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LT4 Hotcam in L31
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Post LT4 Hotcam in L31 
I am putting a LT4 Hotcam in my 97 Chevy L31. I have already got the beehive springs, 1.5 roller rockers. Do I need to get longer or stronger pushrods with this setup?

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I just put the lt4 hotcam and 1.6 roller rockers in my 98 and my machinist measured and determined that stock length pushrods would be fine. We did put stronger pushrods in though. Stronger, but stock length should be fine. You should expect to have some serious idle problems. I'm getting mine tuned soon. Still trying to decide if I want to bother with the 411 swap before the tune.

Darren

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I have the tune from Blackbear so that should take care of the idle issues.

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Please report back once you put the cam in on how it runs. I'm worried the black box ecm doesn't have enough capability to be tuned and have it run right. Are you putting the cam in soon?

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One of the other guys on this board was running (and I believe still is) the black box with an LT4 Hot Cam and a bunch of other mods. It has the capability, but I think there are some advantages to going to a '411... That is entirely up to you, however.

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What I have done is I sold the V6 out of my fullsize and bought a 350 with wire harness and computer. I have rebuilt the engine over the winter and already had the computer tuned. I got the engine running long enought to break it in and it seamed to run nice. Got ready to drive it and had some issues with the tranny. got those fixed and had some issues with idling and starting to the point it would not start. Pulled th valve cover back off and found I had a few bent pushrods. I beleive I over tightened the rockers but wnat to make sure the factory length rods will work for this cam. I hope to have it running again this weekend. I was told the black box could be programmed for the Hotcam. I may decide latter to change to the 411 pcm but that will be down the road.

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Post Re: LT4 Hotcam in L31 
BOWTY wrote:
I am putting a LT4 Hotcam in my 97 Chevy L31. I have already got the beehive springs, 1.5 roller rockers. Do I need to get longer or stronger pushrods with this setup?


take a sharpee and color the valve stem "tip" where the roller tip goes and put the pushrod/roller rocker on and roll the engine over a few times and check where the wear pattern is on the valve stem tip.... that will tell you exactly the answer to this question

http://www.compcams.com/information/Products/Pushrods/

http://www.pontiacstreetperformance.com/psp/valvetraingeom.html

I am not sure of this but don't you have to machine the stock l31 heads to compensate for the larger lift of the lt4 cam to prevent coil bind?

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I would like to try the Hot Cam. I mentioned on another post that this is the "Humble Pie"
combo that CarCraft came up with and made 400hp with headers and such. BOWTY you are
not going to get the full effect of the cam without the 1.6 rockers. I have plans for a new engine
in which I will use the hot cam for now I put 1.6 rockers on my stock L31, that made a huge difference.

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If you didn't already purchased the hot cam and have the 1.5 rockers, How about this one:

Lunati Voodoo 60121 + 1.5 rockers:

Quote:
Voodoo Hyd Roller Cam - LT1 LT4 270/278
Product Description

Lunati's Voodoo series of Hydraulic Roller camshafts deliver more area under the curve than any other series of Hydraulic camshafts. This means more throttle response, quicker acceleration, more vacuum, better efficiency, combined with maximum horsepower and torque!Hydraulic roller, fair idle. Strong power increase in mildly modified engines with excellent throttle response. Will work with stock converter in 383 and up size engines or 2200 RPM stall speed converter in 305-350 cubic inch engines. Likes 3.23-3.73 rear gears. Also the largest cam for inboard/outboard marine applications.

* Advertised Duration (Int/Exh): 270/278
* Duration @ .050 (Int/Exh): 221/229
* Gross Valve Lift (Int/Exh): .515/.530
* LSA/ICL: 112/106
* Valve Lash (Int/Exh): Hyd/Hyd
* RPM Range: 1800-5800
* Includes: Cam Only

Part Number: 60121


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Post Re: LT4 Hotcam in L31 
stroker97k1500 wrote:


I am not sure of this but don't you have to machine the stock l31 heads to compensate for the larger lift of the lt4 cam to prevent coil bind?


http://www.popularhotrodding.com/enginemasters/articles/chevrolet/smallblock/0611em_vortec_small_block/camshaft.html

No machining needed, good to a little more than .550 lift. Don't know how much more, info was not specific.


here is to show the difference between the Comp 787 vs 774 retainers on the 26918 when installed on gen IE vortec heads

787 on the left.....774 on the right




http://209.62.24.218/forums/showthread.php?t=377651&page=3

Edit: added photos.



Last edited by CrazyHoe on Sat May 30, 2009 4:08 am; edited 1 time in total
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Already have the cam and the rockers. I was told I can run the 1.5 rockers without head work abut for the 1.6 I would need head work. I am planning to get it back together Friday night and drive it Saturday hopefully. We will see what happens.

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Well, I should be installing my 26918 this week. I'll let you guys know what I measure.

There's a lot of confusion about these. We'll see.

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WAIT................BOWTY you can't run that cam without machine work.

The Hot Cam is .492 with a 1.5
.525 with a 1.6

a stock vortec head is only good to .460

EDIT : Crazy that article used the EQ vortec replacement head. that is why it's good to .550
the stock head is not.

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L31Sleeper wrote:
WAIT................BOWTY you can't run that cam without machine work.

The Hot Cam is .492 with a 1.5
.525 with a 1.6

a stock vortec head is only good to .460

EDIT : Crazy that article used the EQ vortec replacement head. that is why it's good to .550
the stock head is not.


Like I said, lot's of confusion.

In the article, the EQ vortec are good to 0.563, OEM vortec it's more like .550ish but only with the beehive springs and 787 retainers.

This is what I read (even DV mentions this in his new book), I'll confirm it this week. Smile

Hog wrote:
The ZZ4cam has .474"/.510" lift with 1.5:1 rockers 208/221° dur. at .050". Too much for the stock L31 Vortec heads and stock retainers/valveseals. Stepping up to a 1.6:1 roller rocker will make that lift .504/.540". I might be tempted to stick with the 1.5:1 rocker ratio with the ZZ4 cam. If youw ere runningteh LT4 Hotcam 218/228° .495/.495" lift with 1.5:1 rockers or .525"/.525" with 1.6:1 rockers.

At the higher lift levels I would be looking into screw in rocker arm studs or at least pinning the stock studs into the heads.

You can install a set of LS6 Beehive springs or Comp Cams 26915 or the firmer 26918 springs with the 787-16 steel 7° retainers or 788-16 for the titanium retainers.

The GEN 3 LS1, 5.3, 6.0 4.8 use a different valvestem diameter thus the stock GEN 3 retainers cannot be used even though their valvesprings can be used on the GEn 1E Vortec L31 head.

Any of the above combos will run the ZZ4 cam safely.

A ZZ4 cam will not affect your towing adversly, it will probably improve it.

I would go ZZ4 cam, 1.5:1 roller rockers (narrowbodied rockers are what you need(GMPP has both 1.5 and 1.6:1 roller rockers available as does Crane Cams), Comp Cam Beehives, 787-16 steel retainers.


PCM tuning will bring all this stuff together, and will bring out the power and drivability you seek.


peace
Hog


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You can only go to .480 lift on stock vortec heads,after that you have to machine down the valve guides.
The spring/keeper will bottom out on the guide.

The article your referring to stating it's safe to go farther with vortecs is more than likely talking about one of the other vortec heads.
Besides the stock head that came on the truck,there are aftermarket (from GM) vortec heads that come with the machine work done already.

With stock heads,you will not go farther than .480 without cutting the guides.
An exception would be using a cut down keeper or retainer for a bit more clearance,but not enough for the LT4 cam.
Easy to measure,simply measure from the bottom of your keeper to the top of the valve guide.
Subtract a couple hundreths for safety and you've got your available clearance for valve lift.

Hog has posted these specs up so many times I can't forget them,both here and on FSC.
Might be easier to find all his info on FSC though,search function here sucks much.

Mine are cut down at the guides,with 2.02/1.60 stainless manley severe duty valves, 7/16 screw in studs and 1.6 stainless roller rockers.
(everything still laying on the table waiting on springs to be put together.)

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Quote:
With stock heads,you will not go farther than .480 without cutting the guides


I was under the impression the 787-16 steel retainers also gave more space for more lift.

I read so many times that the beehives and 787-16 steel retainers enable more lift without machine work.

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If if you run the 26915 or 26918 Comp beehive springs along with Comp 787-16 NON-GEN 3 retainers and stock locks, you can run .550" lift on bone stock virgin untouched 1996+ Vortec 350 L31 truck heads.

The beehive springs use a higher installed height which brings the retainer up and away from the stock valve seal.
There was a recent magazine article that had pics of a set of calipers showingthe stock spring and beehive spring clearances.

peace
Hog

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Hog wrote:
If if you run the 26915 or 26918 Comp beehive springs along with Comp 787-16 NON-GEN 3 retainers and stock locks, you can run .550" lift on bone stock virgin untouched 1996+ Vortec 350 L31 truck heads.

The beehive springs use a higher installed height which brings the retainer up and away from the stock valve seal.
There was a recent magazine article that had pics of a set of calipers showingthe stock spring and beehive spring clearances.

peace
Hog


Thanks Pauly.

I'll take some pics this week to confirm this. Howard will not be deceived.

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Cool,so with the beehives you can run the LT4 cam.
Never realized that,I bought some 26915's but just had the shop cut my vortecs down while they had them so ended up selling them.
I love being wrong,I learn something everytime. ;D

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i had the lt4 hot cam and a black box pcm with a black bear tune. it made good power driving around. but idled like ass and liked to ALMOST stall out when my e-fans kicked on.

i swapped to the 0411 and now i have more of that "cammed" sound at idle but it also idles better if that makes sence.

i vote for a 0411 swap. best mod ive done so far.

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