Gas Grade Opinion Help....

[HotRodPC]

BTW I run 89 Octane fuel and put a can of Sea Foam in it every 3rd tank.

Are you using the ESC computer or have you bypassed it??? I just run 87 octane in mine. Only advantage I see to running higher octane is if you are running your timing a bit further advanced. I don't really need the extra performance, so I just keep that timing at stock OEM setting. If I was to recurve the dizzy for quicker advance I'd run 89 too. But, it didn't seem to imporve mpg enough for me to justify it, so I just turned the timing back to OEM and run 87 non ethanol.
I don't use SeaFoam near as often as you. Maybe once every 5000 miles. I'll pour 1/2 the can into about a half tank of fuel, which is 9-11 gallons or so, and run that to empty so I don't dillute it anymore than that, and I'll put the other 1/2 of the can in the crankcase about 300-500 miles before I am changing the oil. It seems to do the trick and when I change my oil every 4500-5000 miles its still got a gold tint too it. Dark gold, but its still gold and looks pretty clean. If the oil was black, I might change it a bit more often, but it seems to be working fine, and I personally think changing oil every 3000 miles is just overkill unless you are towing someting heavy, racing, or just hard city only miles. But as a motor gets older, I will change more often since the rings get tired an more combustion can get past the rings and dillute your oil quicker. If you really take care of an engine, and pay attention ot certain things, you figure out alot about the condition of a motor just by changing the oil. That doesn't work so well if you rarely change your oil though.

 

[DesertBob]

My truck has the Heavy Duty emissions package so no computer (or I don't think I have one) or Cats. I think this was the last year you could get a Chevy truck that had a 4 barrel and ran on leaded fuel. The manual calls for 89 octane. The LT9/350M motor has really low compression (and low power) and was built for Heavy Duty work (4 Bolt Mains) like Service or Fleet trucks. I have heard of these motors running well over 300k. One guy on another board has 425k miles on his. When I say 3 tanks I mean 3 fill ups on both tanks (dual tanks) or about every 1,000 miles. I put 1/2 a bottle in each tank. A clean fuel system is a happy fuel system. Mine burns no oil and makes no funny noises. Leaks like crazy but....

 

[DesertBob]

Is the ESC the box that is on the fire wall? If so it has not been disconnected or bypassed.

 

[CknightK10]

This all sounds so messy.... I am so happy I have a newer TBI setup...... lol

 

[HotRodPC]

Is the ESC the box that is on the fire wall? If so it has not been disconnected or bypassed.

No, the ECS computer, or C3 as its called, is a box about the size of a desktop computer hard drive. Then the harness comes out of the firewall right behind the distrubutor on the passenger side. So what it has is the 4 prong plug that goes to the dizzy, and the wire that goes to the knock sensor on the passenger side of the block about say where the center freeze plug would be. All it really does, it advance the timing as far as possible without pinging. Its exactly what is says it is and nothing more. Electronic Spark Control. There there is another C3 type system also that will have leads to the carb and meter the A/F mixture also along with the ESC. But, heavy duty also has it too. I know of an 86 3/4 ton with 454 had it. Not cats, either. We swapped in a standard HEI dizzy and recurved the dizzy for a bit quicker timing advance and it worked great. But now he must use 89-91 octane of he'll ping cuz timiing advance comes on a bit to much to quick and he don't want to back it down any.


Here is a photo of the ESC computer ECM and the wiring harness to it. That's all there is to it. This is the one without carb control too. You also see the grommet where it comes thru the firewall.

 

[HotRodPC]

This all sounds so messy.... I am so happy I have a newer TBI setup...... lol

TBI is nice, but trust me, this ESC is so simple and only like a 4 prong plug in, a knock sensor wire, and a ground that's all there is to it. No mess about it. I'd prefer TBI over a Carb system though. Not known for lots of power, but good for quick cold starts, and a very durable dependable system with little to no problems provided you don't have a warped throttle body from someone working on it that didn't know their ass...

 

[CknightK10]

TBI is nice, but trust me, this ESC is so simple and only like a 4 prong plug in, a knock sensor wire, and a ground that's all there is to it. No mess about it. I'd prefer TBI over a Carb system though. Not known for lots of power, but good for quick cold starts, and a very durable dependable system with little to no problems provided you don't have a warped throttle body from someone working on it that didn't know their ass...

Ya.. I dont race my truck or anything anyway, but since im in cali this is the best way to go as far as power goes I think.. I dont have hardly any smog stuff because this engine runs clean. I bout it with the swap all BARed and everything so its perfect for me.

 

[CaliDude76]

Ya.. I dont race my truck or anything anyway, but since im in cali this is the best way to go as far as power goes I think.. I dont have hardly any smog stuff because this engine runs clean. I bout it with the swap all BARed and everything so its perfect for me.

That's what I ultimately would like to do.. is do the TBI swap for mine too..

 

[CaliDude76]

Happy to report that I finally had time to tinker with my carb. Couldn't get a hold of a dwell meter, but I did have a vacuum gauge.. so I went from there, and figured what the heck and go with what I had, and the info I gained from you all...

Anywho... I started out with just about 17-18 lbs on the gauge... set the air/mix screws from dead closed to three turns out.... it idled poorly, but as I worked it out.. I got the vacuum to read at just about 21... advanced the timing just a pinch, and gained some more out of it.

Now she runs tops!!... got the dead spot almost completely out of it, (I think i'm gonna get all i'm gonna get out of that old q-jet..lol) and even serviced/recharged my A/C.. (got my vent temp gauge to drop down to about 45 degrees)

Thanks alot for all your input for everybody who posted and replied to me on this post... You and all your knowledge is PRICELESS to me!!!! Thank you all so much!!!!!

 

[crazy4offroad]

Cool man, another tip, after you find vac-best, trim them in (lean) till you cut about 50 rpm off the tach. This is called "lean-best" and makes your plugs last longer.

 

[DesertBob]

Good news. Will have to do the "lean best" adjustment on my truck.