DD Cam and Donnelly Head

[Don M]

LSmith,



I cant talk about the DD cam. What I was trying to say is the practice of doing so is not smart for turbo motors.

One more tidbit. We are trying to cut pumping losses right? What happens to the boost when you blow it out the exhaust valve with overlap? You just created a pumping loss.



Further, any fresh air you inject into a stream of exhaust can cause the raw unburned fuel to burn late or in the pipe causing a higher EGT in the manifold.



Someone recently measured the drive pressure as high as 72 psi in a HX40 with a 12 housing. This is/was at maximum power.



One last clue. As we increase boost over the stock levels... ahh heck Im giving away too much already (censorsed)



Don~

 

[Don M]

Originally posted by JFulmer

Don, I know very little about these trucks, but has anyone ever measured back pressure on the exhaust. I do know that some of the gasser guys fight this and they say that equal back pressure to boost is optimum but it never happens, some have measured 60lbs of back pressure and usually ends up as a blown head gasket... ... ... guess I need to ask them more questions.



Jim

Jim,



Turbos being somewhat of an exhaust restriction can lead to very high back pressure or drive pressure. Imagine a camshaft with overlap designed in on a turbo motor that held the intake and exhaust valve open at the same time. If the drive pressure was higher than the boost the air flow would actually try to reverse flow. If boost was 42psi and the drive pressure was 72psi the air would definantly try to reverse flow. This creates a big effeciency problem and a pumping loss. This is a common problem with guys who hate lag and install a small turbine housing to help spool up.



Adding more overlap only adds to your problem in most cases. Not to mention at low boost levels when the drive pressure is still low the air you are trying to pump into the engine is getting pumped right out an exhaust valve. Ooopps, another pumping loss. Lose, lose situation all the way around to have overlap.



Don~

 

[Joseph Donnelly]

+++Maybe they didn’t want to loose you to the competition with you being somewhat of pack leader and in the spotlight?it's the fact that this cam is taunted around here as a cure all for the horsepower and EGT woes. But then it is not marketed in a practical manner. that makes it not worth taunting at all. +++



Extensive testing has indicated to us that the egt drop is real and can be used as an indicator, just as egt was used before the cam and head swap.



Todd, why so incensed over the camshaft? Before it was invented, you couldn't get it. It is precisely because the profit margin is small that DD can't afford to have it copied. They are still paying off the master cams, and the Cummins parts they start with are expensive--go price the 370 hp marine cam, lifters, gear, bolt, key, and retainer plate. If you don't currently buy stuff from DD, why are you upset? If you are a loyal, long-term customer, call them or me about it.



In the interest of accuracy, no slams intended, loose is the opposite of tight. Lose is the opposite of win. Taunt is a sarcastic challenge or insult. Tout means to canvass for customers.

 

[Todd T]

Ha Ha, change the subject. hey look at me, I got excited and mispelled a word. i must be stupid in that case. dont listen to me I'm just a little guy. make fun of him and he'll go away, eh' Joe.



thats OK, i do know how to spell my name and sign it on a check. chances are, you'll never see that trick though.



why dont you talk about the test base and let us know what the plans of rolling this thing out are? will we EVER be able to buy this through the mail for an install of our own?



roughly, how many folks have these now? what is the spread of the trucks and their usage? how will it work with a stock (unported) head? have you installed one on someone elses porting job? I dont pay for things i can do myself.



BTW since most of us cant get it. it is being taunted. dont get me wrong Joe. this is like looking at the nickle candy when the store is closed for a long weekend.



Todd

 

[Sled Puller]

Todd,

Stupid has two Os, Stoopid, not a U.

 

[cumminsgetme]

Finally had a chance to drive the truck today. It's hard for me to compare the before and after... ... . it's not my truck and not my every day driver. I spent about 20 min in the truck then had my brother drive.



I was surprised at how fast the temp still climbed. We hit 1500 deg around 90 mph (5th @WOT). This afternoon we headed towards Pahrump, along the way is a very good test hill which he drives a couple of times per week. Staying at a constant 70mph he said his egt's were running about 250deg cooler. Once we got off the mountain and leveled out we made a few more test runs.



I was a little hesitant to believe a 400deg drop in egt's, however I didn't tell him this. I didn't want him to change his opinion based on what I had to say. I asked him again how much drop he thinks he is seeing and told him to be honest, not justify the money he spent. He felt that 250-300deg would be pretty realistic. I wish I could test the truck more extensively but I'm realy only able to relay his opinions and help him think logically.



-Cord

 

[Cummins Corvette]

I am with Todd (if I understood him correctly). This whole "in house install for just megabucks because we think you will surely copy our precious cam" is rather ridiculous. Someone brought up a very good point some time ago. The cam in ANY truck could be copied simply by putting a dial indicator on the rocker while you stared at a degree wheel on the crank. Sure the shop manual may call for 29 hrs of labor, but we all know that it can be done in much less time. Heck, I would put money down that I could do the whole thing in 10 hours or less, and I've never personally done it. I would feel gypped if I got a cam from DD, bottom line, but as always, JMO. I am always looking for good deals, and this (jmo) is definetely not one of them.



BTW- I have spoken with someone who has personal experience with this cam, and ya, they felt gypped. They didn't see anywhere near what DD claims as far as mpg and egt. Perhaps some trucks just respond better than others, I don't know. If (more like when) I get a cam it will be from someone else. JMO

Chris AAYS

 

[Cummins Corvette]

Originally posted by Sled Puller

Todd,

Stupid has two Os, Stoopid, not a U.

LOL!!

 

[TxDieselKid]

Originally posted by Cummins Corvette

I am with Todd (if I understood him correctly). This whole "in house install for just megabucks because we think you will surely copy our precious cam" is rather ridiculous.



Sure the shop manual may call for 29 hrs of labor, but we all know that it can be done in much less time. Heck, I would put money down that I could do the whole thing in 10 hours or less, and I've never personally done it



BTW- I have spoken with someone who has personal experience with this cam, and ya, they felt gypped. They didn't see anywhere near what DD claims as far as mpg and egt. Perhaps some trucks just respond better than others, I don't know. If (more like when) I get a cam it will be from someone else. JMO

Chris AAYS

Chris,

Think how many people would try and do this, thinking it couldn't be much harder then a gasser cam. I am fairly sure that DD does not charge for 29 hours of work either.



As far as the advertising goes, might be because of the mods that the person had, and how they drive it. Most people I know that have gotten it, LOVE it.



Not trying to call you out, because I think I will get a cam from somewhere else as well.



Andrew

 

[Greg Boardman-RIP]

I drove Fred Swansons truck with the DD cam and it rocks. I can tell you that thing with a HX40 and mentals spooled faster than the little hy that would on my truck. I also noticed that when I went wot I could barely hit 1500*. That is with it turned up. It runs cooler and spools faster. JMHO, Greg

 

[Strick-9]

Cord,



Good report. Does he have a 1800° pyro or is Cade just guessing at the 300° drop? If he was pegging the 1800° gauge, maybe it's more?



What's with the 1500° at 90 mph stuff?



If it was your truck or my truck we'd test WOT EGT at 115-120 mph.



-Chris

 

[Don M]

Chris Anderson,



You can change a cam in 10 hours and you have never done it? You do realize that the tappets have to be changed too? Have you ever tried to change a set of tappets on an assembled Cummins? Do you have the proper tools to change the camshaft as well? The tappet tray, etc?



On another note, have you ever tried to price all the parts from Cummins to just change a stock cam?



Go to Cummins and price the new marine cam, a new set of tappets, new gaskets, the new cam gear (which only fits the marine cam) the long a$$ bolt that holds the gear on the cam, the woodruf key (that little fella is about 12 bucks if I remember right), cam break-in lube, oil, filter, etc.



I'm willing to bet that there are more than a handful of guys that dont even bother to change tappets when they install a new cam and then wonder why they cant get the engine to run right later.



After the upgrade of the marine cam and gear you have a much stronger set-up than before. The marine cam is shot-peened all the way to the new 2 bearing journal, it is made of chilled ductile iron, the upgraded gear is better and the bolt is about 12 inches long that holds the gear to the camshaft. Take a look at the stock gear and cam assembly one day and compare it to the marine set-up you get with DD. There is a world of difference.



The camshaft is a good value when you consider it is installed correctly by professionals, lowers EGT's, spools the turbo faster, and the added strength you need for the increased boost levels is in the cam design as well. You drop off the truck, go pick it up and trade a great product for 2500 bucks. It could not be simpler. Yes, I am getting one this summer. There are none better.



geesh!!



Don~

 

[Snow man]

I cant see why anyone would be mad at DD,its there cam,they spent untold $$ on R&D,and burned the midnight oil. If anyone doesnt like it,they dont have to buy it,they can simply design there own cam,or buy a competitors. If DD did sell it outright,it would have been copied already. What incentive would DD or anyone have to continue to spend money on R&D,and testing,to give it away? Todd,and Cummins Corvette,its so easy for you to sit there and say its wrong,if it was your sweat,money and scraped knuckles that made the finished product,you would not be so quick to sell it to anyone. If im not wrong,to anyone at the power level to need a cam-2500 is a drop in the bucket,youv'e already spent 4-5K on an auto to hold the power,it will likely blow once a year if your lucky probably 4000 on the engine between the fueling boxes,injectors,turbo or turbos,exhaust,intake,etc. . your already breaking parts if your using the power at all. all this on a 35K truck. Like Stephan has posted,he smoked his motor,due to high EGT's,so the 2500 would have paid for itself right there.

 

[Cummins Corvette]

You all have a good point. Maybe it is worth it. And Don, I have seen two cam swaps, one a DD cam, and one another brand (I helped a little on that one). In niether case were the lifter/tappets changed. I don't see why they would need to be. ??? If the benifit ever outweighs the cost (in my mind) I will get one. IMO it is not worth it right now.

 

[TxDieselKid]

Originally posted by Don M

Yes, I am getting one this summer. There are none better.



Don~

Don,

Glad to hear that you are getting one, are you going to drive all the way, or is Joe going to "supervise"?



Your not going to wait and see what Piers' cam will be like?



Serious questions,

Andrew

 

[Don M]

Chris,



Your kidding about the tappets not being changed out when the cam was right? Anyone knows that parts wear together. You dont even have to be a mechanic to know this. Dont you always return pistons to their same cylinder? Camshafts have difficult lot in the engine. The forces between the tappet and the cam surface is enormous. Not changing the tappets can be suicide to the lobes. Further if you just poke a camshaft into an engine and not properly break it in. You have just shortened the life of that camshaft exponentially.



How were you able to watch a DD cam that is not mail order or available without in-house install being installed? DD supplies new tappets with their camshafts as well, so where did they get off to?



You come on this forum a lot and make a bunch of noise and nonsense with just about every post you make. Well nature has shown what it has given you to get noticed in life. Nature also gave the polecat (skunk) a rather gross means of getting noticed or a way of being important too.



Don~

 

[Ethdee]

Lifters wear to match the cam lobes. If you R&R a camshaft and lifters, you keep them matched so they all go back in the same place. If you don't, you'll get accelerated wear down the road.



New cam, new lifters. It's always been that way, at least since I can remember.



Jim

 

[Cummins Corvette]

Originally posted by Don M

Chris,





How were you able to watch a DD cam that is not mail order or available without in-house install being installed? DD supplies new tappets with their camshafts as well, so where did they get off to?



Don~

I watched the DD cam installed by Ken Jones into the Edge Products 2002 truck. He used wooden dowels to hold up the old tappets while he swapped sticks. The new tappets must have gotten lost or something. Now that you mention the reasons for changing the tappets at the same time, I can see your point. They wear as a matched set, and although I new that, I must have had a dumb-a$$ attack when I was watching the cams being swapped. You are right; the lifters need to be changed too. How do you do that without taking the engine out? Sorry for stirring up muck, I am just learning (and re-learning). Thanks

Chris



P. S. - in both cam swaps that I watched, it took less than 6 hours. But that was without changing the lifters.

 

[Sled Puller]

Originally posted by Don M

Chris,







You come on this forum a lot and make a bunch of noise and nonsense with just about every post you make. Well nature has shown what it has given you to get noticed in life. Nature also gave the polecat (skunk) a rather gross means of getting noticed or a way of being important too.



Don~

Don~ you bully.





Chris you have had some VERY valid points, points that the "other" side don't like.



Fight the good fight man!





I find it odd that a man of Dons capabilitys needs DD to install a camshaft for him.

Surely they would send you, of all people, a cam.



If Don M can't be trusted, then who can??????

 

[TxDieselKid]

Originally posted by Sled Puller



Surely they would send you, of all people, a cam.



If Don M can't be trusted, then who can??????

LMFAO!!!:-laf :-laf :-laf



Kinda what I was thinking.



Andrew