terrrrrible miles/per/gallon

[claybill]

just took my street rod (360 auto 4bbl hot cam lean as could be done)on the first 20 mile trip....6mpg!!!!! 13 degrees timing. absolutely no leaks, and choke is manual and wide open. new plug wires..etc all just done.

i am told the cam is the culprit, and was warned that it would load up and make driving rough. well for 5 miles it was fun..then it loaded up and slugged along..great at 70-75...but damn! i guess i will get a stock cam right away!

6mpg...maybe less!!

every week is another grand!! but for some reason i love this car!!

claybill

[Plymouthy Adams]

get the stock 340 profile cam..be sure it has split duration intake exhaust..this is a very streetable cam..yet super responsive and will perform across the entire spectrum...they used this 340 cam in the later 360 E58 Police Interceptors

[greg g]

Clay, street rods are typically way over carbureted. I forget what you have for an engine but you probably don;t need much more than a 600 cfm carb. And everybody always goes with a square bore throttle deal (primaries and secondaries the same size)double pumpers.

Before you pull the engine apart, you should try to determin what you have for a carb, and then address that. Or take another spin with the secondary wired closed. also what is your air cleaner situation, nothing like a restricted air flow through a two big carb to make for an inefficient engine.

[claybill]

thanks greg, but new large aircleaNER..600 cfm 4bbl not a double pumper..

we have dialed in everythng and it still loads up ...6mpg!!!

i thnk i'll get that 340 profile cam

thanks all.

bill

[greg g]

did you pull a vacuum test, and check you vacuum advance?

[Plymouthy Adams]

that engine is best fed with a Carter AFB if running aftermarket intake..I perfer to use the late model dual plane cast iron and the thermosquad carb..the secondaries will only flow what the engine can burn at the moment as it is vacuum operated..can flow through to 850 CFM if needed..should be smooth roll-on power across the entire spectrum...mimic the 340/E58 and you shold not go wrong...

[JIPJOBXX]

Thats what holding me back from buying a 81 Ford Pickup truck with a 460 in it. Cool truck, great exhaust system and really straight for a 1000 dollars but probably gets maybe 10 MPG at the most. Anyone here have a F250 with a 460 in it?

[kencombs]

If you mean that the engine begins to lope, run rich, blow black smoke etc, the problem is not the cam or over carbed but a defective carb in some way.

Float setting, defective float, high fuel pressure etc all can cause those symtoms.

[Mustang6147]

Why would the cam make it load up??? Sounds like the carb is needing tuned. How big of a cam (lift, dur @50) You may also consider getting an exhaust gas reader. They are a little pricey, but your local dyno shop may let you use there equipment on there dyno to insure you are getting a good burn. I wouldnt dig into your engine just yet. Dyno's ussually charge $80 for 3 pulls. letting you make adj betweenpulls, and there computers will help you tune heading the right way.

Keep in mind, the cam and torque converter need to match. This is a common miscalculation, and a cuase for alot of frustration. I had a 302 with a double pumper 850 holley. It was tuned properly and I had no issues. Inside your carb is a powervalve. If your vacuum in the engine is low 6 or 7 then this valve needs to belowered to a 2.5. Stock it is set at 6.5. I always plug mine. My advice is go to the Holley website and read about this.

Edited March 2, 2010 by Mustang6147

[dezeldoc]

Bill, no matter what you do 360's don't get any millage. they are kinda like a big block chevy, run good but suck the fuel! if you want millage pull it and get a 318 and it should get close to 20.

on edit; just read you have a holley, throw that thing in the trash and put an edelbrock or carter on it, holleys are the most temperamental carb their is! power valves go out all the time, the air bleeds plug up all the time, just an all around pain in the rump!

Edited March 2, 2010 by dezeldoc

[thrashingcows]

I second the cast spread bore intake and a thermoquad carb.

I have this set-up on my 87 dodge ram 3/4 ton with a 360 auto. I run around locally and get 10-12 miles to the gallon....not great but better then the stock set-up. Also running those small primaries will help increase the fuel mileage.

TQ's are a little tricky to tune but once you get them dialed in they run beautiful.

I also have the same spread bore and TQ on the 440 in my wagon, I get 13-15 mpg on a motor with close to 100,000 miles on it!!

[Rodney Bullock]

Hey BIll, If it loads up after you run it for a while it has to be the carb. The cam is the cam. If you are running a holley and it is not the new type(non power valve blow out) I might want to look into getting one. The new Edelbrock carbs are ok however all carbs must be dailed in. If it is loading up run it then check the plugs, if you have raw gas that is not being burned you need a hotter plug. These street rods burn rich abd they need that you will hurt the set up if you run it lean.

You have to experiment with someone elses build. By not knowing what they did sometimes you have to go back and change everything. This is what I did. AS some one else said the intake should be dual plane, the vacum advance should work and if it is adjustable the better. A holley is very delicate if it does not idle well that's the power valve. when they go yopu have to idle them up alot. make sure you have the small hoses on the right ports. The distributor is hooked up to the partial vac port it does not require vac all the time. Is your trans linkage hooked up right? On a Mopar the trans has a rod coming off the carb linkage that tells the trans when to shift and engages the passing gear. Show us the engine compartment if you can.

[Andydodge]

Bill, also check the accelerator pump "cams", the little plastic ramp that the holley accelerator linkage pivots onm, they can be bought as a set of about 6-8 and can adjust the way the pump kicks in, also check that you have the 30/35cc accelerator pump and not the 50cc pump...and also change the size 12 right foot for a size 10.......lol.........lol........andyd

[randroid]

Folks,

I don't really have anything to add to this conversation other than to remark about how fascinating it is. Discussing the theorem of the balance between all the goodies that lay between our right foot and the open road is helpful not only to the setup in question but gets us thinking more openly about our own personal rides and their foibles. Thank you.

In the mid-seventies I needed to drop school to earn more money to return to school so I sold Dodges for well over a year, and I learned quickly that the 360 was a more economic engine than the 318 but knew better than to ever mention this. You should get a lot more milage than 8 mpg, and this point was driven home rather forcefully when I met a gentleman who had a blown 360 with a single small 4bbl in a late 30's Austin. I asked him why only a single small carb and he asked me how much faster than 140 mph I wanted to go in his hot rod car? I had no more questions.

Thanks again for all your input.

-Randy

[claybill]

thanks for ALL the input and ideas to remedy this problem..i have written it all down.

I have a mechanic in whom i have high faith and trust in his ability..as he is a engine builder for stock cars and etc etc....with extreme detail. settings are all written down in his logbook for "BILLS CAR'

he rebuilt the carb and set EVERYTHING knowing it was runing rich. he absolutely checked everything. carb is now documented and like new..all of the things discussed lately were addressed during the rebuild..but i am not sure of the exact settings he came up with.

i will see him today and talk about your suggestions....(or when he has time )

bill