum of 3â€￾Hg to 7â€￾ Hg and 12â€￾ Hg in park @ 1000 rpm. Just about anything would be an improvement in the vacuum department.

What dose RDP denote?

How much of a step up, if you will, is a 280/270 grind over Doc’s RV 15? I would like to take as much advantage of my increased compression & better breathing as possible without loosing low end torque production, and still get a steady 9-10’Hg or better in gear idle to facilitate carburetor tuning.

[quote]The RV15M RDP is a Mild cam. It provides a built up engine with a pretty good flow, while keeping valve train loads in check. A compromise, if you will.[/quote]

Valve train loads with solid lifter cams is an important consideration.

[quote]Considering my build, it get's pretty good economy[/quote]

Is you engine build similar to mine, and what kind of fuel mileage are you getting? Currently I’m running in the 15 -17 mpg range, ok for the third car, but better would not be unwelcomed.

Bill

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

Reverse Dual Pattern.
A "Dual Pattern" cam is where the intake lobe shape (profile or "master") is different from the exhaust lobe.
Most Dual Pattern cams run more profile on the exhaust lobe, a RDP cam runs more profile on the intake lobe.
DD

Thanks Doc, I often struggle with anachronisms, and abbreviations as well. This exposes another layer of the onion to learn about, and drill into my thick skull. I hadn’t thought much about duration & amplitude of valve movement in relation to its counter part until now.
Running more profile on an intake lobe makes since to me by providing a less restrictive fill time of the combustion chamber to gasses under atmospheric pressure. Hot exhaust gasses are under much higher pressure than the cold charge, generate a higher velocity once the valve opens, and would require less time to move the increased volume to the exhaust manifold.

I’m guessing overlap aids in savaging, or removal of lingering low pressure exhaust gasses by the entering fresh charge, and at the same time helps suck in that fresh charge. I can see as that overlap event is shortened or lengthened, the dynamic compression ratio moves up or down.

I just have to come up with the best compromise for my situation.

Bill

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67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

If you have a slant 6 powered car that weighs 3200# running a 15.0 on street tires, I think that is pretty good. Ryan's Dart Weighs 3300# and has only run a best of 14.8 with street slicks and 4:30 gears. And it certainly doesn't feel like a slouch when your driving it. It probably ran mid 19's from the factory.

Rick

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2 Mopars come with Spark plug tubes. One is a world class, racing machine. The other is a 426 CI. boat anchor!

12.70 @ 104.6

You need to consider your transmission....

Unless you're manually shifting an automatic or change the automatic shift points, a larger cam is generally wasted on an automatic because it will shift too soon.


So

LESS IS BETTER

with an automatic

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Ed
64 Valiant 225 / 904 / 42:1 manual steering / 9" drum brakes

Hi Bill,

Our builds come at it from different directions.

I opted to build a long rod stroker.

198 Rods, 4.475" weld up crank. Toyota 3.445" pistons, 300 Ford valves.
And also some silly stuff.

In park I've got 19-20 inches of mercury on the gauge. Even with the 3.50 gears, it can pull 20+ mpg. If I would let it.

CJ

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Part of Tyrde-Browne Racing