Earlier this year I took my car out and ran some decent times for a first time down the strip. Fast forward 6 months or so to October 13th this year and I make it out to the track again. Things go sour. First run of the night when I am in third gear about 5500rpm or so the revs stop climbing and start flatlining like valve float, I keep in it until I hear a backfire through the intake and through my bypass valve.
I check everything after the run, looks good. I turn up the timing a bit seeing if that will help, my wot timing was set for 25 degrees, this time I had it to 28.
After half track again same thing happens except I hear a pop and lots of ticking. After the race I pull over but don't see anything obvious. I was able to limp the car home. When I got home I saw my valve cover breathers were expelling much more smoke then usual.

Today I pull my valve covers and remove all my supercharger plumbing. I see the loud ticking was coming from a blown header gasket. My valvetrain looked fine, pushrods still rotate by hand with the valves in the closed position, no slack anywhere, all polylocks still tight. With engine cranking (fuel/spark disabled) all my rockers are moving fine. Valve train appears fine.

So what caused this rpm floating issue when I had no issue last time out racing 6 months ago?

I think the excess smoke came from burning oil because the header gasket blew between the 3/5 cylinders and I saw that my valve cover gasket was toasted there too. The exhaust gases probably were burning up the oil inside the cover.

I also found my knock sensor (one wire) was cooked against my header, I have a theory but I am not sure how knock sensors work that perhaps the wire that burned also was grounding and perhaps causing spark retard?

If anyone takes the time to read and analyze what I wrote, additional input would be awesome. Thanks

 

How new are your valve springs? I would take a close look at those. Just throwing it out there.

 

I wouldn't think that I could tell someone that runs in the 10s anything they didn't already know. I believe that the only rule of thumb about valve float is that whenever you run into it, the next time you encounter it you will be at a lower RPM. This will prove itself out over and over until something breaks or it floats at 3000 RPM. Check your springs.

 

Springs are the stock 1.55" .650" max lift that came on the heads. The heads only have around 1000 miles on them. I am at .602/.598 lift with my cam and my 1.7 rockers

 

If it was mine I would pull a couple off and test them. If the quality of the steel in the springs was questionable, you just never know.

 

The above and actually pull the pushrods out to check them all for straightness. Roll them on a glass table or something very flat
Make sure no springs are broken, compression test wouldnt hurt.

Do you run a fuel pressure gauge when its under load?

WIhtout a knock sensor you could have hurt things. Running it again probably not a good idea after the first run but its done.

 

Yeah it may be springs. A cam like yours may be beating them springs up and they no longer can control the valves

Whats specs on the cam? Hyd roller? Do you know what the pressures and rate the current springs are?

 

The knock sensor not being on line with a burnt wire would be of interest to me if it where mine. Certainly would effect the advance of the ignition timing. I wouldn't hurt to check the valve springs as normal maintenance either.

 

stock springs.would change them asap

 

comp cams hydraulic roller, the nitrous hp nx288hr grind, 236/258 duration @ .050" .520/.540 lift (1.5 rockers) on a 108 centerline. I can provide more info if requested. No info on the springs, they are stock springs that were per installed on my edelbrock vic jr 77629 heads that were just advertised as 1.55" springs good for .650 lift. I can't find more info on them.

I have a mechanical fluid gauge on my fuel rail under the hood I use for checking idle pressures with and without vacuum to the fpr. I run a -10 fuel line with a aeromotive A1000 pump and a sumped gas tank. I dont think fuel flow is a problem.
My max timing at WOT is set for 25 degrees, i moved it to 28 for the second run that made no difference. A false knock sensor due to my burned wire would only lower the timing further up to a maximum of 10 degrees.

not stock springs, but stock with the provided cylinders heads I mentioned above.


Thanks everyone for looking over my thread. This weekend I will re install a new knock sensor wire and put back together my new header gaskets and see what happens! more input is always appreciated.

 

Dont believe the springs would be an issue unless they are solid roller springs on hydraulic lifters. Could be collapsing but if it ran fine awhile ago i wouldnt think it be a problem now.

Kinda sounds ignition related like breaking up due to lack of spark or something. Fuel should be plenty but id definately look it over as well. Fuel filter good? Pumps not faulty? I had a friend have a similar issue. Was a bad a1000 pump

 

Well dig in there and let us know what the heck you find out bro.

 

If I still have issues after putting it back together do you think I should swap spark plugs or at least inspect them? They are fairly new. I think they are standard autolites. If it is not spark then fuel pressure would be the next thing to look at correct? My only fuel pressure gauge is a mechanical one on the fuel rail, if I was fuel starved wouldnt my AFR show me going lean? I do have a wideband for the holley hp auto tuning afterall. At least this way I will know if its fuel or spark related.

Will be firing it back up monday!

 

Fuel pressure is something to look at. Definately check plug wires and spark plugs. Go over the basics. Ignition i would think would show up any time any gear but in 3rd thats the most load so it may just have issues there. If its fuel it may be most noticeable by 3rd gear because of the increased load as well.

Valve float could show at any time but the last motor i helped tune the float occurred most notably in 3rd gear. So thats also a possibility.

 

On my turbo'd 1981 Malibu using the old style Accel 6 ecm I had the same thing happen. The knock sensor shorted to the crossover pipe, all the timing was pulled and the exhaust manifold gaskets fried. The exhaust got really hot at 6* total timing. That's my bet. Other than that no harm was done. Good Luck!

 

Ya bud, this is what I am banking on as well. Thanks for the positive outlook!

 

If youre running race fuel id change the fuel filter too but it does sound like an ignition issue.

 

91 octane.

 

Well hope you find out what is wrong with her today. Let us know what you are finding out.

 

Weird i discovered a similar problem on my own car this weekend but not exactly like yours.

I hit a "wall" around 6000 rpm on high boost which is 14-15 for me at the moment. Low boost 6-10 i havent noticed it. Pulled to 6500 or so. So i am thinking either ignition spark blow out problems or valvesprings. However i dont have the popping or ticking or any other problems like you describe but i am gonna look into my plug gaps first. I wouldnt expect valve float to stop motor from pulling rpm. I have seen bad float and yet still pull rpm after it floated. Hopefully only ignition related

 

I have every monday/tuesday off so tomorrow is my iroc reassembly and drive day. Ill have results and hopefully you do too! If I still have issues I am going to try a spark plug swap. What kind of timing do you run on street gas?

 

Mine cut out on me at the track kinda like that once,turned out to be corrosion in the the plug from fuel tank/pump to the body/plug connector..

 

Mine is very aggressive but its all in the heads... My old setup with afr's took about 34 deg at wot n/a and from there i went down 1 deg per psi boost or so. I was at 27 deg at 6 psi with afr's. Now i am at 36 deg. 11 psi i used to run about 18-19 deg now i am at 33. At 15 psi i was at 14 deg timing with AFR heads. Now i am at 25.

Huge difference with this setup and i would not advise these numbers. 1 to 1.2 deg per psi is a safe start but you mileage may vary. Depends on the heads

 

Well I put the engine back together and it fired up fine but the valve cover smoke is still really excessive and coming from both covers. My oil is not registering on my dipstick. I topped off the oil with about half a quart before driving 40 miles to my house from where I was storing the car. Only from my house I drove another 60 miles round trip to the track where I had my two drag races. I don't see how the oil would have been consumed that fast when I had no previous consumption issues but perhaps I starved the motor for oil and fried my piston rings?

 

Need to do a leak down and compression test perhaps to get an idea where its at.

 

I would think he would have a miss if it was a piston problem. Blowing back oil sure does sound like a ring issue. Got me to thinking about this chart that speaks about different ring gaps for applications.

 

You can see with supercharged application a pretty wide ring gap. When the ring ends butt against each other the ring flips scoring the bore and thus pressurization of the oil which would force the oil into the top haft. I hope I'm wrong for his sake.

 

Orr-it's not that I don't totally agree with you.I just wanted to add for the readership that short of a clue to which cylinder to look closely are there isn't anything in a test that replaces the need for a teardown and inspection.

 

Well it ends up being fried piston rings.

What should I do, bother with pulling the motor and doing a new ring and piston job, maybe taking my block to .040 over?

OR..

budget 6.0 iron block build?

 

Re ring hone would be easier cheaper i would think

My issue wasnt plug gap. I gotta check the springs. Head and cam guy may have miscommmunicated and put them in at wrong install height. :doh

 

Oh damn, sorry for rubbing my bad luck off on ya.
at least it's winter, right?

 

Have you figured out the cause of the ring failure??. Was it ring gap??. Where you retarding the ignition on the top end??. Was it too hot??. The way I am thinking,sure you can hone it but I would think first you would want to know the root cause.

 

Yup i am done for the year. Track closed and i an not finishing new mods anytime soon. Gonna look at springs this weekend but get it ready for new brake system and general maintenance

 

No, not really.. Gap was custom filed by myself, Maybe I made a mistake back when I filed them but I did adjust accordingly to a supercharged application. This was not my first time filing piston rings either though so who knows. Engine never got over 220 and that only happened on one long drive about a month ago. Either way I gotta pull the block and get it prepped again.

What do you guys think of Total Seal Gapless rings?

 

It has been a while and ring gap was the original failure that caused my pistons to explode. I ended up going with Total Seal rings but not their gapless design.
I ended up getting a new block and starting with another 383 build this time with diamond pistons, lower compression (8:1) and one step down smaller cam (see sig). All in all, I got it fired up and moving today and next step is some city driving for fuel tuning.
I also backed off my timing at WOT from 25 to 20 degrees and scaled it across the board so at my lowest rpm I am sitting 2 degrees lower as well once in boost. I am playing everything more conservative and will work my way back up from here in the tune.

Pics and video for anyone that cares to see an update.





click for video
https://www.facebook.com/photo.php?v=686117231403312

 

glad to see you got it back together..

From personal experience I don't think insufficient ring gap was your problem.

More likely it was a combination of: insufficient octane, too much boost, & too much timing which lead to detonation, and that (detonation) is what damaged the rings / pistons. Having a shorted out knock sensor did not help matters.

Perhaps 91 octane premium is all you can buy in your area at the gas stations But at the track, if I were you, I would use 100 octane unleaded, that will offer you an extra margin of safety when racing.

Nothing wrong with being conservative with the tune until you get this sorted out but try to run a higher octane fuel..

In the long term you could develop a "street tune" for 91 octane and a "track tune" for 100

I would not push the envelope with boost and timing on 91 octane fuel on the street or at the track.

Even though your static compression is a low 8:1, under boost & WOT your dynamic compression may raise to the point that 91 octane fuel begins to cause detonation.


I took the NA route with my build for now, but long term I plan to do a F-2 with a blow thru carb.


Good luck and keep me posted.

 

Thanks, I also have a methanol kit ready to go. It is just an on/off kit. I was thinking starting a switch at 6psi with it.

 

Good to hear you are back together. Lower compression will help this setup but then again smaller cam will keep cylinder pressure up so it may offset alittle

Good idea to make sure you are way low on timing and work your way up. 91 is low octane but you can live on it with a good tune. It just wont make power like a 93 oct or higher setup will but wont be far off a 93 tune. Thats not much of a difference lol

Once you creep up on the tune i'd say go with a meth kit since you arent intercooled. Should help prevent detonation. Cooler charge is worth its weight in gold

 

I would spend the money and get an air to air intercooler, I assumed you had one?

Shoot for high 11s low 12s on your AFRS at WOT. The richer mix will help keeps things cool.

But without an intercooler you can't control air intake temp. meth inj. will help but I don't think it will be enough with 91 octane.. unless you dump a lot of fuel at WOT.

This is what E85 guys do... they run a really fat fuel curve... because even though the fuel is only 94-99 octane the alcohol has a greater cooling affect than gasoline, but you need to run it fat... high 11s low 12s afrs using the gasoline scale.

with 91 octane and no intercooler I honestly would not push more than 6-8 psi.. until I knew the tune was sorted out..

You need to get into the habit of pulling and reading the spark plugs (really reading them with a magnifier to look for signs of detonation etc.) .. don't rely on AFrs alone.

 

If you ran straight meth in the injection kit and ran a large nozzle it would be enough for his boost levels and 10 sec power. For some builds if you rely mostly on meth as the fuel from injecting through huge nozzles then you run risk of motor failure if meth pump dies. Your gas tune has to be leaner to allow meth to become your primary fuel and if meth pump dies, your left over lean high timing low oct gas tune will certainly kill the motor

But you wont need alot of methanol to get decent cooling effects for 10 sec power. Every little bit helps but an intercooler is always a good idea

 

IMO would be more comfortable with an intercooler versus a pump as the primary means of lowering intake temps. It has to be a bottom feeding intercooler with this chassis

 

Why cant I run an intercooler to be fed in the front two pockets where foglights used to be?

 

I suppose but that would make for very long slender (custom) sized intercooler. and I am not sure it would give you the surface area needed to cool the charge.

I am by no means and expert with this.. If I were you, why not contact Progcharger and see what they recommend for sizing.

I am familiar with a 3rd gen Formula with an intercooler.. bottom fed so
I know it is possible.

 

Formulas dont have an open bumper like our camaros. a nice big 4inch fmic will do wonders on the front of his car. Id keep the meth kit on it also.

Travis get the biggest treadstone fmic you can stuff under there. The one orr has is a nice one.