kyle97

Im helping my brother build a 383 for his 97 formula. Im curious if what happend to us is common or not. Basically, the rods needed to be clearanced near the end of the rod bolts to prevent the cam lobes from hitting them.

The block has been line-honed with new caps installed, we clearanced the block for an eagle cast stroker crank, and installed the crank, eagle SIR rods and KB pistons. At this point, the crank was able to spin freely all 360 degrees.

Once we installed our cc305 cam and cloyes OE replacement timing set, we tried turning the engine again. This time, we found that the lower portion of every rod pair hits a cam lobe, near the bottom of the rod bolt. We triple checked the timing set alignment, and also degreed the crank to verify nothing was screwed up with it (we are still assuming the cc305 is properly ground, but i guess that could be screwed up too). Finally, we ground down the rods and fixed the problem.

Anyways, it spins now, but i was wondering if anyone else has had this problem? We thought maybe slack in the timing set could be an issue. All the parts are brand new though, so im not sure what to think.

streetbad

What is the base circle diameter of your cc305?? How much material did you have to grind off of the rods?

1racerdude

Ya want at least .050 clearance. If ya took much off of the rods it ruins your balance job.
Common problem.

T/A Racer

woah thats exactly the same setup im putting together right now. how much did you have to take off the rods and exactly where at. do you have any pics of the rods after grinding. any other issues with this setup? also did you zero deck the block and what cc of piston are you using. heads?

1racerdude

A machine shop will get them all the same weight after grinding. This will prevent balance problems. Just firing up and grinding rod's if ya have never done it, is not advise.

kyle97

The rod made a sharp corner at the contact point, so we rounded off the edge. Around 1/16" material was removed. Im not sure on the base circle of the cc305, ill have to check back with ya'll on the weekend when i can measure, and maybe snap some pics of the rods.

I'm also concerned about needing to re-balance -- i was thinking that maybe we could weight the pistons and rods and match things up so the all the piston/rod assemblies weight the same again. This motor is not going to run high rpms (we're leaving in the stock rev limiter setting). So maybe we can get away with a less than perfect balance.


The block was not zero-decked, the pistons are -18cc, and we're using stock heads.

87lt1rx7

cam may need to be reground to a small base circle

HaynesFaithZ28

With a 383 you have to run a small circle cam. Call Comp and either send them your cam to recut or order a new one from them. Don't grind your rods because you will ruin your balance and the motor will not run like you want it too.

CANTONRACER

Not with Lunati I-beams.

OneFlyn95z28

Very common issue if you do not use rod's marketes as "stroker" rods

I am there are meny more but here are the ones I have seen fit no problems

Callies
Lunati Pro mod's
Eagle 3D "H" beams
and a few others that escape me at the moment

This is why many recomend a good mock up before final assembly and balance

Mindgame

Fix the rods... don't reduce the base circle.

This is a common problem with stroker builds but you did the right thing in verifying the cam timing. When I do this I only grind as little as possible, leaving just ~.020 clearance. Never had one hit, even spinning 7500+rpm with not-so-light piston assemblies and GM steel cranks. If you take the minimum you won't need a rebalance unless you're building a race-only deal.

-Mindgame

T/A Racer

hey if you could get some pics of those rods that would be awesome help for me. ive just got all my parts(same setup as you), and will be assembling my stroker here soon. i just want to use some pics for reference. thanks

WS Sick

I have the same set-up but with a different cam and I needed no clearance, I did notice you said you had the block line honed, I wonder if this is a factor?

Also the CC 305 has a 114 lobe sep whereas all the cams I have built 383s with have had 112 or less, this could put the lobe in a more interference prone postion as well.

But in every book I have read and every machinist I have talked to they mention that a little of the rod may need to be ground off for clearance of the cam.