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Ls2 403 with L92 heads looking for improvement

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Old 12-01-2016, 08:10 AM   #41
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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?
The larger displacement stroker needs more air and fuel to feed it. So, it will need more duration and lift to feed it with a given heads and intake. With this, generally comes more overlap.

There is no certain or magic number or amount of overlap. I hate making generalizations, but on street sized cams, as the overlap goes up the cam gets more powerful in the upper RPM. The sweet spot for you will be where acceptable manners and desired power output meet. That could be negative 5 degrees, 0 degrees or posiitive 10 degrees at .050".

I think if most street car enthusiasts chose thier camshaft based on driving experience alone, they would choose less aggressive cams than most do. But, we all get excited by a big dyno number and/or a tough sounding idle. A well designed mild camshaft will make just as much power or more up to around 5500 RPM than a comparably aggressive camshaft. But, it wont make that big peak horsepower that we can boast about. The struggle is real
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Old 12-01-2016, 08:45 AM   #42
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Originally Posted by CAMMOTION PERF View Post
The larger displacement stroker needs more air and fuel to feed it. So, it will need more duration and lift to feed it with a given heads and intake. With this, generally comes more overlap. There is no certain or magic number or amount of overlap. I hate making generalizations, but on street sized cams, as the overlap goes up the cam gets more powerful in the upper RPM. The sweet spot for you will be where acceptable manners and desired power output meet. That could be negative 5 degrees, 0 degrees or posiitive 10 degrees at .050". I think if most street car enthusiasts chose thier camshaft based on driving experience alone, they would choose less aggressive cams than most do. But, we all get excited by a big dyno number and/or a tough sounding idle. A well designed mild camshaft will make just as much power or more up to around 5500 RPM than a comparably aggressive camshaft. But, it wont make that big peak horsepower that we can boast about. The struggle is real
Your not kidding about the struggle. Honestly I'd probably be alright with only making 467 rwhp in a 403 if the drivability was better. The bucking gets so bad at times I think I'm going need to visit a chiropractor lol. What's your suggestion on cams you offer for a L92 headed N/a stroker? Car sees 50/50 street and track. I'm thinking about selling this cam and getting in touch with you guys
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Old 12-01-2016, 08:47 AM   #43
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And Lord knows that we love to tape dyno graphs to our dicks and swing them around.
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Old 12-01-2016, 08:48 AM   #44
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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.
Makes sense. I really appreciate all your help thus far.
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Old 12-01-2016, 10:04 AM   #45
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Your not kidding about the struggle. Honestly I'd probably be alright with only making 467 rwhp in a 403 if the drivability was better. The bucking gets so bad at times I think I'm going need to visit a chiropractor lol. What's your suggestion on cams you offer for a L92 headed N/a stroker? Car sees 50/50 street and track. I'm thinking about selling this cam and getting in touch with you guys
I created a camshaft just for guys who wanted the extra torque of a stroker, but still wanted great street manners. It is the "Stealthy Stroker": http://store.cammotion.com/stealthy-...rectangle-port . This camshaft will drive great. It will have good power everywhere and never irritate you. However, it will not set the dyno on fire. It is 230/240 on 116+4 with .621" lift. It has 3 degrees of overlap at .050"

A reasonable compromise might be something like a custom 234/242 on 115+4. This camshaft will have 8 degrees of overlap. With this camshaft, you will still have a defined lope, but much milder than what you have now. It will still buck a bit, but at a much lower RPM. This camshaft is not a dyno killer either, but it will make a more than the Stealthy Stroker.
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Old 12-01-2016, 11:29 AM   #46
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Good thread. The shape of the dyno graph is what interests me the most. As with this setup the power starts to nose over at around 6300 rpm. With the 18.5* of overlap it does seem a bit short.

One thing I've learned is camshaft overlap is not the "only" thing to help carry power higher. My little under square 383 w/ 1 3/4 headers & 5* of overlap screams to 7k. I've only seen up to 6600 on a dyno chart & that's my peak power.

Sounds like a sweet GTO. I think your on the right path.
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Old 12-01-2016, 02:10 PM   #47
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I created a camshaft just for guys who wanted the extra torque of a stroker, but still wanted great street manners. It is the "Stealthy Stroker": http://store.cammotion.com/stealthy-...rectangle-port . This camshaft will drive great. It will have good power everywhere and never irritate you. However, it will not set the dyno on fire. It is 230/240 on 116+4 with .621" lift. It has 3 degrees of overlap at .050"

A reasonable compromise might be something like a custom 234/242 on 115+4. This camshaft will have 8 degrees of overlap. With this camshaft, you will still have a defined lope, but much milder than what you have now. It will still buck a bit, but at a much lower RPM. This camshaft is not a dyno killer either, but it will make a more than the Stealthy Stroker.

I'm really interested in that cam (Stealthy Stroker), do you offer them for catdral port heads as well?, I have a set of PRC 237 heads that I would like to use on my 416 LS3 based engine.
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Old 12-02-2016, 08:27 AM   #48
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I'm really interested in that cam (Stealthy Stroker), do you offer them for catdral port heads as well?, I have a set of PRC 237 heads that I would like to use on my 416 LS3 based engine.
Yes we do. Here it is:
http://store.cammotion.com/stealthy-...-port-camshaft
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Old 12-13-2016, 05:47 PM   #49
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Originally Posted by CAMMOTION PERF View Post
I created a camshaft just for guys who wanted the extra torque of a stroker, but still wanted great street manners. It is the "Stealthy Stroker": http://store.cammotion.com/stealthy-...rectangle-port . This camshaft will drive great. It will have good power everywhere and never irritate you. However, it will not set the dyno on fire. It is 230/240 on 116+4 with .621" lift. It has 3 degrees of overlap at .050"

A reasonable compromise might be something like a custom 234/242 on 115+4. This camshaft will have 8 degrees of overlap. With this camshaft, you will still have a defined lope, but much milder than what you have now. It will still buck a bit, but at a much lower RPM. This camshaft is not a dyno killer either, but it will make a more than the Stealthy Stroker.
The OP's static compression is only 10.9:1. Wouldn't that later intake closing point from the 116 and 115 LSA bleed down too much cylinder pressure to not lose a noticeable amount of mid range and low end? He already complained the motor was soft down low. Plus stock LS3 heads aren't exactly the most efficient casting out there.

A cam with say, 230/238 on a 112 would only be 10 degrees overlap. My h/c combo had 8 degrees and was smooth coasting in 6th gear all the way down to 1100. Granted I had cathedrals, but just a thought...


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Old 12-14-2016, 09:59 AM   #50
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The OP's static compression is only 10.9:1. Wouldn't that later intake closing point from the 116 and 115 LSA bleed down too much cylinder pressure to not lose a noticeable amount of mid range and low end?
Actually, the camshaft that I offered to the OP closes the intake valve 3.5 degrees earlier than his current camshaft:

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Old 12-17-2016, 05:56 PM   #51
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Old 12-18-2016, 04:10 PM   #52
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Well, I finally got my 403 build done and tuned back in May. After driving it for a few months I'm fairly happy with it but I came far short of my goal of at least 500whp. I've attached the Dyno sheet below. Car made 467 434 on a know to be stingy mustang Dyno. The car just doesn't feel very torquey to me and seems to run out of steam faster than I'd like. I spoke with btr where I bought my cam and they are insisting 1 7/8 headers will really open this setup up, but I'm a little skeptical of this. I kind of feel maybe the cam is leaving some on the table. With all the voodoo floating around out there on cam selection for rectangle port heads I'm not sure now if I made the right choice. Looking for suggestions as to what I could do to improve this setup and gain some hp and torque. Looking to keep it n/a. My current setup is listed below. Car is tuned on speed density. Thanks for the help

2006 GTO 6speed manual Ls2 block -Full Manley 403 rotating assembly with -4cc flat tops with reliefs -Rings gapped for N/a - Johnson 2110 lifters @ .035 preload -stock rockers with trunion upgrade -Stock L92 heads with btr .660 springs -Stock LS3 .051 thick head gaskets -static compression 10.9:1 -Btr N/a stroker cam Cam specs are 239/254 .624"/.595" 114+3. -Fast 102 lsxr manifold with NW102 throttle body -Pacesetter 1 3/4 headers with catless mids to custom 3in exhaust -stock ls3 injectors currently at 92% duty cycle. New 70Lb injectors and dw265 fuel pump waiting to go in. Attachment 549301
Any updates? have swapped in another cam?
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Old 01-02-2017, 06:15 PM   #53
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No not yet, works been busy with the oil industry picking up again. Hopefully this week I'll have it all buttoned up. I'm going to keep my current cam for now, I'm also switching tuners. Both my previous and current tuner have mustang dyno's and my car has been within 5 whp between the two dyno's. I should have a update next week.
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Old 01-12-2017, 02:20 PM   #54
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Well just a small update. Finally got my piston to deck height measurements and on average I'm about .004 in the hole. Ordered some .036 thick cometics and they should be here in a week or so since they weren't in stock. I'll keep updating here as I get closer to getting this thing done.
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Old 01-19-2017, 06:55 AM   #55
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In for updates.
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Old 02-22-2017, 09:06 AM   #56
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Well cars back together and running very well, it's leaned out a good bit at full throttle so hopefully that translates to more airflow. Car goes in for tuning on the 8th. I'll have the results posted as soon as Its done.
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Old 03-06-2017, 05:02 PM   #57
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In for results!!
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Old 03-08-2017, 06:11 PM   #58
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Well guys I did it 501rwhp/ 466rwtq on the same dyno stock l92 heads, thinner .036 head gaskets and 1 7/8 kooks headers. It gained 15-20 across the rest of the entire curve. I'll get the sheet posted once i get home.
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Old 03-08-2017, 10:08 PM   #59
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Very nice. Was this on the same dyno as before which I think you said was a Mustang dyno?
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Old 03-09-2017, 12:04 AM   #60
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Good job man!, quench is more important than most of us think.
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