Real Fiero Tech

LS7 1.8:1 rocker on left, LZ4 rocker screw in middle, LZ4 1.7:1 rocker on right



The shoulder on the LZ4 machine screw is ~0.4mm (0.016") too large for the LS7 rocker pivot. The LS7 rocker pivot hole will have to be opened up a bit to use the LZ4 rocker screw or maybe LS7 rocker screws are the the proper length and shoulder diameter.

LS7 1.8:1 rocker on left, LZ4 1.7:1 rocker in middle, LZ4 rocker screw on right



LS7 1.8:1 rocker is slightly longer but seems to share the same distance from pivot center to push rod. More measurements later.



LS7 rocker above with LZ4 screw. Screw stops where shoulder meets rocker pivot.



LS7 rocker on LZ4 rocker pedestal and using LZ4 screw before any mods to LS7 rocker. The contact area of the LS7 rocker to the valve stem is slightly off center of the valve stem when the valve is fully closed.

More pics to come after removing valve spring and checking the full range of motion.

GM
GEN III / GEN IV V-8
LS1/LS2/LS6 1997/2007 HARDWARE
http://www.billavista.com/tech/pdf_inde ... nsions.pdf

LS7 1.8:1 rocker on LZ4 head and pedestal.


You can see the the rocker walks off to the side of the valve stem with a M8 screw installed as the valve gets lifted in the video below.
https://i.imgur.com/6ZxEpKG.mp4

CaptainHindsight wrote: ↑Thu May 20, 2021 5:48 pm
The shoulder on the LZ4 machine screw is ~0.4mm (0.016") too large for the LS7 rocker pivot. The LS7 rocker pivot hole will have to be opened up a bit to use the LZ4 rocker screw or maybe LS7 rocker screws are the the proper length and shoulder diameter.

If you use a mill to bore that hole offset instead of just drilling it out, you can move the rocker 0.010 or so away from the valve tip to help the geometry a smidge. Is the rocker bolt an 8mm? What diameter is the shoulder?

The LZ4 pedestal, head and screw are all M8 x 1.25.

The shoulder on the LZ4 rocker screw is 8.4mm.

The through hole in the LZ4 rocker pivot is 8.4mm

The through hole in the LS7 rocker pivot is 8mm.

The wall thickness of the LS7 rocker pivot at its thinnest point is 5mm.

Thanks for sharing the vid. Good quality. You vould prob use the ls7 but accelerated guide wear would say occur. Just how fast they would wear out is the question.

I have to see about putting an offset in to change the rocker position. I still have to check the clearances for the pushrods and the valve covers if i do so. Not sure yet how far i want to go into changing rockers, pedestals, pushrods and fabricating valve covers, etc. etc. if need be. How many HP will I gain?

Elongation of the rocker pivot through hole will weaken the pivot and require a shim to keep it from sliding.

Views of the rocker holes and pedestals. One pedestal on, one off, should be obvious.







Another pic of the LS7 1.8:1 rocker when pushing the valve down.

CaptainHindsight wrote: ↑Thu May 20, 2021 8:19 pm The LZ4 pedestal, head and screw are all M8 x 1.25.

The shoulder on the LZ4 rocker screw is 8.4mm.

The through hole in the LZ4 rocker pivot is 8.4mm

The through hole in the LS7 rocker pivot is 8mm.

The wall thickness of the LS7 rocker pivot at its thinnest point is 5mm.

Ok, so you could move the rocker pivot up to 1.25mm away from the valve by offset-drilling the bolt hole in the cylinder head for an M10x1.5 helicoil. You could offset the rocker a further 1mm away by offset boring the bolt hole out to 10mm. A total of 2.25mm or 0.088" movement of the rocker looks like it could be enough to get the mid-lift contact centered on the valve tip.

EDIT: Hmm.... the rocker pedestal has a curved seat, so you'd have to offset bore it as well.

Thanks for sharing the pics and info about the rocker bolt. The ls7 uses an 8mm bolt as well but its probably not stepped like the lz bolt.

It seems obvious that swapping to ls7 isnt a wise choice. There would be little gains and increased side load wear to the valve guide and valves

A cam swap with bearing spacers to get more power seems like the better way to go vs trying to get more power with a rocker swap. Especially if you are tearing down the whole engine for a rebuild anyways.

Cam swaps can add 40-50 hp to an lz

Shaun41178(2) wrote: ↑Fri May 21, 2021 10:34 am A cam swap with bearing spacers to get more power seems like the better way to go vs trying to get more power with a rocker swap. Especially if you are tearing down the whole engine for a rebuild anyways.

Cam swaps can add 40-50 hp to an lz

If you have the engine apart, do the machine work to use the 1.8 rockers. What I outlined is actually not that difficult... as long as it's enough which has not been established yet. If you're tearing the engine down for a build, installing bearing spacers, etc... Why would you not do simple machine work to the heads to fit 1.8 rockers? Especially if you're also doing machine work to the guides and spring seats to deal with a high lift cam...

300 WHP from a cam/springs LZ9? Sounds like fun!

I'm not planning a cam swap. I'm planning on keeping the VVT. I'm just making simple improvements for reliability and a little performance. It will be a daily driver for someone and I don't want to service much besides filters and fluids for quite a while.

If max power was the goal I can just buy an aluminum big block with a blower and run nitro methane.

https://www.shafiroff.com/chevy-drag-ra ... engine.php

https://www.steveschmidtracing.com/raci ... man-series

https://www.gochampion.com/racing-engin ... evy-1.html

I'm just happy to provide useful pics, measurements and info for those that might be wondering how or what if.

The question of how to use LS7 1.8:1 rockers on LZ9/4 heads was an unanswered question on several threads here and other forums.

I appreciate you going through and posting what you've found.

FWIW, these are comp "Magnum" roller rockers on an LZ9 cylinder head.





The shaft of the rocker arms are too wide to fit. I bought them on a whim, and figured if they didn't fit, I could install them on my truck, which has a gen III LS.

Are VVT-friendly regrinds a thing yet?

Honest Don wrote: ↑Fri May 21, 2021 6:43 pm Are VVT-friendly regrinds a thing yet?

I think the biggest problem with this is the pressed on lobes, I think most camshaft regrinders don't like messing with them.

I'm going to measure a cam I have in storage and see about having some blanks made, eventually.

ericjon262 wrote: ↑Fri May 21, 2021 6:46 pm

Honest Don wrote: ↑Fri May 21, 2021 6:43 pm Are VVT-friendly regrinds a thing yet?

I think the biggest problem with this is the pressed on lobes, I think most camshaft regrinders don't like messing with them.

I'm going to measure a cam I have in storage and see about having some blanks made, eventually.

Ironically, about the easiest possible way to make low volume cams is to assemble them from lobes and shafts via heat shrink fit. However, I think adding a keyway and a key to prevent rotation of the lobe on the shaft would probably satisfy the idiots who don't want to regrind assembled cams. FFS, heat shrink press fits transmit hundreds to a few thousand ftlbs of torque in transmissions... they shouldn't be pushing that hard on the cam to regrind it.

CaptainHindsight wrote: ↑Fri May 21, 2021 5:28 pm I'm just happy to provide useful pics, measurements and info for those that might be wondering how or what if.

The question of how to use LS7 1.8:1 rockers on LZ9/4 heads was an unanswered question on several threads here and other forums.

Yes. And thanks again. I had wondered for a couple years but never got around to checking myself so iy saved me time and money.

The Dark Side of Will wrote: ↑Fri May 21, 2021 11:36 am l.

300 WHP from a cam/springs LZ9? Sounds like fun!

75mm tb, cam swap, longtubes is all you need to to get 300 crank hp.

300 whp would take a bit more work obviously. Id say my 3900 without turbo would make around 250 whp. I just have a 75mm tb and cam and through a manual.

Josh riedl did 238 whp through an 4t65 with tb, cam, and homemade headers.

Header flanges are available for the lz engines. I picked up a set a while back from a place in oregon

Shaun41178(2) wrote: ↑Fri May 21, 2021 11:05 pm

The Dark Side of Will wrote: ↑Fri May 21, 2021 11:36 am l.

300 WHP from a cam/springs LZ9? Sounds like fun!

75mm tb, cam swap, longtubes is all you need to to get 300 crank hp.

300 whp would take a bit more work obviously. Id say my 3900 without turbo would make around 250 whp. I just have a 75mm tb and cam and through a manual.

Josh riedl did 238 whp through an 4t65 with tb, cam, and homemade headers.

Header flanges are available for the lz engines. I picked up a set a while back from a place in oregon

I also have a drawing for a set of LZx flanges that I drew. hopefully before too long I'll be in a position that I can produce them myself.

I build all sorts of custom robots and 5+ axis machines as well as additive manufacturing tech. I could print sand molds and cast aluminum rockers or cam blanks and grind them. It just more of a project than I planned.

@ericjon262 What ratio are the comp "Magnum" roller rockers? If they were to magically shrink and fit on the pedestals, how would they ride on the valve stems?

Do you know who makes the header flanges? I might pick some up vs plasma cut them.

District fabrication is where I got the flanges.

(503) 505-4456

Districtfab.com