I've got an 89 F150 four by with a four speed and a 351W that I built, I just did the mass air.com, mass air conversion...yep it was expensive but definitely worth it, runs much better. The engines not to wild, punched it 30 over, still have the stock intake and injectors, just bumped the fuel pressure up a couple psi for the cam, Heddman headers with a true duel exhaust system. My problem is pinging...I know the compression cant be over 9.5, I run 91 octane in it all the time and I've been running my timing around 10 degrees. But I still get some rattling on the higher rpm side. I backed the timing off to 6 degrees tonight, pinging is gone but so is my power. I still get noise at 8 degrees too. Anybody have any other suggestions other than running octane booster? I dont know of any other reasons for a ping other than the timing to high or crappy gas. Any suggestions are appreciated...thanks!

 

knock sensor working...are you good on fuel pressure at higher RPMs? a weak pump will cause rattling if it cant keep up at higher rpms...it goes lean

 

Pretty sure the knock sensors workin...its not that old, I replaced all the sensors when I went thro the motor. But I've had probs with napa parts before too. I never thought of low fuel press, have to stick the guage on the windshild and taker for a drive.

 

With all your mods and changes this info might be of no value. Knock sensor as was just stated above and also we found back in the 70's that we could run more advance when we had good EGR flow. Go figure.

 

Well hearing that....is it possible my problem is that I removed the egr? My headers didnt have an outlet for the egr tube and I wasnt about to ruin the ceramic coating they had on them so I just took the valve off and made a cover for the intake. There is no emmisions system left on my truck, air pump, cat...all that crap is gone.

 

So a lil update...my trucks got a 351, I forgot 5.8s dont have a knock sensor. I checked my fuel press, at idle its got 39psi and I dont really notice much of a chance when I rev it up a bit...unplugged the vac line to my regulator and it goes up...as it should. Took a couple plugs out...and it seems like the front 4 cyls are running rich. the back four look a lil better but not like they should. I'm pretty stumped here, anybody that can help I'd sure appreciate any other ideas.

 

coil good...?

When the EGR valve is open or flowing the recirculated gas actually cools the cylinder and thus you can get away with much more timing...

you wont be pinging on the rich cylinders either as an overly rich charge also cools the cylinders and takes up the slack for timing...

check the base and back it off by 2deg until the pinging is gone...then find out why the cylinders differentiate in plug color...

mass air flow sensor up to the task...? new or old?

were the Injectors cleaned during the rebuild....

what thermostat do you have in the engine...and does it ping cold or just when it is hot...?

dirty injectors can spray everywhere but where it counts...that alone can cause issue...

 

Try some sunoco ultra 94 and see what happens, if not, I read or heard from my mechanic friend there is a thing called an octane spout, if you remove it the pinging might stop. Also if it runs hot it will ping.

 

As far as i know the coil is good....its a msd TFI blaster coil, but just for ****s and giggles I think I'm going to put the stock coil back on, back when I had the MSD 6A box on I had a terrible ignition miss under load so I said forget it.

The injectors did get rebuilt when I built the engine, and as far as backing the timing off I've done that, usually run my base at 10. I went clear back to 6 degrees before it went away but then it runs like hell.

I'm completely baffled at why the plugs are diff colors, specially why the front 4 are darker than the back 4. The maf was calibrated from massair.com when I bought the kit so I know its up to the task.

Its got a stock 190 t stat in it, I was told not to go cooler with it being as it will cause the engine to run rich.

The motor doesnt seem to run overly hot, I've had the truck for 9 years and its always run with the needle on the N on normal. Its hard for me to say whether or not its pinging when its cold, I'm a fan of warming things up and I've got 4 miles of dirt roads to drive before I hit the pavement so I usually dont drive very fast. But I guess when I do stomp on it when its cold it dont notice it.

The front ends all tore apart right now...changing ball joints and steering parts so I cant do a whole lot of tinkering right now but after tmrw I'll have it all put together and aligned.

 

I really dont like to run a Tstat that hot...160 for myself and 180 tops...

sounds like a vacuum leak somewhere on the back half of the intake manifold or something....

the MSD box should cause issue under load that would be in the Ignition module itself...backing off the timing...the MSD would just pronounce and issue already there because it is burning all the fuel and if it is having trouble leaning itself out then the strong spark of the box would really show it...

I just put a 6A box on mine and it did improve alot...I actually have some good passing power now where as before it was sluggish..

make sure the O2 sensor is reading right...you made sure not to touch the end with anything when you put it in right....any foreign material on the end will render it useless....

when you built the engine did you fluff the tops of the pistons to remove all the sharp edges...this can lead to pinging if not done...