3rdgen Fbody with 3500 heads

[19Cutlass94]

wow! looks good! nice and clean parts! haha

[ForcedFirebird]

Got the cam bearings in after a slight snag yesterday, also the crank, rods and pistons are done...

[El_Diablo]

IIRC, the pistons are actually the same units from the ls1... anyone can correct me if they wish, just something i remember hearing

seems the 3.9 takes a lot from the lsx series

The shims don't work, as SuperDave has discovered. We need to use LS1 seats modified to fit. This will keep the springs centered.

I'm trying to recall correctly since I don't have the extra heads with me at the moment but my LS6 springs are installed on 3900 heads which I recall having seals with a built on seat. It would make sense given that LS6 springs were installed on the HO engine at the SEMA show and the stock heads are designed after the LSx heads.

When I compared the stock 3900 springs to the LS6 springs I only noted a slight height difference. On the other hand since they are stronger I didn't install the LS6 springs with the metal dampening cup that was installed with the stock springs that added about .040" more preload by shortening the install height. I'm not using any type of shim.

[ForcedFirebird]

I was concerned for a moment about the springs having installed LS6 spr on my heads. Are the springs that different that the stock 3500 springs can be run without a seat and the LS springs can not?

The 3900 valve stem seals have seats has anyone considered them for a better fit or are they likely the same as the LS seals since the heads were designed after the LS1 LS6 heads.

The shims don't work, as SuperDave has discovered. We need to use LS1 seats modified to fit. This will keep the springs centered.



Worked on my engine finally for a little bit today instead of everyone else's, lol. Got another 3500 comming in tomorrow, and will be dissasembling/cleaning all day.

Got the cam bearings out...



And honed the cylinders...











Now I got to order the rings (hopefully tonight after the kids are in bed), and maybe this week the crank, cam bearings and oil pump will go in.

I was concerned for a moment about the springs having installed LS6 spr on my heads. Are the springs that different that the stock 3500 springs can be run without a seat and the LS springs can not?

The 3900 valve stem seals have seats has anyone considered them for a better fit or are they likely the same as the LS seals since the heads were designed after the LS1 LS6 heads.

[loner666]

the shims were used as the seats as the stock seats dont work..the LS6 springs dont fit over them (i have them still BTW somewhere if you want them and the springs) the bent valve are because the alignment pin on my cam broke allowing it to turn which caused the valve to be open at the wrong time and BAM!! lol..i wasnt to happy to find out the the pin broke

[Superdave]

i've used just SBC copper shims like that on 2 different 3x00 engines, no problems yet!

the LS1 seats do keep the spring centered, i'm planning on swapping to those this winter...

[ForcedFirebird]

Those shims are what some people use for seats. I use the ls1 spring seats.

AHHH, I posted that the shims were on there, maybe you missed it. Do the LS1 seats keep the springs centered? Eh, I'll just pick up a set of the springs from the store later and use the shims for now.

Just want to get this thing back together! I'm going to run into more problems after the install, I'm sure.

Anybody have a Vortech truck TB cable laying around, lol. That's the only one I know that is long enough to reach around the TB on a 3.4 hybrid .

[SappySE107]

Those shims are what some people use for seats. I use the ls1 spring seats.

[ForcedFirebird]

Oh man I hope that isn't the case!

Well, I don't see any seats here...



Not too concerned bacause basically I paid for shipping to get the heads with the springs, but I was hoping to rebuild these heads to sell


Could be the reason for a bent valve in each head?

[SappySE107]

Oh man I hope that isn't the case!

[ForcedFirebird]

The yellow LS6 springs do not fit the stock seal/seat combination. You need to use the isky seats, or bore the ID of the LS1 seats to fit the guide. Then you use those seals.

Oh, I see now. you guys are going to have to bear with me here. I bought the used heads from loner666 with the yellow spring conversion already on them. I just went to the garage and lifted a couple of the shims and see what you mean now.

Actually, there doesn't appear to be any seats on these 3400 heads, I'll get some pics in a few...

[SappySE107]

The yellow LS6 springs do not fit the stock seal/seat combination. You need to use the isky seats, or bore the ID of the LS1 seats to fit the guide. Then you use those seals.

[ForcedFirebird]

The fit around the guide is the problem. The 318 need to be shaved on the ID to fit the guide easier. The 2.2 seals are direct fit. I have no idea why you would want to run all exhaust seals though. I used intake and exhaust from the 2.2.

Maybe you misunderstood the question. I bought two complete sets of Cavi seals (4int, 4exh). Is there a reason we NEED to use these, it seems as though the 3500 seals would work fine. This is my first time dealing with the spring swap, and just didn't understand the reasoning behind the seals and shims (unless the yellow springs require a 1.6" install ht).

I'm sure I'll upgrade to some better springs, but this was a cheap way to get running with all the collecting of parts that's been going on over here .