18MPG in my LIFTED burb this weekend! And a problem...

[redz 1970 K5]

So, on Friday I installed my MSD 6A ignition. I had the headers installed on Wednesday and then I put the MSD 8.5mm Super Conductors Saturday.

I took the truck on the highway on Saturday, and no kidding my MPG was 18!!! 270 miles, 15 gallons. I topped off before the trip and topped off after the trip. My odometer is right on too. 65MPG and I even got on it a few times.

These mods definitely had a large impact on mileage since I was around 13MPG pre mods.

I only have ONE issue, and it isn't an easy one... Since I installed the headers in particular, I have a light pinging in low rpms off idle. When I am taking off from a stop, it pings off idle, probably between maybe 1000-1500 and then it doesn't ping anymore or when shifting gears??? I checked my advance, truck is at base timing and my ignition is for the most part new. Can a lean or rich condition cause pinging? I am thinking that the O2 sensor (brand new) might not be reporting the A/F mixture correctly to the ECM now because of the headers. I don't know what else it could be.

I will probably run some of this fuel down, run a 91 and see if it goes away. I am currently running 85, which is usually ok and what I have been running for months. The headers did something and I am scratching my head...

Here are a few pics of the goodies.

8.5mms


MSD


Cool mini tach that I will put in the corner in the A-pillar and dash; SOOO nice to track RPMs again.


ANY, and I mean ANY ideas on my pinging problem would be much appreciated... Thanks!

[82c10]

probably just a leak, retighten the bolts

[redz 1970 K5]

I know the difference between an exhaust leak and a ping... In your opinion, why would a minor exhaust leak cause pinging??

I did snug the bolts back up 2 days after the header install.

[82c10]

Originally Posted by redz 1970 K5

I know the difference between an exhaust leak and a ping... In your opinion, why would a minor exhaust leak cause pinging??

I did snug the bolts back up 2 days after the header install.

a header leak, and pinging sound the same to me, and the answer to your question would be because of air escaping, my buddy's truck has a bolt brole off on the manifold, and it leaks, and sounds like a ping

[84 400]

wow if your getting 18 mpg highway that is crazy! I mean that is really good for a truck of your size and lift and tire drag. Sounds really nice to me. Wish i could be of more help on the ping issue. sounds like you on the right track by switching to higher octain gas. Could also be somthing on the tbi.

[84slopwaggin]

I've heard that headers do tend to cause the engine to run a little on the lean side(carb). I don't know how this relates to a FI system. Maybe you have to relocate your O2 sensor to give a more accurate reading. I thought that there was a 02 bung welded into the collector in some applications. I'm no pro just tossing thoughts.

[redz 1970 K5]

The headers did have an 02 bung welded in. As a matter of fact, it's pretty close to the original location +/- an inch or two. I know that because the o2 sensors wire is very short and it still plugged in without an issue.

Another point I remembered when I put the facts together is that it makes the ping sound on closed or open loop AND since it's not giving any codes, I don't think the problem is related to the ECM processing the o2 sensor wrong and running too lean. The engine temps haven't changed at all.

I am really leaning towards the fuel thing right now... I will burn some more of this tank down and get some 91 in there and see if it persists. At least one less thing to troubleshoot right?

I have an Xtreme EFI throttle body waiting to go on, and with it an adjustable fuel pressure regulator and gauge hookup. It will be interesting to see where fuel pressure is at on my current system. Guys seem to think the system stock really likes 13psi or so, where it comes from Chevy around 10-11psi. That could help too. Or just add ANOTHER factor in... Maybe I should forget about that stuff until I get this figured out.

[Zoomad75]

Adding fuel pressure is going to consume more fuel. I think the lean running with headers is due to the increased scavenging effect the headers provide.

Adding fuel pressure should compensate for it. But it would be interesting to know just what exactly the O2 sensor is actually reading though. Do you have acces to a Tech 1 or other scanner type device that you could monitor it with? With one you should be able to see the O2 running lean or not. Another thing to look at is even though the O2 sensor looks to be in about the same location as stock, the exhaust tends to hold less heat when running though headers compared to cast manifolds. At lower engine speeds the O2 may not have enough heat to read correctly. That error forces different changes to happen to fuel and spark timing. Having the ability to monitor the O2 sensor reading would help prove/disprove that. Might have to go to a heated O2 sensor. I'm just not sure if the newer ones run in a compatible range for the older TBI system.

Just a few random thoughts late at night.

[Srubydo1986]

msd increased fuel economy i wonder if it would help my 350 carborated took a fi engine from my blazer and put it im my truck removed the computer junk and through on a carb that i understand.

But fuel injection was nice but the switch looked hard and i didn have my c10 at the time

[redz 1970 K5]

Well, scratch exhaust leaks as a possible candidate. I took the truck to the shop and had them thoroughly check all connections. They did find a tiny place they missed welding going into the cat, but that wasn't the issue.

It is quiet as a mouse (no pun intended), and the ping sound remains. I am going to call thorley too and see if they have any ideas.

[MylilBowTie]

I say your running lean and it wouldn't hurt to install a heated O2 sensor in place of your stock one. TBI units come from the factory on the lean side and when you install better upgrades intake side or exhaust it will show up. If you can hookup a scanner and see what the O2 is reading and take a look at the knock count it has that would help. What color injectors do you have? Engine size? What is your timing set at with the est wire disconnected?

[piecesparts]

IS IT a PING, or is it that you are now hearing your exhaust notes through the thinner walls of your headers, not the heavy cast iron manifolds that you used to have? That is common with new headers. The second thing that I would check is the exhaust leak, it is very possible, especially if you just put on the headers. You need to tighten them after the first couple of uses to get them snug. I put teflon tape on my header bolts to keep them from backing out. It works great and is easy to remove later. (just wrap it around the threads, like you would a fitting for a water line). Now that you are running headers, you COULD be slightly LEAN on your fuel mixture, better flow/same fuel thinking here. Have you considered changing your T/stat to one that is slightly cooler, giving you a denser fuel charge. I run a 180 degree T/stat, it helps. What plugs are you running? Are they set at the right gap? MSD likes their plugs to be standard (non-Platinum plugs) with the gapped around .035 to .040 . I called them just a couple of months ago when I changed out plugs on my DD truck. Are you running a computer chip, still? Maybe you should either get rid of it, or upgrade the chip.

[redz 1970 K5]

Great insight fellas, and good input piecesparts.

As it turned out, when I got my fuel down enough, I went to a busy Chevron right off of the freeway and put in 91 fuel to top off again. No more pinging. I don't think it was the octane since I am running a stock motor with low compression, but I think I had some bad gas from either my last fill up. I usually go to this little country bumpkin store and get gas on my way to work.

No more. I will just stick to the busier brand name places off of the interstate from here on. Hours after filling up, I was really trying to put a heavy load on the motor and it wouldn't ping at all. I didn't change anything else but the fuel.

As far as the plugs, they are the stock AC Delco parts right from the manual. I do want to get in and regap them an additional .005 though.

Thanks again!

[redz 1970 K5]

Ah, so I started getting the 'pinging' noise again. I figured out what it was though! Well, after installing the Thorley's, the shifter wouldn't shift beyond OD because the linkage would hit the y-pipe. Well, I found out that even when the truck was in OD, it was hovering right above the y-pipe, and it must have been close enough to make physical contact sometimes. It was causing my mystery ping.

I hacked about 3/4" off of the shift linkage and no more 'ping'! Plus I can get it through the full range and all of the way into 1 now.