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new cam blues-help!


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my brother has a silverado 5.3l 4x4. it's a 2000 ext cab. he recently put a cam in and now seems to have lost power compared to before. the night after the install it seemed awesome to him. he called me so excited. now however it seems to have less power than stock and especially below 2500 rpm. his quarter mile time is in the 17's instead of 16.5 also a code was thrown. it's the random misfire code, p0300 i think. i have racked my brain trying to help him. i have looked at some hptuner forums and truck forums and some hot cams can throw a code i've heard. well what do you do to fix that so he's got a good running truck again. we need some help trying to fix this problem. he's 17 almost 18 and has a great truck he thought he was improving on and as his older brother i'm trying to help him fix it (28 yrs old). n-e-way what can you guys suggest

 

jasonsdakota

2004 dakota 4.7 v8 2wd auto

high output mopar cams

exhaust

4.10 gears

 

lukes silverado

2000 5.3 4x4 ext cab auto

210 duration cam (192 stock)

cai, nelson tune (neither tune runs great with cam)

stock 3.42 gears

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Guest chevydeerhunter
my brother has a silverado 5.3l 4x4. it's a 2000 ext cab. he recently put a cam in and now seems to have lost power compared to before. the night after the install it seemed awesome to him. he called me so excited. now however it seems to have less power than stock and especially below 2500 rpm. his quarter mile time is in the 17's instead of 16.5  also a code was thrown. it's the random misfire code, p0300 i think. i have racked my brain trying to help him. i have looked at some hptuner forums and truck forums and some hot cams can throw a code i've heard. well what do you do to fix that so he's got a good running truck again. we need some help trying to fix this problem. he's 17 almost 18 and has a great truck he thought he was improving on and as his older brother i'm trying to help him fix it (28 yrs old). n-e-way what can you guys suggest

 

jasonsdakota

2004 dakota 4.7 v8 2wd auto

high output mopar cams

exhaust

4.10 gears

 

lukes silverado

2000 5.3 4x4 ext cab auto

210 duration cam (192 stock)

cai, nelson tune (neither tune runs great with cam)

stock 3.42 gears

 

 

 

 

 

I'm going to ask an obvious question here. Was the cam properly broken in? What is the advertised lift and is everything else stock on his ride?

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There is no break in for a roller cam. I did this cam thing on a 5.7. louzy results. Less power louzy idle. most pleasurable cam i ever installed was a tiny lift short duration zero overlap economy cam in a 454. thing ran like a diesel, awesome tire ripping low end torque, top end good. I wasn't racing it but the driving and trailer towing was truly great. the factory cam is surprisingly good.

 

ken

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The problem with cams is that they need to be designed to match the other components on the motor. Cams are tricky, they will deliver more power at one end and more torque at the other end. The best way to increase power all around that I have found was the addition of the 1.6:1 comp cams rockers. They fool the motor into thinking that it has a bigger cam and therefore amplifies the stock numbers. Buying a cam and installing it is a tricky business. The lobe need to match the seat pressure and spring rate. The entire package needs to be designed for what he wants. If he is looking for power at the top end, he will loose it at the bottom, etc. Hope this helps. Try the Crane web site or the comp cams website for recomendations. As far as the code part, I have heard this happening in cams that were inexpensive and not fully designed for the application.

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I agree completely, you trade something to get something else. the stock cam is a reasonable trade off for power, torque and driveability. You never get anything for nothing. I think the 3.42 gears on the vehicle in question don't mate well with a more radical cam.

 

I know the situation really sucks because I have been there. If it were mine, and I were not racing, I would go with an itty bitty economy cam or back to the stock. driving fun comes from low end torque not 6000 rpm power.

 

The stock cam in my 5.3 surprises me every time I floor it at 70 and watch the speedo slide past 100 even in my 5000 lb blunt object and the tire smoke at stoplight grand prixs intimidates oponents and I only have 3.73s.

 

ken

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I can see possibly several things happening. If a high lift / long duration cam was used the power band will be significantly higher in the RPM range. The higher the power band, typically the lower the low end torque. That combined with GM's notorious torque management system would suggest to me that the truck would fall flat on its face.

 

The PCM is programmed to control the engine within specified parameters. With a high lift / long duration cam, you are adding much more air to the cylinder. Is the computer corresponding with enough fuel? Added air/fuel means increased cylinder pressure is the spark knock sensor detecting detonation and changing the timing to compensate?

 

If the cam, valve springs, intake, and exhaust are all designed to work together, then have the PCM reprogrammed I think you will be amazed at the results.

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I can see possibly several things happening.  If a high lift / long duration cam was used the power band will be significantly higher in the RPM range.  The higher the power band, typically the lower the low end torque.  That combined with GM's notorious torque management system would suggest to me that the truck would fall flat on its face.

 

The PCM is programmed to control the engine within specified parameters.  With a high lift / long duration cam, you are adding much more air to the cylinder.  Is the computer corresponding with enough fuel?  Added air/fuel means increased cylinder pressure is the spark knock sensor detecting detonation and changing the timing to compensate? 

 

If the cam, valve springs, intake, and exhaust are all designed to work together, then have the PCM reprogrammed I think you will be amazed at the results.

 

 

 

 

bowler,

that's good advice. we tried the reprogrammed pcm thing and maybe it is running lean. i have heard the random misfire code can be caused from running lean with a fat cam. should we try larger injectors, or adjustable fuel pressure regulator. could this stop that code and more importantly, cause the truck to run like it's suppose to.

it's suppose to be a fairly mild cam. we're not exactally blazing on the top end. it's just plain below average now. do we need bigger injectors? if so, what is the stock size injector and what size should we go with.

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A number of years ago I had an 86 Full size Jimmy with a 5.0. I wanted some extra pulling power for towing. I was reluctant to change the cam. While investigating cams, I discovered that the RV and Towing cams had a short duration and the exhaust lift was typically higher than the intake. The higher the lift, and longer the duration the higher the power band went in the RPMs.

 

As a result I decided to experiment by replacing my stock 1.5 exhaust rockers with 1.6. The results were great. The engine breathed a lot better and had much more low end torque.

 

I live in Western PA. There are a lot of hills near my home. Before changing the exhaust rockers, the torque converter would always unlock on certain hills at highway speeds. After the change on the same roads, it was rare that the torque converter would ever unlock.

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These are good points. There is a lot of manure out there about "rv" cams and more power from certain cams. bottom line is that the stock cam is quite good and was chosen by decent engineers after much experimentation.

 

Moving the torque curve up to a higher rpm may be great if you are racing but stinks in normal driving. Give me increased low-end torque anyday. that is what feels good under your foot.

 

I would like to know more about the rocker ratio thing, I wonder what the trade-offs are on that. there must be some negative about that or they would be there from the factory. wouldn't they do a zero cost improvement to advertise more power.

 

I am not knocking the rocker ratio thing, I just want to know more about the concept and why it isn't done at the factory.

 

Ken

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The downsides....

 

Higher ratio rockers are a little tougher on the stock valve springs. There were designed to compress only so much. The new rockers compress them a little more. That also might put a little more pressure on the cam and rollers (a little more resistance). The valves are also moving further each stroke so a little more wear on the guides as well but with a good oil and regular changes I don't really see a problem. I would think that as long as your not hitting the top of the piston you should be fine.

 

DEWFPO

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The downsides....

 

Higher ratio rockers are a little tougher on the stock valve springs.  There were designed to compress only so much.  The new rockers compress them a little more.  That also might put a little more pressure on the cam and rollers (a little more resistance).  The valves are also moving further each stroke so a little more wear on the guides as well but with a good oil and regular changes I don't really see a problem.    I would think that as long as your not hitting the top of the piston you should be fine.

 

DEWFPO

 

 

 

 

 

But would it hurt low end TQ? Or just maybe a broader TQ curve?

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