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Degree Cam For MPG? https://slantsix.org/forum/viewtopic.php?t=34772	Page 1 of 1

Author:	Rug_Trucker [ Thu Apr 09, 2009 6:31 am ]
Post subject:	Degree Cam For MPG?
Was going to degree my stock cam in the Dart for the auto and 2:7? gears. The SS/BBD is ready to drop on the engine.

Author:	Reed [ Thu Apr 09, 2009 8:26 am ]
Post subject:
I am by no means an engine building guru, but my understanding is that advancing the cam lowers the power band. On my brother's van (1983 shorty, 225/727/3.2 gears)because of manufacturing flaws in the timing set, the cam ended up being six degree advanced. I left it alone and the van get 20-21 MPG on the highway. There are other modifications that have been done to the van, but I can't help but think that part of the economy gain was the cam being advanced. i am sure other more knowledgeable folks will chime in.

Author:	Rug_Trucker [ Thu Apr 09, 2009 5:38 pm ]
Post subject:
Now I am wondering if I should drop in the mild MP cam I have. I have a set of lifters too. They are the barbell type.

Author:	DusterIdiot [ Thu Apr 09, 2009 5:46 pm ]
Post subject:	By no means the law...
Quote: I am by no means an engine building guru, but my understanding is that advancing the cam lowers the power band. You have to define 'powerband'...to most people 'powerband' for some reason equates to 'horsepower' and they never seem to grab the concept of 'useable torqueband'... Generally- when you retard a cam it raises the horsepower peak, but you loose some torque in the process- if you advance the cam, this tends to give you a better peak torque (putting it where you might be ablke to use it...like in the /mid-range), and lowers the peak HP slightly... For a 'stock' slant cam 4 degrees of advance would be OK and get you a few more ft/lbs of torque for a couple less HP at say 4000 rpm... One of the more interesting comments I've ever heard from a professional in the field was to watch your torqueband and see how it realtes to your gas mileage... oddly on my motor with the "RV cam" my torqueband was very flat over a long rpm range and my mileage was very consistent on drives... I would suspect a few others could chime in and talk about their 28 mpg and seeing that the highway rpm compares to their projected torque peak... But then again everything is very subjective to builds, cam, compression, carb, timing, climate, altitude, driving style, vehicle shape and weight, and how well you maintain your vehicle... -D.Idiot

Author:	Rug_Trucker [ Thu Apr 09, 2009 6:34 pm ]
Post subject:
Mostly highway driving is what I am thinking.

Author:	Reed [ Thu Apr 09, 2009 6:59 pm ]
Post subject:
DI makes excellent points, and if anything I say is contradictory to what he says, listen to him. I am not saying that advancing the cam makes more horsepower, but it will make more power at a lower RPM, closer to where you "need" it on a street motor for MPG. Of course, I am going off of stuff I have read in back issues of the Slant Six News, I still have yet to build a performance motor...

Author:	DusterIdiot [ Thu Apr 09, 2009 7:31 pm ]
Post subject:	Lol...
Keep going Reed, it's good to get the party started, then get some more info. It's interesting how many books are written about the 'voodoo' of cam science and timing, and 'the basic' concepts are easy...it's when you get into 'scavenging', lobe separation, compression...etc... that there's a lot going on that needs to be looked at and see how it comes along... Literally you can get good mileage from two different slant builds, coming from different directions.... and they work because they are using some of those 'extras' that you think about: In case one, by using a short overlap cam with moderate lift and moderate lobe separation (RV Cam), with 'stock' hardware you can have a great torqueband in the streetable range and get decent gas mileage... In another instance you can run high compression use a tight lobe separation that would allow both sets of valves to be open longer for scavenging, but allow some 'bleed down' to occur in cylinder pressure...but keep a 'sane' duration and valve lift, you will get the same numbers or better in terms of HP and Torque, but it may be a little finicky at the low rpm band, but that can be helped by changing the rear ratio to something kinder... Everything will depend on where you are looking to go with it and what improvements you'll make...there are some 'concepts' to learn but there is still more to look at once you think you have a handle on the basics... There is more than one way to get there...taking the path not chosen last time makes the adventure more fun the next time.... -D.Idiot

Author:	Aggressive Ted [ Thu Apr 09, 2009 10:02 pm ]
Post subject:
On the E254 grind advanced to 4 degrees is nice power with a 2.76 rear ratio. I like it allot. It can take allot of timing as well 55 to 60 degrees total for good highway mileage. I like the punchy feel of the cam at 4 degrees advance since most of my driving is between 2000 and 2500 rpm. The torque hit is strong from 1500 on up. That is where I need the power on the twisty back roads and on the freeway hills.

Author:	66aCUDA [ Fri Apr 10, 2009 6:10 am ]
Post subject:
Ted How far does yours pull to? It really comes down to what you want and when you want it. My driving habits and conditions here in the Delta of Arkansas are MUCH different that the habits I had in Ohio. We have VERY straight roads that you can see for miles on.(so we have a tendancy to drive faster) and since I can drive around most towns(and we dont have any cities) I spend more of my time at 55-80 than 45 down. Frank

Author:	Rug_Trucker [ Fri Apr 10, 2009 9:48 am ]
Post subject:
I think I am going to forget about the cam swap for now. Untested BBD is going on there and don't want to risk wiping the cam trying to get it to work. OK back on task here. Where and what do I need to advance the cam? Well just the parts, where to buy offset crank or cam dowels?

Author:	Aggressive Ted [ Fri Apr 10, 2009 12:17 pm ]
Post subject:
Frank, Quote: How far does yours pull to? It really comes down to what you want and when you want it. My driving habits and conditions here in the Delta of Arkansas are MUCH different that the habits I had in Ohio. We have VERY straight roads that you can see for miles on.(so we have a tendancy to drive faster) and since I can drive around most towns(and we dont have any cities) I spend more of my time at 55-80 than 45 down. Frank My earlier comment was referring to it not being a slug any longer at 45 mph. It is coming up on the torque curve hard at that point. The stock engine was very sluggish in that range. It pulls very hard and quickly up to 90 mph, then it levels off. I am thinking that the little 1920 single barrel can only allow so much air flow and acts like a limiter. That will all change soon this spring when I bolt on a Holley 4360 Economaster spread bore that I got from Reed. That should provide a little more air flow to find out where it stops pulling. I cruise right around 2500 rpm which is 60-65 mph with 2.76 gears and P225 60's. The car actually gets better mileage at 2750 to 2800 rpm, I am at a full 60 degrees of advance at that rpm. It gets almost 30 mpg up there. I drive very aggressively and do allot of passing on the back roads so it has good bottom end spunk from 40 mph on up. That is why my average mileage drops down but on long trips it's great and the faster the better. I can keep the vacuum gauge between 16 and 20 inches at 70 -75mph. It feels like it is right in the pocket for overall power and efficiency. Our speed limits out here force us to keep it down though.

Author:	DusterIdiot [ Fri Apr 10, 2009 8:57 pm ]
Post subject:	A couple ways...
Quote: Where and what do I need to advance the cam? Well just the parts, where to buy offset crank or cam dowels? One way to advance it is to ask for the cam ground with the advance into the lobe pattern... Another would be to buy something like the rollmaster chain set and set the crank sprocket... The more common way is to degree the cam, then use a bushing set by drilling out the cam timing gear and installing the bushing (they come in a set of 0 to 4 or 6 degrees depending on manufacturer)... the bushings are the same for all motors so you can just grab the bushing kit from MP, or Crane, Comp, etc.... Good luck! -D.Idiot

Author:	Rug_Trucker [ Sat Apr 11, 2009 6:15 am ]
Post subject:
Got the gear and chain from Cox Brothers 5 years ago. It was intended for the Duster. It showed up late. Stock cam. I was told I could drill the cam bigger and use other type parts. BTW update on Crane cams, they went under.

Author:	DusterIdiot [ Sat Apr 11, 2009 12:17 pm ]
Post subject:	Yep..
Quote: BTW update on Crane cams, they went under. But oddly my local auto shop was able to get me a bushing set and assembly lube both from Crane out of their warehouse... We're going to see a lot of changes sometimes not for the better over the next few years when it comes to autoparts... -D.idiot

Author:	Rug_Trucker [ Sun Apr 12, 2009 5:36 am ]
Post subject:
Thanks DI

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