LS3 top end swap

[Gelf VXR]

ringram said:

I dont think there will be any point changing cams mate.
That is so close there is no point as its within normal cam variation. IMO you should use the spend on something else.

Im going with a 222/230-112 LSA - 112 ICL for my pending LS3 (was thinking of a 114, but after the Big Meet I realise cam overlap is good)

Only a tiny bit larger. But then the engine is ~3% larger than the LS2 anyway.

Your probably right, but cams paid for, I wanted to change the valves and stem seals, so it will go in eventually

[mikeyb1987]

Gelf VXR said:

I just got my cam data from FTI for a custom cam after submitting their cam spec form, my criteria was for a daily driver, UK emmisions compliant, no loss of bottom end, maximum torque under the curve, and to pull to 6400rpm. Purchase is required before you can receive the spec.

Taking into consideration I would be swapping in LS3 hollow valves, increase compression slightly from .051 stock head gasket to .040 cometic gaskets,retaining 1.85:1 rockers. I also have a modified RC LS3 intake with runner bars + ¬8CFM

I wasn't too surprised to see the spec hardly changed from the SLP cam I already have installed

Installed SLP cam 216/229 113+3 .330/.331

Custom FTI cam 219/229 113+4 .340/.342 (.629/.633)


I was thinking maybe upto 223/231, but looking online 219/223 (LS3 valves) or 219/227 (L92 valves)is popular small cam now

http://www.g8board.com/forums/showthread.php?t=837...

http://www.gmhightechperformance.com/tech/lsx_engi...



Unfortunately im still out of the country working, itll be some time before i can get in installed

The 223/231 cam is the one I have.

If you need some new L92 valves with retainers, look on ebay

[Gelf VXR]

mikeyb1987 said:

The 223/231 cam is the one I have.

If you need some new L92 valves with retainers, look on ebay

I've ordered LS3 valves

Did you get your emissions checked yet?

[mikeyb1987]

Gelf VXR said:

mikeyb1987 said:

The 223/231 cam is the one I have.

If you need some new L92 valves with retainers, look on ebay

I've ordered LS3 valves

Did you get your emissions checked yet?

Nice- LS3 valves are what I run.

Nope, still need to get the emissions checked- hopefully I'll get them checked in the next month or so.

[Gelf VXR]

Gelf VXR said:

ringram said:

I dont think there will be any point changing cams mate.
That is so close there is no point as its within normal cam variation. IMO you should use the spend on something else.

Im going with a 222/230-112 LSA - 112 ICL for my pending LS3 (was thinking of a 114, but after the Big Meet I realise cam overlap is good)

Only a tiny bit larger. But then the engine is ~3% larger than the LS2 anyway.

Your probably right, but cams paid for, I wanted to change the valves and stem seals, so it will go in eventually

There is one other important aspect and that's lobe design, all I know at this stage is that their asssymetrical, but not what degree

[ringram]

Probably fast lift with slower seating!?

But with a tad extra duration and lift you will have a few more BHP there. Maybe 10rwhp, but I guess you will find out later.
I doubt valve change will add anything except stability at higher rpm.
If you are swapping valves maybe you should look at a good valve job and clean up the valve pockets that will probably add similar power on top.

http://www.speedtalk.com/forum/viewtopic.php?f=1&a...

[Gelf VXR]

ringram said:

Probably fast lift with slower seating!?

But with a tad extra duration and lift you will have a few more BHP there. Maybe 10rwhp, but I guess you will find out later.
I doubt valve change will add anything except stability at higher rpm.
If you are swapping valves maybe you should look at a good valve job and clean up the valve pockets that will probably add similar power on top.

http://www.speedtalk.com/forum/viewtopic.php?f=1&a...

Good idea while the heads are off, I'd like to see improvements to the low ~ mid lift, and tidy up the exhaust port, any recommendations for who can perform this service in UK, I assume the new LS3 valves can be modified and used?

should have thought of this before I sent off the cam form....

[ringram]

http://serdi.co.uk/serdi2/portal/main/?Section=20%...

[Gelf VXR]

ringram said:

http://serdi.co.uk/serdi2/portal/main/?Section=20%...

You know someone who has had there LS heads worked there, testimonial?


This is what I mean about not pulling up top, first two images are of my VE table with stock cam, next two are with the SLP cam, VE drops of a ledge after 5600rpm, i suspect valve train stability issue.





[url]


Added dyno graph, also shows torque dropping off

|http://thumbsnap.com/rR0huhEg[/url]

Edited by Gelf VXR on Thursday 10th July 09:37

[ringram]

Gm rockers ftw...

[Gelf VXR]

ringram said:

Gm rockers ftw...

Are you sure for short duration aggressive lobes and high lift?

The grunion upgrade is to stop the needle bearings from falling into the engine when the do fail, meaning they do fail often?

http://www.superchevy.com/how-to/vemp-0703-corvett...


there's a problem it needs investigating

Could be too week springs, push rods, L92 valves, a combination of all, I'm sure FTI would have an opinion if the rockers inhibited RPM? I'm inclined to believe its springs if binding has caused the seals to pop off

Time will tell

Interesting read on lifter pump up, Ed has recommended minimum seat pressure 150~155 with LS3 hollow valves, my patriot golds are only 135 with L92 solid valves...

http://www.cranecams.com/faqview.php?s_id=33

Edited by Gelf VXR on Thursday 10th July 13:22

[ringram]

Yeah its weight over the valve apparently. So valves. springs, retainers, rockers etc.
OEM rockers might not like that lift as much. But some pretty hard core engines run OEM rockers.
Maybe you need more spring with the heavy valves and rockers as you note.

I will be using oem rockers with single conical springs. KISS principle and staying close to OEM spec where possible to stay close to tested operating parameters. The more you change the more you diverge from what GM has spent millions on testing.

[MyM8V8]

Gelf VXR said:

ringram said:

Gm rockers ftw...

Are you sure for short duration aggressive lobes and high lift?

The grunion upgrade is to stop the needle bearings from falling into the engine when the do fail, meaning they do fail often?

http://www.superchevy.com/how-to/vemp-0703-corvett...


there's a problem it needs investigating

Could be too week springs, push rods, L92 valves, a combination of all, I'm sure FTI would have an opinion if the rockers inhibited RPM? I'm inclined to believe its springs if binding has caused the seals to pop off

Time will tell

Interesting read on lifter pump up, Ed has recommended minimum seat pressure 150~155 with LS3 hollow valves, my patriot golds are only 135 with L92 solid valves...

http://www.cranecams.com/faqview.php?s_id=33

Edited by Gelf VXR on Thursday 10th July 13:22

If you speak the Craig at Dynotorque he is a firm believer (IIRC) that the stock rockers are what are needed and that the YTs cause flutter at high end.

Having said that I had no problems with Cathedral port LS2 heads using YT's (224-232 .585 x .583.) I'd give re installing the stock rockers as a control.

[Gelf VXR]

MyM8V8 said:

If you speak the Craig at Dynotorque he is a firm believer (IIRC) that the stock rockers are what are needed and that the YTs cause flutter at high end.

Having said that I had no problems with Cathedral port LS2 heads using YT's (224-232 .585 x .583.) I'd give re installing the stock rockers as a control.

YTs vs stocks are certainly hotly debated, Ive searched online for definitive data to come to a conclusion, I found this interesting thread "valve float" in which Brian Tooley and Ed Curtis have posted, some good and a few more with bad experiences noted, my conclusions are stocks are good for low lift long duration even upto 8K, higher lift and the swipe patern is too wide for the valve stems. The YTs need careful consideration to valve spring rates, require hollow valves, light retainers etc to get them to perform as desired.

My cam and valve train is spec'd for use with 1.85 YT's, 6.5K red line, fingers crossed...

http://www.yellowbullet.com/forum/showthread.php?t...

Edited by Gelf VXR on Monday 14th July 14:08

[ringram]

Sounds like a plan.
I like the decisiveness and willingness to put your plans into action and money on the line

The DYOR is also good. Nobody has all the answers and an informed decision is a good start.

[mikeyb1987]

Update! With sports cats the car is MOT compliant



It's close on the fast idle, but a pass is a pass. The tune is less than perfect, so I imagine the fast idle can be improved.

Just thought I'd update/confirm the cam is emissions compliant, in case others are thinking about cam specs.

Mike

[mikeyb1987]

A post in another thread made me realise I hadn't updated this thread for my results at Thunder road this year:

Best in class with a top speed of 169.20mph in a standing mile

Just need to find a way to squeeze an additional 0.8mph out of the car!!

[SturdyHSV]

mikeyb1987 said:

A post in another thread made me realise I hadn't updated this thread for my results at Thunder road this year:

Best in class with a top speed of 169.20mph in a standing mile

Just need to find a way to squeeze an additional 0.8mph out of the car!!

Some ideas (not all of them brilliant ):

• Non-nostril bonnet
• Remove the rear spoiler
• Remove the wipers?
• Tape up some panel gaps

As you can tell, I'm of the mind a little bit of an aero improvement might be all you need. That or favourable weather (cold, no headwind)

[VinceM]

mikeyb1987 said:

A post in another thread made me realise I hadn't updated this thread for my results at Thunder road this year:

Best in class with a top speed of 169.20mph in a standing mile

Just need to find a way to squeeze an additional 0.8mph out of the car!!

If memory serves correctly there was a slight headwind on the day this year, a slight change in direction might have yielded a higher speed for us all

[pah250]

VinceM said:

mikeyb1987 said:

A post in another thread made me realise I hadn't updated this thread for my results at Thunder road this year:

Best in class with a top speed of 169.20mph in a standing mile

Just need to find a way to squeeze an additional 0.8mph out of the car!!

If memory serves correctly there was a slight headwind on the day this year, a slight change in direction might have yielded a higher speed for us all

I think Mikey did remove his spolier on the last run.

I wish I'd removed mine now, as it might have got me into 2nd or even 1st overall.