I've had a few friends reccomend having my crank "micro-polished" but I'm wondering if it's really necessary? I'm replacing my bearings (rod and main) but my crank looks to be in great condition. The motor only has about 80k miles on it. I figured I'd do a total rebuild since I had to pull the motor and transmission....

Just as a side note, this motor probably won't see past 5500RPM - ever. It's a CrossFire so I'll probably only wind it up to about 5000RPM.

 

If the bearings came out in good condition it's probably not necessary, but miking all the journals, checking for straightness, magnafluxing, and micropolishing is usually part of a careful "blueprint" rebuild of a high performance engine.

Duke

 

Hi ken!

Micropolishing is "high tech" name for crankpolishing wich is usually done at #600-800 paper. You can do it your self,just look at any high performance engine book for instructions.

 

Actually I just had another friend reccomend the same thing! I think I'll just hit it with some really fine grit sandpaper myself. The motor only has 80k miles and is pretty decent.

Thanks for the advice!

 

BE CAREFULL. Don't make any marks/scratches go across the journals. You need to make sure they all go around it or you will have a possible chance of bearing failure. I don't recomend doing it youself, if it looks good and the old bearings also look good, just let it go. You don't know how much you are taking off, and unless you have a way to spin the crank while polishing it you can cause low spots. I know you are only talking .0001-.001 of material, but it can make the difference if you are already on the loose side of specs! :cheers:

 

Well ,cant do much harm with #600 - #800 paper. just polish enough to get smoot surface .You wont be able to see any change in diameter . Make sure you look how to do it right. Every high performace engine book has it covered.

 

I polish cranks with 600 grit paper and a round leather rope about 6 feet long. You wrap the paper around the crank journal then wrap the belt around the outside of the paper, then with a pack and forth motion on the roller belt you cause the paper to rapidly roll around the crank journal. You do not just take emery paper and start polishing away. The roller rope makes a fast easy job of it. :)

 

Why the self imposed rpm limit? There is horsepower in those rpms. Are you keeping it as a restoration?

RACE ON!!!

 

Not with the crossfire there isn't ;)

 

Twinnie,

Shhh! Please keep your voice (?) down. I don't want my car to hear you. Until it learns better, this worn out, stock long block, L83 seems to thrive on 5700-6000 rpm shift points. Who knows what it might do with a cam and some headers.

RACE ON!!!

 

Dude, I had a crossfire too [;)] mine ran to 5500 rpm but it was crap at idle (wouldn't run smooth, didn't really care but sometimes it was somewhat annoying)

You can shift at 5700-6000 but don't you feel it loses a lot of oomph when you pass 4500 rpms or so?

Do you still have the stock intake?

Marck

 

Twinnie,

I don't rev it that high, "just because I can". It produces the best 1/4 mile times with those shift points. A month or so ago, when my trans was taking forever, to shift into 3rd, I occasionally left in 2nd across the finish line. The power was way off above 62-6300 rpms, but it was a toss up in ET and I think the trans lasted a few weeks longer by not subjecting it to those full throttle 2-3 shifts. It has run a best of 13.92 at sea level using the NHRA correction factor.

I have ported the stock intake. I have 2" bored out throttle bodies, other than that, the engine is untouched. It has 150,000 miles on it, including over 700, 1/4 mile passes. It burns a quart of oil in under 200 miles. The poor old engine is just flat, worn out, but it just keeps going faster. The long block is untouched. The valve covers have been off only once, and that was to replace the leaking gaskets. Obviously, from the above, it has all the stock internals, cam, timing chain, and everything else that is begging to be changed. Unmodified, factory exhaust manifolds, stock 3.08 gears, stock computer with stock chip, and full smog equipment (less cat. converter) round out the list of how stock this "runner" really is. BTW, smooth idle @ 700 rpms in drive.

It will be freshened, and more, this winter. I'm having trouble keeping up with the oil expense, as it is my "main" transportation. I'm hoping to see a 12 (corrected) in the spring. A stock Crossfire, CAN benefit from higher revs, if you feed it.

RACE ON!!!

 

Is that you "Stingray"?

Only a ported manifold and 2"TB's? Sorry but I don't believe for one minute it really makes good torque that high in the rpm range. Do you want the high revs to make more Hp?
As for the induction system, the heads are really really poor, after the manifold they are a serious limiting factor, then there's the cam. That cam is not designed to make power that high (short duration, high LCA, small overlap), then there's the stock manifolds....

I think I know the crossfire pretty well (I've tinkered with it long enough) and I have never broken into the 12's and I modified mine quite a bit, did all the things (smooth heads, bowl port, headers, true duals, thinned throttle shafts, fuel pressure regulator, removed swirl plates, ported the manifold to where it couldn't get any larger, adjusted lifters to only have 0.008" hydraulic action left in them, 1,6 rollers,...and so on.. and so on) I live at almost 0ft elevation too.

I may be a sceptic but I will believe the 12's if it's on the juice.

Not trying to start an arguement here.

Marck



[Modified by Twinnie, 5:51 PM 10/19/2002]

 

No, I've got a new cam going in it with new aluminum cylinder heads (L98.) The cam is based more on the lower end but I think I see your point - if you rev high in let's say 1st gear - you'd be making more horsepower at 5500 RPM than you would if you had dropped it into 2nd gear at 2000RPM or so - is that what you're talking about? You may not be making the potential horsepower you COULD be but it's still more than at lower RPM's.

Just as a note, here's the mods that are going in the car:

taller K&N filters
2" TB's
Larger injectors (66#?)
VAFPR
custom phenolic lid (no swirl plates)
ported intake (matched runners, not hogged out)
ported L98 heads (intake runner will be filled to match ported CrossFire, also ceramic coated valves/chamber/exhaust port - C/R 10.5~11:1)
ceramic coated stock pistons
moly rings
new bearings (main and rod)
main studs
ECM ('8746, not '7747)
ceramic coated Dynomax headers
"massaged" catalytic converter
some sort of custom exhaust cutouts (haven't decided yet)

 

Just a note about the micro polishing - I grabbed a 1/2" drill and a 3/8" socket adapter I had and put the balancer bolt in place; I've already cleaned up the mains but I wanted to polish the rod journals a bit at least. I made a "strap" of 1000 grit (that's all I had) wet/dry paper and used masking tape to make a strap holder deal. I held the drill in one hand and held the strap on the journals with the other. Ran it for about 30 seconds or so on each journal and that seemed to clean it up quite a bit and make it even more shiny.

BTW, CFI-EFI, forgot to mention my camshaft specs:

216/216 @.050" lift, .454"/.454" lift, 110LCA - advertised durations of 290/290.

 

Ken73,

Yes! I'm not saying that it produces max HP @ 57-6000 rpms. I'm saying that those shift point produce the quickest ETs. One wants to shift where he is utilizing the maxinum available horsepower. The greatest area under the curve, so to speak.
Yours sounds like a nice sensible build up. With that combination of parts I can see why forays into the 5500 rpm range may prove fruitless. That is a good all-around cam. It's a whole bunch better than the stocker I'm using. Some more intake work may change what you can get out of it.

Twinnie,

The 13.92 is FACT. The 12's are mere speculation. I am building one heck of an engine. I have serious concerns about the "Crossfires" ability to feed it. I may very well have to go to a larger induction system, but at least I will have the "Crossfire" on it for the initial firing. I will report in the spring.

RACE ON!!!

 

I'm talking about the 12's not the high 13's, let there be no mistake there :D I don't know what you're gonna do but you obviously have it planned out :0 I'm looking forward to seeing what you come up with.

I kind of like the budget way of modding the crossfire, using L98 heads and just sa many tricks as you can and then seeing what it can do.

What manifold are you considering on using?

Marck


[Modified by Twinnie, 9:29 PM 10/20/2002]