LT-1 valvesprings

[turbo buicks]

ive heard you can use LT-1 valvesprings but not the new LT-1 valve springs out of a 4th gen Z28 or vette. if true where can you get them then?

 

[chris]

At your local 'quality' parts store.

 

[TurboWh1]

does anyone have a correct part# for federal mogul valve springs??

 

[49-blues]

i believe they might be #3927142

 

[turbo buicks]

now these valvesprings we are talking about are the right ones and wont wipe a stock cam's lobes or go bad on me in 5K miles like i have heard the stock ones did, correct?

 

[49-blues]

i believe these are the correct number for the older style lt1 springs-should be between 105-110 lbs seat pressure but i would get nick micale or other engine builders confirmation the number.i have the springs from johns performance and i believe thats the number.

 

[TurboWh1]

i need a federal mogul#, not the GM # as i cannot cross the number-3927142 to a federal mogul (i work at a parts store)

 

[49-blues]

or better yet check with jack cotton- i think he sells them also

 

[salvageV6]

You might want to consider the Comp Cams 980's that are right near the GM high spec. limit for the stock cam.

Used without the stock cups. Measured a large sample of 2 sets I used and right at 85lbs all within 2lbs.

Just my .02.

 

[turbo buicks]

how many #'s are the factory springs "supposed" to be? will 100# springs wipe the lobes off a stock cam?

 

[87LtdT]

Don't know but why risk it?? I'd do what Salvage says...CC980 without the cups. Our engines are not high rev'ers so we don't need real stiff springs to close the valves instantly. The stiffer the spring... the more chance for lobe wiping.

CC980's are about 85 lbs installed...LT-1's are 100-105...add 9-10 more pounds to either if you re-use the stock cups. I too measured CC980's and found them to be very consistent. Measured a set of LT-1's too and they were very inconsistent. No question which I'd use.

Regards, Bob

 

[49-blues]

just FYI the LT-1 springs i got were all within 1 or 2 lbs of each other @ 105-110 lbs,but if you dont feel safe use the 980 s.

 

[49-blues]

whats the seat pressure for the cc 981 s?

 

[87LtdT]

I think you are referring to spring force...often referred to as seat pressure.

About a year ago I measured my stock 34k mile springs, CC980's, CC979's, LT-1's...all on the same machine.

Measured data (units are pounds):
1.70" 1.25" Measured Rate Advertised Rate
Stock 68 176 241 lb/in 276 lb/in
CC979 73 180 239 267
CC980 76 197 269 307
LT-1 99 245 325 ???

Advertised:
CC981 105 295 423

Hopefully the columns came out right...the point is the CC981's are very stiff springs....I would recommend them only for real racers who anticipate changing cams frequently.

Regards, Bob

 

[gofstbuick]

Originally posted by 49-blues
i believe they might be #3927142

There is really no such thing as a early SBC LT1 or Z/28 valve spring, they are all the same spring for the 1970 LT1 (370hp/350) and the 1967-69 Z/28 (290hp/302). That valve spring belongs with Chevrolet first and second racing design camshaft (a GM special HP racing mechanical flat tappet camshaft). It is rated at 110# closed @ 1.7 installed height with 365# open pressure. There is a late model LT1 valve spring for the LT1 hydraulic roller engine, and it has different specs.
IMHO, I would check with the cam manufacturer or machinist prior to installing this spring (3927142) or any other with any stock or aftermarket camshaft. I would hate to give you a valve spring recommendation and suddenly your cam goes flat. I checked with Poston prior to using this set up.

 

[GNSCOTT]

I think Cottons recommends 90lb springs. Had too many prbles w/ the LT1's