hey guys with wut sin my sig i get like 4-7 mpg and its absolutly horrible. now is there anyway to help this out cause between this trans and gas my car is for sale at the momment. thanks guys

Theres gotta be something not working right. Did you check your plugs, timing, how does the car run? I think with your setup you should be getting at least 13mpg.

car runs fine, its a bit rich, the plugs migth be fouled but i don't think that woudl matter much. and the timming is at lik 8 i think

Get rid of the cam. It is too big for mileage and bigger than you need for street power. Get one with these specs. 214/224 @.050 .442/.465" lift on 112 centers. This cam or one real close to it will have much more efficiencty and torque at your cruise rpm.
And in your overall usable power band. Don't go any bigger.

Then you can lean out the primary side of the carb a few steps.
(Metering rod change.)
Ignition timing should be something like this.
12 to 14* initial advanceing to 32 to 36* at high rpm 3000+
with 10 to 15 deg of vacuum advance at high cruise.
You can regain the peak horsepower of your big cam by porting your S/R heads. There is tons of room for improvement here.
Port match the intake and head ports too.
Combine the two (mild camshft and porting) and you'll be farther ahead everywhere. Mileage, power, driveability.
Selecting a cam that is too large for good overall street power and mileage is probabily the most common mistake.

Lean out the carb primary side, downsize the camshaft and improve the cylinder head flow, increase the compression ratio to as close to 10:1 as you can, (thin gasket/ head shaveing) and optimize the ignition timing and you'll see your overall street performance and mileage really improve.
Then you'll go faster on less gas and enjoy the car again.

Your going to need a calibration kit #1480 or depending on how lean you need to go #1487. Edelcrap doesent reccomend any 750cfm carbs for small blocks so dont be supprised if you fuind yourself working up from stock 1406 specs and still find yourself rich, especially on the secondary side.

Hey!
I'd like to jump in on this one as well, rather than starting my own post. I'm running the motor in my sig. (detailed specs. of the Holley kit can be found here on Holley's website: SysteMax Kit Specs I haven't gotten the engine fully broken in yet (probably 250 miles or so on it), but so far, with my 6 speed and 3:73 gears I'm really lucky if I get 10 mpg, with my 600 cfm Holley (was on my old 305, going to upgrade to a 750, per Holley's recommendations) I am really hoping to be able to get 20+ MPG out of this setup once everything is tuned. Is that an unreasonable goal? I really hoped that throwing in the 6 speed would help my fuel economy, but so far it's no better than with the old 305 and my T-5. Any thoughts on this? Also, I'm planning on getting a 750 Holley vac. sec. carb, which is what Holley recommends for the SysteMax kit, anybody have an opinion on what might be a better carb, mileage vs. performance-wise? Any thoughts or suggestions are greatly appreciated!!!

Thanks!

-Paul

yea i coudl downsize the cam and make it slower but thats pointless, this cam is fairly mild.i am not gonna rip apart my engine at all cause all the parts and matched and it runs its *** off. fastest car me and my freinds have drivin in all motor and its mild. i am just lookin to see if maybe i can put a diff carb on or do sumthing easy to help it. also i hear u can hook a vacum guage your carb and tune it till u get the highest vacum reading and u are tuned. now is this true?? i am gonna start running synthetic oil, change my plugs with some good one, go down one more step with the metering rods and see how it is. oh yea and if any1 can help me with my electric choke let me know cause i can;t get it right. thanks

Your cam isnt a real killer but its not hardly mild considering its not somthing used for a daily driver. Try a smaller carb or the calibration kit I reccomended. You will find how to use a vacuum guage here http://www.thirdgen.org/techbb2/show...hreadid=148047

good luck!

It's not really pointless to change the cam for better mileage--that is what you asked wasn't it? Sure it will hurt power, but mileage and power tend to be opposites. Sounds like you and your friends run it really hard--what is the mileage when driving on the highway nicely. I can get close to 20 with my 82 camaro on the highway if I drive nice, and less than 5 on cruise night when I'm ripping around town. Smaller carb with a leaner calibration from the start like a holley 600 vacuum secondary might help mileage, but it could take some power from you. Highest vacuum at idle will adjust your idle mixture(only the idle mixture), but could help mileage if it's idling way to rich. Synthetic oil won't help much. Plugs will help if the current plugs aren't working correctly. Sure we can help you with the electric choke problem--exactly what is the problem? If it's not opening all the way, that will kill mileage.

89 Formula:
You making a dangerous assumption that swapping cams
to a "smaller one" will slow you down.
The small *potential loss* in peak high rpm horspower
will be more than made up for in a gain in overall power thru the usable rpm range. Big cam timing and stock cylinder heads
don't work that will and are very inefficient.
especially when combined with a stock low stall converter and modest gearing.

Your car may feel like a killer machine, but the tale of the tape
can be a real eye opener. The " Butt Dyno" can be very deceiving.
Have you ever run it at the track and got a time slip on it.?
Look in the reader's ride section of this site for my car and see if it will run that fast in the quarter mile.
Not likely eh..... Can't be that wimpy of a camshaft eh.
I've tried that cam u have, before. It does have a strong top end charge, and definatly has a cool idle ,,but the smaller one is better overall. For a car used like yours and mine. And way better on gas.
Your 230/230 .480/480 cam needs high gearing and a 3000 stall converter
to keep it in its best power band. 3000 to 6200 rpm.
Also needs more headflow to work well.
Try the easy stuff like playing with the carb and ignition,
I know you'll pick up some gains there.
But if it still is pretty harsh on gas, them consider a change in
your build. This cam and lifter set Is like $100 (sorry $79)at Summit.
It has much stronger low end grunt and pulls strong to 5000/5500. Better overall net (as installed power)
especially if you improve the heads for more flow.
Next time your out cruising have an eye on your tach (while your sweating over the fuel guage sinking) {sorry} and see
what rpm you cruise at and what rpm range you usually use.
camshaft selection is always a compromise, trading low end for top end. If that was the ultimate best cam *for you* Comp Cams wouldn't need a catalog, right.

Just some food for thought..... Good Luck

well i woudl really hate to change my cam cause thats alot of work and i only have 1300 miles on the engine.the cam makes power form 2-6 and i usually keep it under 2500 to try to save some gas. the car is a stick and i have 3.27 gears witch are to low for the engine but i can't affored gears for a 9-bolt rigth now. being that i am only 17 and money is hard to come by i am thinking that i might sell my car for leik $5-5500 and buy a little 4 cylinder car or a truck thats good on gas and then save and build sumtin fast on the side. cause no matter wut i do with this set up i am lookin at liek 10 miles to the gallon max stayin out of the pedle and thats a bit pricey when u run high test gas. now if i change out my cam i will be getting smoked by the stangs here and all they have is bolt ons and are 13.6-9. i don;t get it, mayeb its there fuel injection or sumtin and they all get great gas milage. well thanks guys

Well for $79 and some gaskets and an afternoons work,
you could find out what those pesky mustangs are doing
that seems to work.

Having been there , done that, I think you'll be plesently suprised all around.

wut do u mean? u lost me, i am guessing u mean spend the 79 bucks and get a new cam? cause all the stangs around here have the biggest cams with stock intakes and ****. liek these things sound like 11 secound cars. so i don't get it

What you have is not working. It's hard on gas and don't go either. Obviously something is wrong.

Camshafts don't make horsepower. A big cam by itself will not make power. The head and induction system has to flow.
AIR. The cam wants to operate at high rpm but the heads
can't breath well enough to fill the cylinders at high rpm.
So the motor doesn't make any power.
If you improved your cylinder heads to actually move some air
then the motor would get a good breath of air at high rpm where the cam works and you be making power.
This motor would still require a high rear gear and converter
and would still be hard on gas. But it would go good.

Why not improve the heads by porting them with bigger valves
so the motor makes power at high rpm and then use a moderate cam so the motor has a wide powerband and is efficient at
the rpms you drive at. It will still make real good power
at high rpm. better than you have now even with the smaller cam.
You'll have a faster car that is better on gas.
You S/R heads barely flow much more air then a stock 250HP smog head. as you get them. But they have lots of potential and can be improved a lot. They were designed to be a superior casting that replaces a stock GM head that if you want, you can port them out and have a good high horsepower head. It's up to you to port them.
Look at the LT4 corvette motor and the LS-1 and LS-6 corvette
motors. Good breathing heads and a moderate cam.
Good cruising mileage and loads of power. Thats how I build my motor. Good heads and a moderate cam. I get pretty good mileage and it goes like hell. Faster then those Pesky Mustangs.
And I can afford to drive it. It also sailed thru a smog test.
The big cam/ poor breathing head package never works and just emptys your wallet. But the moderate cam/ good head package works pretty good overall.
If you drive with a lead foot all the time you;re going to use more gas. No doubt. But if your motor is efficient in the range
you use it ( moderate cam timing) and good breathing heads/ induction and you drive like you got an egg duct taped to the gas pedal you'll be suprised.

You carb is probabily too rich and your distributor probabily needs attention but if you combine all of the above you'll have your cake and get to eat it too. Then what's your car worth? $Worth keeping.$ Won't cost you $5500 either.

quadgoat:

I'll bet you can guess what my adivice is going to be...

Check out the optional 50state legal cam for your System max
package. Much smaller. Theres a reason for that. More efficient in the rpm range where they test for smog at and more efficient
in the range you cruise at.
Your present system max cam is even bigger than the above poster with the bad mileage. makes serious power on the dyno
but eats fuel on the street. Because it it not in its best range
at the speed you cruise at.
A smaller cam like the one above will only give up about 10/20 hp
at best under the "as installed" conditions ( rear wheel power)
it will be more efficient over a wider range and be a big step in the right direction to doubleing your poor mileage.
Only $79 too.
You probabily could lean out your carb a bit too and play with the distributor and get some gain. but don't expect your car to cruise efficiently in 5th or 6th with a big cam.
At least you have a decent head so your not that far away.
The 750VS 3310 carb can work well too. Again the primary jetting is a little rich out of the box. Change the 72's for some 69 or 70 primary jets
and mileage and cruise will be much cleaner. You can up the secondary jetting a bit to compensate at WOT,,, if it needs it.
Try that on your 600 VS carb. Get the primary jetting down to
at or near #62 jets and then up the secondary jetting to about #75/76 to maintain WOT power.

Just for reference, the Summit PN for that cam and lifter set is
SUM-K1103 $79US plus shipping.

F-BIRD'88,
haha, yea I had a feeling that was coming. Well, I will definitely keep that PN, but for now I think I'm just gonna mess with the carb some. I just got the motor in the car and I don't feel like putting it out of commission for a cam change right now, but from what I've read out of earlier posts in this thread it sounds like a cam change is what I'm really going to have to do to get maximum fuel economy. I definitely appreciate your input and I will give the jet changes a shot, you think I should just stick with my 600 for now? or would it gain me anything to grab a 750 vac. sec.? One thing that I've definitely noticed about my motor is that it really runs smooth, it has a bit of lope at idle, but not as much as I would have expected. The motor really runs a lot smoother than I expect a big-cammed motor to run. I can even drop it in 6th gear at 45 mph, taching less than 2000rpm and she'll respond and go fairly smoothly, which surprises me. Is that weird, or am I weird? hehe

I had the 3310-S 750 on my '69 GTO with a 400 big block and it would get something in the vicinity of 13-14 mpg around town with the muncie 4 speed, but I don't know what that motor had for a cam (how embarrassing is that? lol) In any case. I suppose swapping out a cam isn't all that bad, and maybe I should do it sooner rather than later. I really appreciate the help and input :-D

-Paul

Paul Run the car at 45mph in 6th at low rpm , witha vacuum guage hooked up to manifold vacuum.
Read the guage while doing theis low cruise in 6 th.

Pull the primary bowl off and see what vacuum valve is stamped on the power valve. It must be .5 higher then the lowest guage reading at cruise in 6th. Other wise the power (enriched)circuit is on. (powervalve open).
If the guage said 4", get a 4.5" powervalve.

Your Old GTO likely had a cam with very simular specs
as this summit cam . The old 068 "S" cam had 212/224@.050 duration and .4xx lift with wide lobe separation.

Okay, I'll do that, I'm gonna be home from college for a month of Christmas break, so I'll check that out. Should I just go for it with my 600 cfm vac. sec. carb that I'm running now, or should I grab a 750 and work on tuning that? I guess I just need some help deciding if I should get the 750 or just stick with the 600. If I do the vacuum guage check though it should be the same no matter what carb I'm running, since the engine will make the same vacuum with either carb, right? That would mean that if I do it with the 600 I could just swap the correct power valve into the 750 when I get it, right? I've never tuned a carb before, so forgive my ignorance. I never touched the 750 I put on the GTO, just dropped it on and drove, so I'm learning all about tuning as I go Anyway, I really appreciate all the help you've given so far, and if you have any input on the 600 vs 750 debate or any other suggestions they would definitely be appreciated!

Thanks so much!

-Paul

I'd work with the 600 for a while. It will work well
wonce you tune it. made a mistake . If the vacuum guage says 4"
at cruise in 6th, then the right power valve would be one with a rateing slightly lower like 3.5"

If the guage says 5" get a 4.5" power valve.

The 750 will make more power but the 600 may be a little better on gas once dialed in. You can buy good used 750 3310's.
they are quite common. Usually only needing a rebuild kit.
When you get one and get it dialed in, then you could sell off your 600. net $0 cost.

I've had the same Holley carb for like 30 yrs. It's actually a 715cfm VS Ford OEM 427ci carb from the 60's. Just keep moving it from car to car. I also have a Edelbrock 750 #1407 which works well too. easy to tune. They both perform the same. Quarter mile et and MPH.

Thanks so much for all the help! I'll do the vacuum check when I'm home and get the power valve taken care of, I haven't done much highway driving so I'll try some and get a good reading on how I'm really doing mileage wise, but I really appreciate all the help and advice! Thanks so much!

-Paul

89formula#1, FBird has given you some solid advice. i've yet to see him steer someone wrong so you can trust his judgement