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Old 07-18-2013, 05:34 PM
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5.7 vortec

I have a 1998 GM Z71 with a 30 over 5.7 with the factory heads. I would like to up grade the heads to 202 versions of the vortec heads and a good RV cam. What are the factory heads that I have on it now? These are stock heads I'm sure they are not the 906 or the 062 version can anybody help me? I need more power for pulling a camper.

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Old 07-18-2013, 05:45 PM
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If your current motor is the original motor,you have either 906,or,062 Vortec heads.If they have been changed,give us the casting # on them,so,we can determine what they are.For the use you stated,you want to stay with the 1.94 valves rather than 2.02's.The 906 & 062's are the best GM cast production heads to date.All 96 & up 5.7 engines were equipped with these heads.
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Old 07-18-2013, 06:13 PM
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Gm 5.7

I just talked to a friend of mine he told me to feel around the back side of the heads for the markings what I have are the saw tooth markings which should be the 906. what about changing the stock cam to an RV power cam? I thought about contacting Com Cam to see what they say. I just looking for some low end power, is there a chip that can be changed?
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Old 07-18-2013, 06:43 PM
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Gm 5.7

Will headers and a tuned exhaust help with low end power? I would like to stick with a quite exhaust system as well.
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Old 07-18-2013, 07:16 PM
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Sounds like you need a steeper rear end ratio. What size tires are you running? what rear end and what gears does it have currently? Was it just rebuilt to stock specs when it was taken .030 over? Any CELs currently?
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Old 07-18-2013, 07:37 PM
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Yes headers & an exhaust are the 1st thing you should do.Nuthin else will help much w/o a good exhaust.You don't have to have it loud to get good performance.Your truck has an OBD2 engine management.No chips.You will have to have the PCM tuned in person,or,you can get a mailorder tune.A good tune & good exhaust are the 2 best things you can do.Any change you make cam,headers,etc will need a tune to get the full benefits & in most cases to run good.A good cam for the stock engine is 1 I am fixin to use in my 5.7 rebuild.It is a GM roller cam & used in the HT383 & Ramjet engines.It produces lots of lowend torque for pulling.Part # is 14097395. You can find them on EBay sometimes for as low as $99.That's cheap for a new roller cam.Most of em around $300.With a tune,that cam,& headers,you can easily be between 300 to 350 HP. 375 ft/lb of torque.I am currently building a 350 using this cam.As far as headers go,longtube are the best,but,i'm using a midlength becuz of ground clearance.There's a lot you can do depending on your budget,but,the tune & exhaust are the 2 best gains for the money.If you really want some torque,you could always stroke it to a 383 cu in.
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Old 07-18-2013, 07:48 PM
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As Valkyrie5.7 stated in his post,your gear ratio is important as well for pulling.I think most Z71's came w/ a 3:42. With a .030 over fresh rebuild,you should be running pretty good if everything is tuned & setup rite.If you are gettin CELs,deal with that 1st to see what improvements that makes.It only takes 1 bad sensor or malfunctioning part can throw your performance'milage etc outta wack.
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Old 07-18-2013, 10:10 PM
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Gm 5.7

1998 Z71 I bought this truck new even though it has 300,000 miles on it still looks great and runs good just want more power.

I had the engine gone through about 20,000 miles or so. I'm running 285/16 tire and I think it has 342 rear gears.

What is a CEL? sorry, I'm 62 & old school I've had plenty of hot rods over the years but this electronic stuff is over my head, I just figured that with the 30 over and the flat top pistions that I would have more low end power.

If I install headers and a different cam how do I go about tuning the engine? Timing adjustment or what?

I was thinking about short headers but I'm hearing different.
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Old 07-18-2013, 10:55 PM
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Quote:
Originally Posted by GM/Jeep View Post
I just talked to a friend of mine he told me to feel around the back side of the heads for the markings what I have are the saw tooth markings which should be the 906. what about changing the stock cam to an RV power cam? I thought about contacting Com Cam to see what they say. I just looking for some low end power, is there a chip that can be changed?
The sawtooth is the 062.


The 906 is lumpy


Do not waste your money on cutting in larger valves.
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Old 07-19-2013, 04:06 AM
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If you are running flat top pistons @ .030 over,your compression is probably a little high.That motor is equipped w/ a Knox sensor.That sensor will retard your timing if it senses detonation.That very well may be why you don't have the power.If the deck wasn't cut during rebuild & a thick head gasket was used,the quench is also excessive which can make detonation even worse.Also,if the Rebuilder used Rebuilder pistons with a 1.54 compression hgt combined with a stock deck,thick gasket,you have no quench to help deter detonation.Is there anyway you can get the part #'s for the actual parts used in the rebuild? CEL is you Check Engine Light on you dash.
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Old 07-19-2013, 04:10 AM
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What are you pulling with the truck?Approx wght?
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Old 07-19-2013, 04:21 AM
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Quote:
Originally Posted by GM/Jeep View Post
1998 Z71 I bought this truck new even though it has 300,000 miles on it still looks great and runs good just want more power.

I had the engine gone through about 20,000 miles or so. I'm running 285/16 tire and I think it has 342 rear gears.

What is a CEL? sorry, I'm 62 & old school I've had plenty of hot rods over the years but this electronic stuff is over my head, I just figured that with the 30 over and the flat top pistions that I would have more low end power.

If I install headers and a different cam how do I go about tuning the engine? Timing adjustment or what?

I was thinking about short headers but I'm hearing different.
It's best to have the tune done in person.You will need to tell the tuner everything installed in/on engine.The tuner may datalog to see the current operating conditions,then make adj in the PCM for best performance & milage.Mailorder tunes are OK,but,it may take more than once to nail it down w/o dataloggin 1st.Just a tune alone could gain you 20 HP or more.For you stated use,long or short headers prolly won't matter that much.Just stay from the shortys w/ small collectors.Ideally,you want the 3" collectors.
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Old 07-19-2013, 07:46 AM
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DO NOT try to set the timing on your engine.Timiing is constantly controlled thru the PCM.It is only adjustable by using a programmer.
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Old 07-20-2013, 06:02 PM
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(tried to write this last night but my power went out at 10pm thanks to a sweet monsoon storm here in Phoenix.)

As has been said above, to tune it, you'll need to approach someone who does aftermarket tuning for these trucks specifically. Here is my recommendation, there's many other people that do tuning:

Black Bear Performance :: Custom Tuning Solutions for 96 and newer GM Vehicles

Do you have the specs on when you had the engine rebuilt? We can tell you whether or not the compression ratio is too high for the knock sensor to compensate for in such a way that it won't kill your timing. Things like if the heads and block were resurfaced, head gasket thickness, compression height on piston and valve relief size of the flat tops. I can't tell you with certainty what your compression ratio is without this info.

3.42s *aren't* the worst gears ever but with larger tires, you could afford to gear a little more steeply. I run rather short tires on my 305-vortec 96 C2500. It has 3.73s in the back and towing is no issue. It's yanked trailers that were twice it's weight around town no problem. Depending on your tire size, the most bang for your buck would be to get a set of 4.11s if you're going to be towing often. The torque multiplication created from gearing with far outperform any bolt-ons, especially for how inexpensive they'll be.

If you can't pull what you need to pull with 4.11s and a vortec 350, you're likely going to need a big block or diesel, and I'd say it's time to step up to a 1-ton.
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