Finally!!

[GMDAD]

Guys,
Been 9-10 months since I've worked on the Monza (parked). Original post "Cam Choice". Anyway after the motor running
rougher, low, now erratic vac. readings & even less power,enough was enough. Tear down revealed; 5 wiped out lobes and wrong position on cam sprocket, suprised it even ran. New cam:398/420 194/204 on 112, added 1.6 rockers (couldn't help myself) bringing it to 424/448, no other changes. Runs good/smooth, 17" steady vac. After "25 min. break in" on cam and 200 miles in town driving took "road trip" to Challis, Id. One way; 280 miles, 65-70m.p.h.= 25.1 mpg and at 2.75 gal. I'm quite thankful but want more. Would dropping down to 500 cfm Edelbrock (from 600) gain me 1.5-2 mpg? Any thoughts/suggestions would be appreciated, Thanks, G.

[Sirshredalot]

How many cubic inches do you have?

The 500's are more caliberated for performance and the 600 electric choke is going to be better for gas mileage.
Even though the 600 is bigger its going to get you better gas mileage.

Do you do moslty around town driving? Highway? Both?
The tune up is the best way to tighten the gasoline belt.
Make sure youve got a good set of wires on it as well as a new cap and rotor....make sure the plug is getting all the spark that it can.
Also...run standard resistor or copper spark plugs...toss that platinum junk if you have it in there.

if you have a 350 than that 25 MPG is pretty darn good.

Is tranny a stick or automatic? If its an automatic than a lockup converter will saves you some gas....if its a stick and you dont have a really steep rear gear than adding some more timing initially will help cruising in final gear....youll need less throttle to sruise at a given rpm.

Hope this helps....but youmight be asking alot.....25 and some change is pretty good for a V8

Let us know
God bless
-Shred

[GMDAD]

Combo is 305+ .30, 1.94/1.50 f/t pistons, 200r4 w/lockup conv. 3.42 gears. All new plugs,wires,dist. etc. Yeah I guess I should just be happy with 25.1mpg and that I finally can run down the road!! B.T.W.this is now my daily driver.....hence the basically stock cam. I was figuring on smaller cfm due to the fact this motor will never see anything past 4500rpm....if even that. Besides that this is where the heads will run out of steam also. I figured on using a 500 marine carb that I picked up for 50 bucks. Don't know jets or metering rod sizes yet. Doesn't have the pvc, timed of full ports though. Can these be drilled out or am I just going to run into problems??? Thanks.

[Sirshredalot]

Those mods are going to be more hassle than they are worth because the 600 will net you better mileage and perform just as well...and you already have it installed.

If youre looking for better mileage...might look into a late model rochester. One with the coolant temperature activate enrichment plug on the top of the carb....Good carbs...most people call these the "computer controlled emissions" carbs.
The gains however would be minimal.

I would say that you are probably getting about as good as you are going to get with regards to mileage.

Sounds like a great daily driver...Wish mine was on the road...Frown.
The heads on that engine will be good up to 5500 on that 305 but I think that cam will run out before then.

Are you running headers or manifolds? Headers will net you some better mileage also....coupled with a good low restriction exhaust system.....a decent flowing muffler or two with 2 or 2 1/4" pipes.
A Y-pipe will help with the mileage and the midrange torque...but Im assuming you already have plenty of that.

Does your 200R4 have a shift kit or is it stock?
A shift kit greatlyreduces slippage between shifts and lag time which can all use extra gas...and reduce tranny life. If it is stock than Id recomend a mild "stage 1" shift kit just to make the shifts a little quicker...not "harder".

Some more small things that might add up to some gains wouuld be new bearings in the rear end and new synthetic gear lube in the Diff.
Make sure no brakes are sticking or not releasing fully.
The easier it rolls....the easier it goes.

God bless
-Shred

[GMDAD]

Shred,
Stk manifolds, 2 1/4" dual exh w/18" glasspacks, no crossover. rebuilt Stk 200r4 w/new stk.conv., rearend just rebuilt (last year). Your right....too much b.s. on gaining a minimal at best on the carb switch. A shift kit is a possibility in the near future. It is all a matter of $$$$$! The new 2 1/4" pipe & glasspacks were laying around from a buddies "forgotten project", 25 dollar exhaust system?? You bet. No tech, Redneck set up but the price was right!
Thanks, G.

[mad max motorsports]

Fresh engine?
Just drive it more, after about 5k you should see a slight increase in mileage.

Add a "CAI" hose if you don't have one already. It will improve low end torque leading to improved FE and is inexpensive.

If you have the money switch to full roller rockers for reduced resistance.

I had a similer setup on a '79 El Camino SS with 350/350 and was able to get just over 26mpg hwy.

[greg72]

I can understand the inherent beauty in a functional full exhaust for $25 , however i would trade out the glasspacks for a set of decent turbo type mufflers when i had the chance or money or both

As you pointed out glasspacks are decidedly no or low tech. In some cases they can actually rob power when the inside diameter is small enough to have any type of noise dampening abilities. Also the air inside them gets very turbulent bouncing through the louvers.

[barebonesracecars]

10-4 on those glasspacks. One of the worst-flowing mufflers out there.

I'd say your mileage now is pretty good. From this point you'll likely see only small gains here and there from tuning, but you've already been given several suggestions.

[GMDAD]

Guys,
Thanks for all the input and suggestions . Yeah this daily driver will be racking up the miles quickly........32 miles round trip everyday just to work. 3.10 a gallon here for 87octane just sucks. Trust me as soon as some "extra" money comes in that "school bus sound" when you half throttle the thing will be taken care of! That droning tone at 55 mph is really hard to stand also. As they say..... you get what you pay for. Later, G.