74u

iTrader: (9)

I recently bought a 99ss M6 with a LS2 stroker in it.

TSP 402 - Eagle Crank, Eagle H-Beams, Diamond pistons, 10.8scr
Patriot stage 3 heads
244/248 - - .619/.619 (w/1.85 Comp Pro Magnum RR's) - - 112 LSA
Fast 92 ported to approx 95mm
95mm TB & 100mm MAF
FLP 1 3/4 long tubes
4.10 gears

Previous owner says it dyno'd 471whp with valve float issues which are still present today. I took it to the track Saturday on regular radials and ran 11.93 @ 119.6mph (2.00 sixty...1100DA) launching at idle.

I'm not concerned with the ET as I know some tires would probably put me in low 11's.

The heads on my motor were used in a previous build and are higher mileage than the rest of the build. I believe the valve guides are worn and I want to address valve float (screams to 6500 rpm then hits a wall due to valve float). So I want to freshen up the heads, or upgrade all together if absolutely necessary. What would you do?

I also think the 1 3/4 headers are on the small side. Would it be worth the cost of upgrading to 1 7/8?

Do you guys see any other opportunities I've missed?

redtan

iTrader: (5)

What gear and RPM are you going by the traps? Depending on your setup, a gear change might put you in a better spot at the top and gain some mph.

Also why are you launching at idle? That defeats the whole purpose of steep gears. You might as well go to a wider gear and gain some top end since you're not really going to lose out of the hole punch with that launch.

Fixing your valve float issues and revving that sumbitch to 7000+ will definitely get some top end.

Bigger headers will also pick you up some power, maybe even a 102 FAST.

HioSSilver

iTrader: (8)

Get rid of the 4.10's for some 3.90's or 3.73's. You're not utilizing the gear anyway on street tires. Put a light weight clutch in it, 1 7/8 headers, port the actual runners of the fast and not just the opening and you could pick up what you want and then some.

FastKat

iTrader: (10)

One of the hot-rod magazines did an article on LS engines and tested different headers. Everything they tested responded very well to 1-7/8 headers over 1-3/4 headers.

DietCoke

iTrader: (18)

2" headers, stock rockers, and a bigger/better cam. easy 5mph

valve float is from those heavy rockers

74u

iTrader: (9)

4th gear around 66-6700rpm though I think I was holding it a bit past the line. Launching at idle due to lack of traction on street tires. I agree the valve float has got to go...the car revs so fast to 64-6500 then noses over all the sudden...I'm sure it would pull pretty close to 7k.

It has a Textralia clutch in it now...very light pedal and great feel. I'm already planning 3.89's and a S60...but this season I want to buy/build horsepower.

In your opinion would the headers be worth $1000+? I'm glad to do it unless someone tells me i would gain more by spending it on heads...

I forgot to tell everybody, this car is driven to work 4 days/week in traffic jams, etc.
What's wrong with the current cam? I would almost want to go smaller if i was gonna start over...this cam surges pretty bad.

Also, do you think I could fix my valve float with better springs? I'd hate to give up lift by going back stock, but if better springs won't fix it...guess that's what I'll do.

slow trap

iTrader: (22)

my motor is similar to yours with only a few small differences and puts down mid 53x rwhp with the cutout open,mid 51x closed. mine has more scr/dcr. mid 11.x compression, 1 3/4 lt's, 244/248 on a 110 +1, home ported 90/90 that I mainly just deridged, 85 mm maf.
an 1 3/4 tube and a 90/90 setup can glow quite a bit of air. yeah I am sure 1 7/8 and a ported 102 would pick up alittle but I doubt it would be enough to justify the change. fix that valve float issue and some drag radials and report back.

slow trap

iTrader: (22)

my motor is similar to yours with only a few small differences and puts down mid 53x rwhp with the cutout open,mid 51x closed. mine has more scr/dcr. mid 11.x compression, 1 3/4 lt's, 244/248 on a 110 +1, home ported 90/90 that I mainly just deridged, 85 mm maf.
an 1 3/4 tube and a 90/90 setup can glow quite a bit of air. yeah I am sure 1 7/8 and a ported 102 would pick up alittle but I doubt it would be enough to justify the change. fix that valve float issue and some drag radials and report back.

DietCoke

iTrader: (18)

If that cam surges, your tune is junk. I have a 257/272 cam on a 109ls in my car and it drives like a baby. Find a new tuner, the cam isn't the problem. There is nothing WRONG with your cam, it just wont make power. It is too small for the airflow needs of a 408. You also need a bigger exhaust split.

jlrz28

iTrader: (7)

As everyone else has said get the stock rockers with the trunion upgrade. Get the car tuned by a competent tuner after that is done. Next I would get some tires. If your worried about the heads send em off to a reputable shop to have them gone through. If its near the price of a new set of heads why not pick up a set of TEA LS6 or 215 heads? Then go from there.


On another note
Not sure about $1k for headers I bought the 1 7/8 Hookers for $400-$600.

ls1kbush

iTrader: (2)

Stock rockers and new tuner should fix all your problems and make the car more enjoyable. I have a 255/263 cam in my 402 with a m6 with a 3.55 gear and no surge.

74u

iTrader: (9)

So far I've decided I'm going to get 1 7/8 headers. I was originally thinking Kooks, but now thinking some TSP stainless would save a few bucks. Also, going to go back to stock rockers with a trunion upgrade. My next question is whether I will have enough cam...

I just looked at the spec card and it's .335/.334 lobe lift. So when I go back to a 1.7 ratio I'm looking at .569/.567 valve lift...I wonder how much power is being left on the table?

So, still haven't decided if I'm gonna do a head, or cam upgrade.

If I were to buy new cathedral heads...what do you guys think about TFS 220 as cast on my 402? Woth the money over TEA, or other ported stockers?

jwindbigler

iTrader: (20)

If you get better springs, that should fix your valve float issue. I had my stock valves float on me at about 6300-6400. Better springs would have negated that.

With the 102mm intake, youd have to switch out your heads to the LS3 style. (unless FAST has changed something in the last couple years, so someone please correct me if Im wrong)

I think that if you swapped out your springs and perhaps got 3.73 gears, youd get the 4-5mph you're looking for

Johnnystock

iTrader: (6)

Dont change the cam until you tried the stock rockers. Work one solution at a time.
-stock rockers
-check springs if you still have valvefloat
-bigger headers
-bigger cam and better tune

74u

iTrader: (9)

Normally I'd agree 100% but a rocker swap alone is going to drop my valve lift into the .560's. Doesn't that seem bad for a H/C/I stroker?

JakeFusion

iTrader: (7)

No... unless the midlift flow of those Patriot heads stink.