ramairbrc

iTrader: (1)

My brother-in-law just installed a Vortec Q-trim with methanol injection on his car. He bought the entire kit, down to the better fuel pump. The engine is not stock, but has 10:1 pistons, bigger cam, better heads and bigger injectors. After the install he started the car on the first try and it ran with a smooth idle. He loaded it on the trailer and took it to the tuner. They called him the next day and said: it seems that at 5,000 your engine makes a "wastegate" type sound and you lose power. The boost gauge went to 8 lbs, and didn't really drop off after the sound started but the car lost power. After a couple such runs to try and find the problem they stopped because they believe the rear main seal went, so they shut it off and told him to come get it. BTW: it made 470 rwhp before the power dropped off.

If it weren't for the better fuel pump, I would have figured it was fuel starved. What could possibly cause a Vortec to make a wastegate type sound at approximately the same rpm? The bypass value?

Any thoughts? Thanks, Bob

JMBLOWNWS6

iTrader: (17)

Id make sure the PCV system is up to the task. Too much crank pressure can blow out the seal. I could be wrong. I also check the bypass bosch valve.

ramairbrc

iTrader: (1)

I spoke with him about the PCV, which he said was hooked up. But then I read about installing a "better" PCV and grommet from a turbo Supra? Does that sound right?

BTW: thanks for your quick response. I hope other members with be so kind and share as well.

ramairbrc

iTrader: (1)

So, no other members with sage advice?

777

iTrader: (21)

My guess would be either too much crankcase pressure (best guess) or you have a leak in some of your piping when the boost comes on. 95% chance you need a breather valve for your crankcase. I really don't see how it could be anything else. It would cause the sound and the rear main seal to go.

ramairbrc

iTrader: (1)

He checked and checked yesterday and today, and saw no leaks from the rear main seal. My guess was that the oil leaked out the dipstick tube but the shop thought it came from the rear main.

He reattached the PCV and it seemed to work, but I haven't spoken to him since.

I do think the crankcase is being pressurized as well.

LS1_boostdscoob

wastegate type sound? and losing power... im gonna say hes got a boost leak, or ignition isnt keepin up with the boost...
crankcase preesure shouldnt increase that much otherwise he got bad rings...

ramairbrc

iTrader: (1)

Isn't it odd that it's not just a "wastegate type sound" but at a certain rpm it happens each time? Wouldn't a boost leak be a leak the entire time?

I thought it was fuel starvation at first, but he has the recommended pump set up, and shows good fuel pressure the entire time.