Hey guys, my friend needs my help. he wants to add a cam and longtubes to his 98 4x4 silverado with a vortec 350 in it. i told him that he might be able to get a LT4 hotcam in there since this engine is based on the LT1 right? can someone let me know if it would work, or what would be a similar thing? thanks!

 

its based off of LSx series.

 

Yes it will work. The 5.7 in the truck is more Gen-1 based. But it will work if you use the short gear pin.

 

whats the short gear pin?

 

The pin on the front of the cam that drives the waterpump...

 

It's the Pin that goes in the Timing Chain Gear, and goes into the Opti on the LTX Engines. The Water Pump is Gear Driven on the LTX's..

 

It will fit, like already mentioned, by shortening the pin. I wouldn't do it however. That PCM stops triggering the injectors consistently about 5400 RPM. I would use a smaller cam myself. He might have the idle he wants, but will be throwing away low end and the PCM won't allow him to get the top end that cam is capable of.

Good luck, Ed

 

Thats what i ment...

 

THIS SETUP WILL NOT FIT A STOCK VORTEC 350!!!

unless you pull the heads and have the guides milled down, you'll be in for a HUGE surprise the second you fire it up.


stock vortec heads will only accept AT MAX .480 lift valve lift. the retainer will hit the guide with anything above that.

 

It's good..

 

what cam would you guys reccomend then? he wants the best cam he can get. and how do you change the 5400 limiter?

 

He will have to get it programmed. Then he can use any Cam he wants to really.

 

in a skewed kind of way, a CPI vortec engine is set up like that of an old IDI diesel engine.(minus the whole compression-ignition deal)

they have 1 "injector" that directs fuel to 8 nozzles individually. that open up under a specific pressure, not by electrical current like any other injection system does.

I've never heard of there being any problems with RPM potential, BUT, this is setup like any old diesel is. and there are no diesel that I know of that run that high of an RPM, so it may be in the design of the system that can't differentiate injector "pulses" in that high of an RPM?

anyway, a hot cam WILL NOT CLEAR THE VALVE GUIDES just keep that in mind.

 

Crane makes a set of valve springs/retainers that fit and allow up over .500" lift w/ stock Vortecs (the retainer design allows for more clearance w/ the valve guide boss). They are sold as listed for iron LT1 heads (ie the LT1 heads on Impala SSs, etc) which have a similar guide boss/retainer clearance issue as the Vortecs and are also limited to smaller diameter springs like the vortecs. I don't recall the part number of the kit off hand though.

He'd want to run better valve springs on any cam he adds btw regardless of the clearance issue, the stock springs are weak crap that won't control anything much bigger than the factory cam, and if you don't cut the valve seats in the heads bigger you stuck w/ 1.25 or something similar diameter springs. If he goes w/ the crane spring/retainer kit he'll need to doublecheck the max lift, I know it's over .500 but I don't recall if it's over the .525" lift of the hotcam w/ 1.6 rockers. If not he can run the hotcam w/ standard 1.5 ratio rockers yeilding something like .492 lift if memory serves. He'd probably want to drill and pin the rocker studs when running an aggressive cam too to avoid having them pull out, should be able to do that w/ the heads still on the engine.

The truly "proper" thing to do is remove the heads, have the valvespring seats cut for larger diameter springs, have the guides cut down and new seals installed, and have the pressed in rocker studs replaced w/ screw in studs. Then he can run most any streetable cam at least as far as the heads are concerned, I don't know anything about issues w/ the factory fuel injection in the trucks.

 

I'm afraid you are mistaken. They have 8 injectors with tubes connected to "popets" at the runners. They are sequential injection. The injectors are not the RPM limiter, it is the PCM.

 

I wasn't aware that vortec trucks were SEFI seeing that they don't rely on the crank sensor for engine management. just for diagnostic purposes (like the '96-'97 lt1's). to be true sequential injection a motor has to have 2 position readings 1) reading which cylinder(s) is/are on TDC and 2) whether they are on the compression stroke, or the exhaust stroke.


I've never messed with one first hand, but it was my understanding that the first TRUE SEFI truck engine was the new LSx based engines.

 

Years later,but blah.

They are actually CSFI-Central sequential fuel injection.
Referring to the centrally located sequential injectors-it utilizes both a CMP and a CKP sensor. (not to be confused with CPFI/CPI used until 95-which is simply Central Port Injection)
CPI is batch fired and CSFI is sequentially fired.

Sorry to wake the dead,but for people like me that actually do searches it helps to add in info when you can for someone later on.

 

if you run ls6 beehive springs and 787 retainers it allows a rough max lift of .550

 

Over a 10 year thread!

 

It's a newbie tradition.