vettenuts

iTrader: (4)

I was always under the impression that the shims for the springs went under the valve spring seat. However, I have found them above the seat on my new heads. The seat is part of the one piece valve seal/seat. Does the location matter, since they won't fit below the seal/seat anyhow? I believe them to be the hardened shims from Comp.

SideStep

Hmmm... Mine were under the spring seat/cup... But heck if they will not fit under, they will not fit under... Sounds like that is what you have to do...

vettenuts

iTrader: (4)

That is all I have seen as well. Not sure if it makes a difference.

redtail2426

iTrader: (10)

if they were thick shims then i would def put it under the spring to keep the shim from becoming another moving part that adds weight to your valvetrain.If they are thin then dont worry about it.They make shims to fit any heads in any size,just have to find them.

SideStep

The springs are under the spring no matter what, on an LSx head. They are either under the spring and the seat/cup, or just under the spring and on top of the seat/cup...

redtail2426

iTrader: (10)

wow that was some good cheeba,sorry for the post i read that very wrong.

vettenuts

iTrader: (4)

I am thinking it doesn't matter but would sure love to hear that from someone who does a lot of head work.

PREDATOR-Z

Hmm, good point. On my Beehive 918's I put them under the seat. Perhaps with non beehive they go over the seat??? Or is it particular to certain size spring??

Patrick G

iTrader: (14)

My shims went under my spring cups (Comp 921 springs, AFR 205 heads).

vettenuts

iTrader: (4)

These are beehive. I think the issue for me are the seals since they are one piece seal/seat. If you shim under the seat the seal will move up and off of the valve guide.

This is the way the heads came, they are the Dart 205's.

FRISKY

The shim should be under the cup. A shim placed under the spring is probably the wrong size and that was the only place they could get it to fit.

Moxie

vettenuts had it right. Placing the shim under the 1-piece seat/seal raises the seal, so the seal may not seat all the way down on top of the guide. Also, it raises the seat, reducing the distance to retainer interference. Techincally, you could put the shims under the seat, however, over the seat is preferred.

Dart331Stroker

First off we dont use the wrong parts when we assemble heads. Second it doesnt matter with that head either way because of the one piece seal/shim. 3rd take into consideration the fact if you shim under, one you move the seal up higher on the guide so you dont get all the grip, two it moves the seal closer to the bottom of the retainer. This obviously would cause a problem with retainer to seal interference and will decrease the gross lift that you could run, lets say it can normally handle .640 from seal to retainer, now you shim under the seal/shim with a .040 shim now it can only clear a .600 lift camshaft. See the dilemma.

Parts are machined with tolerances, and in some cases heads out there may use very little shim or none at all, and in this case it may be under, and still allow the head company to achieve the larger clearance range.

Intake and exhaust shims shouldnt necessarily match as the valve lengths are different from intake to exhaust on the LS heads, and also when you install springs you are setting up for peak lift, spring pressure for that lift point, and this is affected by installed height, so you might have .040 under some, .015 under some, none or .060 who knows, thats why professionals use spring height micrometers to measure, and shim accordingly!

You know Dart has a tech email address and can answer these questions correctly after all they build over 40,000 heads per year, who can be more qualified to answer these questions. darttech@dartheads.com

PREDATOR-Z

Good info, that is why we post here. Thank you for being here too

FRISKY

My bad... Somehow I missed the part about the seat/seal being one piece. I have never seen one built like that.

Dart331Stroker

it is the exact same seal GM gets from US Seal for the LS heads. US Seal is local here in Michigan and supplies us with the same seal. Thanks

vettenuts

iTrader: (4)

Thanks for all the information Dart331Stroker. I have actually been in contact with Greg Wold with questions via e-mail (he probably thinks I am a pain by now ), but many times it is to the benefit of all here on LS1Tech to get correct information from the manufacturer and that is why I also posted here. I didn't see any other way the shims would fit correctly, but I also have never seen it done this way and my two LS1 books show them under the seat.

As for the seals, I have priced the GM one piece seal/seat and they are not cheap!!!! Good to know the seals are also quality parts

I did carefully remove them making sure I lubed up the seal before removal. I am assuming I can re-use them as they look perfect and I don't think they seal on the threaded portion of the guide anyhow.

Moxie

Yep you can re-use them, as long as they're not damaged. Nope, you're not a pain. You have enough sense to ask questions before you do something, instead of after breaking parts.

As for the LS1 books, I'm not sure why they chose to put the shims underneath the seats. Like I said, you could do it that way, however, we prefer them over the seats, for the reasons mentioned above.

vettenuts

iTrader: (4)

Greg,

Thanks, I think I sent this to you in an e-mail, it appears that the Dart heads are shimmed so all the seat pressures are the same. Is there an advantage/disadvantage to putting a little more pressure under the heavier intake valve, or is it more important to have consistant pressure on all 16?

Moxie

Consistent on all 16. LoL, Bob, you are thinking wayy too hard. Install the heads and go burn some rubber!