Some of you may know about my 383 thread.

The machinist called me today, with a problem. I have a non small base circle 280XFI cam, 6" forged I Beams with regular fasteners, scat 9000 series 3.75" crank in a 4 bolt GM block. The block has been line bored.

The problem is that the rod bolts are hitting the cam. The machinist said that I could either get new rods with capscrews, or a small base circle cam. He said that he would recommend getting the small base circle cam, even though it would only gain me .050 of an inch.

I asked him if going to rods with capscrews would gain me more clearance, he said yes but then he would have to disassemble the shortblock, rebalance the rotating assembly, and then reassemble it, which would cost more money than getting a small base circle cam.

The third option would be to grind the bolts on the rods. Would the grinding of the rod bolts be enough to throw off the balance of the rotating assembly?

Need some help here.

Thanks,


Jeremy

 

Grinding on the football head rod bolts is what back yard mechanics do after drinking 2 cases of beer.
Not the best way of taking care of the problem you have.

What brand of "I" beam rods do you have?
Scat?
RPM rods?

Best to get a stroker Middle weight design sbc 6.0 c-c length rod.

And a small base circle cam if you are planning on having high valve lifts above .600"

Rebalance the rotating assembly as necessary.

Likely cheep china made rods you have causing the grief.

Get what you pay for $$.

BR

 

Well I disagree. My 383 that I had built recently by a very reputable Cascar engine builder,did exactly that.I had the same concern but he assured me it will be fine.I did however use ARP bolts.

 

Sounds like the small base circle cam is the most cost effective solution at this point. Does the machinist think it will provide the clearance needed or is he guessing?

On my 396 build we went with Crower Sportsman stroker rods to make sure there was no cam interference. The rods are a bit pricey, but quality rods is where you want to spend money. They had larger 7/16 bolts and better clearance.

 

I just built a 383 with the same parts you did, super ram scat 9000 crank, xfi280, but with the scat 6.0 cap screw rods and still needed to clearance the rods. Small base cam may be a better obtion for you

 

He is guessing. The guy is somewhat of an ignorant *******.

He told me "well if you get a small base circle cam, there is no guarantee it will work..you may have to get the new rods too"

I am totally fine with it, its just the way he said it that bothered me. He talks to me like I am stupid, and laughs about it "haha you could try to go with the capscrew rods first.." I asked him if he could see through the bottom of the block to see which cylinders rod bolts were hitting the cam and he said "uhh it was either 1 or 2 and then either 5 or 6"---NICE.

The rods are 6" forged, for some reason i want to say eagle. I'm not totally sure though, i bought it used.

 

You never want to grind on a through bolt style connecting bolt head on a high performance engine build.

You are taking a very big gamble if the rod bolt will hold up or not at high RPM's and very high reciprocating loads present.

The connecting rod cap fasteners are the most highly loaded fastener inside of every conventional bearing insert type engine.

Stroker middle weight design connecting rod like what CROWER manufactures will give you plenty of rod big end to cam lobe clearance on a standard deck / stock cam tunnel location SBC.

No way of knowing if a Small base circle cam will clear or not unless your engine builder built an exactly identical engine combo as what you have now prior.
Exact prior experience & correctly chosen parts to correct interference problem.

Or he can take one of your piston & rod assemblies & grind .050" off each rod bolt head.
Reinstall the same piston- rod.
Rotate the engine over by hand and recheck carefully with a flashlight & wire type feeler gauge for enough big end rod to cam clearance.

Then purchase the small base circle cam.

Press out the ground on connecting rod bolts.
Replace them with new rod bolts.
Likely will have to resize that connecting rod on the big end.
Cut cap & rehone to minimum big end spec size in 1/10,000ths " inches.
Because through connecting rod bolts seldom relocate the connecting rod fork body with the cap end perfectly after replacing rod bolts.
TIR of through rod bolts very greatly at times.
Throws locaction of assembled connecting rod parting line off center.
And throws big end bore size off too.

Middel weight stroker design rods are best.
Crower my choice of rods too.
American steel & machined in house.
Sporstman series are affordable & 100 times better than off shore china rods.

BR

 

Read what I wrote last to you.

Carefully visualize what is going on & my explanation to you.

Hopefully make logical sense to you then.

 

http://www.summitracing.com/parts/SCA-26000P/?rtype=10

Is this scat rod capable of doing the same thing? I'd rather not spend so much if I can get by with these. They should more than stand up what i am going to throw at them.

@87vette:

It does make logical sense to me, but he doesn't really seem to give 2 ***** about it. Basically wants to get paid and he lays no value in pleasing his customers. I know that its not his fault that the rods are hitting the cam, his attitude towards the entire thing is what bothers me.

 

I had engine builders build me racing motors in my early 20's in Chicago.
They acted just like you the machinist you are describing now.

My engines I had anywhere from $10K to 15k in parts & paid the engine machinist builder another $3k in labor & engine dyno time.

I got treated like a a POS because I did not bring him a $50K to $100K pro stock racing engine to build & he could not make $20K in labor off of me.

I found a small 1 man machine shop 100 miles south of Chicago in Hickville.
LOL

My friend Steve is 1,000 times more caring, honest always, lets me watch him machine.
Often has me double check with Micrometers & dial bore gauges to make sure I am happy.


You found the best then if you find a machine shop like I use.

I do my own Valvejobs/ have all the equipment at home.
3- angles standard a fare.
Do 5- angles if there is enough room present.

BR

 

I can only advise from here.
I did that tonight for you.

If you don't like the guy & don't trust him.

Then get your engine out of that machine shop & go elsewhere.

We are both in the USA.

Freedom of choice & speech is our GOD Given right for everyone.

Brian R.

 

OK,

I looked at your summit link.

take it for what its worth.
Don't get offended.
My opinion only.
Does not have to be yours.

For Less than $238 for a set of 6.0" c-c sbc connecting rods.............
There is no way in hell they are American made.
Some guy in China is getting hit with bull whips to spit out 1,000 of those same connecting rods every hour.
He is getting paid less than $.50 cents per hour and no benefits.
He probably is a machinist craftsman.
But his Chineese Boss is a super A>>>>>>>>>>>>>hole.
And he has a family to feed at home.
So spits out as many of those connecting rods per hour as he can to please his boss & get his $$ paycheck by the end of the week.
Its not the worker's fault.
Its his superiors in charge.

The reason CROWER & other American performance parts cost more is because they are using all American made - sourced materials & Paying their machinists & other employees decent wages.
Above $.50 cents per hour.

KEEPS EVERYONE HAPPY & YOU IF YOU PURCHASE & USE THEIR TOP NOTCH AMERICAN MADE PARTS.

You need to spend at least $600 - $900 to get a super high quality set of All American made connecting rods.

Its how I see it.
And have since 1991.

BR

 

Hes being straight with you there is no way to really tell til its assembled regardless of how it "should" fit. if he did...and he had to tear it down hes going to eat a lot of labor.

Welcome to strokerland. Its worth it though youll never build smaller again.

 

Any engine builder that knows stroker motors will put the engine together for a trail fit to find any clearance problems.The small base circle cam seems your best bet right now.

 

Absolutely. Will admit cap screws are better but are not absolutely necessary.

 

No re-balancing required if bolts are ground on for clearance?

Seems like there would be and re-balancing the setup is unavoidable.

If bolts/nuts can't be included in the balance procedure, how much will ground heads affect balance?

Should set-up/clearance-checking be part of a mock-up? If so, should Pawnge be charged (extra) for the problem -- if rebalancing is necessary?

 

The Crower Sportman Stroker rods run $700. The labor to rework the engine could add up fast if you try cheaper alternatives and they don't work. As 87 Vette mentioned, the rods see the most loads of any engine part. That's where you want to spend the extra dollars.

Your machinist probably should have mocked up the engine to check for clearance first. Mine did. But you will likely have a tough time getting him to admit that and share any responsibility. At this point you need to find a way to minimize his effort so you can get your engine home. You'll forget all about this part once that engine is running. Good Luck.

 

Mountain out of a molehill.
Grind the bolts equally, and check the big end weight with the machinists scale and jig. You will likley remove 1 gram or less to make it work.
1 gram off the big end ain't ****.
When a rotator assembly is balanced, there is an oil weight that is guessed for the math. God knows if it is accurate. Balancing is a careful, well planned mathmatical guess.
Guys have been kissing rod bolt heads with the grinder for as long as they have been building strokers.
I was not even aware of a stroker rod until the mid to late 90's.

 

That was my advice when he was over here. I was surprised the guy was making a big deal about it. Clearance it and lets get it in the car!

 

Yup. Too many guys on the internet preach the gospel of the best parts money can buy. You cant buy a guarantees, only better odds.
Street/strip cars do not break rods or rod bolts.
Almost never, anyway.