Crank is okay. Rebuild: How to proceed questions

[2wrench]

Machine shop says crank okay. Wants old main bearing
caps to do work on the crank (which needs machining down 10,000ths).

About main bearing caps: I noted front to back which
position they were removed 1-4. Can't say that I didn't
remove a bolt and put back on a different side -- though
I don't think I did this --

So I've read putting them back into same place is important.
Would it matter if the placement orientation is correct,
but the bolt that was on the left is now on the right?
How perfect does this have to be?

I think this was on my original parts list for new. So
if they are new, does the machinist need the new ones
to turn the crank to the necessary spec or can I give him
the old to use for his purposes and place new when received?

Also, my rod from cylinder #4 was busted. Do you know if
I can replace just that one rod? Is it now necessary to
replace all six? If I buy one, does it have to be
machined to the crank by the shop?

Finally, is it better to have the machine shop place
things like crank, pistons and thrust washers?

Enough for now? Whewwww.

 

[DrEntropy]

The crank needs to be checked to determine if it's "true" and probably cut undersize by 0.010". The caps are needed to be sure of crank alignment in the block. Bolt "order" isn't as critical as cap arrangement/order. Ideally the shop needs to know the original main and rod journal daimeters and running clearance.

You can replace just the one rod, but take all six to the machine shop so they can balance them to be of the same weight... Pistons, rods, crank and flywheel with new bearings and thrust washers and they can balance it as an assembly. Reciprocating mass is a funny thing... half an ounce at RPM can become POUNDS of force out of balance.

 

[Bugeye58]

Placement of the caps is very important, but the bolts aren't critical, However, if you are replacing the bolts, or preferably upgrading to ARP hardware, <u>I</u> would want the new bolts in place for the line hone.
You can just replace one rod, but make sure the shop re-sizes all six of them. The same fastener protocol applies here. Use what you will be using for the final assembly.
Unless you have all of the proper tools for the final assembly, I think it may be better to have the shop do it.
Make sure you get measurement sheets for all dimensions and clearances that they work to.
I always double check any machine work I have done, even if I do it myself.
Jeff

 

[DrEntropy]

Re: Crank is okay. Rebuild: How to proceed quest

/bcforum/images/%%GRAEMLIN_URL%%/lol.gif

*tickety-tack-tack*

Jeff 'n I have done it again! /bcforum/images/%%GRAEMLIN_URL%%/wink.gif

 

[Bugeye58]

Re: Crank is okay. Rebuild: How to proceed quest

Yeah, the great minds strike again. /bcforum/images/%%GRAEMLIN_URL%%/grin.gif
I was actually editing my original post when you entered yours!
Jeff

 

[2wrench]

Re: Crank is okay. Rebuild: How to proceed quest

Dr, I quote pertinent info:

"-- Pistons, rods, crank and flywheel with new bearings and thrust washers and they can balance it as an assembly."

So if I say to the machine shop: Balance the engine,
is the above what happens?

They install the pistons; rods; crank and flywheel
with the new bearings and thrust washers?

I was told he would charge $175 to balance the engine.
If this is what this means, I waunnit.

Let me presume the answer is yes. What other
parts (if any) must I deliver to him along with what
info/specs so he can do a good job for me?

I need to look at my prospective parts list earlier
created and begin to order/pull.

Can't go to pistons because I don't know what size
yet....chicken and the egg????

Thanks in advance,

 

[DrEntropy]

Re: Crank is okay. Rebuild: How to proceed quest

hmmm... I begin to smell fish.

Ask THEM what they need, and in what order. It's possible to balance rods one to another in sets, big end vs. small end but desireable to balance the assembly (crank, rods, pistons, flywheel) as a whole. The block is the starting point. What the five undamaged holes dictate as the final overbore size, to be matched in the sleeved bore. That will give you a piston (over)size. From there the crank spec's will dictate a regrind (if necessary) in 0.010" increments of undersize to determine bearings to get. Main journals and rod journals are two different things, BTW... I.E.: If the rod journals need cutting due to damage or roughness it doesn't necessarily follow that the mains journals need cutting undersize unless they also show evidence of damage. Thrust washers will likely be a non-issue.

We're all virtual by-standers here, trying to "see" what's occuring with your mill. These engines are "all-of-a-piece" and should be considered as -systems-. What is done to one bit will have effect on the rest. Keep posting thoughts and feedback info and we'll all do our best to offer what info/experience/expertise we can to put your beast back on the road. But we're only as good as the info YOU provide for eval.

 

[vettedog72]

Re: Crank is okay. Rebuild: How to proceed quest

What happens to the fly wheel; does it get balanced with the crank? Some people do the pressure plate too. In addition to matching weight of the rods, I would have them trued and the big end checked for roundness and the small end bush brought to spec's. Decking the block was popular at one time, I don't know if people still do it. With the rod all the way through the cylinder wall rod you might have a little flatness issue on the top of the block that woukld be cured with the decking. Its fun spending another mans money.

 

[Bugeye58]

Re: Crank is okay. Rebuild: How to proceed quest

Yes, the flywheel gets balanced with the crank, as does all of the rotating mass, including the front pulley.
Decking the block is standard procedure in my book. Not only to true the surface, but to optimize the piston height.
Jeff

 

[2wrench]

Re: Crank is okay. Rebuild: How to proceed quest

Okay. So far, he's asked for main bearing caps. Says
then he can give a closer estimate of costs.

You smelling fish causes me concern. So, what's
fishy? Is it something I've communicated (maybe
poorly) or something the machinist has asked for?

Just trying to be careful, here.

 

[hondo402000]

Re: Crank is okay. Rebuild: How to proceed quest

You Might as well have cam berings installed too, which are spitfire cam bearing if not already done. You could have the engined blueprinted, which as I understand when an engine is blue printed it means, if a part is to be machined to 0.100 with a tolerance of +/- 0.005
the machined part will be exactly 0.100 not 0.095 and not 0.105, yes keep the details comming, a rebuild might be comming for me in the future

hondo

 

[DrEntropy]

Re: Crank is okay. Rebuild: How to proceed quest

Just the order of things. Carts before horses. You need to know what pistons to get, whether the crank is in need of regrind to order bearings... Main caps to check alignment of block... it's my nature to be a skeptic. All seems right though. No worries!

hondo makes a point: cam bearings will need renewing, too. That job is best done by the machinists. The engine you have will likely need them reamed a bit after the install and it's a job requiring a precisely aligned reaming tool. A real PITA for a "one-man band" in a home garage. If you intend to replace the cam, decide which one and hand it over to the shop for precise fitting.

...are we havin' fun yet? /bcforum/images/%%GRAEMLIN_URL%%/laugh.gif

 

[Brosky]

Re: Crank is okay. Rebuild: How to proceed quest

Listen to the Doctor. He is absolutely correct, as usual.

The machine shop needs everything that is going back in the engine to be able to properly check or machine it as a matched setup.

 

[DrEntropy]

Re: Crank is okay. Rebuild: How to proceed quest

Listen to the Doctor. He is absolutely correct, as usual.

feh... 'cept when I'm not. Don't let Hap see that: He figgers I'm fulla, mmm, err... /bcforum/images/%%GRAEMLIN_URL%%/jester.gif

 

[BryanC]

Re: Crank is okay. Rebuild: How to proceed quest

cam bearings will need renewing, too.

Well, only if you have cam bearings. The TR6 didn't come with cam bearings. The cam runs in the cast iron block. It is possible to ream the block and install bearings from a Spitfire. Not every shop has the capability to do that. There is some debate about whether it is necessary to have bearings installed - many folks say that you don't need them unless you're going to a higher lift cam or are building a race engine.

Bryan

 

[Brosky]

Re: Crank is okay. Rebuild: How to proceed quest

Bryan,

You are correct also about the original configuration. I'm going to rebuild a spare block for my TR6 this summer and will probably go to some variation (GP2) of a new higher lift cam. There have been many on both sides of the cam bearing fence, but most machine shops that I've talked to will want to install the bearings, just to insure that the new cam will have a perfectly matched mating surface.

Once you're in there is the time to get all of this done. I don't think that it's that much more to do it all at once. I will want mine line bored and I believe that the cam bearings are a secondary part of that process.

 

[DrEntropy]

Re: Crank is okay. Rebuild: How to proceed quest

My bad, Bryan! I was remembering a Spit 1500, not the 6. But the method of line boring the cam journals and installing babbeted Spit bearings has real merit IMO: Guaranteed straight and fitted for the cam of choice.

See, Paul?!? I'm fulla. /bcforum/images/%%GRAEMLIN_URL%%/wink.gif

 

[2wrench]

Re: Crank is okay. Rebuild: How to proceed quest

Thanks, all. Seems the more I hear, the more I am
leaning toward rebuilding completely stock to help
minimize mistakes.

You know what they say, Paul: You have to listen to
the doctor.

 

[Norton47]

Re: Crank is okay. Rebuild: How to proceed quest

2wrench
Exactly my feeling. I had a totally stock engine built.
I talked with my machinist, and unless you really want to go all the way cam, breathing mods, header, so forth and so on, and want or need the HP, just go stock and have a nice reliable, long lasting engine.
I figure if I want more power, I will go with the supercharger kit later. Bolts on and you can take it off, later if you want.
Power is there on tap, when you want it, otherwise the engine is normal.
With a rebuilt stock engine I have a great foundation. Cost me $2384.00 with tax.

 

[Brosky]

Re: Crank is okay. Rebuild: How to proceed quest

I'm leaning towards the PI cam profile and with my reworked head, tri carbs, headers, ignition and appx. 9.5 to 1 compression, it should run pretty well and will be reliable. I will also be doing the Fidanza aluminum flywheel and I just ordered the lightweight alloy plates for the front and rear of the engine.

I'll probably go with a new aluminum radiator and the electric fan conversion as well.

I do not want a car that won't idle in traffic and overheats constantly either, so I'll stay close to stock, but will push it with factory designed internal mods.