Earlier this year after doing the winter thing, I dynoed the car on a DynoJet and did 612/525 at 6900 RPMs on 13psi. I was stoked, since I was making 70rwhp more than last year in which I was running consistent 10.70s-10.80s at 130-132.

I went to the track a couple of weeks later and was pulling consistent low 11s at 119-121, barely managing a 10.91@121 at the end of the day. I was only back-halfing 20mph where I usually see 28mph. The car outwardly was running great. Good A/F, no breaking up, no smoke, nothing.

A week later I put it on a Mustang Dyno and found a lot of converter chatter/slippage and the car making peak power at only 6000 RPMs. I replaced it with a Circle-D, which resolved the chattering/slipping, but was now making peak power at 5800 RPMs. During all dynos, the A/F was 11.6 across the board, the car didn't break up or smoke, and boost was nice and linear.

So, after talking with several LSX guys, it was up to either the valve springs being worn or something in the engine being hurt.

Yesterday the shop called and told me to sit down. I was fearing for the worst.

Seven years of boost on a stock bottom end, hundreds of passes to 7k RPMs, street "duty", etc. Here it comes.

Compression tests came back at 160-175psi in all cylinders, the #8 being at 160. Leak down tests came back at 7-8% across all cylinders. I was amazed, as were some other people I talked to.

We then pulled a couple valve springs and found that they could be compressed by hand. Three year old PRC duals. Yeah, I didn't know they needed replaced every year let alone on a boosted application. I called and spoke to Gunnar at Patriot today and he recommended their Xtreme series springs due to my cam and a boosted engine (224/230, .581/.592, 114 Comp XER). They're backordered until Thursday, but he's being really cool and overnighting them to me for free for Friday delivery.

Big sigh of relief and a lesson learned

 

You should never wait for springs to break before you replacement. I replace mine every year. It it not a hard job and they are cheap enough.

 

This is the first "major" fast car I've had making this kinda power. They're not broken, just really worn which seriously seemed to happen over a period of a couple weeks.

I know better now and will replace them every winter now.

 

My power also falls off at 6000rpms, I was thinking it could possibly be the valve springs. After reading your post I think I am right. Thanks for posting.

 

No problem, that's why I like this place

 

No **** right, of all the forums I look at even my girlfriend noticed that this is the most professionally ran and helpful site.

 

Easy to change out springs on a corvette maybe. Not on our f bodies with half the springs under the cowl. I hate the keepers from hell as I call them.

I guess if you run your car that hard and take it up to redline so often it might need springs more often.

 

Glad to hear Ant.
Seems some really old bastard told you valve springs about a month ago

 

Do you by chance have any of the dyno graphs that you could post?

 

Lol, I can't wait to see that old man get his car finished

I have the original graph before the converter, so this one shows the chatter. I'll have one after the new converter tomorrow, the shop has to send it to me.

 

Car is still down, Patriot was backordered and said the springs should be here by Tuesday