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Early signs of wiping a lobe??

843 Views 25 Replies 5 Participants Last post by  MR Buick
Is slow spoolup at take off and if cruising about 20-25mph and getting after it it spools slooow signs of a lobe on it's way out?If I'm doing 45mph or more in 3rd or 4th gear and get on it it spools up like crazy.Or does that sound like the puck not sealing properly?Motor has 6k miles since being freshened and cheap flat tappet cam.Problems started after installing bluetops,9 1/2" l/u conv.,TA51and power plate.Car spooled up fast with stock setup.I have 42psi f.p.tried to lower a bit to see if it was just rich but it didn't like it and tried Lubrant and J.C. chips.Any ideas would be appreciated. rant
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does not sound like a lobe to me.

When you stall the car against the brake, what rpm to you see?



Steve Wood:
does not sound like a lobe to me.

When you stall the car against the brake, what rpm to you see?
2800 rpm and 0 lbs of boost,but it spools up quick stalling against the brake.Just driving slow and punching it it takes forever for the boost gauge to move. dunno
a buddy of mine wiped a stock cam and he told me one of the signs is a lot of detonation where there shouldnt be any, like 5 psi, half throttle getting 5* KR.
It's not detonating at 15 psi of boost so hopefully that rules out the camshaft.Haven't found an exhaust leak and can't hear one,doesn't mean ther isn't one somewhere but d/s header has been welded so its not leaking between 3-5 cyls.Would a leak on the pass/side header to turbo flange cause wicked slow spool or would it more likely be a puck problem? uzi powersix
2800 and 0 lbs? sounds like y our turbo to me.
firebird_1252:
2800 and 0 lbs? sounds like y our turbo to me.
dunno Turbo only has a couple hundred miles on it.It pulls real hard when it does boost up,just spools slow.Would a leak at the 3bolt header flange make it spool that slow? :confused:
It could.

What does the rpm read when you brake to 10#?



Can't hold any boost at the line.But it spools fairly quick launching at 2800rpm.But on the street if I take off slow and punch it ,it won't spool up until it hits third gear. rant
MR Buick:
Can't hold any boost at the line.But it spools fairly quick launching at 2800rpm.But on the street if I take off slow and punch it ,it won't spool up until it hits third gear. rant
i can hold almost 10psi at the track at like 2650
Sounds like a converter problem to me. To get a 51 to spool, you need to be able to build several pounds of boost against the brake. I personally, think a 3000 rpm stall is best. By this, I mean you should be about to build 7-10# of boost against the brake around 3000 rpm.

If you are in third gear, there is more load on the engine and more heat in the exhaust so it will spool better then.



I have a Precision 9 1/2" l/u 3000-3200.It seemed tight when I first installed it.So I sent it back for my free adjustment and they added 400 more stall and it still feels tight.Prolly has 30 miles since they adjusted it,only had a couple hundred miles on it before they adjusted it.They said it looked fine when they had it there. dunno
Only you can determine the stall. They go by experience but it does not always work out.

By your description, it should pull around 10# of boost against the brake at 3600 rpm. At any rate, it should have no problem building some boost at 2800-3000 rpm.



Thanks for the help everyone.Maybe I shoulda bought a 9/11 converter. dunno rant
If you can stall the converter to 2800 rpm's and it's rated for 3000 I don't see a problem. Fine engine tuning will get you closer to your stall mark. Your problem is with boost. Boost should start climbing around 1500 rpm's. No matter if it's a 2400 stall or a 4000 stall. If it's not then you have to look elsewhere. Pull the elbow off and inlet pipe off and see if you have bent, melted or missing fins. This is the turbo that had fin meltdown problems as per "Reds Hotair" member here. If not look for a pig rich condition, cracked manifolds, fouled plugs, bad injector and the list goes on
I agree with Ed, It could well be the turbo. If the car is not making boost, it won't make enuf power to bring the car up very far on the converter. I have not seen a TA51 but I would think it would make some boost at 2800. If everything is right.

The PTE51s like a bit more converter from what I have seen yet I have seen posts saying it worked well with some 2800 converters so yours ought to show some boost, I would think. Check the puck for seal before getting radical. :)



Well,I got a chance to work on the car.Took off elbow,puck seems to be sealing.Still won't build boost by braking.At full boost the boost gauge is erratic,the needle moves back and forth from 14-16lbs really fast.Pulled d/s valve cover,rockers appear to have the same travel to the naked eye eek! Plugs are burning clean,doesn't appear rich.Car idles and runs smooth,scanmaster #s look good.Does the boost gauge fluttering back and forth sound like the cam going bad or would it be turbo related?
I don't think it would be cam related..that is opinion rather than fact, of course.



Thanks Steve, for keeping me pointed in the right direction.Car ran great stock,then I threw in new turbo,injectors and t.converter and it hasn't been right since.I'm gonna see if I can find a turbo locally to try on the car to see if that helps.Taking the one out of the other GN sounds like too much work. ugh

<small>[ June 07, 2003, 04:12 PM: Message edited by: MR Buick ]</small>
Damn, you sound like me.

Just for the heck of it, reach in the inlet and see if the shaft wiggles a lot when you shake it.

It's a bit strange that it spools okay when you go from a roll but you cannot build boost when stopped. Sounds like the converter is not loose enuf, but, as Ed pointed out, that turbo should not take a lot of stall to make boost. If it will come to 2800 against the brake, it should be making some amount of boost.

Just for clarification, do you have a TA 51 or a PTE 51? What a/r ratio?



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