worn out valve springs.... I think I have them....

[Blazer406]

Hey guys,

I bought a theft recovery '87 GN that has 139k miles on the original motor and tranny. It has been sitting for 4 years. I have done the basic stuff for something that has sat so long. I changed the fuel pump and filter. I drained all the old gas and replaced with new 93. I changed the plugs and wires. I bought a DS. I reset the IAC per the "how-to" on gnttype.org. I also set the TPS per the "how-to" on gnttype.org. In all this testing.... I have been using the time slip feature of DS and logged about 10 runs made out here in the country on a long straight-away. The car seems to run good....except I think it should be making more MPH..(DS shows 93-94 through the quarter).. so..... I decided that I would start just before the straight-away.... there is a decent downhill slope...leading me into the flat where I usually run. I started about 400' before it got into the flat..... anotherwords... the first 400' or so was downhill.... I wanted to stay in it past what DS says was the quarter.... and see what speed it logged.... made the run..... felt good.... power kinda flattened out at the top of third......stayed in it probably 400-500 feet past what would have been the quarter......got back home and looked at log..... sure enough... I stayed in in for about 1700'...... top speed.... 95 mph.....????? .... It is like it just can't rev anymore past 94-95 mph....

I purchased the valve springs.... a month or so ago (was really one of the first things I bought) .... but haven't put them in..... Does this case above seem like a "textbook" case of worn valve springs......

Also.... what top speed should a stock car have in third gear.... with stock gearing and tire size.....

Currently, my car is bone stock down to the original airbox and catalytic converter...... ( probably won't be that way for much longer )

 

[microELVIS]

Easiest way to tell bad valve springs is rpm in second as far as I know. Mine wouldnt redline in second with bad springs. But I could still get 13.20s.

When i took them out I could somewhat squish them with my hand. I guess one thing you could do is just remove one spring and see if you could squish it with your hand. Chances are though that at that many miles they are gone or starting. I gained 2 mph just from springs.

 

[GANGSTER]

worn valve springs will make the motor flatten out and not want to rev, but these motors really dont rev high to begin with. while im sure you most likely need them on a 139k motor, im not sure that they are your problem.
What kind of boost are you making? are all your conections on the pipes good? is the motor just tired? id start with compression and leak down before wasting time trying to replace valve springs in the car, that is not a fun job.

 

[Blazer406]

worn valve springs will make the motor flatten out and not want to rev, but these motors really dont rev high to begin with. while im sure you most likely need them on a 139k motor, im not sure that they are your problem.
What kind of boost are you making? are all your conections on the pipes good? is the motor just tired? id start with compression and leak down before wasting time trying to replace valve springs in the car, that is not a fun job.

I ran a static compression check when I replaced the plugs.... showed 135# - 140# on every cylinder.... spinning motor over a few seconds.... with throttle blade open...... haven't done a leak-down test.....

I plan on installing my autometer liquid-filled boost gauge... sometime this week.....to see where I am at.

All the under hood plumbing looks to be in order...

0 knock count and 0 knock retard too

looks like I have the green light for another # or two of boost.