Upgrade to 708 Lumpy Cam or aftermarket?

[PowerKraus]

I am looking to port and polish my heads and figured while they are off, I might as well drop in a cam...assuming a few things. So I need a little help/advice here.

This will go in my 2002 GTS that I run a little 100 shot of nitrous through every so often. I'd like the cam to 'drop it' using existing springs, rockers, lifters, timing chain, stock rear gears, and only minor tuning that can be had with the VEC II. I'll be opening up the exhaust too with freer flowing muffs, etc.

Anyway, I know I'll never get the same wicked sound like from my LS6 408 stroker, but I am hoping for something better than the UPS truck ;

Is the 708 cam worth it, or would the better bang for the buck be to use an off the shelf grind from Comp or the like?

 

[Tom F&L GoR]

Cam removal interferes with front frame crossmember, so ask around for the tricks to angle the block upwards and avoid extra work/time. Tator will know.

 

[GTS-R 001]

A car with the 708 cam in it is much more Muscle Carish than any of the vipers without it, my 97 RT/10 shakes when at a red light almost to the point where you wonder if you have a broken engine mount ( but not quite ) My wife thinks the car is broken, She drives an 06 coupe everyday to work and back and I have owned and driven a 92, 96 GTS, 97 Rt/10, a 98 GTS, a Y2K GTS, an 03 SRT10 and an 06 Coupe, the 708 cam is the nicest of the bunch. Dan Cragin also just recommended a 708 for my engine build on my Y2K GTS to make 800 HP with one of his superchargers.

 

[Mccarlin]

the 708 cam was only in the 98 and 99 years correct?

 

[99 R/T 10]

708 was 96-99, BUT by the specs, the 98-99 cams had .001 more lift

Cam specs at the bottom of the page.

 

[Joseph Dell]

The cam is so good that some tuners even did a custom grind of it to add some lift.

I LOVE this cam on a SC motor!

JD

 

[Dimitrios]

i have a 708 cam on my car and its great with the roe SC and ported heads.

 

[jk]

I put a 708 in my 2000 when I did heads. The only thing I regret now, and you might consider, is an adjustable timing chain so you can centerline the cam. This will typically require you to have the end of the cam machined to fit the mounting requirements of an adjustable chain setup. I think most require a three bolt setup versus the stock two bolts.

 

[PDCjonny]

My car is very lumpy at idle, people ask what aftermarket cam I have in it. They can't believe it's stock with the rough idle. ('98 GTS)

 

[EllowViper]

JK, Are you referring to degreeing the cam at install? All the ones I've done (non-Vipers) I've advanced/******** via offset keys on the crank gear or generically via the advance/zero/retard "dots" on the crank gear. From your post, I assume the Viper timing gear set-up does not afford you the "luxury" of degreeing the cam in this manner.

 

[KWIK96]

I have a 708 and SC on my 01 and I like it. It is not "over" lumpy, just purrrrfect

 

[FE 065]

I've never heard of an adjustable timing chain..You must mean something about the cam gear etc

 

[jk]

Take a look here for a picture of the adjustable timing chain set.

http://www.waverleychrysler.ca/parts4.asp

Note that camshaft must be drilled and tapped for 3 gear mounting bolts. And yes, more specifically, I was talking about degreeing the camshaft. I had a conversation a while ago with Dan Cragin and he mentioned the specs on what he felt worked best with heads and a 708 cam.

 

[splochocki]

What are all the specs on the 708 lumpy cam? lift, seperation, etc?

 

[EllowViper]

Interesting that the stocker would use a two bolt timing chain gear vice the typical three (I trust your analysis but will need to check my manual just to be sure). Even stranger is that MOPAR performance would offer the timing chain set as a three bolt set-up requiring the modifications you suggest in order for it to be used on a stock cam. I wonder if the "MOPAR Performance Camshaft" has the three bolt holes for the sprocket.

 

[99 R/T 10]

Look at the 5th post down and cliiiiick.

 

[EllowViper]

OK now I'm scratching my head. My service manual shows a single camshaft bolt and washer torqued to 55 ft lbs and not a two bolt set-up. I would assume the 708 cam therefor requires a matched timing gear set with the aforementioned two bolt timing gear set-up and could not be used with a "stock" timing gear. This is a good discussion since many times upgrades do not get into the "I wish I would have known that" related parts/issues until you've already committed to the investment.

 

[KepRght]

all the advice i have heard is "use the comp coupe cam"

but im no where near ready to do heads & cam so i havent looked deeper. i believe the comp coupe cam is also the 708.

 

[viperrt96]

I got the 708 cam in my GenI - I love it!
I installed mine per DC's specs. I would check with the real tuners to see where the cam will work best for your set-up. I think we advanced ours something like 10 or 12 degrees from centerline. I don't recall exactly. Dan at DC can tell you. I used the stock timing gear set and chain. You are right it uses one camshaft bolt and a pin for positioning. I elongated the pin slot on the cam gear and only what I needed. I installed it first then I took my readings. I only needed a couple of more degrees. I slotted the pin opening until I got it right where I needed it. I'm fortunate to have access to a machine shop so it was easy. You could do it by hand I guess. The pin rested against the very end of my slotted hole and that was in the direction of the pull. I used loctite on the bolt so I'm pretty confident it won't go anywhere. And if you are thinking about buying the Mopar performance keyway sets. They don't work. They are not for a Viper crank.

The biggest plus to running the 708 cam is it will run (obviously) very well with your factory computer. A custom grind camshaft in most cases would require someone to re-calibrate your ECM.

Another plus is running 1.7 RR's with the 708. It has an advertised lift of .541 for both the Intake/Exhaust. That's calculated on 1.6 rockers (stock). When you go to 1.7 it changes that lift to .574 - Theoretical of course. Don’t worry about changing your valve springs. They can handle it. Good luck!

 

[Tom F&L GoR]

I was told the Gen 2 cams won't go into a Gen 1?

 

[viperrt96]

I was told the Gen 2 cams won't go into a Gen 1?

It's an exact fit. No modifications at all.

 

[IEATVETS]

I was told the Gen 2 cams won't go into a Gen 1?

Yup, you was told wrong.

 

[viperrt96]

Here's a pic

Like I said it's a direct bolt in.

 

[Bratatatat]

Anyone have a sound clip they can share???

 

[PowerKraus]

Well, thank you all for the good advice. Y'all provided me some great information in this post. Made my choice an easy one...a 708 cam it is. I'm a little skeptical of installing at a 10 to 12 degree advance? Or maybe I am too used to the LS motors were a 4 degree advance is the most you'll see. However, that spec is something easily checked out with a vendor....

Now, any advice on where to buy one new? I would assume a vendor would cut a better deal than the stealership?

Thanks again !

 

[EllowViper]

As I dust off some old brain cells, let me think back on the rule of thumb for degreeing a cam. On my small block MOPAR, I would run about 4 degree advance for better low RPM cylinder loading sacrificing power above 4500-5500 RPM and about 4 degree retard for better high RPM cylinder loading ergo 3500-6500 RPM; to account for the carb/manifold/short stroke and gearing vs vehicle weight I was running at the time. I guess with the long intake runners, relatively long stroke, gearing and weight, the 488 loves to get the valves opened and load the cylinders. The 66 degrees of valve overlap in the 708 allows the long runners to continue to fill the combustion chamber due to the velocity of the incoming air charge down those long runners. In lieu of a dual plane/runner intake, this probably consumed some significant engineering time to get that optimized. I wonder why DC reverted to a 60 degree overlap vice the 66 degree???

 

[KenH]

I wonder why DC reverted to a 60 degree overlap vice the 66 degree???

I would suspect that it was emissions driven. The more overlap, the more mixing of intake and exhaust charges and the poorer the emissions. Probably also to minimize neutral gear rattle that some owners complained about.

The only difference between the 708 and the newer cam is the overlap. Lift and duration remain virtually the same.

 

[EllowViper]

Ken,
How do you like your set-up? You've got basically what I'm after less the 3:55s. PM me if you've got the time.

 

[viperrt96]

I got the 708 cam in my GenI - I love it!
I installed mine per DC's specs. I would check with the real tuners to see where the cam will work best for your set-up. I think we advanced ours something like 10 or 12 degrees from centerline.

I said the above by mistake. I went back and checked my notes. I checked true centerline first and got a true reading of 116 degrees. Dan told me to set the cam at 119 true centerline. So I only advanced it 3 degrees. Sorry about the confusing but that was over two years ago and I had forgotten some of the details.

 

[PowerKraus]

Viperrt96,

Hey, I understand. Over the past few years I've been working on a LS6 with nitrous, LS 408 Stroker, Buick turbo V6, LS2 in a Trailblazer SS, and the Viper. Including turbo tuning and nitrous tuning. Started with LS1 edit on the LS6, then EFI Live on the LS6, Direct Scan for the Buick, HPTuners for the Trailblazer SS, and VEC II on the Viper. To top if off I am over 40 (brain cell issues), so needless to say, I can get mixed up too. So far though, I have not made a hugef error, like buying a FAST system for my GN and ordering it with the 8-cylinder option



Well, after writing all that out....its no wonder I'm out of money