402 Tune-up
 

A few months ago my Longhorn ran good but didn't have the power I would like. Lately it's running very rough, shaking and gurgling that gets worse when I give it gas. I don't have the time to tune it up myself so I'll take it to a local shop. Any suggestions on what all should be done for a good tune up?
I'll get new plugs and wires but not sure what else.

Also when I take the gas cap off it releases a lot of pressure blowing out. I've replaced the cap once already but it hasn't changed anything. Any ideas?

Re: 402 Tune-up
 

Check your fuel filter. Also make sure your running the correct gas cap. What year is the truck. You may need a vented gas cap. It sounds like your fuel filter is clogged and is building up pressure in the tank, as well as not feeding the carb. I had what sounds like the same problem on another truck. It was definitely the fuel filter. Change both the inline one (if you don't have one get one) and the filter in the inlet of the carb. JMO. Hope it helps.
SHawn
Shawn

Re: 402 Tune-up
 

It's a 72. I'm not sure how it all works but why would the pressure be pushing air out of the tank and not sucking it in?

Re: 402 Tune-up
 

Here is the list of things I do for a tune up.

plugs
wires
cap
rotor
condenser
if still running points, adjust them or replace
check belts, replace if needed
fuel filter(s)
check air cleaner, replace if needed
oil change (if with in the limits)
check diff, trans, brakes, coolant

You may have a weak spark. You may want to check the coil as well. My truck was doing the same thing, plus a starter issue.

Re: 402 Tune-up
 

Thanks for the list. Having a shop do this I'm worried about the cost. Any idea of a ballpark of what it should cost?

Re: 402 Tune-up
 

I would guess between 250-350 if done by a mechanic.

It all depends on what they replace or not. You can always say, please do this, this, and this, but can you check this, this, and this as well and let me know? It isn't one of those things that needs to be done all at once.

One of the times I did a tune up, it took me 3 weekends to do. I first did the plugs, wires, cap,condenser, rotor, and adjusted my points. The next weekend I did the fuel and air filters and replaced the belts. The following weekend I took it in to my BIL's Jiffy Lube and had the fluids checked.

Total cost was around $150.

Re: 402 Tune-up
 

If you don't know the history of the truck you may want to go a bit more in depth.The above suggestions are great if you have a solid foundation.If the engine is worn they will not help as much as if it's in good shape.
That said,the place I would start(again not knowing the condition of the engine) is with a compression test.It will tell you if the engine has good compression and if the cylinders are making even power.
If you know the engine is in good shape you may want to skip this depending on cost.