Anyone got the specs for a 6.5 cam shaft. lift, duration, lobe seperation ect ect. Any aftermarket vendors that offer other than stock cam profiles ? I can have mine reground to custom specs, but its not cheap. Thanks

Gmctd and I were discusing the possible changes that could be made and he mentioned
a vendor that sold a aftermarket cam for the 6.5. (competition cams?)

My thought was that if you increased peak lift (pointer lobes) you could open the valves more per actuation.
The stock engine is designed to have valve overlap, so the intake stroke comes in as the exhaust is going.
Only problem with this is back pressure in the exhaust manifolds can force exhaust back into the intake stroke
killing your efficency.

Edited by: quantum mechanic

I'm probably going to buck up and take one of my stock cams laying around over to Reher Morrison and have it cam doctor'd just to see what they actually are.

Crane has offered a regrind for many years which increases lift by reducing base circle diameter - primarily for naturally aspirated engines trying to get as much 15psi atmosphere in as possible.


In a n\a gasoline engine cam timing, lift, and overlap (for cylinder 'scavenging') must be juggled to ensure adequate incoming fuel-air charge. Cam is tuned for a particular rpm band, and not much good outside of that band.


Turbocharged 6.2\6.5L Diesel - (remembering, here, that I'm speaking strictly from a practical, every day street driven reliable truck standpoint)


1 - fuel is not part of the incoming charge - fuel can be cranked in to suit - timing and lift changes not required


2 - no intake\exhaust valve shrouding - cylinder head is flat - increased lift not required


3 - Boost fills cylinder volume faster than 3500rpm flow rate requires - again, timing, lift and overlap changes not required


4 - overlap does not reduce fuel charge or incoming air charge - free up exhaust path thru turbine will allow Boost to blow previous charge remnants from cylinder


5 - power can be reliably increased by -


a- freeing up intake path to compressor, also including some minor intake port-matching (my intake had only one runner needing less than 1\16" on one wall)


b - freeing up exhaust system from (and including) turbine


c - adding charge-air cooling, most effective in towing\hauling


d - altering inj timing - factory setting is for warranty considerations


e - altering inj fuel quantity - factory limited for no charge-air cooling


f - reducing compression ratio - more Boost (fresh air) can be cranked in without exceeding original cylinder pressures - more fresh air = more fuel = more power


Alternate views welcome........

All im needing are the factory cam specs. I cant find anyone that knows what the specs are. There are handfulls of aftermarket cams out there for cummins 5.9 liter engines, and those cam swaps are providing these guys with awsome amounts of pay off with just a simple cam swap. So my theory is why cant I do the same to my 6.5 and reap some of the same benifits. Of course everything im hopeing to gain is purely unfounded because, I dont know a person anywhere that has changed the cam profile on thier 6.5. I have done every thing I can to make power, from injectors, to pistons and intercooler and turbo, and Im almost tapped out, with out delving into other areas of this engine to pull out more power. I agree with your post GMCTD that in theory a cam swap is not needed at all and the stock cam should be just fine. But I am still very interested in trying a new cam and seeing what I gain if anything from it. My whole base for trying everything here is taking what the power strokers and cummins perfomance crowd has been doing and trying to apply some of those asspects to my 6.5.. Seems like there are just very few people out there that are venturing very far into this engines, out side of the normal ,available performance parts . My whole approach to this engine build up is just seeing what happens, and if it works out, I will be suprised and if not then im back to where I started with nothing lost. Edited by: DarrenPayne

Darren,


I think some of it has to do with direct vs indirect injection, the indirect injection & pre-combustion set up of the 6.5 does not lend to much if any benefit from cam modification, I don't know this for sure but I think I remember something like that in a discussion over at "The Page" some time back. For factory specs I'm sure you could call Crane or one of the others for a replacemenmt cam & they could give you the factory specs, I could not find anything in my GM manual.Edited by: Turbine Doc

Thanks for the info Turbine, I think im going to join the page tonight and see if I cant track down that thread your talking about.Seems like all roads point there anyway in the end. guess i need to break down and pay and become a member. I will proably call crane or comp cams tomorow and and see if they can set me up with the specs. Thanks for the input guys.

Darren,

What cam changes are being made in other diesel engines?
just interested in the basics.
I have always been a fan of split duration cams
and the low end torque they make and I've wondered why I couldn't do something
similar to my 6.5's cam.
Edited by: quantum mechanic

Darren , I hope you find it part of the reason behind this site was a serious system crash over at TDP some of the archival stuff got lost, they have updated their server but alas some of the best stuff has gone to internet heaven. I do recommend though that you join there as it is also a good resource, it was the 1st site I was with. I've been there since 2000, you will find a lot of us dual post at both sites, full memebership give you access to some neat tech stuff

Might give Bill Heath at Heath Diesel a call, see what he was running in a twin-turbo 600hp 6.2L drag truck back in '93.

TRY DELTA CAMS OUT IN TACOMA THE HAVE 3 LEVELS FOR THE 6.2L


SO I'M SURE THEY HAVE SOMETHING FOR THE 6.5L

The major flow gains will come from fatter lobes. Duration at .050" is what needs to be stretched a bit. Increased lift helps some,but the little bit of bench work that I had done showed that the point of diminishing return on increasing the lift was quite low IIRC.





I put the Crane in my '96. Honestly dunno if it helped or hindered...

I can see how longer duration, with a mild peak increase would benifit flow.
Anyone ever tested a split duration cam with an increased exhaust duration?

The Theory being the sooner/longer you open the exhaust valves, the more exhaust you can flow.
Perhaps this is better suited to a higher compression 6.5 (21:1) and not an 18:1 which needs more intake compression
to make the same power.