L98 to LT4 spring upgrade, need help.
 

Hi, My L98 iron haed are at the machine shop after porting and gasket matching them. They are done except for the springs. I bought a set of LT4 green stripe springs from Pace for a really good price. They are the exact spec I needed, 100 on seat, 330 at .50. The only problem is my machinist told me if he opens up the seats to 1.40 for these springs there won't be enough of a ridge around the seat to hold the spring in place. He asked me to find someone else who has already run this set up and what they did to fix it. Any help is appreciatted, Thanks.

Re: L98 to LT4 spring upgrade, need help.
 

Why does he have to go so big?
ZZ4/LT4 springs are only 1.32" Od.

http://sdparts.com/details/gm-perfor...parts/12495494

Maybe use the LT4 spring seat ( shim ) # 10212809 and either machine the guide bosses to suit or open the shim inner hole up to fit your heads as other have done on Vortec heads

https://www.thirdgen.org/forums/post...985-post6.html

Re: L98 to LT4 spring upgrade, need help.
 

I measured them when I got them and they miked 1.34. My machinist told me the seat cutter for that was 1.40. I still don't know, I'll call him back tomarro and ask. Thanks

Re: L98 to LT4 spring upgrade, need help.
 

I think you just need to make sure you have the right spring seat/locator and run it. Alot of heads come cut for larger springs but doesnt mean they run them. I think my AFR's can fit a 1.5" spring but they run 1.27" from the factory. The spring is gonna move regardless, they all do. They rotate around alittle but they shouldnt be bouncing around side to side unless you have valve float.

I think those LT4 spring shims will locate the spring I.D. and keep it from walking around. Thats probably your best bet.

May I ask what cam you are running and why LT4 springs? You can find springs with similar load specs that are smaller diameter and drop right in. Manley 22410's are nice springs. Granted they may not be as cheap but you dont want to cheap out on valvesprings

Re: L98 to LT4 spring upgrade, need help.
 

Its a stock cam, I think. I took the oil pan off and found she has a rebuild in her past, complete with a new #8 rod. I'm picking up a set of dial indicators to check the cam but I think it's a stock L98. It has GMPP 1.6 rockers. I was just looking for a kinda stock upgrade. The LT4's fit the spec my machinist gave me and I thought 1.25 to 1.34 wouldn't be a big deal. He says he dose not have a cutter in that size and it would move too much with a 1.40 seat. I bought the springs and retainers from Pace for like $70. I thought I was getting a deal. Thanks for the reply!

Re: L98 to LT4 spring upgrade, need help.
 

yeah if its a stock cam, i'd swap on stock style springs. Maybe LT1 springs? Comp 981's could even work and are fairly cheap. Dont need much spring to control a stock cam.

Re: L98 to LT4 spring upgrade, need help.
 

Orr, the LT's are a stock style spring. Just no dampers. It's whats used in th ZZ crate motors. Thats why I got them, I figuredit would be drama free!