QUOTE=fmc400 wrote:

I think you're getting a "placebo effect" with the premium gas. High octane fuel means it can be compressed farther before detonating than lower octane fuel. If you are running a stock engine and it doesn't have detonation problems, then upping the octane is wasted money because the added potential does not get used. If you actually put your truck on a dyno machine with 87 and 93 octane fuel, you would see very little or no difference at all. I'm saying that it's a common misconception that premium fuel makes you go faster. If you are under this misconception and you spend a lot of extra money to fill up with it, it's natural for the truck to "feel" faster. I assure you though it's not.

Anyone who wants to dispute my claim should show me documented facts and dyno charts comparing a stock engine vs. octane rating. Until someone can do that, "race gas" remains a misconception. And for people's future reference, "my grandpa always ran it that way, so you're wrong" does not count as scientific evidence.
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WH90 didn't say anything about premium gas making the truck run faster or racing or anything related to speed. He said it does a lot better on premium. The reason it does better on premium is that the higher octane burns SLOWER than lower octane gas. This slower burn results in a nice slow push against the piston and the valves as it explodes. So the valves are less likely to ping and clatter. Low octane gas explodes more rapidly. The rapid bam, bam, bam, helps loose valves clatter when cold or when accelerating up hill, giving you that nice diesel like clatter.

 

Ill try to It dont clatter real bad if you rev it up when you first start it up the truck dont run on short trips min of 30 miles a day

 

Right, it does sound like a mini diesel when it clatters

 

I would remove the valve cover. Check for a sludge like build up. On some engines, depending on the engine oil used , the short distance driven, the design of the engine, the temperature of the thermostat installed, the climate that the engine operates in, the ability of the engine to breath well or not thru the crankcase ventalation system contribute to the build-up of sludge.

Often times when the valve cover is removed the sludge can be very thick. On some engines, Handfulls can be scooped out with a scraper. This is why you have to be careful with engine oil cleaners. They can cause the sludge to loosen and then plug up the oil gallies. Restricting oil flow to the lifters and across the rockers or slow the flow of oil back to the pan. Or wind up in the pan restricting the oil pickup tube. This may have already happend if you bought the truck used and could contribute to your problem.

With the valve cover removed and everything cleaned up you can check for loose rockers and the rocker assembly. You can then run the engine and watch the oil flow. (yea, it might splatter a little) Listen for clatter and try to determine if a lifter is taking longer than normal to pump up to take up valve train slack. Using a mechanics stethescope you can probe along and pinpoint the location and source of the noise.

Yes, a screw driver, rubber hose and other items can be used for a makeshift stethescope. A few advantages of the stethescope are: They can be purchased at just about any auto parts store. They usually cost no more than $15. Since they use a long very thin metal rod they can detect noise very well and pinpoint with more precision than a screwdriver or rubber hose. The stethescope has TWO ear probes that go in the ears for stereo feedback. (The screwdriver only goes to one ear on most people) When the screwdriver is used the head has to almost always be turned 90 degrees to the side making seeing what you are doing difficult. The stethescope allows the operator to look directly at what is being probed.

A few other uses are to probe the fuel injectors for a pounding injector. That can sound alot like a rod knock, or loose valve, except it is high up on the engine. And to locate a squeal. As in the front or rear alternator bearing? Water pump? Air pump? A/C compressor? Power steering pump? Timming chain slap? Timming gear whine? All very easy to pinpoint with the stethescope.

You said the truck has no power when cold.

Another easy test is to do a compression test to determine if the lack of power is compression related or a temp/fuel related problem until fully warmed up.

SO, do a compression test on the engine when cold. Then drive it around and get it fully warmed up and do the same test again. Compare the cold and hot readings. Are they very close? Quite a bit different but basically equal values per cylinder both cold test and hot test? OR, do the cylinders each vary between each other both cold and hot greater than 10%? The results should help indicate weather the engine generally has good compression overall. Or, bad compression cold and good hot might indicate loose valves when cold and seated valves when hot.

Remember when doing this test, confir with the manual. Most require that the throttle is wired in the full open position. And all spark plugs removed. If you have any doubts about your battery not being in the best condition, hook a battery charger to it to ensure the motor will spin at maximum crank speed for each test.

 

Do you have a full six quarts of oil in it? My 84 will clatter if the oil is down a pint only. Fill to top of mark and it is good to go.

 

This was a misinterpretation on my part; I read "better" as quicker.