kaptinkafeen

iTrader: (2)

Well guys, I need some information.
For the time being, I have decided to put my roller cam swap upgrade on the back-burner until the next winter project "to do list" get's written
I need some help in deciding what cam selection to go with for this season.

I have a stock 355cid,
5.7" rods
vortec 305cic heads casting #12552520 - stock valves 1.84int, 1.5exh
edelbrock rpm airgap intake manifold

I have not opened up the engine yet, so I have no idea of what pistons are inside. ( I really don't want to pull the heads off if I can help it)

My Questions are as follows. How much lift can I run safely with stock rocker arms, without fear of bending valves, and before I need to have the heads re-worked to accept a higher lift cam? Again, I don't want to put any $ into these heads...
Intended application is for weekend road-race - open track days. Require enough vac, to run factory brakes.
Stock rear-end with 3:42's, WC T5 trans. Max RPM would be in the 5500-5800 range.
I was looking into the following cams from lunati:
hyd - #20109: 292dur, g.lift of .480"
hyd - #30113: 290/280dur, g/lift of .489/.520
I am not against running a solid lifter cam either, and have no problems with adjusting lash etc. (so if you have any suggestions in this department....)
This is a seasonal upgrade.
TIA
Andrew

Sonix

iTrader: (1)

I'd look at a solid cam for sure. Around .500" lift, and 235*+ duration. One of those .500" lift limited cams would work nice. Since it's not a daily driver, and you've got a stick shift, go higher on the duration. Those baby vortecs should be ok with that. The small valves will tame the cam a tad.

"stock" 355cid? How's that possible? A 355 has been rebuilt eh?

Usually vortecs experience port stall at .520" lift or so, so .500" is a good place to be. Be sure to check clearance, you may want .050" offset locks, and .050" worth of spring shims to bring your retainers above the valve seals safely.
I'm thinking like the 266XOS.

kaptinkafeen

iTrader: (2)

Thanks Sonix,
By stock 355cid, I meant that the long block assembly I was given was stated to be a crate motor - block csting # 14093638...But you're right.
But can I even run a cam with .500" of lift using these stock heads? Without offset locks and shims? I assume I can only check clearance if I pull the heads off - something that I don't want to do if possible, and this is why I was wondering if anyone knew what the 'safe' lift figures could be without any measuring.
A 'plug and play' situation if possible. Pull the old cam and install the new one.
One other thing...with a cam pushing 235*(or more) would there be any vac issues for the brakes?
Sorry, I am a newbie to this stuff...
Thanks again
-Andrew

Sonix

iTrader: (1)

You can run up to around .470" lift without even looking at clearance issues. Theoretically, I mean I still would but...

No no, no need to remove the heads to check clearance, i'm not talking piston to valve clearance here, you certainly don't have to worry about that. (I'd still check it, but just by rotating the motor over by hand a few times before firing it up. I'm sure you'll be fine though). That'd be checked when you're setting your lash so...

Offset locks = $11, shims = $13 or so. This is the option that requires no machining, it's instead of cutting down the guide boss. So if you can get .470" lift stock, with .050" offset locks and shimming up the springs for a decent seat pressure (you essentially just move the spring and retainer up .050"), you now have .520" safe lift before the retainer smokes the guide boss. Again, check the clearance with a feeler gauge, with the heads on. You can check it now, if you have a dial indicator or know how much your stock cam lifts open the valves, turn it over to max lift and see how much clearance you have below your retainer. Then think about how much extra lift you're adding, then see if you'll still have a ~.050" safety margin. If so, you're done. If not, use the offset locks.

235* should be "ok" for brakes. You *might* notice a difference. Especially if you can't figure out the tuning issue. You'll want more base timing for sure, maybe even locked out at max. Worst case scenario is you need to use a $40 vacuum can. Not like you need to swap to hydroboost brakes or run a vacuum pump for the brakes or something.

kaptinkafeen

iTrader: (2)

Good stuff
Thanks Sonix.
I just downloaded Comp cams info on the 266XOS Oval track series cams. Time to do some more research With the heads I have, comp ratio should be close to 9:1 or maybe a bit higher @ 9:5:1, not much more, that grid you recommended fits my application well with max lift on the int side of .501 and .510 on the exh.
Another newbie question. When using shims and the offset retainers, any issue(s) with stock valve stem lenght?
-Andrew

Sonix

iTrader: (1)

Hmm, that CR is a tad low. I thought the vortec 305 heads had itty bitty chambers? Oh right, you're not taking off the heads, so there isn't much you can do about it. Ok, well double check your math on that, I figured it'd be a bit higher. Know what dish size the pistons are? Or deck height?

No, i'm pretty sure there is no issue with stock length valves. I can't say i've done this though, just heard about it as being one solution to that problem. There's probably a reason why it's note more common, maybe someone else can shed some light on it.

kaptinkafeen

iTrader: (2)

these heads have a 58cc chamber - beyond this, unless I open up the engine, I have no clue of piston type or the deck height.... I guess there is really is no easy solution to 'know' what you are doing and dealing with when upgrading to a more radical cam unless you pull the heads off.
I checked the cost of shims - $26usd and the offset locks that produce an installed height of +.05 without provisions for lash caps $22.00usd.
I would have to measure the inside and outside diameter of the springs to get the correct shims but, in addition, would I have to get special sized vale seals too? Do I need lash caps in this situation?
Never done this before... that why I have all the q'tions.
TIA
-Andrew

Sonix

iTrader: (1)

This is a basic, el cheapo rebuild? Like stock cast pistons, no decking of the block etc etc?

I'm coming up with 9.6 if you have a .025" deck height and .041" gasket. 9.2 with .045" deck height (1.54" pin height rebuilder pistons).
So absolute worst case is 9.2, 9.6 is a better one, and it might have been decked when rebuilt, that's a fair assumption if the motor was ever overheated...

Right right, you're in good ol' CA there.
I forget what springs are on the vortecs, but i'd guess they're 1.25" OD. It's not too difficult to measure them though. They should be the "normal" size springs, so you should be able to get the "normal" shims. I might recommend PM'ing F-bird'88. He's dealt with vortec heads, and knows a fair bit about shimming springs, lash caps, etc. He's in your neck of the woods, might be able to recommend a place to get your parts locally and save some loonies too He's good with doing things "on the cheap".

Your retainer would be a bit higher, so you have more chance of the rocker hitting the retainer on the sides. Lash caps give you a bit taller of target for the rocker to hit. Probably a good idea.

But yea, you're coming close to the edge of my expertise here I can't help but think F-bird'88 is the one to talk to now.

If you think your CR is down in the low 9's, then maybe one step below that 266XOS. I think there is one, one step below.

kaptinkafeen

iTrader: (2)

Will do.
I took a look to see if there was a 'smaller' cam in the oval track series - the 266 was the smallest choice.
I will call comps tech line see what they have to suggest.

-Andrew