Raising compression on LS1 and other C5 mods over winter

[Cujet]

I haven't autocrossed in years but for autocross the best bang for your buck is tires and suspension. Getting the gearing right might be worthwhile but the little bit of HP you will gain from your proposed mods will not improve your times that much. If you are modifying your car you are no longer in a stock class so an improved suspension set up and sticky tires should be allowed. I don't know your proficiency level but you should also consider some driving instruction from a pro. That can really knock your times down.

YES! Autocross is generally strongly biased towards low speed grip. To that end, there are very specific setups that help.

I was kind of guessing that the OP wanted more acceleration for practical reasons.

 

[clinebarger]

Yes, I realize new pushrods will be needed as well as most likely valve springs...I have an email to Texas Speed right now asking their guidance.
I do have 241 heads...not easy to find 243's around here at a decent price, but I will keep looking.
I have found accounts of several people taking 0.050" off and using stock intakes with no mods. Also Lingenfelter engineering says max safe with no mods is 0.050"
Was already going to use a 0.041" head gasket to help with CR
My neighbor owns this race shop, and will most likely do final tuning.
https://offthelineperformance.com/?...GYHpBWhRQaL2dt6rNFRhf6lf-o_kOfvMaAlgvEALw_wcB

799's are the same head, 243 & 799 castings came on millions of Gen IV 4.8/5.3 engines.

 

[clinebarger]

Off topic, Forgive me!

LZ1 6.0L's (Hybrid Vortec 6000) can be had pretty cheap, AFM & VVT delete, Refresh with a 24x crank reluctor & 1x Cam gear, Custom grind.
It's basically a LS2 with AFM & VVT, Has either 799 or 243 heads.

 

[DriveHard]

OP, while off topic, in the normally aspirated world, the old claim that there is no replacement for displacement, still holds true. It is often difficult to get significantly more torque from a specific engine that is already well tuned. A huge increase in HP requires RPM and airflow.

I'm reading between the lines and it seems that you want considerably more than the 20HP you'll gain with your planned mods.

With that in mind, why disassemble the engine at all? Just install a supercharger and enjoy the powa!

While I agree 100%, and love the response. I'm on the path of learning new things. I have rebuilt engines from the ground up and made considerable more power, I have added and refined forced induction for more power. I have never played with compression ratio and rocker arms for added power, and I have not seen dyno results from just those changes...which seem to be quite simple and lower budget. It seems I will get 3-5% for both changes...if I get an added 25hp from these I would be more than happy ;-)

 

[DriveHard]

I haven't autocrossed in years but for autocross the best bang for your buck is tires and suspension. Getting the gearing right might be worthwhile but the little bit of HP you will gain from your proposed mods will not improve your times that much. If you are modifying your car you are no longer in a stock class so an improved suspension set up and sticky tires should be allowed. I don't know your proficiency level but you should also consider some driving instruction from a pro. That can really knock your times down.

Correct. The gear change is for AutoX, the power adders is for me to have fun and learn. I am already not in the stock class with long tubes, intake, and a tune...so why not push the envelope of the class I am in?

 

[DriveHard]

Off topic, Forgive me!

LZ1 6.0L's (Hybrid Vortec 6000) can be had pretty cheap, AFM & VVT delete, Refresh with a 24x crank reluctor & 1x Cam gear, Custom grind.
It's basically a LS2 with AFM & VVT, Has either 799 or 243 heads.

I'm not on a path to pull the engine right now. Just play with some characteristics of the one I have.

 

[berniedd]

I'm reading between the lines and it seems that you want considerably more than the 20HP you'll gain with your planned mods.

With that in mind, why disassemble the engine at all? Just install a supercharger and enjoy the powa!

I completely agree. Plus, it is reversible and the supercharger boost pressure/power gain can be adjustable.

 

[DriveHard]

It doesn’t truly increase duration as that is ground into the cam. But it increases the area under the curve because the valve is lifted off the seat slightly earlier and held off slightly later. It does not give the same effect as actual added duration as a lobe change would do.

Sure, it’s a modification, but now you’re changing where the rocker contacts the valve tip, and pushrods will change, and for all the added cost there, in keeping with your other fairly low-buck and low-complexity mods you’d be better served with the trunnion kit and keeping the stock ratio. It’s pretty well proven that LS rockers are well-designed and strong for a factory offering, and that the headaches induced by changing ratios are much greater than the minimal performance benefit.

I will have to change push rods for the milling of the heads anyways, so why not do the rockers as well? I agree it is a good design, and hard to beat, but if the only change is different push rods, and I already have to do that...why not play?

 

[SubieRubyRoo]

I will have to change push rods for the milling of the heads anyways, so why not do the rockers as well? I agree it is a good design, and hard to beat, but if the only change is different push rods, and I already have to do that...why not play?

Because any stock rocker in 1.8 is not going to line up since the LS7 heads have offset intake rocker tips, and for the cost you’ll spend on aftermarket you can make other changes that will bring much bigger results than changing the ratio.

Besides, have you thought about replacing valve springs since you’re at 100k? I’d do new polished beehive springs and titanium retainers before rocker arms. Stock rockers are good to at least 7k RPM anyways, plus with milling the heads and increasing lift now you need to worry about PTV clearance around TDC.

 

[DriveHard]

Because any stock rocker in 1.8 is not going to line up since the LS7 heads have offset intake rocker tips, and for the cost you’ll spend on aftermarket you can make other changes that will bring much bigger results than changing the ratio.

Besides, have you thought about replacing valve springs since you’re at 100k? I’d do new polished beehive springs and titanium retainers before rocker arms. Stock rockers are good to at least 7k RPM anyways, plus with milling the heads and increasing lift now you need to worry about PTV clearance around TDC.

Yes, I planned on doing springs as well...figured it was due, as it is often revved to redline and held there for a second or two.
I need to get out the pencil and do some math, as I have not answered the PTV question yet.

 

[OVERKILL]

Yes, I planned on doing springs as well...figured it was due, as it is often revved to redline and held there for a second or two.
I need to get out the pencil and do some math, as I have not answered the PTV question yet.

You should clay it to confirm, if that's the route you are going. I'm not sure what the stock P2V is on that engine, it could be that the 1.8's don't have a meaningful impact, but a wise man always checks.

 

[SubieRubyRoo]

You should clay it to confirm, if that's the route you are going. I'm not sure what the stock P2V is on that engine, it could be that the 1.8's don't have a meaningful impact, but a wise man always checks.

The unwise man is frequently buying some new valves & maybe a few pistons

OP I’d also add a new double-roller timing set to your list of mods. I forget which brands have them that fit under stock covers, but the added strength won’t be a waste considering your stock set has 100k. Probably be a good move to replace the oil pump as well with one of the Melling ones.

 

[clinebarger]

The unwise man is frequently buying some new valves & maybe a few pistons

OP I’d also add a new double-roller timing set to your list of mods. I forget which brands have them that fit under stock covers, but the added strength won’t be a waste considering your stock set has 100k. Probably be a good move to replace the oil pump as well with one of the Melling ones.

C5-R & C6-R single row roller Iwis timing chains hold up very well, Hinson Motorsports is likely the easiest source. Don't think he wants to pull the front cover as the steering rack is in the way of pulling the balancer.

 

[DriveHard]

C5-R & C6-R single row roller Iwis timing chains hold up very well, Hinson Motorsports is likely the easiest source. Don't think he wants to pull the front cover as the steering rack is in the way of pulling the balancer.

ding ding ding...yes, I'm not set up to pull an engine right now, and I didn't want to get that deep. Another reason I wasn't looking at bolt on superchargers for the moment. Cam change, timing change, supercharger (requires pinning the pulley), are all off the table for right now. I am in the middle of getting a car for my mother in law up and running good, as well as getting my son's first car (Mini Cooper) ready to drive and first AutoX events next summer. I would love to be greedy with my time on the Vette...but other irons in the fire and all...

 

[ls1mike]

-I am NOT changing the cam...I want to keep that stock.

My 00 LS1 has been cammed for 60,000 miles, you don't have to pull the heads and is very streetable and easy to daily drive. My WS6 is the car my kid learned to drive 6 speed on with a McLeod twin disk clutch.

If you are pulling the heads and doing pushrods, rocker arms and valve springs I don't understand not wanting to do the cam.