3400 rebuild, LS1 valve springs?

[JoeMayo]

I've done some reading, here's my situation, let me know what you guys think. I'm rebuilding a '99 3400 for road course enduro racing. Motor runs fine, has 150k on it, needs LIM gasket, going to do head gaskets and port/polish while I'm at it. No plans for a cam, this is already a big enough upgrade from the old MPFI.

I've read about valve float on stock 3400s, especially with high mileage. I will probably set the rev limiter at 6, but would like to be able to string it out and hold it there without float.

From what I've read, LS2/LS6 valve springs are too stiff for a stock cam, but LS1 springs are just a bit stiffer than stock 3400. Also, 3500 springs aren't any different?

So, what I'm looking at is a set of LS1 springs and seats, and 3.1 MPFI seals. Would this work well with the stock 3400 cam to eliminate high-RPM float? Is there an aftermarket spring option, or other drop-in replacement that will fit the stock spring seats, or are LS1 springs the way to go? TIA.

[AaronGTR]

Just out of curiousity what type of racing are you going to do with it? Anyway, that sounds like a good plan to me. LS1 springs are just barely stiffer than stock LA1 springs. Slightly stiffer seat pressure at the LA1 install height, and about the same open pressure. I wouldn't say LS6 springs are too stiff to use with a stock cam, but yes they probably aren't necessary with a completely stock valve train and not much power mods. It's just kind of a pain having to change the seats and valve seals to use LS1 springs when they aren't much stiffer. Comp makes some LS beehive springs that supposedly will fit over the stock LA1 one piece seat/valve seal, probably because of the ovate wire used to make them. I'm not sure on the pressures on them though. They might be closer to LS6 springs. The info is on here somewher I believe, or you could check the specs from comp.

One last thing... depending on the racing you are doing and how much stress the engine will be under, you might just want to change the cam anyway, even if it's with a stock replacement. The stock cam is hollow with press on lobes and there have been a few failures with the stock shaft cracking. There is an OEM spec replacement you can get that is a solid core one piece ground cam, and I believe it is a Federal Mogul "Sealed Power" brand part.

I've done some reading, here's my situation, let me know what you guys think. I'm rebuilding a '99 3400 for road course enduro racing. Motor runs fine, has 150k on it, needs LIM gasket, going to do head gaskets and port/polish while I'm at it. No plans for a cam, this is already a big enough upgrade from the old MPFI.

I've read about valve float on stock 3400s, especially with high mileage. I will probably set the rev limiter at 6, but would like to be able to string it out and hold it there without float.

From what I've read, LS2/LS6 valve springs are too stiff for a stock cam, but LS1 springs are just a bit stiffer than stock 3400. Also, 3500 springs aren't any different?

So, what I'm looking at is a set of LS1 springs and seats, and 3.1 MPFI seals. Would this work well with the stock 3400 cam to eliminate high-RPM float? Is there an aftermarket spring option, or other drop-in replacement that will fit the stock spring seats, or are LS1 springs the way to go? TIA.

[Z26-T]

this is also a nice "bolt-on" option

http://wot-tech.com/shop/all/comp-cams-26986-valve-springs/prod_37.html

I know a few beretta guys that use them on their DDs with 6200 rpm. Nice thing is that it uses all stock stuff so you don't have to worry about the seats and such.

[bob442]

this is also a nice "bolt-on" option

http://wot-tech.com/shop/all/comp-cams-26986-valve-springs/prod_37.html

I know a few beretta guys that use them on their DDs with 6200 rpm. Nice thing is that it uses all stock stuff so you don't have to worry about the seats and such.

i thought you did have to chance the seats and such with the comp springs... this is news to me, Sweet!

[Superdave]

this is also a nice "bolt-on" option

http://wot-tech.com/shop/all/comp-cams-26986-valve-springs/prod_37.html

I know a few beretta guys that use them on their DDs with 6200 rpm. Nice thing is that it uses all stock stuff so you don't have to worry about the seats and such.

These would be ideal.

LS1 springs require too much work for basically nothing, the LS6's work fine on a stock cam but again, it's extra work that you can avoid by just getting the correct springs.

[JoeMayo]

Thanks for all the helpful replies.

One last thing... depending on the racing you are doing and how much stress the engine will be under, you might just want to change the cam anyway, even if it's with a stock replacement. The stock cam is hollow with press on lobes and there have been a few failures with the stock shaft cracking. There is an OEM spec replacement you can get that is a solid core one piece ground cam, and I believe it is a Federal Mogul "Sealed Power" brand part.

This is really surprising--has me all scared now. Guess I'm going to have to do some research on how these fail and factor that into my decision. The Sealed Power OEM replacement cam looks like it goes for $200. That's almost as much as a performance camshaft, so it doesn't seem worth it to me.

[AaronGTR]

Well, yeah it's not cheap but neither is a new OEM one. $206 from gmpartsdirect and it's the same weak design. $200 for a stronger one with stock specs. Performance cam is $330 so I wouldn't say they are that close in price... but if you want to spend the money you could get a mild performance street cam and get a bump in power with no loss in reliability and it would work with those springs from comp.