Went to the race track today and noted a problem of missing/surge/thrashing noise at about 5300 rpm's. Could this be valve float?
I am running 1.6 full roller rockers and stock valve springs and camshaft. Do I need better springs with this set up?
Jim :confused:

 

That would be my guess.

When you do new and stronger springs, toss the oil shredders atop the springs and consider Ti retainers to push your valve float even higher.

This is my setup with ProMagnums and no float at over 5,600rpm.

 

in a word, yep.

Welcome to the world of small block Chevy...

how to fix... thats a good question. If you really wanna raise the redline, you need a different cam. Also, get a roller cam. roller lifters... you already have the roller rockers!

I would also think that some tighter springs won't hurt, either, plus, titanium retainers.

thats where I would start!!

 

Are you running Bosch Platinum plugs by any chance?
Tony

 

KLLRVT(Tony),
Yes I am running Bosch platinum +4 plugs
and TPiS wires. Do you know something that I don't?
Jim :confused:

 

GET rid of those plugs, I had similar problems in my car with them. The car acted like it got to the rev limter early. I chased the problem for months, until someone asked about my plugs. I STRONGLY reccomend you get some Autolites, and I bet your problem disappears.
Tony

 

Tony is dead on! We have seen the same thing, although I would recommend NGK plugs. We have used the Autolites and NGK's and the NGK seem to be the best overall plug.
Good Luck,

 

Thanks for all the replies. Chris and Tony,
what plugs would be a good choice? What number is the NGK? Are any AC Delco plugs a good choice?
As you described, it acts just like going up against a rev limiter, then shift and it pulls like a bear until you hit 5200 rpm's.
All helpful hits would be appreciated.
Jim :conehead

 

Ok...you guys are wrong with the "get rid of bosch plat's".

I followed your advice. I got a set of Rapid Fires to replace my "stock" plugs ( so I thought ) just as GP.

Of course, when I pulled the "stock" ones, they were Bosch Plat's. The real kicker is, I think they ran smoother than my new Rapid Fires...so I think I'm gonna put in the old Bosch plugs again.

BTW: My rev--spit-sputter-ping-rev crap problem went away when I put in new valve springs on my 106K mi. L98, if you were still curious :)


[Modified by BBA, 7:14 PM 10/16/2001]

 

BBA - I do not appreciate you calling me "Bogus", is there any reason for you to insult me? What did I ever do to you? I bet you do not even drive you car hard enough to notice the problem that the Bosch plugs can cause. I have a few choice words for you, but I value my membership with this forum, so I will keep them to myself (although I may send you a personalized E-mail).You may find that this is a "bogus" problem, but for me it was the problem. I suggested a measly $9.00 repair. if it is not the problem, it is a marginal amount at best to be wrong. Much less expensive and much less time consuming than changing other things.

VETTE PUNK - I suggest that you try Autolite spark plugs, I have had great results with these plugs, plus they are cheap as well.
Tony


[Modified by KLLRVET, 12:52 PM 10/16/2001]

 

I gotta agree BBA. There really is no need to insult others on this forum. As Tony said and I said, we have both had this happen in the past. Does that mean that it is definitly the problem? No! But it is a strong possibility and a very cheap option to check.

JMHO, but there really is no place on this board for insults. This is a place to learn and that is what we are all here to do.

 

I've never had a high RPM ignition issue on either car. Since it is suspect here, install a HyperTech coil/cap/rotor combo. If the problem pesists switch to stock spark plugs with cut-back ground electrode and gapped to .045". If it is still an issue, look to the valve train.

BTW, if it is valve float the problem RPM should drop over time as the springs get more fatigued each time you take her up there (they overheat rapidly at float).

 

Ok...I edited my comment...I mean no direct insult, only that you assumption is dead wrong from what I have seen on my own car and in many years of being a mechanic.

As for running the car hard... 7000 RPM for years on the same set of Platinums.
That was my street car with a 383 short rod cast crank motor ( Du'h...7000RPM...yea!!)

I ran my L98 as high as it would go with my Platinums. Yes it broke up at RPM...even went into pinging at WOT above 3500-5000RPM...then I changed to Rapid Fires on the ADVICE of BOTH of you. THEY MADE NO DIFFERENCEAT ALL

Changing my valve springs COMPLETELY CURED THE HIGH RPM PINGING CRAP

Nothing to do with spark plugs at ALL.

And, to insult you further...the car ran SMOOTHER with the Platinums that were in it than after putting the Rapid Fires in! Thats why I am going to put them back in.

Anyone want a set of Rapid Fires? Cheap?

 

BBA Thanks for your years of wonderful wisdom that you share with us.

Do we all here agree that there may be different things that cause very similar problems?!?! Do we all agree that because this did not fix BBA's car that Tony and I must be FOS (full of sh...well) about our experience.

BBA, no offense, but if you don't see the above as a strong possibility, I surely would not want you working on my car...
JMHO,

 

It's not that I don't see it as a strong possibility.

Instead I see two people who blast one brand out of prejeduce.

And, if you knew ANYTHING about the L98 motor, you would know that ALL of them with hi mileage have Hi RPM WOT ping/crap performance IF they have the stock springs. You would also know that the stock springs were slightly inadequate from teh factory...but the L98 was never meant to turn RPM's so it didn't matter. Lighter springs gave better economy due to lower drag.

I have tried everything one can try to fix the hi rpm crap performance of the hi milage L98...short of disabling the knock sensor, the valve spring replacement has been the only thing that has cured it.

So, in this instance I can pretty definitely say this person needs better valve springs...and even more so now that he is using 1.6:1 rockers.

Now, in all YOUR years of experinces...why did you not pick up on these little details?

PS: I don't think I would want YOU working on my car either :D

 

The point you are missing, was that the suggestion I made was out of personal experience, not prejeduce. I have nothing against Bosch plugs, i rum the in my truck right now. I have only seen from mine, and other examples that the platimuns in certian circumstances, seem to cause a high RPM miss, kind of like hitting the rev limiter.
Maybe you are so experienced as a mechanic, that you have gotten full of yourself. I have known a few like that. They ignore the easy possibilties because they "know" so much about what they are doing.

By the way, if you say I made the suggestion that Bosch plugs were your problem, I can guarantee you I DID NOT say to use Rapid Fire plugs, so you might be mistaken in who offered you what advice. I ALWAYS suggest Autolites. I would not be surprised if your car ran evenbetter if you tried them now!!!! :D
Tony


[Modified by KLLRVET, 5:31 AM 10/17/2001]

 

The last time I tried autolites...they ran fine for all of about the amount of time it took me to get out of the driveway. In fact, at Chrysler, they use double plat autolites factory...you want to know how many of them drop the electrodes off in the cylinder? Almost EVERY ONE.

For that reason, I would NEVER suggest autolites, thankyou.

 

Hey guys, I've been chewed on this forum before for recommending against a certain brand. Bosch +4's included. Understand that I don't blast them from silly prejudice, I blast them because in my experience they suck. I wouldn't buy anything but a Bosch o2 sensor, it's not specific brand problems, it's crappy products within a brand. I hate Cavaliers, but that wont' stop me from buying a Chevrolet. I thought the +4 plugs were a good idea until I tried them, that's when I made up my mind.

Personally I'm always inclined to try the cheapest solution first. Why must people get mad when that is suggested?????

 

just to throw some fuel on the fire here,

From personal experience, after my mods i had lost an NGK and opted to put Bosch Plats in, the car had a terrible high rpm miss. the weekend after, i changed to autolites and backed off on my valve lash. the problem cleared up. then i fouled out my NGK's 3 weeks ago when my Ignition control module went out, i tossed in the Bosch platinums figuring it was most likely the valve lash that caused the problem, but the miss was there again and even worse then before. i went to advance auto grabbed 8 autolites and slapped them in and the car has never run so good. i am getting ready to order a set of TR6 plugs for my car bvecause of higher compression and because the NGK's ran excellent before the module went out. i thihnk maybe the extra energy needed to cross the plug from higher compression lent itself to finish of the module and this is why im going with a colder plug and going to close the gap some from factory specs. so, I for one can say beyond a shadow of a doubt that the bosch platinums "IN MY SPECIFIC CASE" were a cause to a high (above 5k) RPM miss that felt like the engine was going to come apart. felt like i lost spark on 3-4 cylinders it was so bad. Rastlin a member here was with me on the before and after runs, same night and the difference was unbelieveable! so, for 9 bucks and 30 minutes of time, it is not a bad test to try, i am a beleiver in plugs making a difference where as before i figured one was about as good as the other! best of luck in working the problem out! let us know how things come along!

ps it might be that the engine needs a forged 383 stroker kit with stage II heads and a solid roller cam, complete computer revamp and fully lightened valvetrain for spinning above 8k, oh and get good plugs because some of them don't like to do there job above 5k :yesnod: :lol: and some of my peers say im an extremist, ha go figure!

:D chris

 

Forum members/friends: Since this topic has created a great amount of dicussion I will change my sparkplugs and test the car by Saturday evening. I plan on using either stock AC Delco or NGK plugs. If I choose the NGK plugs what number is correct? My NAPA store says a FR4 is correct but other members say a TR5 or TR55 is used. As a side note, my car has TPiS wires,new coil,cap,rotor and all the correct plug wire retainers and wire routing. If the sparkplugs do not correct this condition, I will then install new and better valve springs and test the car. I will post all results. Thanks for everyones input.
Jim (Vette Punk) :conehead