I am running a 415 ci TPI Accel Gen 7 ECM, Wideband O2, Dual Sync Dizzy, Aluminium Brodix Track 1 heads. My fuel is mapped in between 12.7-13.2 at WOT and it holding when on the gas, the problem is I have a horrible ping and have done all I know to correct it. My compression ratio is about 9.8 running 93 octane gas, my cam is a hydraulic Roller 277/286 .535/.550 110 Intake Centerline, cranking compression is 180 psi, timing has been checked with a light and is consistant with the ECM and has been locked out between 28-36 with the same results.

Can anybody offer any solutions to correct this ping?

 

Interesting. What fuel pressure are you running at? To me your compression seems to be a little low. When I build my 383 I'm looking at going around 10.5 to 11.0. Hoping for 10.5 though since I still have to try and make it through emissions.

Also, what CC are your heads?

 

The fuel pressure is about 40, still running the stock FPR and a Mallory 60FI pump, my heads are 67cc, I just ran the numbers and I am at 10.1.

I have been fighting this for 2 years.. luckly this is not my daily driver, its pinged with a 3 different PROM's in the stock ECM, its pinged with the Gen 7 with iron heads at 72cc and a .078 thick head gasket at 9.56:1.

I have an indash A/F guage and I know when under power I am not leaning out.

Thanks

 

10.3:1 running on 91 octane, thats the best they sell us here in Phoenix AZ. If we had 93 I would be running at 11.0:1

Did you degree your cam?

 

Man something must be way off with my motor if your okay with 10.3.... can I ask what your cranking compression and cam specs are, whats your total timing? You can PM me if you don't want the numbers in the public.

Yes the cam was degreed in according to the cam card, I want to say it was 110.

Thanks..

 

LOL, its a public forum and so are all the specs of my combo

Anyway, the cam is a CC XR276HR-12 224/230 .535/.544 on 1.6 rollers.

Timing is 36* through 4800rpm and 34* after that.

No cranking compression, the motor runs and revs silky smooth, never felt the need to check it however I think I will sometime within the week. Oh and its a 385.

She is making some damn good power and trapping 113.5mph at the track.

 

Colder plugs might help you. Any idea which cylinder is pinging or is it all of them? check to make sure you're not getting excessive oil in the cylinders, check to make sure the pcv system is working correctly, if it's not excessive crank case pressure can affect ring seal and cause detonation, also how sure are you on that compression ratio? It wouldn't be the first time that a math error has caused a problem. Also check that you have the correct timing pointer for your engine and balancer. There are different ones and they have been known to get mixed up, especially aftermarket ones, which can really mess things up because the timing light will read wrong. I assume you checked your O2 sensor to make sure it's reading correctly as well Good luck, sometimes these things are hard to track down.

Oh stupid question, but I assume your hearing the ping, not reading it off the knock sensor? sometimes noisy engine components will set off the sensor.

BTW I'm running 10.5:1 on a 406 with aluminum heads with no issues at all, even if I only run 89 octane.

 

Yeah thats some good info for tracking the problem down.

I run a fairly cool plug in my motor, an NGK 6.

I also prepared my motor to be detonation resistant:

Polished piston tops
Deburred and fully polished combustion chambers
.040 quench height
CAI
180 T-stat

If you got a problem with oil in your chambers then you are gonna have a problem with detonation.

What do your plugs look like?

You might enjoy this read, even though you really arent running high copression.

http://www.popularhotrodding.com/tec...power_squeeze/

 

I really appreciate the info, your cam is fairly similar to the one I run, I spoke to COMP yesterday to see about a custom grind to bleed off some cylinder pressure but I don't see enough difference between our cams to make that much difference.

I run a Heat Range 9 plug, thats about as cool as I wanted to go are you sure its a 6? I thought the 7 was on the hot side and 10 was the cool side.

I am hearing the ping there is no denying it, everybody around me hears it to, the Wideband O2 is brand new and was checked out by Noah at Accel before it was shipped to me.

My plugs are a bit black but I suspect thats from the 02 failure I had last week which was causing a rich condition.

I am going to double check TDC and make sure my timing mark is right and dump out of Seqential fuel mode and run Batch for now and check the phasing on the dizzy. This thing is driving me nuts.. I was seriously considering pulling the motor and building a Dish top 434 or 447 at around 9.3:1.

Thanks!

 

I dont know what brand of plugs you are running, but different manufacturers have different convensions for rating their plugs.

The only plugs I deal with are NGK. An NGK 4 is the heat range of a stock L98 motor. An NGK 5 is what they run in the highly efficient chambers of the Vortec, LS1, and LS6 engines. I run the 6 due to the high speeds of the piston in a stoker motor with a 5.7 rod.

So depending on your brand of plug your range of 9 may not mean anyhting realative to an NGK.

 

I am running a NGK 5672a-9 I believe , this is the same plug we run on the dyno for our alky motors..

I may have found the root of my problems.. my new set of injectors has a problem and one is not firing, tested with a noid light and I am getting power so I have to pull the darn fuel rail out and swap in a new one if it shows up tomorrow..

I will keep you posted..

Thanks!

 

I run the BKR6e-11

6 gives the heat range and -11 defines the gap out of the box.

 

I run around 11.5:1 with 93 octane.

I was reading your specs and everything seems good until I got to the stock fuel pressure regulator?

Let us know how you make out.

 

Check your quench gap. To effectively control detonation you need a quench gap of .04 to .05, once you get past .05 you are no longer able to effectively control detonation and you will have problems with compression ratios above 9.5 to 1.

 

I'm running 10.5 with 93 octane in my 383 with cast iron heads

 

I run 94 Sunoco and even Phillips 93 with 12:1 compression and NO spark knock according to my Auto X-ray. Of course I've got a Be-cool radiator and three fans to keep the temps at never more than 190, I've got .040" quench, polished AFR chambers, 6" rods, the coldest AC plug you can buy, and a big 241/241 camshaft to bleed off all that extra cylinder pressure. So to all who say you can't run high comp. on pump gas, check your resources. If you build your motor for high comp and are willing sto spend some extra money for good parts you can get away with this kind of compression.

 

I am not following the term Quench Gap? Can you elaborate?

 

I think I answered my own question.... Quench is Piston down bore plus head gasket thickness right?

If so in order to reduce compression I didn't deck this block so its .023 in the hole and I am running a .078 Cometic head gasket so my quench is .101".

Is this correct?

 

If that is the case then you got problems my friend, big problems.

A quech motor uses the "quech height gap" to compress air and force it out sideways into the chamber. Creating turbulance that forces even distribution of the charge. This in effect also cools hot spots that build up on the piston head and bore wall.

You gotta get that right or that dog will bite you forever.

 

Have you looked this over yet.

http://www.popularhotrodding.com/te..._power_squeeze/

 

I was reading it as you posted, all I can say is DAMN !!!!

I fully understand what they are saying and it makes sense, my problem is how am I going to keep the CI resonable and keep my quench to a min?

If I have to build a new motor its going to be a 434, but this will require a dish piston now I wonder how a dish top affects the quench?

Does anybody know?

I can get a set of alum heads with a 72 cc chamber and if I can get a piston with a 18cc dish. Deck it to .005" and run a .030 cometic gasket that will get my CI at 10.08.

Decisions...... Decisions.....

 

Dude, what are you worried about?

Just get a GM .024 gasket, be done with it.

Just change head gaskets.

 

A .024" gasket will have me at 11.3 now that has got to be a little high for pump gas.

I am not trying to be a PITA about this but I have over 4k invested in this fuel injection after the initial motor build trying to beat this ping. I just want to make the right decision before spending any more money.

 

im running 10.5 on my 406.

 

I have eliminated every option I have other then pulling the motor down, the quench gap has got to be my problem and its going to be corrected.

My plan as of now is a set of AFR 210 Race Ready 76cc heads, I am going to deck the block down to .0025" in the hole and run a set of .040 cometic gaskets. That will get my quench gap to .0425 and my compression ratio to 10.65.

Does anybody see a problem with this?

Thanks for your time!

 

Sounds perfect.

I still think you will be fine with just a gasket swap and the compression that will result if you can still buy 93 octane in your town.

10.3 on 91, for me.