Boback1

My car makes great power with this setup, 551 rwhp with a hurt engine but surges like no other. I've heard stroker engines can soak up cam surge better than smaller engines but this cam surge is crazy. When cruising around parking lots in 1st or 2nd it violently shakes my car. I had brian tooley custom spec me a cam and it exceeded my power goals but I'm starting to get thoughts of going to a smaller cam. The cam surge is making the car not fun to drive. Just wondering if my cam's overlap should be surging this bad or it's a tune issue. My cam has an over lap of 21.5 degrees. My last motor was an ls1 with an ms3 cam so that's all I have to compare. I'm about to rebuild my motor for really bad blow by and 2 cylinders with 29 percent leakdown so debating on going to a smaller cam. Wouldn't mind losing 10-15 hp for better drivability but I would love to stick with this cam of it can be tuned out.

243/256 .627/.596 114+4
Ls3 416
11:8:1 compression
Tea tfs 235 nitrous port
Stock rockers with comp trunion
Fast 102
Holley 95mm throttle body
Johnson lifters
3/8 pushrods
93 octane
Mantic twin disc clutch

gagliano7

Are you sure the tune is good? It is a big cam but with those cubes i figured it would tune nice. I am a fan of smaller cams so i would go smaller but i would think a good tuner could fix it. What kind of car is this in? Are you throttle by cable or wire. I would also post in the tuning section for responses on your setup and tuning.

JakeFusion

iTrader: (7)

21 degrees is still a lot on a 416 if you want anything like stock-like drivability. I would be willing to bet the tune is garbage for drivability and they spent time on the WOT power numbers. It takes a lot longer to dial in drivability, especially with a big motor and big cam.

It will drive better than the MS3 did in a 346 tho. Considerably so.

Do you have access to the tune? If not, can you throw a vacuum gauge on it and see what it idles at and what happens when you rev it or drive it around? That can tell you if there's something going on with the hurt motor adding to the issue.

Boback1

yes i can post the tune. how do i do it? it is a cable driven throttle body. it is in a 1997 nissan 240sx. i need to check the vacuum.I've had an issue with this motor every since i dropped it in. it won't rev pass 6200 rpm. it hits a hard cut and back fires. checked every single limiter multiple times. me and my tuner have gone over the tune so many times i gave up. tried everything besides pulling the motor and checking the reluctor wheel. everything in this motor is new besides rocker arms. it for sure has loss power from when it was new.

the ls1/ms3 cam motor drove way better than this setup which really suprised me.

JakeFusion

iTrader: (7)

Sounds like you have a lot of other issues going on.

Boback1

yes it does. the motor is coming out soon to check and rebuild . But just wanted to get opinions of the cam before i pull the motor and swap to a smaller cam.If you say it should drive better than the ls1/ms3 setup then i'll stick with this cam and gonna assume the extreme cam surge is related to problems with motor. Was also thinking of converting to newer style ecu with dbw and 58x reluctor if it needs it. do you still want to see the tune?

JakeFusion

iTrader: (7)

Yeah, you can post it as an attachment. HPTuners or EFILive?

The Gen III PCM doesn't handle big cams as well as the newer PCMs. I'd consider upgrading to a E38 and doing the 58X. There's a lot more adjust-ability to make a big cam behave very well with the newer PCMs.

Boback1

it's hptuners.
ok so its worth it to swap to a newer pcm and os. now is the stock ls7 90mm good enough for this setup or will i need to get the nw102 ?

Darth_V8r

iTrader: (4)

I have a friend with a larger cam than that in a 388. Not getting really bad surge. I wonder if the blowby is bad enough that you are getting unbalanced power output?

NEstyle

iTrader: (1)

I have 19.5 degrees of overlap in a 364 and it only surges a very little bit after tuning, and only when the converter is locked. I hope my tuner can get the last little bit of surging to go away.

455GTO

iTrader: (18)

If you haven't already tried to replace the crankshaft position sensor I would give that a shot. I had the exact same issue on my stroker motor when I tried to reuse my CPS sensor from my LS1. Swapped in a new sensor and was able to rev to the moon.

Boback1

That's what I was hoping to hear. I knew the surge shouldn't be this bad.
I have replaced the crank sensor with a new one and one from a known good running car. Only thing I haven't tried is putting some grease on the sensor and spin the motor a little to see if the reluctor is too far back or forward. But it's kind of too late for that I think. The engine is definetly hurt. Compression is good but leakdown is bad.

JakeFusion

iTrader: (7)

Pull the motor and get it right. You can't tune a hurt motor.

If it made 550 with a 6200 limit, that's a strong motor... especially with that sort of blowby. Get that sumbitch fixed!

Gen III PCM should be good enough. I wouldn't pull it just yet. Get the motor working right. And then try.

Gen IV is what I would have started with though. But it's not a cheap upgrade.

Also--are you using an aftermarket harness or stock? Some of the aftermarket harnesses can be ****.

Boback1

Yeah it definetly still holds its own . I have a -10an on each valve cover and valley cover vent going to a vented catch can and the dipstick still pops up. I have to tie wire it down to keep it from popping up.

It's a wiring specialties harness made for ls1 swap into my car. I was using this harness with my ls1/ms3 setup and it was working perfect. That motor revved to 7000 rpm all day

Here's a pic of the dyno but no torque. It was just to verify the power. 2nd pic shows torque but the dyno was way off.
https://photos.google.com/search/_tr...Ye1QYuGG2QnorM

https://photos.google.com/photo/AF1Q...r4IoZ6PwFFp5cr

Darth_V8r

iTrader: (4)

If you're building up that much pressure I really think that's you're primary issue. Two -10 lines should honestly be enough to keep it vented

AnotherWs6

iTrader: (17)

Yeah, sumpin dont sound vernon.

00pooterSS

iTrader: (40)

The 6200 thing.. sounds like the ignition timing is freaking out or possibly losing valve control/floating them. But I'm with everyone else, no point in trying to fix the surge with the motor hurt. You can only smear so much lipstick on a pig.

Boback1

I'm gonna have everything checked when i pull the engine. I've been having this problem for 2 years and could never figure it out. new pcm's,crank senor's,cam sensor's,coils,plugs,fuel system,02 senors, even using a picoscope to check for cam and crank sensor wave to make sure it's not dropping out. everything looks perfect until it happens. But none the less the engine is coming out and i think i'm gonna convert over to an e38 pcm and dbw. Heard it's better at making big cam's run smoother, plus i wanna do flex fuel to use e85.

Is it worth buying a nw102 throttle body over using a ported stock ls7 90mm throttle body ?

Thank to everyone for the help and replying.

Jimbo1367

That's what I always thought about my ex-wife.

G Atsma

Whoa.... now that's a cold shot, man! lol