[FordLover18]

i have a 1979 Mustang with a 1969 Boss 302 in it we put an offenhouser tunnel ram system on it. we are running dual holley 4160 carbs and we just can't get the thing to run right. we got it to run finally but it won't idle. we get it to idle at about 2500 rpm's and when we back the carbs down so we are idleing at 1000 rpm's it starts to shake and finally dies. if anyone has any ideas on how we could tune the carbs to get it to run or what else we could try. i would appreciate the help but i know that the carbs aren't tunned right if anyone knows how to tune them i would appreciate it. reply or email me.

Evan Stott,
MustngFan@yahoo.com

[The Greek]

I don't want to ruin your day, but I think that you're way over carbed. That tunnel ram set up isn't going to idle at 1000 RPM because there is so much volume to fill that you can't establish enough intake velocity until the engine is turning 2500.

Unless this is a race only engine, the intake combination is totally wrong for a street driven car. What are you looking for with this set up? Remember this is only a 302. More details on the engine combination would be nice.

[FordLover18]

it was basically built for a show car, but we wanted the street/strip capability. one reason we had that intake is because it is the only one we could find to fit the Boss 302.

[cindys_sn95]

greek is right, it aint gonna idle to good. but sounds like you have a vacuum leak!

[The Greek]

Edelbrock, I believe, has single carb intake manifolds for the Boss 302. What you really need to do is install a single 4 barrel with 600 CFM and vacuum secondaries which is what a 4160 has. If the CFM rating of your current carbs is about 600, use one of them.

You will then have a decent running engine with street/strip capabilities. The current set up just isn't going to work. It just isn't streetable. You need to look at your engine as a package. Slapping on a huge intake system without taking into consideration exhaust capabilities, head flow capabilities, camshaft characteristics and engine displacement will result in what you have. An engine that won't idle at a decent speed and performance that is going to be a disappointment.

Again you fail to mention how this engine is built. You need to do some reading up so that you won't be throwing on unusable components and wasting money on an engine combination that is all wrong. You need to decide what purpose this engine is primarily going to be used for. This may be an exaggeration, but you wouldn't put a top fuel engine in a street car because it wouldn't be drivable. It's purpose is for racing and it's set up that way. The package is all wrong for the street.

[FordLover18]

my dad put this car together when he first got the 79 mustang it had a 4 cylinder in it. he blew the 4 cylinder and put in a 302. the 302 at first had a hillborn fuel injection system on it with clevland heads. he got a pair of 302 boss heads from somone and put them on and got a tunnel ram. it is a 69 302 block with 70 boss 302 heads and an offenhouser tunnel ram. we have had this thing running before and have drove it to shows and other places. this motor stock would put out about 270 hp but ours is putting out about 350 hp we know it will idle at 1000 rpms we have had it there we just don't know how to tune the carburetors right. if we could some help on how to tune dual carbs it would help us. but we know it will run as a street car.

[The Greek]

You first need to make sure that the ignition system and timing is right. If you don't know where the base timing needs to be, start with 10 degrees before top dead center "BTC". The ignition may be at fault and not the carbs. You may need to turn the distributor until the engine runs its best because setting the base timing won't be possible because the centrifical advance has probably kicked in at 2500 RPM. You'll have to find a sweet spot until the RPM can be dropped and the advance isn't kicking in.

How long has the engine been sitting without being run? Stale gas would be a problem with how it idles. Clogged idle circuits in the carbs another. Then there is the possibility of that vacuum leak. Spray some carb cleaner or WD-40 around the carb bases and where the intake meets the heads. If the engine speed increases, you've found a vacuum leak. Have the intake and carb base bolts been retorqued? Gaskets will shrink over time.

With any carb that has been sitting for a long time with old gas in the fuel bowls, a disassembly and cleaning and a possible rebuild will be needed. Always have the ignition straightened out first before attempting to tune the carbs.

If the distributor has a vacuum advance, the diaphram may be ruptured and the engine will suck in air from that point. Disconnect and plug the hose that runs to the carb until the engine is running right.