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after researching for awhile i decided i want to go with the lt4 hot cam. was wandering if anyone has done this to an l31 on this msg board. was looking for some heads up as to what i might run into or if its prety straight forward. did you do just the cam or the whole kit??? what exactly all will i need parts wise, remember reading about geting diferent springs for the 1.6 rockers??? thanks id really like to get started on this ordering parts and so forth, thank you.
 

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The LT4 hot cam in the L31...

The L31 Vortec heads can only accept a max lift of around .460" before running into retainer to valve guide interference.

The LT4 hotcam's specs are always advertised using 1.6 ratio rockers
.525"/.525"
118/228
112

In order too accept the lift of the LT4 hotcam the vortec heads can either have the guides cut down or you can use COMPs Beehive 26916 or 26918 springs.

However, stay away from the 774 retainers (from personal experience), they are meant for LSx engines and were miss-printed in the the build of "Project humble pie" by CarCraft. They built a Vortec headed SBC with the LT4 hotcam and used 26918/774 and pulled 401hp/426TQ. (non-fuel injected) By using these retainers in real life they will have too much spring pressure and will eventually ruin the hydraulic roller lifters if not pull the studs unless modified.

Now, in order to get Vortec heads to accept 1.6 ratio rockers the pushrod holes need to get drilled out to 1/2". If you're going to use 1.6 rockers, most (like myself) will use aftermarket rollers. Be sure to get self aligning narrow body rockers. Most aftermarket roller rockers will use poly lock type nuts and will stand too tall for OE covers. In order to use tall valve covers on the L31 the A/C brackets needs to get modified and the compressor shimmed upwards to clear the covers as well as a new serp belt.

The LT4 hotcam, new in it's GMPP form, comes from the factory designed to work in LTx type SBC's with the cam driven optispark and the dowl pin is much to long to fit behind a non-LTx timing cover. That dowl pin is designed to get pressed/tapped into the cam itself until the desired pin length is achieved. Thus allowing it to be used in any SBC. This being said, the LT4 hotcam was originally created with the intention of being used in the '96 vettes & '97 SLP camaro SS & SLP firehawk... my point being; Light weight F-body cars. To get the most out of any higher RPM cam in a 4000lb+ pickup, look into a 2500rpm stall (or there abouts) converter for your application. Long tube headers & rear gears will also drastically help, but aren't necessary with a cam of this slight of a duration

From my personal experience, the L31 fuel injection with the updated injector spider (19lbs a min) will run out of possible fuel control long before the cam can make it's peak power. I would strongly suggest looking into the marine L31 injection swap so you can upgrade to any flow rate injectors your heart desires. That is, if you want to stay F.I.

Any mail order custom tuner should be able to flash you a tune that will be able to make the combination street friendly, idle friendly, reliable and have some decent power on demand. But for the DIY kind of performance hobbiest and to get the most out of your engine I'd suggest picking up your own computer tuning software, learning everything you physically & mentally can handle about PCM tuning and parameters and do weeks if not months of tuning tweeks, data logs, tweeks, logs. Than as soon as the season changes you than tweek & log for those atmospheric conditions.

Cheers ~Mykk
 

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Wow, awesome technical response. Good reading.
 
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