docwyte

I've got a set of cnc ported 243 heads ready to install. Do you guys think I'll need them to hit mid 360's?

TonyG

Huh? You were already past that figure.

I don't understand.

TonyG

eclou

docwyte

Nope, I'm still at 336rwhp. Had the car retuned, got pretty much the same hp, but with less timing.

Hence me going with a different cam and I'm going to ditch the cats and have them flanged so I can run them when needed.

TonyG

Was that the same with the tune I sent you?

This makes zero sense.

336RWHP is nothing for a bolt-on'ed, mile cammed, headers/exhaust LS1.

Have you done a leak down on the engine?


TonyG

95ONE

Most LS1's back in the late 90s were making 300whp stock. 335-345 with Intake headers and exhaust / tune. Add a cam to that and you should be near 360and higher. ..

TonyG

The factory rating was what was because of the log type headers, the small exhaust, the cats, and an extremely mild cam.

Headers, dual exhaust, and a cam and a tune routinely add 75HP.

Most stock LS1's with headers, dual exhaust, no cats, a tune, and a LS6 or better intake manifold (which Doc has) can easily make over 380RWHP on pump gas.

Mine made 389RWHP on bone stock 241 heads.

Eclou's made over 375RWHP on his first round of tuning...which I'm sure will improve.

The trick is not to over cam it or over time it and have a good exhaust and at least the LS6 intake (or better). An enlarged TB helps as does as straight shot from the air cleaner to TB.

Doc's 336RWHP is off in light of his mods. Something is off. He should start with a leak down test and go from there.


TonyG

eclou

Bruce keep in mind my run was on a Mustang dyno. I know we can't compare apples and oranges but most runs on Mustang dynos read conservatively vs Dynojets. Just for kicks I might do a pull on Carboy's Dynojet after I get the car back - all my other dynos for the 2.5L were done on their rollers.

2bridges

Well I get your point, but for anyone interested here are flow results for LS1/LS6 heads with and without manifold.

Without Manifolds - Headflow Only:
Cylinder Head Intake Manifold .200" .300" .350" .400" .450" .500" .550" .600"
Stock LS1 N/A 137 187 207 223 228 237 242 243
Stock LS6 N/A 156 204 225 243 257 268 275 278

With Manifolds:
Cylinder Head Intake Manifold .200" .300" .350" .400" .450" .500" .550" .600"
Stock LS1 LS1 136 184 200 214 222 227 229 235
Stock LS1 LS6 136 186 206 223 227 236 241 242
Stock LS6 LS1 156 199 212 224 232 238 243 247
Stock LS6 LS6 154 204 220 235 247 257 263 265

Cam duration (how long the valve is open) typically increases with lift, so yes a cam with higher lift cam and more duration will make more peak power in general. Obviously these chracteristics may shift the powerband.

reasoning that you will make no more power with .550 lift vs .500 lift is not typically the case with cam profile taken into consideration.

docwyte

Eclou has no cats, a ported throttle body, was running without an air filter, has slightly ported 241 heads and has a more wild cam then me.

My plan is to remove my cats, go with a much larger K&N air intake that will also push the MAF away from the air filter, add a cam with some split (226-230 vs the 224/224 I have now) and then retune. I suspect these changes will get me to where you guys are.

I've talked with several other converted LS 944 owners who are making the same power as I am with the same equipment.

With Eclou making the power he is with the same headers I am, but with a more wild cam and a more open intake, I know I can make the same if I basically duplicate it. My tuner here feels my cam is too flat and that's what is causing the hp loss.

Jfrahm

Are you maxed out on rocker ratio?

TonyG

I disagree.

If the head isn't increasing in flow, there's no point to lift the valve off the seat further. All that does is wear out valve springs faster.

And because he's got a roller cam, he can get the ramp he needs to get the duration he wants at a lift that doesn't exceed .550 with what ever lsa he wants.

And according to GM published data in the GMPP Catalog (page 197), the stock LS6 & LS2 intake/exhaust w/o intake are as follows (in cfm):

.200" .300" .400" .500" .600"

Intake
136 196 237 260 260

Exhaust
104 136 157 169 180


The LS1 head flows even less.


TonyG

2bridges

We are arguing semantics to a degree, but you originally stated anything above .5 lift is ineffective for LS1 and LS6 stock castings.

For the LS6 243 castings that is not the case. Real world flow numbers and actual before/after dyno results (cam swap only) show significant gains.

For LS1 241 castings I tend to agree - the juice is not worth the squeeze.

And for both LS1/LS6 non ported castings , lift above .550 again is not worth the valve train abuse for the insignificant gains

TonyG

What's interesting to note is how the LS6/LS2 style exhaust port flow keeps going up past .600" in stock form. That could be capitalized on for sure...

TonyG

eclou

Well I have gotten to drive the car a couple of times for maybe a total of 30-45 min. I am very impressed. The power delivery is much different than the K27/6 I ran, with torque just everywhere. The power does not tail off at redline either, if anything the car pulls harder past 6k rpm. Very quick throttle response and easy to modulate with the right foot. I think this will be a blessing on the track.

The power steering (running a modified GM PS pump) feels the same, the clutch is a bit stiffer than before which is good, and I love the hydroboost brakes compared to my old failing brake booster. I cannot wait to get this beast on the track. I replaced a few panels with fiberglass and CF so I figure 50-70 pounds lighter than before.

I discussed with Eric at TPC the possibility of developing a budget package for a swap based on the L33 aluminum 5.3L truck motor. This motor was in the extended cab Silverados on a few years and should be able to output within 15-25hp of a comparable LS1 with the same mods. The difference being the L33 longblock is plentiful and can be pulled from a salvage yard for maybe $600 vs $1500-2500 for a used LS1.