Comments interspersed below...Brian
At 10:12 AM 1/24/98 -0500, you wrote:
>As some of you know, I have decided to completely rebuild the 1275 that is
>sitting in my '67 Sprite MKIV (Vicky). I took the engine to a Racing Engine
>shop that does machine work to have the engine checked out and just got the
>engine and the verdict back. Scary thing is the engine is now in pieces and I
>didn't have the advantage of taking it apart, so putting it back together
>again will be a lucky combination of prayer and Haynes (the manual, not the
>underwear, although in some ways I will be flying by the seat of my undies).
>LOL
It's not hard, and ask if you get lost. Main thing is to decide now that
you'll probably assemble it three times before you're done, to check various
things, so don't get impatient...
>
>Anyway--Several questions to those of you who know much more than me about
>these things:
>
>1. The engine crank, rod bearing bores, Maiin bearing bores,and everything
>else, bearing-wise checked out ok. The bearing weren't even bad although I
>will be replacing them since I am there. Two biggie problems: The cylinder
>has previously been bored and oversized pistons have been fitted. The bore
>checks out at 2.809. This exceeds the top limit indicated in the shop manual
>for the largest oversize piston. The machinist recommended that I would need
>to bore, sleeve, and re bore the cylinder to fit the existing pistons to
>regain engine health.
1275's bore succesfully to 73.5 mm, which is well over your current bore of
71.35 mm, and 73.5 pistons are very available. This gives a size of 1380,
and a very nice street motor - easy 100 hp.
>
>2. He also said the bolts were loose in the rods--I think when they are
>loosened that they fit into the holes loosley. Is this normal? Of course
>when they are torqued they are tight and do not move. Are they OK as long as
>I can get them to the recommended torque and they are tight in the rods at
>that torque (And locktabs set, of course)?
DO NOT use lock tabs. I know the factory did, but they are an abomination.
They are soft metal that causes the rod bolts to lose their torque since the
soft metal squishes. Either buy ARP bolts from a competition shop, or get
new stock bolts and nuts, or re-use the old ones if they're perfect. The
stock bolts will be a loose fit in the rods, although many aftermarket bolts
are knurled to a tight fit. The bolts will not loosen if they're torqued
correctly, so don't use any locktite on them either, it's not required.
Same goes for the main cap bolts or studs, the flywheel bolts, and the head
studs. ARP makes fasteners for all of these applications that significantly
strengthen the assembly, since they can be torqued to higher values than the
stock fasteners, and higher torque is what makes the assembly strong. The
only place I use loctite in the engine is the front pulley bolt.
>
>3. We have discussed hot-tanking the block. Everything I have read indicates
>that the cam bearings MUST be replaced after hot tanking. I read somewhere
>else that this required special equipment--even a special reamer to ream out
>the old bearings. What to do here? Is this something the machinist is
>expected to do, or can I do this myself (in my noviced condition).
Hot tanking the block is good, but not absolutely essential. It will remove
the cam bearings. It is a pain in the butt to replace them, and they should
be sized after being installed, and you should do that with a reamer. Based
on the fact that your crank, etc, is good, then I'd personally just wash the
block with lots of soap and water, and then WD-40. You did get the crank
crack tested (magnafluxed) didn't you?
>
>4. Some discussion of plastiguage has been passed along on e-mail and on this
>network. Could somebody tell me about that? Here is what I dont understand
>about plastiguage: I just had my engine micrometered by a machinst--He said I
>neede the REGULAR sized bearings. OK! So is the plastiguage a plastic
>material that I would squeeze onto the bearing surfaces of the OLD bearings,
>retorqueing everything, that dries and upon checking the thickness is a check
>on the machinists findings? Or is the plastiguage used on the NEW bearings?
>This seems redundant because once the new bearings are bought to fit
>(according to a machinist with a micrometer) what is the point of squirting a
>plastic material in to prove that you just wasted your money?
Plastigauge is a thin thread of plastic that, when squeezed between the new
bearing and the journal, is squished to a flat ribbon. By comparing the
width of the ribbon to a series of samples printed on the package, you get a
very good indication that the bearings are correct. Why do it? Because
once in a long while, the bearings get mis-packaged, and you have say .020
over rather than zero over. This is part of proper engine building, and
taking responsiblity for the job, rather than trusting the machinist. Your
choice - I always measure. It's the difference between a craftsman and an
assembler. A craftsman takes pride in the work, and an assembler just wants
to go home at 5 pm.
Call Winners Circle (they have a nice web site) to ask about the 73.5
pistons. Use new tappets if the old ones aren't perfect, or if you're
putting in a new cam (a 285 would be perfect for a 1380!) or if you get them
out of order. Check the harmonic balancer very carefully to see if the
rubber is deteriorating - they're getting pretty old now, and tend to come
apart. Use lots of oil when you assemble the engine, and I always put moly
grease on the camshaft.
>
>I will be progressing slowly as I read your responses. I will appreciate any
>and all input. Also any tips, ideas, logic, philosophy, jokes, horror stories
>are welcome. Thanks guys.
>
>----David Campbell
>
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