Losing boost at 6400rpm. Help!

[suprahero]

I know it's not the intercooler piping or the intercooler itself. All of that is brand new. I checked very very close today around the brake booster and intake and I can't find anything. I haven't checked the valve clearance on the head yet though. I had the guys at the machine shop buld it so I was hoping that it was right. I know they didn't have any extra shims though so they could be off. I can check them all tomorrow evening or thursday.

Does anyone know off the top of their head how much tolerance I should have for the intake and how much for the exhaust? If nobody knows then I'm sure I can look it up.

I don't know much about the head since I'm not a mechanic but for those that do, could I lose that much air around the valves if they weren't shimm'd correctly? Thanks.

 

[tissimo]

Are you saying that on the exhaust side one set of valves won't be open at all times. When I was testing my valves to see how far they opened it seem'd like one set of intake valves were open at all times.

I'm not exactly sure what you mean? One set of intake vavles should never be opened all the time durring a revolution.

 

[suprahero]

I'm sorry Justin. What I mean is, out of the six sets of valves, there will always be one set open.........not the same ones everytime, but one of the six sets. I just took for granted that the exhaust side would be the same. That's how come I didn't think you could turn the crank and seal it off. I wish you lived closer...........I believe if I had someone's help with this, I could get it fixed.

 

[tissimo]

I'm sorry Justin. What I mean is, out of the six sets of valves, there will always be one set open.........not the same ones everytime, but one of the six sets. I just took for granted that the exhaust side would be the same. That's how come I didn't think you could turn the crank and seal it off. I wish you lived closer...........I believe if I had someone's help with this, I could get it fixed.

yea but most of the time (except that small point where they overlap) one side will be closed where the other is open. So even if the intake valve is open itll just fill the Cyl but not run into the exhaust since the valves are closed (exhaust valves). At TDC of the exhaust stroke going into the intake stroke, both valves are slightly open, if you rotate the crank itll seal off one set of valves and will prevent the air from passing through to the exhaust.

Now that I think about it, I highly doubt you have a valve problem though as your compression numbers are decent and all consistant (if they were really low or inconsistant then you might have something).

 

[suprahero]

Damnit man..........I was hoping we were on to something. I'm running out of things to check. I'll still check the clearance between the lobes and the buckets to see if they're off. I have to do something, even if it's wrong. Thanks again.

 

[Turbo Drifter]

Now that I think about it, I highly doubt you have a valve problem though as your compression numbers are decent and all consistant (if they were really low or inconsistant then you might have something).

Sigh.....yeah your right, I totally missed that.

Jeremy

 

[Bigzavs]

jay, clearance wise, Ross @ Dynosaur Performance in saginaw, shimmed my 268's at .010" clearance (or as close as he could get to it) for intake and exhaust

 

[suprahero]

It seems like one side was .08 and the other was .10 but I can't remember which side is which. I'll check them and post the results without shimming them just to see where they're at.

 

[tekdeus]

Valve float at high rpm?

 

[suprahero]

I have the Crower springs and retainers so I wouldn't think so, but who knows.

 

[tissimo]

It seems like one side was .08 and the other was .10 but I can't remember which side is which. I'll check them and post the results without shimming them just to see where they're at.

.008 intake and a .010 exhaust iirc.

 

[suprahero]

I just checked the clearance between the lobe and shim on each valve. Some of them are pretty bad off.


.......EXHAUST.................INTAKE...........
12......0.0130....................0.007............
11......0.0130....................0.007............
10......0.0140....................0.008............
09......0.0145....................0.008............
08......0.0135....................0.009............
07......0.0135....................0.009............
06......0.0155....................0.011............
05......0.0155....................0.009............
04......0.0140....................0.009............
03......0.0125....................0.009............
02......0.0130....................0.008............
01......0.0120....................0.007............

I'm sure some of these are out of the tolerance allowed. Would it be worth it to take these out and see what shims I could use and then order some new ones? What tolerance do you guys use as a guide? I guess I can look it up in the tsrm and see what they suggest, but I also want to know what you guys think are good numbers if they're different from the manual. Thanks.

 

[tissimo]

toyotas specs are .008-.012 for the exhaust and .006-.010 for the intakes. I would adjust them so they're within those specs.

 

[suprahero]

Thanks Justin.

 

[ForcedTorque]

Could that be the whole problem here, or is the search still on???????????????????????????

I want to see this beast running next month for sure, this afternoon would be GREAT!

Jay did you say you have lost your Targa top? Or have you just lost you're top chasing this problem?

I have one if you need it.

 

[suprahero]

The search is still on for the elusive boost thief. I'm going to fix these though. I was hoping someone might have some assorted shims that I could use and then give them back when I'm done. I'll replace them with the ones that I take out of my car and give them whatever they think they're worth. I have to replace eleven of the twelve on the exhaust side and only one on the intake side.

 

[IJ.]

The 7's are way too tight J.

Your Cams should have come with a timing tag that also had the lash settings on it.

Stock settings aren't correct ie: my Cams require 13 minimum, I run 15 on a fr4esh build to allow for it to settle and the slight recession you get as the parts mate.

If you deduct 2 from the 7 when everything is hot it could possibly hang the valves open. (do you hear any popping or strange engine sounds when it's dropping boost?)

 

[suprahero]

No, I don't hear anything at all when it loses boost. I can't even feel the loss of power when it loses it either. I will see if I can find out what the cam car said about the lash. I have a copy of it somewhere, but I have to find it. Thanks.

 

[IJ.]

I'm not at all convinced it has anything to do with your problem J as if it were hanging Valves open you'd feel/hear it and it wouldn't be long before it did the Hari Kari thing.

But having said that 7 is wayyy too tight.

 

[Turbo Drifter]

Jay can you do a test for me? I want you to hook up your boost gauge to the vac niple on the turbo and go for a drive. If you have 2nd guage to test with then I would use that. I want to see if you are really losing boost or if you have a leak on the vac line that goes to the guage and EMS.

Are they getting there signal off the same place? or line?

Is there change here that you are not really losing boost and that its just leak on the vac line?

I'm only asking this as you say there is no notisable loss in power.

Jeremy