I'm looking for suggestions on what camshaft will give the best mpg's in an iron head 3.1 engine. I found the following link while using the search function, and would like to know if anyone has any experience with the camshafts contained on the page (or any other camshafts!):

http://members.shaw.ca/bett...o/camshaft_guide.htm

I currently have a low mileage 3.1 with a H272 camshaft and will be doing some repairs. In it's current state, the engine would give 24-26 mpg on a good day. Since I do a lot of driving for work, fuel efficiency is more important than going faster at 5,000 rpm. If a stock Fiero camshaft would get the best mileage, I'm open to that, too.

Thanks!

I guess I'll mention that I'm looking at the Comp Cams 240H, as it has a lower rpm operating range and I'm looking for the smooth operation (again, don't need fast, and I know I wouldn't get it with that camshaft) with good fuel efficiency and don't plan on doing any 4500+ rpm driving.

I would suggest the Edelbrock 3790 camshaft. With my old 3.2 stroker engine and a Getrag 5-spd, it averaged about 34 mpg on a long road trip (about 6500 miles). It averaged mid-20s around town. The Edelbrock camshaft will put your peak torque in the 2000-4000 RPM range, which is good for everyday driving.

Thanks for the reply--and nice numbers! Out of curiosity, how does the Edelbrock camshaft, with its different intake and exhaust durations, compare to (for example) the Comp Cams 252H, which has equal intake and exhaust durations? Not sure I understand the reasoning for that, or what the effects are.

A different cam may help. but it's a lot work for a small return. With most cars, shifting a somewhat higher RPMs will improve gas millage, sometimes significantly whereas lugging an engine kills HP and gas millage. The 60 deg V6 with a stock intake negates using that method and will hurt gas millage as the engines get very above 4 - 4.5K RPM. With a stock intake the trick is shift before 4k while not lugging the engine. If you really want to get better gas millage, get yourself a good vacuum gauge and keep your manifold vacuum above 13", don't let drop into the single digits. That means, no shifting too soon, no pedal to the floor etc. Yeah, it's not much fun but it will save you lot of fuel.

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trueleo.com
RSpiderII@aol.com

quote Originally posted by go_home_red: Thanks for the reply--and nice numbers! Out of curiosity, how does the Edelbrock camshaft, with its different intake and exhaust durations, compare to (for example) the Comp Cams 252H, which has equal intake and exhaust durations? Not sure I understand the reasoning for that, or what the effects are.

As I understand it, longer duration exhaust helps scavenge the cylinder for the next intake event. This works best for a normally aspirated engine. A forced induction engine doesn't need the help from scavenging since the air/fuel is pushed into the intake stroke therefore an even exhaust/intake duration works best.

Also affected by duration is lobe separation angle which determines overlap. Narrower for N/A engines and wider for boosted engines. I've read the new Corvette with a supercharger has an LSA of 122*. I think most cams are in the 106-114 range.

[This message has been edited by Hudini (edited 03-19-2012).]

split duration camshafts generaly have a broader power band..I prefer this type of camshaft for any daily driven build and is all i use in anything i build unless i was building a drag car with a high stall torque converter

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--Mark--
Yellow 88 GT 5speed
87 GT 3400 swap project

[This message has been edited by 86 toy (edited 03-19-2012).]

Good vacuum is a key detail, some miss this point, though it was already posted. I'm just reiterating.

..Your best bet for MPG increase is to port the stock exhaust manifolds,if you have not done this,also use a turbo muffler (i use dynomax) It always helps to have a free flowing exhaust & add one of the EMC modified from another G.M car..
port match & Equalize throat porting with mild clean up of ports & bowl.


NO FIERO MODIFICATIONS CAN REACH FULL POTENTIAL IF THE STOCK
FIERO EXHAUST MANIFOLDS ARE LEFT STOCK,THERE IS BLOCKAGE..
When gas went to 50 cent a gallon people were shocked & vacuum gages were common to save expensive 50 cent a gallon gas..

[This message has been edited by uhlanstan (edited 03-19-2012).]

As mentioned above, the "dual pattern" camshaft will broaden the torque band. It will also help to maintain manifold vacuum. So it will idle smooth, and will have good throttle response. Drive it conservatively, and you should get good MPG results.

Well, if you are really looking for economy in the long run, swap in a 6 speed...