Ls2 403 with L92 heads looking for improvement - Page 2 - LS1TECH



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Ls2 403 with L92 heads looking for improvement

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Old 09-27-2016, 08:32 AM   #21
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Did you figure it out? I'm looking to build almost the exact same motor and looking for 500+ for my road race car
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Old 10-01-2016, 09:30 AM   #22
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The heads are chocking it, get a set of PRC 237's and you will be amaized
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Old 10-01-2016, 10:54 AM   #23
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My setup with a 408 with Scoogin Dickey cnc lsa heads with stock ls3 intake and 1 3/4 ps headers made 506/ 468 with a bad clutch and a smaller cam than his.
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Old 10-08-2016, 09:58 PM   #24
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Your headers are definitely too small.

I wouldn't focus much on a dyno number. You just need to get to the track and see how it runs and what is the trap speed, and then you'll know where you stand. Every dyno is different so one guy with a 500 RWHP number could be slower than another guy with a 450 RWHP number. My car was stuck in the mid 400's on the dyno too but I went to the drag strip and walked away on the big end from 500+ RWHP cars that were tested on different dynos. In one case my trap speed was +10 mph faster than one of those "500 RWHP" turbo cars.

I have 20 degrees of overlap with my iron 427 stroker and I can get down to 1300 rpm without any bucking. LS3 top end (PRC ported heads), FAST 102-R, NW 102 throttle body, yadda yadda.

Initially I did have a lot of bucking at low/no load situations below 2000 rpm. I fixed it by playing with a combination of things...

* Primary problem was too much fuel at no load condition. I had to lean out the fuel quite a bit at 0% throttle position. That totally eliminated bucking with deceleration.

* I had to shift the Idle Air Control ramp down to a higher rpm because IAC was initiating some of the bucking.

* I changed injector end angle to create more torque at low engine speed. That fixed bucking at light throttle below 1800 rpm, and made a huge difference in low rpm torque -- especially off idle. Your cam is huge in comparison to stock and the original injector end angles aren't appropriate any more.
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Old 10-09-2016, 09:43 AM   #25
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QwkTrip,
Thanks for sharing.
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Old 10-09-2016, 03:21 PM   #26
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Sorry for my lack of response. Works been hectic. Had the car retuned 2 weeks ago. The bucking seems to be better. I do plan on changing head gaskets in the next month once the nice weather is gone so that my quench is optimized.
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Old 10-09-2016, 03:29 PM   #27
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Qwktrip I'm not too fixated on dyno numbers at the moment. I was at a dyno day a few days ago and made 504/ 480 on a dyno jet vs my tuners mustang dyno.

As far as injector angles go any way you can enlighten me as to how that works? I had the tune touched up but still get some bucking between 1700-2000. I'm running dw 60Lb injectors now which are actually 72lb at 58 psi

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Your headers are definitely too small. I wouldn't focus much on a dyno number. You just need to get to the track and see how it runs and what is the trap speed, and then you'll know where you stand. Every dyno is different so one guy with a 500 RWHP number could be slower than another guy with a 450 RWHP number. My car was stuck in the mid 400's on the dyno too but I went to the drag strip and walked away on the big end from 500+ RWHP cars that were tested on different dynos. In one case my trap speed was +10 mph faster than one of those "500 RWHP" turbo cars. I have 20 degrees of overlap with my iron 427 stroker and I can get down to 1300 rpm without any bucking. LS3 top end (PRC ported heads), FAST 102-R, NW 102 throttle body, yadda yadda. Initially I did have a lot of bucking at low/no load situations below 2000 rpm. I fixed it by playing with a combination of things... * Primary problem was too much fuel at no load condition. I had to lean out the fuel quite a bit at 0% throttle position. That totally eliminated bucking with deceleration. * I had to shift the Idle Air Control ramp down to a higher rpm because IAC was initiating some of the bucking. * I changed injector end angle to create more torque at low engine speed. That fixed bucking at light throttle below 1800 rpm, and made a huge difference in low rpm torque -- especially off idle. Your cam is huge in comparison to stock and the original injector end angles aren't appropriate any more.
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Old 10-24-2016, 01:01 PM   #28
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+1 on checking your buddy's work. Had a friend not ensure pushrods/lifters were making cam contact which led to the rocker arm turning sideways. Had me running super rich on 7 cylinders and almost put a pushrod through the valve cover =/
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Old 11-16-2016, 06:25 PM   #29
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Well scored a set of used 1 7/8 kooks for a killer deal a few days ago. When I get home from work I'll be changing the head gaskets to adjust my quench down to optimum as well.

Still debating on if I should waste any money on porting these L92 heads while they are off. Maybe atleast have the exhaust side hand ported since the intake side already flows so well. Anyone have input or experience on doing this?
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Old 11-16-2016, 10:16 PM   #30
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Up to you, but I'd be more inclined to leave the heads alone and see how much the headers really do help.

Just for reference, I'm at 490/470 with my 404 and a stock LS3 topend.
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Old 11-17-2016, 12:02 AM   #31
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Up to you, but I'd be more inclined to leave the heads alone and see how much the headers really do help. Just for reference, I'm at 490/470 with my 404 and a stock LS3 topend.
That's kind of what I'm thinking. I'm sure with the tighter quench and headers I'll see some gain out of it.

What kind of dyno did you run yours on? Just want to make sure I compare apples to apples here.
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Old 11-18-2016, 06:47 AM   #32
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My GTO was on a DynoJet and the numbers were SAE corrected. M6 ,3.73s, and Kooks stepped headers with a 2.5" exhaust. The cam is a 231/239 on a 115 LSA. The lift is in the .600-.620 range.
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Old 11-30-2016, 08:18 AM   #33
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Ok so I got my driver side head off in preparation to go to a thinner head gasket to get quench in the ideal zone. For only having 3k miles on this motor and always having a catch can this sure seems like a lot of carbon build up. Would this be due to my quench not being ideal? Am I right in my thought process? Car used maybe Half a quart of oil in the last 3k miles. Any thoughts on this?


Ls2 403 with L92 heads looking for improvement-image-2398350817.jpg
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Old 11-30-2016, 10:22 AM   #34
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I got exactly the same cam as you have and I also got it from BTR, my engine is a 416 based on LS3 and I'm using the same heads. my Dyno number is so similar at 468/434. I too have some surging when cruising at 1500-2000 rpm which is very annoying. I got 1 7/8 dynatech headers. I' too ' was expecting something north of 500 RWHP!.

Finally, I got so mad about drivability of this sh*t, so I swapped the BTR cam with a LPE GT11 very tamed cam, and the car now is so much quite and smooth to drive (almost as stock), and the dyno numbers where 458/428, I lost only 10 hp going down to GT11, so I think there is something not right about this cam that it just can't get all the potential of this engine combo.

I will be watching you closely to see what will happen with your plan, I really wish you a good luck, I really know how you feel, I've been there, lol.
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Old 11-30-2016, 12:17 PM   #35
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Quote:
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I got exactly the same cam as you have and I also got it from BTR, my engine is a 416 based on LS3 and I'm using the same heads. my Dyno number is so similar at 468/434. I too have some surging when cruising at 1500-2000 rpm which is very annoying. I got 1 7/8 dynatech headers. I' too ' was expecting something north of 500 RWHP!. Finally, I got so mad about drivability of this sh*t, so I swapped the BTR cam with a LPE GT11 very tamed cam, and the car now is so much quite and smooth to drive (almost as stock), and the dyno numbers where 458/428, I lost only 10 hp going down to GT11, so I think there is something not right about this cam that it just can't get all the potential of this engine combo. I will be watching you closely to see what will happen with your plan, I really wish you a good luck, I really know how you feel, I've been there, lol.
Yep I was a little frustrated. Especially after speaking with Brian himself. He claimed it had excellent drivability and should be very close to 500 with my exact setup. We'll see how my new upgrades do. In a second conversation with him he agreed that getting my quench and going to 1 7/8 should new me a good bit more power. Honestly I'd be happy with just another 20 wheel on stock l92 heads. We shall see I guess
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Old 11-30-2016, 02:39 PM   #36
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Yep I was a little frustrated. Especially after speaking with Brian himself. He claimed it had excellent drivability and should be very close to 500 with my exact setup. We'll see how my new upgrades do. In a second conversation with him he agreed that getting my quench and going to 1 7/8 should new me a good bit more power. Honestly I'd be happy with just another 20 wheel on stock l92 heads. We shall see I guess
He told exactly the same thing. but as the guys said, 18* of overlap is too much for any street driven car no matter how good the tuner is.

I already got another custom cam spec'ed by Patrick G and cut by TSP, along with cathedral port PRC 237 heads which I'm going to install in a month or two, I guess between my case and your case, we will know exactly if this cam is worth sh*t.
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Old 11-30-2016, 06:22 PM   #37
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The carbon does look a little heavy on the exhaust side on that piston, but with the reversion that is going on, the engine isn't effectively exhausting the cylinder in that 1500-1800 RPM range, which could explain the build-up.
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Old 11-30-2016, 07:03 PM   #38
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On the drivability issue, that is something I really try to spend time talking to people about because it is subjective. What one guy will say "drives like stock" another guy will say is a bucking, annoying, bad driving experience.

Another problem with this is walking the fine line of performance vs street manners. I talk to customers all the time who don't want any bucking or drivability sacrifices, but they also want to impress their friends with a big dyno number. These two qualities are typically at odds with one another in a naturally aspirated engine.

As many knowledgeable posters said above, it is all in the overlap in this case. Two valve events make up the overlap: The intake valve open event and the exhaust valve close event. The intake valve open event has to be relatively early because that helps the intake tract effectively feed the needs of the larger stroker engine. The exhaust valve close tunes the overlap and cleans the combustion chamber.

The exhaust valve close is something you could reduce here to reduce your overlap and improve your manners. The sacrifice you will make is upper RPM horsepower. You would have to decide if you want to make that trade.
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Old 11-30-2016, 11:22 PM   #39
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Quote:
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On the drivability issue, that is something I really try to spend time talking to people about because it is subjective. What one guy will say "drives like stock" another guy will say is a bucking, annoying, bad driving experience.

Another problem with this is walking the fine line of performance vs street manners. I talk to customers all the time who don't want any bucking or drivability sacrifices, but they also want to impress their friends with a big dyno number. These two qualities are typically at odds with one another in a naturally aspirated engine.

As many knowledgeable posters said above, it is all in the overlap in this case. Two valve events make up the overlap: The intake valve open event and the exhaust valve close event. The intake valve open event has to be relatively early because that helps the intake tract effectively feed the needs of the larger stroker engine. The exhaust valve close tunes the overlap and cleans the combustion chamber.

The exhaust valve close is something you could reduce here to reduce your overlap and improve your manners. The sacrifice you will make is upper RPM horsepower. You would have to decide if you want to make that trade.

Thanks for the great info, this really summarize it so cleanly. I have one question, though, Will a larger displacement engine (a stroker) be effected less with overlap than stock displacement, like 416 stroker LS3 vs 376 stock?

For example, I had a cam with 12* overlap in a stock LS2 which was not so great in low RPM, if I ever use the same cam in 416, will I be seeing less surging/bucking at the same RPM?

Is there a borderline where I can have enough overlap to make a good scavenging effect but not enough to cause any low RPM drivability issue?
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Old 12-01-2016, 07:27 AM   #40
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I really wish I'd of spoke to cam motion like I first planned when I was building the motor I'm thinking of maybe selling this btr cam and giving them a call.
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