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What makes an engine "ping" in upper RPM?

K85 Octane

K85 Octane

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I have always had this issue with my truck. It doesn't ping down low in 2nd or 3rd, it tends to make that ball bearing rattle sound in the upper rpm of 2nd and 3rd.

Example: Pulling a loooooong steep hill. As soon as it downshifts from 4th to 3rd, it start pinging and I have to get out of it until it's happy again.

I have added tons of fuel and taken away tons of fuel through the FAST programmer. My normal A/F ratio is 13.5 IIRC but I've had it from 12:1 up to 14.7:1. Always pings
I do not have my vacuum advance hooked up. Haven't had it in 6 years and it runs the freeway great. But it is gutless with hills, holds OD nicely but gutless even with a downshift.
My ProBillet MSD has the slowest springs and quickest stop put in it. At idle it's somewhere around 14* IIRC. Revving up in PARK it hits 36* @ around 3500 RPM. .......... Oh gezzz, don't hold me to that. It's been a long time since I cared LOL. I just drive it like a grandma, saves my trans anyway. But it has always been gutless.

Lastly, I just pulled the wires and dizzy out. I forgot to put the O-rings on the dizzy shaft years ago. Never bothered with it until someone said that's why my oil pressure reads lower than normal. I dunno. So I'm making some fresh wires to route things nicely and adding those O-rings. Not sure if that pertains to this or not.

400sb, TBI heads, ProProducts intake, FAST EZ, this cam....

Dyno.jpg
 
I think the tbi heads are killing your motor. Googling them, they are done by 4000 rpm on a stock 350. On a mild 400 they are over before 3500.

I'd like to see what some Vortec heads would do for it.
 
throw some race octane booster in a tank full of 91 octane or a can of race gas in your tank. get the octane up to 93-94 and see if it still pings. that will tell you if its octane related. just because the gas station says its 91 doesn't mean its 91. My dad had a Saab with a turbo'd race motor in it and that thing pinged like a machine gun when you got near the rev limiter on 91 octane (and this was in the 80's when gas was really gas). That motor just liked the high octane stuff
 
ChrisPerry said:
I think the tbi heads are killing your motor. Googling them, they are done by 4000 rpm on a stock 350. On a mild 400 they are over before 3500.

I'd like to see what some Vortec heads would do for it.
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Well, I think they are TBI heads. They are steel, but have the combustion and intake runner of a Vortec, plus I "think" the intake bolts are different, can't remember :( Also, they were cut out pretty aggressively in the runners and ported. The builder said the same thing you did so that's why he worked the ports a bunch. Wish I had a picture...
 
I have very little experience with gas engines but in the past with our race motors a ping at high rpm was a fuel issue. Like was mentioned above try boosting the octane level. 93 with octane booster if you can get it. Can't hurt to try i guess.
 
Hey Brent I just realized you said Springs in your distributor aren't using the fast electronically controlled fuel injection? Why aren't you letting it control your timing?
 
It could be a fuel delivery issue. I run iron Vortec heads and have never had a problem running 87, and they're higher compression than the TBI heads. A weak fuel pump, clogged filter, or faulty regulator could be causing a fuel starvation or pressure drop off issue at higher RPM. I'd hook up a fuel pressure gauge and see if you can rule it out. If your Fast has wideband O2, I'd keep an eye on it during a pull and see if it's leaning out.
 
You can drown away ping with fuel, but typically that's for forced induction. Getting below 13 is probably plenty for pulling hills. Is this the FAST with 3 AFR settings? Where are you adding or taking away the fuel? You'll have to read back AFR in real time to know if it's changing anything.

But if you have ping and don't know where your timing is at, check that out. You can try turning the whole dizzy back for troubleshooting. 22 degrees mechanical advance is reasonable, but 36 degrees sounds like a lot under heavy load. I would put the vacuum advance on to get 10-14 degrees and turn the base down closer to 0. This would give about the same total advance for fuel economy but dial back the timing in the higher RPMs where you're getting pinging.
 
Static compression is 9.3:1. yes, "iron Vortec" sounds like mine too haha
EZ EFI does not control spark
This has pinged with the brand new Walbro and ACDelco pumps.
Fuel pressure is set to 43psi, FAST brand though I would need to set up a camera to watch it during a pull
Injector duty during WOT has never hit 100%
A/F ratio is pretty steady around what I set it at, I never see it lean out during my testing pulls
Yes, A/F is set for "Idle, Cruise, WOT" plus the "accelerator pump" setting or whatever it's FI term is.

I wonder if I should send my dizzy out to get tested.
Soooo, I will put everything back together like I had it. I have access to a 76 station with 100 octane I could mix in. Give that a try. After that pull some timing out and hook up the vac advance. I also noticed at one point the vac advance would advance some 15* and do some of that at idle. The FAST TB nipple is a ported location for the dizzy, not manifold. Not sure which I should use.
 
K85 Octane said:
I also noticed at one point the vac advance would advance some 15* and do some of that at idle.
Click to expand...

If you are getting vac advance at idle I would check for vacuum leaks, seems like an indication that you might be dropping below 12inHg(roughly, not all vac advances are the same). I'm not familiar with EZ-EFI but I think it would make some assumptions of engine vacuum levels through the MAP sensor in order to build fuel maps and a leak might cause some issues.
 
K85 Octane said:
The FAST TB nipple is a ported location for the dizzy, not manifold. Not sure which I should use.
Click to expand...

Use manifold vacuum. Ported is for emissions. As Blue85 said, run less mechanical at idle, and let vacuum handle the low load (idle/cruise) timing.

Just curious, I know the 400's had steam ports drilled, I don't know their function, is it possible those heads were not drilled to match, and the chambers are getting hotter than they should as load increases?
 
I will try the manifold vac when I reassemble everything. Also, the heads were drilled.

I've been too busy with work to do anything :( and the last thing I did was pull the leaking $$$Griffin radiator out for inpection. BOTH Griffin radiators are leaking!!!! C10/K5
 
K85 Octane said:
I will try the manifold vac when I reassemble everything. Also, the heads were drilled.

I've been too busy with work to do anything :( and the last thing I did was pull the leaking $$$Griffin radiator out for inpection. BOTH Griffin radiators are leaking!!!! C10/K5
Click to expand...

If you've got the time and inclination, depending on how much advance your vac canister will pull, if you run base timing at 8*, you might be able to get idle up around 20*, which may make it idle really good as long as fueling is ok.

Been a long time since I dealt with a non-computer controlled timing setup, but IIRC most of the 70's and 80's GM stuff ran around 8* of base timing, so I imagine you shouldn't have any problem starting it. From there it would be a simple matter of advancing/retarding the distributor if you notice any ill-effects under specific conditions.

If fueling is enough (12-13-ish to 1) when it's pinging, I would not try and crutch it with more fuel. And as fueling and timing are inter-related, when you change timing, fueling is likely to need some tweaking as well.
 
Stop looking at fuel and get serious with timing. Whats the real total mechanical advance? Is there vacuum advance? Free revving an engine will get close to what you want but there is no load. As you put load on you are getting ping, thats timing if you have changed the fuel as stated. Slow advance with a cam of that size will make it pretty lazy.

Now on to fuel. 13.5 is wrong for the fuel today, unless you can verify its true ethanol free...... If you cant, you need to be in the 12.5-12.7 area under power.
 
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