Help with Cam Selection For my 94 Z71 Build

[David Barry]

LSA you can run depends on the duration. The stock GM 305 TBI cams are on a 109* LSA. The stock GM TBI Marine 305 and 350 cams are also on a 109 LSA.

The nice thing about OBD1 stuff is the equipment to tune them is still available and not nearly as expensive as the OBD2 stuff.

I real time tune my OBD1 stuff with a Moates Autoprom Emulator.

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L31 - I spoke with a knowledgeable mechanic today who has pretty much convinced me that my 240,00 mile driven Sierra would not hold up well if I have a new cam put in. Should I decide not to, would acquiring OBD1 testing equipment adjust my engine far better than my computer with a Hypertech chip in it?

 

[df2x4]

L31 - I spoke with a knowledgeable mechanic today who has pretty much convinced me that my 240,00 mile driven Sierra would not hold up well if I have a new cam put in. Should I decide not to, would acquiring OBD1 testing equipment adjust my engine far better than my computer with a Hypertech chip in it?

Just wanted to caution you that L31MaxExpress has been caught spreading false information on other forums. I would take any advice he gives you with a grain of salt and double check with reputable sources.

That said, I can guarantee you that a custom tune with that Moates hardware/software would be miles ahead of any HyperTech or other drop-in performance chip. There will be a learning curve to it though.

 

[RDF1]

L31 - I spoke with a knowledgeable mechanic today who has pretty much convinced me that my 240,00 mile driven Sierra would not hold up well if I have a new cam put in. Should I decide not to, would acquiring OBD1 testing equipment adjust my engine far better than my computer with a Hypertech chip in it?

The truck wouldn't hold up well?
Or the engine?
Not quite sure what he would be talking about unless he thought you were going to do heads and cam on the original engine?

Sent from my HiDiNg PlAcE

 

[xx94Z71xx]

how much did that setup run you? i have a laptop already. plus i would need to learn how to use the software. i would really like to learn how to do something like the setup you have there. I would like to set it and forget it tho.

my cam and lifters came in today, so im almost ready to start putting everything together.



Dave Berry, not sure what your mechanic is saying either. only thing i can think is that maybe putting a performance cam on a tired motor will shorten the lifespan? 240,000 miles is alot but at the same time if it was maintained properly and not beat it will be fine, although it wouldnt hurt to freshen it up. my truck has over 280k on it and when i had the heads off this spring there was alot less wear then i expected to see. AND it still runs. of course i didnt get a look at the bearings or anything but still.

 

[Supercharged111]

People are stupid. They think performance mods on a high mileage will kill it. I switched to synthetic oil at 160k and put the cam in around 220k and the blower went on around 240k. Find a new mechanic.

Though Fast makes bold claims, he's absolutely correct when he says tolerable LSA depends on duration. It's camshaft 101.

 

[David Barry]

The cam would be be put in my original engine. My mechanic worked on these engines for many years back in the '90s and early 2000s. With so many worn parts, he thinks I'll be disappointed in the limited performance gains. (I've been considering going to synthetic oil.)

I'm no mechanic, but I keep reading that intake duration at 050 should be 206 or below: lobe separation 112 or above for my 350 engine to idle & run smoothly without having to make any changes with the stock computer. It's not a 305 or a marine 350, if that matters.

 

[xx94Z71xx]

personally i think that the cam your adding isnt going to cause you too much trouble. while you have the intake off to install the new cam, you could always go a bit further and take your heads off and get them rebuilt or replace them with a better set. at that point you can also get a good look at what your cylinder walls look like.

i was suprised after all the miles on mine that there wasnt even a ridge at the top of the cylinders.

as far as the bottom end goes can you drop the oil pan on these trucks without removing the engine? been a while since i been underneath mine and cant remember.

 

[L31MaxExpress]

The cam would be be put in my original engine. My mechanic worked on these engines for many years back in the '90s and early 2000s. With so many worn parts, he thinks I'll be disappointed in the limited performance gains. (I've been considering going to synthetic oil.)

I'm no mechanic, but I keep reading that intake duration at 050 should be 206 or below: lobe separation 112 or above for my 350 engine to idle & run smoothly without having to make any changes with the stock computer. It's not a 305 or a marine 350, if that matters.

If you make changes to the stock engine, it would be advisable to make changes to the stock computer. 10-15 years ago when I played with these trucks all the time, I found altering the stock computer alone to offer more power than a cam or headers in an untuned state.

My point of bringing up the 305 or Marine 350 TBI cams was this. If you do a little math on the cams, you will realize that those 109* LSA cams have less overlap than most 112* LSA aftermarket cams.

The 305 cam is 179/194 @ .050, .350/.385 on a 109 LSA and 106 ICL. It idles at 500 rpm with 20-22 in/hg of vacuum.

The 350 Marine cam is 196/206 @ .050, .431/.451 on a 109 LSA and 106 ICL. It idles well at 550 rpm with 18+ in/hg of vacuum.

I have run a 204/214 @ .050, .423/.446" 112 LSA on a 107 ICL cam in a 350 and it makes about 16-17 in/hg. You can usually get this one to run very well on a stock computer chip, however it runs much better when you dial in the fueling and timing.

When you get into tuning, you can pretty much run whatever cam you want.

My old setup was a 11:1 TPI 383 with a 232/240@ .050, .540/.560" lift, 110 LSA, 106* ICL roller cam. Was being run by a 1995 TBI PCM modified for port fuel. That engine made 12 in/hg of vacuum @ 850 rpm out of gear and about 9 in/hg of vacuum in gear.

 

[Supercharged111]

The cam would be be put in my original engine. My mechanic worked on these engines for many years back in the '90s and early 2000s. With so many worn parts, he thinks I'll be disappointed in the limited performance gains. (I've been considering going to synthetic oil.)

I'm no mechanic, but I keep reading that intake duration at 050 should be 206 or below: lobe separation 112 or above for my 350 engine to idle & run smoothly without having to make any changes with the stock computer. It's not a 305 or a marine 350, if that matters.

Mechanics don't build race cars. They don't know half as much as they claim to when it comes to performance. They need to stay in their wheelhouse. They're also, largely, opposed to tuning the computer.

 

[PlayingWithTBI]

I went with the Lunati 10120700 in my build. IMO any mods you do to an engine, you need to "tune" it. I bought a mail order custom chip but wasn't happy with the performance. Now, after downloading TunerPro RT (free) and buying an ALDL OBD1 cable ($60) from http://aldlcable.com I can data log my ECU while driving (another way to do it cheaply). I'm working with Dave w from OldSchoolEFI to fine tune, log some more, and fine tune again until we're happy. He converted my 1227747 ECU from the 2732A EPROM (that needs UV to erase) to a ZIF (Zero Force Insertion) socket and 27FS512 flash EEPROM (~$5/ea) which can be erased and burned in seconds 1,000s of time. There is a multitude of info at http://www.gearhead-efi.com