usdmholden

I'm refreshing a stock 1998 LS1, and plan to swap oil pump, timing chain, etc.

I have no plan to swap the cam as of right now because I don't really want to spend the $800 for a whole kit (cam, springs, pushrods, seals).

So, since I will be buying a new timing chain set, what is the best valve timing for a stock LS1 with a stock 1998 LS1 cam? Car will have a stock LS1 intake and diy ported TB, decent 1 7/8 long tube headers (Accufab), true duals with x pipe, and will be pretty light (Mustang).

At some point I will pull the 806 heads and give them a diy port and valve job, but that won't be until the end of the year at least. I'd mostly just like to get the engine in and the car driving, that is why I'm willing to skip the cam swap while it's apart.

Thanks

usdmholden

So not a popular cam question, I guess I should have expected that.

From searching back circa 2003-2005, it appears as if an .050" intake closing angle of about 40-44 deg ABDC is desirable. However, I've seen no good data on how much advance or retard is ground into the stock cam. The posts have said everything from 4 deg advanced to 3 deg retarded.

I'd planned on retarding the cam to bring up power up in the higher engine speed ranges. I guess I'll time the intake valves iteratively until I hit .050" valve lift about 43 deg ABDC, this makes the ground in advance/retard irrelevant.

Unless there's a better than stock cam kit out there for about $350, which is doubtful.

JakeFusion

iTrader: (7)

I don't recall what the advance is on the stock 98 cam. The specs are: 198/209, .500/.500 119.5 lsa

If no advance, stock timing is approx...

IVO -20.5 BTDC (- indicates ATDC)
IVC 38.5 ABDC
EVO 44 BBDC
EVC -15 ATDC (- indicates BTDC)
ECL 119.5
Overlap -35.5 degrees

Either way, the cam is so small and has such little overlap, you aren't going to gain a whole heck of a lot.

usdmholden

I ran the published numbers through the VE calculator also and saw the numbers you posted.

Retarding the stock cam about 4 degrees gets it in the range of where intake valve closing was recommended, I was sort of hoping someone had done it before.

If retarding the cam picks up 5-10 hp then it's well worth it, especially considering I'm swapping the timing chain anyway which makes the 5-10 hp free. Timing the stock cam on small block Fords with stock heads used to pick up near 2 mph on 1/4 mile trap speeds. Per rule of thumb 2 mph is about 20 hp. I don't know if an LS with much better stock heads than a SBF will pick up more or less, but either way, timing the valve events is free and one extra hp is more than zero.

Thanks.

JakeFusion

iTrader: (7)

I doubt it would. You're just lowering the dynamic compression to push the RPMs up in the range. So unless you're going to up the rev limiter, you're actually going to decrease your midrange power for no appreciable benefit.

usdmholden

It's going in a Mustang which is pretty light and has a steep rear gear, so low end is not really a concern. Rev limiter is not a concern with aftermarket EFI.

Thanks

usdmholden

So to keep the hot topic going...

Fabricated a piston stop, modified the LS1 crank bolt so my SBF timing wheel fit the LS1, rigged up a magnetic mount for the indicator base, and went to town.

Degreed the stock LS1 cam tonight using the OEM 90k mile timing chain. lifter events at .050" were 23 deg ATDC and 40 deg ABDC.

So doing the math it's 180-23+40=197 deg duration at .050.

197/2=98.5

98.5+23=121.5 ICL.

On a 119.5 LSA a 121.5 ICL is retarded 2 degrees.

I'm going to swap the chain for the new JP Performance 5618T I bought, re-time it, and see how it is with the new chain. I'll probably leave it set at 2 deg retard or maybe go to 4 deg retard. Don't really know, it probably won't make much difference either way.