Reground cam, PR lenth, suggestions please...

[mars]

Hello everyone, now I know that you guys don't have hyd. roller cams, and that cams are readily available for your old 3.1's, but I want to pick your brains for a few minutes here,

Here is my dilemna :

I got a cam reground locally, specs are :

Duration : 210? intake / 210? exhaust (@ 0.050" lift)
Lift @lobe : 0.290"
with 1.6 rockers : 0.465"
with 1.5 rockers : 0.435"
Lobe Seperation Angle : 112?

STOCK :

Duration : 196? intake / 196? exhaust (@ 0.050" lift)
Lift @lobe : 0.273"
with 1.6 rockers : 0.437"
with 1.5 rockers : 0.409"
Lobe Seperation Angle : 112?

Now I havent assmembled anything yet, and was wondering if you guys could give me some advice as far as setting this up. I am waiting for a clutch to come in, and have a while till I am running...

Here are my 2 options, might be more than 2, you tell me :

Option 1 : getting adjustable rocker studs, running guide plates, and taking up the "slack" using old style stamped rockers (for now).

This option is basically free, I have a few buddies with Iron head 2.8's, and parts for them are easy.

The lift with these 1.5's is the same as stock give or take 0.001", but I would have proper lifter preload, and more 14* duration than a stock cam.

I can then easily upgrade to roller tip 1.6" in the future.

Option 2 : cutom pushrods... keep the 1.6 ratio 3400 rockers, and get some new PR's, this means more lift, and less friction, as well as some easy as hell to install, low maintenance rockers.

This option scares me though. I have not the slightest clue on how to measure these bad boys, I've searched all over the place.

Say the regind took off 0.010" of the radius of the cam lobe (or base circle radius), can I simply add this to my PR lenth?

According to a few sites, lifter preload is allowed to vary between 0.020 to 0.060, well, according to that spec, my regrind will do very little and still more than likely be in spec...?

IE if my stock cam had .040" preload, the lifter may have dropped to .030" preload, which is a realistic number I would say, it should be fine.

How does that make sense, smaller base circle + "within spec" lifter preload = increased lift? How the hell could you increase lift when removing material?

Discuss, and suggestions please.

Thanks!

[Invasion1]

No Clue  :laugh:

[mars]

No Clue  :laugh:

I know Dave, it's not like I actually expected you to know this either.  hehe.   :icon_rolleyes:   :laugh:

This is for the engine gurus, not the chip tunning rookies. 

[Invasion1]

Ouch  :thinking:

[flybynite]

What I would do is order a pushrod length checker and or some comp cams checking pushrods.When used correctly they will determine the length of the pushrod perfectly. ;)  Later

[sleeperred90tgp]

If your running 3400 heads with the rocker stands with the slot that indexes them it's proly the best setup you can use. With the stand bolted to the Head it makes for one ridged setup. I would defiantly keep this setup in favor of just roller tip rockers or rockers that are just hanging on the  stud.

Yes if you measure both base circles and / by 2 that is how much longer your pushrod has to be to maintain the exact correct geometry. If it's only .010 I would just assemble a couple and check the preload with a bent wire of a known dia. (might need some different wire sizes.) Start with a paper clip(.030) Just slip it under the lifter retainer. If you have more than .020 you should be good to go.

As I am sure you know check for RA and spring clearance.

Let us know how it runs with the new cam. :icon_biggrin:

Jud

[mars]

I will do just that!!

THANKS!

I really wanted to keep the stock rockers as well, so bonus.

EXCELLENT

[TurboGTU]

Just so you know..late 3100 stamped rokers were 1:1.6 . lifter preload is good till your dancing with .01. If you have anti pump ups...forget about it...you need stock preload or more.

[mars]

Just so you know..late 3100 stamped rokers were 1:1.6 . lifter preload is good till your dancing with .01. If you have anti pump ups...forget about it...you need stock preload or more.

The later 1.6's still aren't adjustable though are they?

Are the 2000 3400 lifters anti pump up?  didn't think they were...

[TurboGTU]

Well no..but you could use iron head nut/washer and stud to turn them ajustible.

I don't think gm used anti pump ups. I was just throwing caution just incase you do go aftermaket with anti pump ups.

[mars]

Well no..but you could use iron head nut/washer and stud to turn them ajustible.

Wouldn't happen to know exact years would you?  3100's that had the staped 1.6's...?

Thanks

[TurboGTU]

To my understanding, all non-roller rocker 3100s had them, But I would grab them from a 95 beretta just to be sure. THe Stud/nut setup can be had from almost any iron head 2.8/3.1/3.4.