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Rebuilding the race motor.
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Author:  SpaceFrank [ Thu Jan 08, 2015 2:17 pm ]
Post subject:  Rebuilding the race motor.
We pulled the original 225 (rebuilt properly in 2004) out of my '64 Dart after its 5th LeMons race. Blow-by had risen to excessive levels, cold starting was getting more and more difficult, and a leakdown test revealed (I kid you not) between 26-42% pressure retained with the engine cold. The air noise during the leakdown test was definitely coming from the crankcase, with no detectable sound in either of the manifolds, so I'm assuming the rings are toast. The head is apparently in good shape, as it ran well on the temporary replacement engine, but we'd like to take the opportunity to mill it once we determine our current SCR and have a target in mind for what we want it to be.

Since we plan to disassemble the engine this week/weekend, my first question is what the tolerances are for bore measurements. I have a set of ID mics and a good dial caliper, but I don't know what my target is. I'd like to make the call soon on whether we need machine work done on the block.

Here's the basic plan for rebuilding the engine:
1. After measuring piston-deck clearance, disassemble and visually examine everything. Take measurements of the bore, crank journals, and cam journals (if we decide to pull the cam).
2. CC the head, do the calculations, and figure out how much (if any) we should mill off the head (or block). Do more research and see if we want to bother doing a cam swap.
3. If the bores are in bad shape (gouged, egged, tapered, etc.), then bite the bullet and send it out for machine work, possibly ordering new pistons if the new bore puts us outside of acceptable clearances.
4. Regardless of Step 3, install new rings. It's my understanding that a sloppy garage hone job will require the use of standard iron rings for proper wear-in. If we have the bores machined clean, on the other hand, I'll probably spring for harder Chrome-Moly rings.
5. Have the crank ground and rebalanced if the journals are gouged up. Either way, order new crank bearings appropriate to the journal size, as well as cam bearings if we pull the cam. (Should we go ahead and pull the cam to replace the bearings even if we do re-use this cam?)

I've been doing some research and I feel comfortable that my teammates and I can tackle this, but it'll be the first time I've ever actually assembled an engine. Any advice y'all can give on honing, installing bearings, etc. would be welcome. This might sound crazy, but I've also heard from some sources that if the bores are in very good shape, you should actually leave them as-is and install the new rings without honing. The contention is that hand honing is a pretty rough operation, so unless the bores are gouged, this actually makes the surface finish worse. Any thoughts on this?

My other big question is what DCR to shoot for and how to get there. If my understanding is correct, once we have a target DCR in mind, we can use the cam specs to backtrack to the needed SCR, and then determine the amount of milling/decking that's required. Our current cam is an Isky with .448 lift, 264 duration, and 109 lobe separation. We'd like to continue using 87 octane, if that makes a difference.

The tricky part is that while our setup is currently normally-aspirated, we have vague plans to add turbocharging at some point in the future if we ever get bumped up into a higher race class. Is it feasible for this or any cam to work well NA but still work decently with 5-ish psi of boost? If so, how would this affect our target SCR? Keep in mind that this is an endurance race, and we rarely rev the motor above 4000 RPM on the track. I consider 4500 to be our hard ceiling just for the sake of reliability. Should I just accept that I'll be looking at a cam swap whenever we turbo the thing? Can I install a thicker head gasket to drop the SCR back down a bit? Would switching to 93 octane help?
Author:  Dart270 [ Thu Jan 08, 2015 4:35 pm ]
Post subject: 
Initial thoughts:

Leave cam bearings along, assuming they look OK when you pull it apart. Yes, I would pull cam and look at cam bearings, lifters, cam/pump gear, etc. If the cam and oil pump gears look fine, then reinstall without any changes there.

IMHO, it is crazy to not hone bores for new rings. I cannot see how that would work except for dumb luck.

That cam will work fine with a turbo. A turbo might work better with a smaller cam, but that one is not too big assuming your turbo is on the small side.

I would mill for 8.5 or no more than 9:1 static comp with that cam to still use 87 octane in endurance conditions.

I would guess you'll have to bore and get new pistons, but just a guess. I have never measured anything really in a bore, but have just re-ringed motors that (by eye) did not have glazed walls or busted rings or a big ring ridge.

Do NOT change rod bolts unless you want to resize the rods. Either bolt them back together with the original bolts, or you'll need to resize the rods with new bolts.

Our first LeMons 225 motor lasted 4 races and spun a bearing in the last 1/2 hr of the 4th. That included running it completely out of coolant for a lap in race 2 and blowing a head gasket and overheating, then just putting a head gasket on it to finish. We have a 5000 RPM redline, which should be safe.

Happy Motoring...

Lou
Author:  SpaceFrank [ Fri Jan 23, 2015 2:28 pm ]
Post subject: 
Thanks for the feedback, Lou. Here's some pictures after we pulled the rod and main caps. Since the rebuild, this engine had been through about 4 years of daily driving, 4 years of dead storage, and then two years with 5 full LeMons races. It was running (poorly) and had decent oil pressure when we pulled it. When hot, it was ~15 psi at idle and 40-45 psi under any load.

The rod caps, laid out left to right from the front. Bearings are obviously worn, but I don't know how bad this really is. We marked these and laid them out exactly how they came off, so the #3 and #4 rod bearings were on facing the opposite direction.
Image
Image

Here's another picture when we took the first rod cap off (#3). I need to get some more pictures of the journal surfaces. I'm guessing I will need to get the crank refinished.
Image

The mains were worn more heavily, with slight but visible grooving. These are also laid out left to right from front to back. #3 has a different style of bearing, as you can see. This main cap was also the only one that was difficult to remove. Any idea why this one is different?
Image
Image

I apparently didn't take any pictures of it, but we removed one piston so far (the only one that slid out easily). The compression ring was in two pieces, which explains the very low leakdown result and the increasingly bad blow-by we'd been having for the last couple races. I expect all 6 of them are like this.

Based on what I've seen of the bore condition, I think I can stay away from the machine shop for this rebuild. The bore surfaces look very smooth, and there are no significant ridges either.

More pictures to come as I finish disassembling. For now, I've ordered a "dingle-ball" flex-hone and am reading up on how to use it properly.
Author:  GTS225 [ Fri Jan 23, 2015 3:03 pm ]
Post subject: 
The #3 main bearing also acts as a thrust bearing for use in manual trans equipped cars. When the clutch pedal is pushed in, the force tries to push the flywheel forward. (Newton's laws, you know.) The "sidewalls" of the #3 bearing takes the brunt of the force, rather than the crank being slowly forced against the block's webbing.

Roger
Author:  SpaceFrank [ Fri Jan 23, 2015 6:39 pm ]
Post subject: 
Okay, that makes sense. I knew the engine probably had a thrust bearing, but it hadn't occurred to me that I hadn't seen one yet.

I took a closer look at the crank, and all the journals actually look good. There are visible circumferential lines, but they're all smooth to the touch, I assume I'll just need to mic the diameters at different locations (axially and tangentially) to make sure they're all straight.
Image
Author:  Dart270 [ Fri Jan 23, 2015 7:55 pm ]
Post subject: 
Yep, prolly just throw new bearings in, check with plastigage, and new rings and check for sufficient end gap. Too tight end gap might have caused the busted rings. I run loose ring gaps (high side of stock) on a motor like this that will see some high temps and sustained pounding. I also run loose bearing clearances, around 0.002" on rods and mains. If yours are tight when checking, you might get the crank polished a little to open up the clearances.

Happy building,

Lou
Author:  SpaceFrank [ Sun Jan 25, 2015 3:37 pm ]
Post subject: 
Okay, main and rod journals all look to be within stock tolerance or less than a thou undersized. The numbers on the bearings appear to be stock sized as well. We'll just buy stock bearings, and worst case they'll be a hair loose like Lou recommends.

Bore diameters are already 0.030" oversize, but all are within the FSM's 0.005" tolerance for roundness, and well within spec for taper. Looks like the block won't need any machine work, which is nice.

The top compression rings on all but #6 were broken. In some cases they came out in half a dozen pieces. 2nd rings were broken on a few as well. Makes sense that our end gap might have been too tight; this motor wasn't originally built for racing, after all. We'll definitely go loose on the ring gap when we put it back together.

Wrist pins on some of these pistons seem like they have a little resistance to rotation and axial movement. Others rotate/slide freely. Is this a problem?

One other thing I forgot to mention earlier: when we first took the head off, I turned the engine upside down like a dumbass, and all the lifters fell out. I assume I should buy new lifters rather than installing the old ones mismatched. Is there a problem with bedding in new lifters on an old camshaft?



And of course, now I find myself wondering if I should take the opportunity to replace these Sealed Power cast pistons and rods with something a little more robust. They still look to be in good shape, but if we plan to add a turbo later... I don't know. We have to use regular rings, so they might still be the primary failure point anyway.
Author:  Dart270 [ Mon Jan 26, 2015 7:40 am ]
Post subject: 
You might get by with putting the lifters back in out of order, assuming the faces are not chipped, but new ones would be more reliable and there's no problem with putting new lifters on an old cam. Make sure to break the cam in again as you would with a new cam, and make sure the lifters are spinning when you have done that.

If wrist pins are tight, that might indicate overheated pistons, but if only a bit of resistance then you should be fine. I would run them if it were mine, with new name brand cast rings and wide end gaps.

All else sounds good.

Lou
Author:  Reed [ Mon Jan 26, 2015 7:57 am ]
Post subject: 
Check with your local camshaft shop or machine shop. I can buy resurfaced lifters (solid or hydaulic) for $1 each and a tube of assembly lube for $5.
Author:  SpaceFrank [ Tue Jan 27, 2015 7:25 am ]
Post subject: 
Maybe a dumb question, but how do you make sure the lifters are spinning after break-in?

Also, just to be on the safe side I was thinking about replacing the oil pump with a higher volume or higher pressure aftermarket unit. Any recommendations on that? Reliability is my prime concern.
Author:  Dan-o [ Tue Jan 27, 2015 7:50 am ]
Post subject: 
On a fresh motor, you'll want to run a stock volume pump. HP/HV pumps sap power and put un-needed strain on hardware.
Author:  Dart270 [ Tue Jan 27, 2015 11:56 am ]
Post subject: 
If the pump was working, don't touch it. You could put a 0.060" or so washer under the relief spring to raise pressure to 50 psi or a bit more if needed.

Lou
Author:  sandy in BC [ Tue Jan 27, 2015 2:49 pm ]
Post subject: 
I like the style of motor you are building,

The right donor is just worn enough to give you race clearances after a quick hone and cheap cast iron rings.

I usually remove any ridge with a 3/8 chain saw file. Expect to take 15 mins a cylinder. A quality IPA is handy for keeping a steady hand ....but I dont recommend more than a couple for this operation.

Make sure you file fit the rings to fit each bore.

I measure ring gap by pushing each ring into the bore with an inverted piston. I usually measure the ring in 3 different positions in the bore....top mid and bottom of the ring travel. It takes bore taper into account.

I use a chainsaw raker file for the rings. Do it in a vice ....I stroke on each side....then check again. Keep the ends parallel to each other,,,,no tapered gap.
Author:  Rick Covalt [ Tue Jan 27, 2015 3:50 pm ]
Post subject: 
Quote:
but how do you make sure the lifters are spinning after break-in?
Put a dab of paint on each push rod and watch them after start up.

Rick
Author:  Dart270 [ Tue Jan 27, 2015 5:46 pm ]
Post subject: 
Yep, the pushrods will rotate along with the lifters, so you can look at the pushrod just below the rocker and see is spinning when all is well.

Lou
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