Need Suggestions On What To Do While Engine Is Out For Weird Problem

[92GreenGT]

My car has had a weird problem of making peak power at 3700-3900rpm and I'm trying to figure out why. So far I've narrowed it down to a few things(or a combo of things) so I pulled the engine out of the car to hopefully try and fix it. Here are somethings I've thought of so far:

Bad valvesprings
cam not degreed and installed right
ignition "blow out"

Here is a dyno graph of the car:

As you can see the car is making good power when it makes power before it falls off. The car had a stock TB on it when it was dynoed and I found out that it was leaking like no other so a 70mm Accufab is on it now. My ignition box is on it's way back from Mallory and I'm going to try a set of the bigger Taylor wires out, so hopefully the ignition part is covered. That just leaves me the valvesprings and the cam.

Since the engine is out, should I pull a couple valvesprings and have their pressures checked just to eliminate the possibility? Also, can you degree a cam with the heads on? If not, should I pull the cam out and retard it 4* just to see if that helps it make power up top? Done a leakdown test and everything is in check.

Combo is:
stock bottom end
TFS TW heads
Stock Cam
1.72 roller rockers
Exploder intake
Accufab 70mm TB/Spacer
Hellion Turbo Kit with a Master Power T-70 making 10psi currently(.68 exhaust housing)
SCT MAF meter
#42 injectors
Walbro GSS340 pump

Thanks for any insight.

 

[92GreenGT]

TTT

 

[92GreenGT]

TTT

 

[jrichker]

A wideband A/F meter would help to see if the mixture is going lean at high power levels. Other than an igniton problem, there isn't much else. Are your plugs gapped down to .025-.035 to accomodate the supercharger?

 

[92GreenGT]

A wideband A/F meter would help to see if the mixture is going lean at high power levels. Other than an igniton problem, there isn't much else. Are your plugs gapped down to .025-.035 to accomodate the supercharger?

It has a wideband and it's 11.6 across the board. The plugs did have a .032 gap I believe on the stock ignition so maybe that is the issue. I'm going to gap down to .028 and run the ignition box when it gets back and see if that helps anything.

I didn't degree the stock cam when I installed it, just went dot to dot. Can you degree the cam with the heads still on the block or do you have to remove at least one? I don't really want to put the engine back in and it still not make power like it should. What about testing the valvesprings, they have about 12k miles on them but my stock cam and 1.72 rocker combo should be one of the lowest lift combos possible. Opinions on any of this?

 

[HotFox]

You can degree the cam with the heads on but make sure you have no slop in the valve train, and your lifters do not bleed down. This is not the preferred method and is used to ball park to decide if it jumped a tooth or something.

I have seen a tool that you can test valve spring on the motor it is a bar that slips under the rocker and it will give you a reading on the seat pressure as the bar flexes. You can also pull them off using the fill the cylinder with air and use the clamp to compress.

Did it start misfiring above 3500rpm? A quick test is as jrichker stated shorten the gap up that is a good test on the dyno, it you gained rpm then you know that is the problem. What octane fuel are you running? Could it be to much octane? What is the turbo doing could it be to small? What is the boost above 3500rpm?
What is the base ignition timing, total advance?

I am no export on turbos set ups.
Hellion sold you the kit did you contact them?

If your using a stock 302 block that will not last to long with that kind of power.

Scott

 

[92GreenGT]

Yeah I know about the block, it's going to be fun while it last though! As for your questions:

1. Didn't try a smaller gap because I was waiting on Mallory to send my ignition box back
2. Turbo isn't too small, tried a 76mm with a .96 exhaust housing(we thought the exhaust housing on mine was the issue) and it didn't fix it or make power any higher
3. It didn't misfire through the run at all, that's why I wouldn't face the fact it was the ignition issue
4. Boost is solid across the board, 10psi on the lower hp runs and 13psi on the 449 run
5. 93 octane
6. Total ignition timing was 19* on the 395 or whatever run and 20* on the 405 run, 19* on the 13psi run
7. Tried unhooking the mufflers with no hp or RPM gain, so that isn't a restriction either

What are the signs/sounds of valve float? Everyone there never heard anything out of the normal sounds and it didn't act any different on they dyno than the street. I just don't really know what valve float is like since I've never experienced it before.

Does anyone think I should pull the cam and retard it 4* and put it back together and see how it does? Needing to get this thing done today so I can get it back in the car, appointment for subframe install is Friday and I've already rescheduled once!!

 

[HotFox]

Valve float is a total change in engine sound it just sounds different, higher pitch. I have also been told that it will feel like the motor is running out of fuel when in valve float. If you pull the heads off you will notice that the keepers will be shinny from moving around in the retainer. I would think you might want to stiffen them a bit with the turbo, maybe 10-15lbs on the seat. It defiantly will not hurt anything as long as you don’t get into coil bind. As for the cam retard; what can it hurt? You will only move the power up. The only thing I would be concerned about is keeping a positive pressure on the turbo. Will retarding a stock cam do that? I don’t know. Don’t forget to check valve to piston clearance when retarding cam.

So did you run stock ignition on those dyno pulls?

Scott

 

[HISSIN50]

Dave, I had the same thought - you make that pull with no ignition box?

I'd wait for your (or borrow) a box and see if the issue doesnt just magically go away.

 

[92GreenGT]

Valve float is a total change in engine sound it just sounds different, higher pitch. I have also been told that it will feel like the motor is running out of fuel when in valve float. If you pull the heads off you will notice that the keepers will be shinny from moving around in the retainer. I would think you might want to stiffen them a bit with the turbo, maybe 10-15lbs on the seat. It defiantly will not hurt anything as long as you don’t get into coil bind. As for the cam retard; what can it hurt? You will only move the power up. The only thing I would be concerned about is keeping a positive pressure on the turbo. Will retarding a stock cam do that? I don’t know. Don’t forget to check valve to piston clearance when retarding cam.

So did you run stock ignition on those dyno pulls?

Scott

Thanks for the reply. Maybe I'm over confident in the stock ignition and that is the problem(hopefully!!!!) I've got the rockers off the heads now but they are still on the block, I'll take a picture of the valve pieces tomorrow on the head and you can throw your opinion out about how everything looks. I've heard that about the keepers being shiny but I still a n00b about it so having a second opinion would make me feel better.

Dave, I had the same thought - you make that pull with no ignition box?

I'd wait for your (or borrow) a box and see if the issue doesnt just magically go away.

What's up man! Yep, wouldn't you know it the day before I was scheduled to dyno my ignition box went out. I decided to go for it anyways for the fun of it and see what it would do. I'm glad I did really because it showed me the other issues I had at the time. I'll take a pic of the valvesprings tomorrow and post up tomorrow and see if you guys can tell if they look like they've been floating. I may throw the engine back in because I can always degree the cam in the car just as easy on the stand I guess if it still has the same issue after the ignition box is back.

The best way I can explain the power loss is it feels like it's pulling pulling pulling and then just goes "flat" and stays that way up top. It doesn't pop, crack, miss or anything just kind of stops making power and goes flat. I'm borrowing a buddies set of big taylor wires, will have my ignition box back and plan on tightening the gap up on my plugs just a little. With the boost leaks fixed and the ignition system in top order, if it still doesn't make power up top I'll know it's valvesprings or cam related for sure then.

 

[robbo1987*2.3*]

im a 4 banger guy but

Mine did the same thing once and i messed with iot for a week before i figured out that the cam was a tooth off. Usually when mine will run strong then fall off top end it is a timing issue dont know if that helps any

 

[92GreenGT]

Ugh, it's post like that one that makes me want to pull that cam out and put it back in and try it. I'm on a deadline of having it all done by Friday I just don't know what to do, need to figure it out TODAY.

 

[92GreenGT]

Pulled the timing cover off today and what do you know, cam is one tooth off. Will fix it tomorrow, hopefully between that and the stock ignition and boost leaks that was my issues.