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Post by yammies on Jun 9, 2012 9:31:36 GMT 12
you need to make sure your clutch is centred on the flywheel or you will never get it to slot in. Put the gearbox in gear so you can rotate the shafts as you offer the input shaft to the clutch. you should be able to 'feel' it going in. you shouldn't need a proper gearbox lifter for a chevette box.... I can lift them with one hand....
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Post by gordo on Jun 11, 2012 16:52:29 GMT 12
I use an old input shaft from a 'box that stripped it's constant mesh gear, Sometimes you can line them up correctly by eye, but it has to be very close or it simply wont slide into the spigot bearing in the rear of the crank and you'll be thre for ever - your local Repco/Partsmaster stores should have a univeral that will fit.
Did you use a couple of long dowels to locate the head and head gasket when fitting them? There's a smaller diameter hole in each at each end that can be used with a cut off head bolt (or aftermarket long bolt/shafting) to align them - first time I built an engine I didn't know this and the gasket blew between cylinders as there's very little material there.
Under the washer bottle, and the battery, are the main areas for rust, unfortunately, but relatively easy to fix.
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Post by yammies on Jun 11, 2012 18:03:18 GMT 12
I can second that! and behind the wheel arches front and rear.. and the floor if the battery box and washer bottle have not been got to in time....
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dunc
New Member
Posts: 38
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Post by dunc on Jun 12, 2012 21:22:48 GMT 12
I used a close fitting wooden dowel to try to centre the clutch plate. Not ideal as it really needs to be shouldered, since the clutch plate spline is slightly bigger diameter than the spigot.
Shes all back and reassembled, but i cant get her to run right. Had a few ignition problems and got a electronic kit on the way. Everything else is pretty new, been replaced or been thoroughly checked. Stripped the starter, water pump, alternator, fuel pump everything, before i even tried starting it. Tested all the electrics both sides. The distributor shaft has a small bit of sideways play in it and i think that causes the occasional miss.
At first i suspected valve timing but thats probably unlikely. Managed to get it to idel ok but it wont move far above a fast idle speed. My instincts tell me it is running too rich for some reason. Ive tried playing with the air valve thing and have checked the diaphragm which seems to be OK. If you try to rev it it dies, or one one occasion backfired spectactularly through the inlet (have checked the carb internals since then). Went to test for vacuum leaks and tried spraying engine start direct into the carb first to see what revs would do. It just dies straight away if you spray it anywhere near the carb intake. Exhaust seems to get very hot very quick too but dunno if thats anything to do with it.
Whats next obvious thing to check? Mixture? How do you adjust? Is the new ignition likely to make a difference? The timing is spot on according to my old timing light, but advances quite a bit at a slight rev above idle - is that a centrifugal advance?
Any pointers appreciated.
On the plus side the engine looks tidy! Everythings looking new and I stripped back and polished the rocker and oil filter covers etc and then lacquered them with high temperature clear paint. No good if its not running properly though!
Dunno about the head bolting to the block Gordo. I had the engine reconditioner put the head back on. Ive not used the dowels before when ive done it myself but will do so next time.
Cheers
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Post by gordo on Jun 13, 2012 4:05:31 GMT 12
The centrifugal advance does advance with the rpm, but the vacuum advance can come in quite quickly at a fast idle - that's one reason you have to check it with it disconnected.
One thing that is very important, BTW, is getting the water distibution tube in the right place, as otherwise you may get a lot of detonation and possibly crack the seats. I expect you've got it sorted, though.
The distributors are quite crappy, with both the baseplate and bushes wearing. You can pick up replacement bushes from an auto electrician - I use three as they'll fit - leave them to soak in oil for a while, to impregnate them first. Sometimes you can tweak the baseplate or use several to make up a slop free one. the electronic ignition should cure those problems, though they may be worth doing anyway.
Sometimes the shaft will also be slightly bent - with all these minor issues, they can add up and it's not unusual for the gap tp be advusted to get it to run on 4 cylinders.
The advance springs are, IMO, very slightly too long and they give an irregular idle advance - while I have a timing light, I find it easier to do it statically, holding the rotor back against the stop.
the OEM engine needs 95/96 a nd you'll need a valve lubricant.
I assume you've a manual and overhauled the carb by it's settings? Adjust it right in, large castelated brass nut under the carb', by gentle hand force, then back down two full turns - you can still buy the spanner from a carb shop, or order from your local auto store. early models are reasonable easy to turn by hand, but later versions have a raised casting around them and really need the tool.
By the air valve thing, I assume you mean the hot idle adjustment - a big no-no, as even stock it can lead to problems and if fiddle d with... IIRC, this is also covered in the manual - most adjust it so it never works, anyway.
If you're worried about the cam' timing, if you take off the rocker cover, the inlet and exhaust on #1 or #4 should be rocking and open the same amount - if it's out, it should be obvious. Regarding the valve clearances, it says to do them running - IMO, that's just a good way to ruin 'guages, I just do them hot and leave it at that. I found they would go out of adjustment be 3 or 4 thou per 3k km when using mineral oils but with Mobit 1, there was negligible wear.
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Post by zep on Jul 12, 2012 9:12:00 GMT 12
Hey Gordo, I'm undertaking a 1256 rebuild at the moment too. The plan is roughly: Get it all apart Clean everything by whatever means necessary (i.e. acid dip or just elbow grease, depending on the part) Obtain new consumables Am keeping pistons Tidying up the inlet and exhuast ports. Open the combustion chambers up to the cylinder edge (read this in the Blydenstein chapter). Might replace valve springs with something heavier Lumpy cam Oil filter conversion kit Maybe an oil cooler Some kind of induction (will mention below). Few questions, can I have (along with the block, crank and head) the pistons and rods acid dipped? I will be opening up the combustion chambers a touch, shouldn't be more than a few cc's but that's enough to lower the compression ratio. How much can I safely take off the head to raise the compression ratio without a) the valves hitting the pistons with the stock cam, and b) needing different length pushrods? What is a good cam profile to go for? Bear in mind this is a street car. I don't need to ring it out to 8000 but a nice mid would be cool. Also I would like it to sound foul  Carbyside, Tony says 28/36 Weber. They are hard to find. What about a 32/36? Or I was also thinking, even cheaper would be a Gemini Nikki with is 32/34. Other's have suggested an Alfa Weber, either 36 or 40 IDA I think they are. I really want to do 2x motobike carbs. I was looking at some 36mm carbs from a 900cc bike. Might even be over kill. Anyway, any insight would be awesome! Oh, and I am having a world of trouble getting the inlet valves out. The exhaust valves popped out super easy with the valve spring compressor, but the exhaust ones have bent the tool!! We even welded a 5mm plate on it and it still bent it! \Cheers! |
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Post by gordo on Jul 12, 2012 16:30:45 GMT 12
Hey Gordo, I'm undertaking a 1256 rebuild at the moment too. The plan is roughly: Get it all apart Clean everything by whatever means necessary (i.e. acid dip or just elbow grease, depending on the part) Obtain new consumables Am keeping pistons Tidying up the inlet and exhuast ports. Open the combustion chambers up to the cylinder edge (read this in the Blydenstein chapter). Might replace valve springs with something heavier Lumpy cam Oil filter conversion kit Maybe an oil cooler Some kind of induction (will mention below). Few questions, can I have (along with the block, crank and head) the pistons and rods acid dipped? I will be opening up the combustion chambers a touch, shouldn't be more than a few cc's but that's enough to lower the compression ratio. How much can I safely take off the head to raise the compression ratio without a) the valves hitting the pistons with the stock cam, and b) needing different length pushrods?
I've taken 2mm (or 80 thou') off a head without issues - but that was with recut 3 angle seats that may have been slightly recessed compared to the stock location - it I were doing it again, I'd have the block skimmed to have the pistons 0.25mm (or 10 thou) above the block face, this should give excellent quench and still have plenty of clearance to the head, then just have a clean up skim of the head - However, I had taken quite a lot of material off the chamber around the spark plug and quench too, which may have made quite a bit more difference than just unshrouding the valves..
With the 2mm skimmed, I had to machine some of the bottom of the rocker lock nuts and trim the underside of the rocker cover ribs, as the rockers were just touching, used the OEM pushrods - if you don't take much off, you shouldn't have that worry, though.
You're really going to have to measure up yourself, and see what it works out at - however, I don't see you having a problem if you just skim 1mm (or 40 thou') off - depending whether it's been done before or not will alter that, though.What is a good cam profile to go for? Bear in mind this is a street car. I don't need to ring it out to 8000 but a nice mid would be cool. Also I would like it to sound foul I just used the stock camshaft (remember, if using an aftermarket/reground one that there may be piston clearance issues) as it gave very good midrange and ran out of breath around 6k7rpm, which I put down to the (modified) 150 CD fitted as stock - although I saw 7k4 a couple of times I certainly wouldn't recommend that*! That was with HD Kent (Ford) single valve springs and a 1mm shim on the head!
I would remind you that the OEM collets are MADE OF TOFFEE and the additional stress may result in a dropped valve - I don't see any point in running dual springs as they're not needed for any sensible setup and introduce a lot of expense and muching around. As I said elsewhere, I was considering whether the early Mini collets would fit as they are (were?) available as proper steel ones and they also used 7mm stems - may be something for you to chase up, perhaps suitable springs and lightweight caps as well if you really want to use a lot of rev's?
If you really just want a lumpy idle, you could enrichen the idle mixture...Carbyside, Tony says 28/36 Weber. They are hard to find. What about a 32/36? Or I was also thinking, even cheaper would be a Gemini Nikki with is 32/34. Other's have suggested an Alfa Weber, either 36 or 40 IDA I think they are. I really want to do 2x motobike carbs. I was looking at some 36mm carbs from a 900cc bike. Might even be over kill. I used a modified 150CD Stromberg - the OEM carb - which worked out well, overall but was, I believe, a bit restrictive at high rpm.
The 28/36 would be a little more responsive, probably, but the slightly larger carb would work as well and they were popular options back in the day - but finding one nowadays, or rather the manifold, may be a mission. The Japanese options would also be viable if you can get a manifold.
Best would be either dual choke downdrafts or sidedrafts and, as you point out, m/cycle carbies are gaining a lot of popularity - I don't see 36mm versions as being too big, heck, a 45 Weber or Del'orto was a 'common' fitting back then. Problem would be getting the linkage and jetting sorted, though?Anyway, any insight would be awesome! Oh, and I am having a world of trouble getting the inlet valves out. The exhaust valves popped out super easy with the valve spring compressor, but the exhaust ones have bent the tool!! We even welded a 5mm plate on it and it still bent it! \Cheers! Do you mean the spring retainer/collets are locked in place on the valve, and you can't break them free? Old technique was to put some wood, or similar, under the head of the valve so it was well supported, and to put a socked over the collets on the retainer/cap and smack it with a hammer - a bit rough, but sometimes there wasn't really an alternative. If you mean the spring has been removed, and the valve won't pull through the guide, that is usually due to running loose tappets - the rockers will literally hammer the end of the valve and 'mushroom' the end - sometimes carefull use of a file will clean them up enough to pull the through but in extreme cases, cutting off the head works - but then you need to replace the valve... Oh, you DID put the water distribution tube back in the head? This is very importand as otherwise you can get cracks and other problems. *Stock pistons are rather heavy and I don't much care for all that weight being swung on the stock rod' bolts - although I know some have run well over 8k if I were to use those rev's, I'd look at using some forged, flat top Kent pistons or modified Lotus pistons (same bore) with aftermarket rods machined for the right length and small end for those pistons - thatr would be rather expensive, though, and you would have to REALLY want to! |
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Post by zep on Jul 13, 2012 9:31:49 GMT 12
Okay, that was a lot to read and I have a lot more questions.
1. If I shave the block to have the pistons raised 0.25mm above the deck, won't they hit the head? Also, surely taking this much off would mean the valves would hit them? I do not want to have to modify the pistons with valve recesses.
2. Yes, the spring retainers are locked in place. We strengthened the valve spring compressor and it bent again! We've tried hitting them with a hammer and no luck. Might try give them a squirt of CRC and leave it a few hours this weekend, then try again.
3. Please tell me about this water distribution tube. Where is located?
Thanks Gordo. I don't plan to fit alternative pistons or anything, just because I want to keep this cheap. I want to do as much as I can myself, and only really pay for the block work and having the head skimmed if possible.
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Post by gordo on Jul 13, 2012 18:36:12 GMT 12
Okay, that was a lot to read and I have a lot more questions. 1. If I shave the block to have the pistons raised 0.25mm above the deck, won't they hit the head? Also, surely taking this much off would mean the valves would hit them? I do not want to have to modify the pistons with valve recesses. Head gasket makes up the difference and then some - don't use the GM gasket as it used to be cheap crap - the Repco ones are good.
As far as the valve to piston clearance goes, taking xx of the block is the same as taking xx of the head - but because of the shape of the combustion chamber in the head, you lose maybe 15% more unswept volume which means you get slightly more comression.
If you're a bit hesitant, you can just get the block skimmed to equal the top of the piston, or not bother with anything other than a clean up skim.2. Yes, the spring retainers are locked in place. We strengthened the valve spring compressor and it bent again! We've tried hitting them with a hammer and no luck. Might try give them a squirt of CRC and leave it a few hours this weekend, then try again. As I said, use a socket or piece of wood positioned under the head of the valve so when it gets hit it isn't all spring movement make sure it's square and/or in the middle of the valve so you don't bend the head. Use a fairly large socket that clears the collets (keepers) when you give it a whack.
some penetrating oil or spray can't hurt  3. Please tell me about this water distribution tube. Where is located? Behind the water pump there should be a long tube made of thin brass with holes along it's length. There's a sort of notch in the head casting that a notch in the tube lines up with. I've met people who think it isn't needed - it definitely is!
Thanks Gordo. I don't plan to fit alternative pistons or anything, just because I want to keep this cheap. I want to do as much as I can myself, and only really pay for the block work and having the head skimmed if possible. If you want a racey engine, you can spen a lot and still get nowhere near a (Toyota) 4K's potential, but they can be made to be quite peppy and a surprisingly good drive. |
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Post by wartly on Jul 14, 2012 9:15:52 GMT 12
If you try Bowden automotive in Taupo bay northland they have all sorts of new engine parts fop these
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Post by gordo on Jul 14, 2012 16:08:48 GMT 12
Thanks for that, Alan, I was trying to remember the name of that place.
You got home with the bits OK?
Forgot to mention that if you can use the gear cluster, you'll also need the Viva shifting rod as well - they changed the design at the lever end.
Viva and early 1256 engines used a solid pushrod with narrow guides in the head casting, later engines used hollow pushrods with wider guides - the 'ball' ends' radius seem to be the same, though. Quite handy if you have an early head as by using the later pushrods you can adjust the slots to centralise the rocker pads over the valve tips.
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Post by zep on Jul 15, 2012 16:16:07 GMT 12
Do you know if I can use the Chevette gearbox gearstick with the HA Viva box?
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Post by gordo on Jul 15, 2012 17:35:26 GMT 12
Early chevette lever should be OK, later type had a redign and used a plastic clip which was supposed to reduce rattle and the end of the selector rail was different.
Not sure about the application you're using, but in the past I've used the Viva gearbox in the Chevette but tthe tealshaft housing, the tailshaft (swap over the gears* on the shaft and the selector rail should be changed over.
*later Chevettes had a different 2nd gear helix angle and they DON'T play nice together!
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Post by zep on Jul 16, 2012 9:08:03 GMT 12
I would prefer to keep the Viva gearbox just to make things easier. Done naught on the engine this weekend.
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dunc
New Member
Posts: 38
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Post by dunc on Jul 17, 2012 23:18:26 GMT 12
Hey Zep - good to see someone else is perservering with a 1256 engine. Ill be keen to see how your rebuild goes so keep the updates coming.
My car is running sweet now, just need to get some rust repairs done and shes off for a warrant.
My other project chevette im starting to slowly get parts for. Ideally want to do a 2.3 swap, starting with single cam, but also bought a VN commdore motor and box the other day so that might open up option for an opel 2 litre twin cam if i can find one.
Keen to hear if anyone knows of either 2.3 slant 4 or a 2L opel engine for sale in the south island.
Maybe dumb question, but does anyone know if the VN box can be made to fit the 2.3 slant 4?
Cheers
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