4kc breaking up high rpm

[Braydenj]

Hey guys just picked up a 84 slant nose and am having trouble with tune or timing or both and need a little advice as I’m new to the carby game and want to learn.

so long story short I am 3rd owner first was a older lady who put most of the ks on in then parked it up in the shead for about 2. A guy then brought it off her and did a bit to fix it up and get it running this included 

Fluid change throughout, new rad and hoses, thermo fan, new dizzy elec ign vac adv, coil , leads , plugs, carby rebuild kit, rpm guage, and a few more things not important to the problem. 

so my problem is driving at freeway speeds 80-100kmph (3500 - 4000 rpm 4th gear) the car will have what I can describe as the odd hick-up or cough where it will jolt for a split second and break up only to keep driving normally this happens pretty consistently but at random intervals at this speed (it is fine any other speed however haven’t really tried going above 100 kmph as I don’t intend to). Also to add to the problem when downshifting from 4th to 3rd if I take more then a second or two to downshift the rpm will drop to low and the car stalls out on me unless given a jab of throttle to keep her running. Weather or not this problem is related or not I am not sure. And the final problem I am experiencing is to do with the tuning side of it(I believe ) ,where I find myself not being able to get the idle to drop below 1000 rpm and when I did have it down around that 1000 mark it was not idleing smooth at all.

so what I have done to help progress on my issues. I adjusted my valve clearances that’s helped quiet the motor a lot and make it smother overall. I have done a fresh service throughout new belts oils plugs ect, I messed around with the tune a little to try teach myself a bit about how it all works, and finally I checked my dizzy timing to the motor because I am running 98 octane I have based the timing off 10 degree btdc (that is pretty much my dizzy clocked all the way over to the left or turned anticlockwise as far as it can go. (Please correct me if I’m wrong on this part)

so what I have learned from all this valve clearances helped a bit aswell as a good service I have gained a basic to slightly advanced knowledge of how the tune and timing and all that come into play and work together.

however my problem still exists I could not get the car to run correctly with the timing retarded to where it is supposed to be it would idle horrible and I couldn’t get the rpm to change enough to the point I could start implementing the idle control screw. so I have set it back to where it was where it ran nicely but had the hickups.  After playing around with it richen it a touch I checked plugs and it is still to lean so now I am running out of ideas and things to try

On my list of things to try and check is fule pump, fule filter, check for any vac leaks (fixed one already) and spray around the carby and intake manifold with break clean or something to see if I can notice a rpm change when running to indicate a leak in the gasket. 
 

now I have probably missed a lot of basic steps and things to do so please correct me or point me in the right direction even a basic tuning guide for the 4kc would be mighty helpful or any in-site if any of you have had the same problem or simalar or think you know what the issue might be

sorry for the lengthy post and sorry if it has been covered already cheers wizards 
 

Also there is a pic of Alice in all her glory

[parrot]

The first thing I would be doing is checking the float level in the carb (carb rebuild raises a flag). Edit, saw you have electric ignition. 

Edited July 19, 2024 by parrot

[altezzaclub]

Beautiful! If you paid under $10k you got a bargain! Lovely colour too, the best!

Timing is not related to dizzy  position overall, it depends on where the teeth on the dizzy were when the last person put it in the block.  So it the dizzy is jammed hard against one end of its travel you pull it out and move it back to the middle. Not quite so simple as you will have to turn the oil pump slot a whisker to line up with it.

Do you have a timing light? If not, you can only look inside the4 dizzy at where the arm is as it passes the sensor, just not as accurate.

https://www.rollaclub.com/board/topic/49927-how-to-fix-your-brand-new-ke-motorsport-electronic-distributor/#comment-511594

So you can set the crank to 10deg BTDC and align the corner of the dizzy shaft with that little sensor strip, which is probably what you have done. Those dizzys were pretty crap just out of the box, the advance curve is very flat, so if its the same as mine you have a lot of performance to get out of it.

Second question, does turning the dizzy clockwise advance the ignition or retard it?

OK, I think you idle jet is blocked, or the float level is way out, as Parrot says. You could pull the top off the carb and look inside for dirt in the bottom or signs of corrosion from a dried carb. Measure where the fuel sits from the top and put a photo up on here for others to compare.

The tar in the petrol makes jets smaller if a car is left for a couple of years without running. You might have to take the carb off and strip out all the jets, hose them out with carb cleaner, hose carb cleaner through the drillings where the jets sit and then reassemble.

You should give it a jab of throttle when you're downshifting anyway, rev matching is much easier on a gearbox and the bearings for these gearboxes are no longer obtainable.

So, a clean-out of carb jets, a check of ignition timing, and let us know how you go.

here is what I've learnt and the mistakes I've made with mine-

 

[Braydenj]

Paid bang on the 10k mark was pretty happy with it no major rust or anything very clean car overall interior in near perfect condition to one small rip in carpet and a small crack in one of the door cards.

 

i do not have a timing light so I was using the pull the top of the dizzy off method and lining it the first striker up with 10 degrees 

 

so turning the dizzy to the right advances it it is currently sitting all the way right atm so something is not quite right because lining it up with 10 degrees is all the way in the left position 

 

but yes next step for me was to check the fule filter ect is not blocked and fule pump is pumping with nice flow then go onto checking the float and the keys ect however not really sure what I’m looking at tbh so any help is appreciated 

[altezzaclub]

"So turning the dizzy to the right advances it it is currently sitting all the way right atm so something is not quite right because lining it up with 10 degrees is all the way in the left position "

OK, which way does the rotor turn?  Turning the dizzy the same way as the rotor retards it, turning the dizzy opposite to the rotor advances it. You can tell instantly by looking at the plug leads and the firing order, 1-3-4-2, so following lead 1 to lead 3 will tell you which way it turns. It should look like this, usually with #1 in that 1pm position-

So turning it clockwise retards it, turning it anti-clockwise advances it. Have a re-think on that and re-set the timing just as you did, which is how I did it for decades before I had a timing light. Don't be afraid to stick 15deg on it, these motors handle a lot of advance without a problem.  Remember, advance will raise your isle speed, retarding will slow it down, so factor that into your carb work too.

Lack of fuel from blocked filters or low fuel level will obviously affect the motor at high fuel demands, ie foot hard down accelerating or top speed. Idle uses extremely little fuel, so a blocked filter is unlikely to affect it. Do some reading about pulling a carb top off and getting the jets out, its fiddly and a pain, but not hard.

 

[altezzaclub]

Local Autobarn has timing lights on sale for $50 instead of $80, I thought about buying a new one... I never thought about Cash Converters though.

https://www.cashconverters.com.au/shop/tools-motor-hardware/hand-tools/jumper-leads/timing-light/036800350524

Get yourself one somewhere, you'll use it a lot,especially if you start improving that dizzy advance curve.

https://www.ebay.com.au/itm/144677303073?itmmeta=01J3729Y5SCZXDPPEHW3SR0291&hash=item21af707321:g:D10AAOSwUa1i9KE2&itmprp=enc%3AAQAJAAAA4Do6O0MpInp25mq43h1iBIBaj2CkFt%2FBdtsh0iY3Ss6%2BGQjoCjMYWGYk2ks0Et0q8%2BpmK29RMODpp%2BunbfnFWQehAS954L4Xam68zR9RiSu3jpx3kQOluNHssz7UIPbgL0GknlMk27BadarFvIC0Ci9fyDi00duIVrivK3dBNd5FCVTlm5dwbofVQXZe5pcuYeA5vV%2BTodeGRpp4z1nPxFhZNmB7l7NmVsJTmiAK1LViEfR%2BsuaLtPCkSb%2FnGHWVYqWOdwqjmCm5FabS%2Bn6w%2FApPCGO44I4GIaL%2BO3saBTE8|tkp%3ABk9SR_rip-KZZA

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Ok, in a show of solidarity I've just bought the one on Ebay, my old one isn't even battery powered and I have a  4AGE sitting in the engine bay that will need timing in a day or two.

Edited July 20, 2024 by altezzaclub

[Banjo]

Hi Brayden,

                   Completely concur with Altezzaclub, that the timing light is your best investment, if trouble shooting or setting engine ignition timing.  Visually, it allows you to check static timing, at "idle", and automatic advance, as a result in rpm increase at idle.   You can also check advance under load, by removing the little rubber hose from the dissy, to the inlet manifold, & suck on it, to produce a vacuum, & watch the timing mark, move accordingly.

The only advice I can suggest, is to completely clean around the timing marks on the timing chain cover, & the little "V" groove in the crankshaft pully, on the rear edge.  Paint the grove with a little white paint of "White Out".  The crankshaft pulley, can only be fitted in one position, as it has a single keyway.

 

The only potential problem with the timing marks are; if some one has swapped a 3K or 4K crankshaft pulley, for one from a 5K engine, which has it's timing indent, is a different position; as are the timing marks on the 5K timing chain cover.

Hope You get it sorted, as that is one beautiful Corolla !

Cheers Banjo

 

 

Edited July 21, 2024 by Banjo

[Braydenj]

No worries I’m trying to go off memory here as I am not at the car but now you say that with the dizzy timing I might have that round the wrong way I am honestly not sure will check when I get back home in a week or so time 

 

but will look into a timing light as that might work out to be my best friend here cheers for the help will give those few things a tray and see where it gets me cheers guys

[Banjo]

Hi Brayden,

                    The very first thing you should do, after you have manually turned the the crankshaft over, & have the timing marks lined up, on the crankshaft pulley & zero mark on the timing chain cover; is to lift the dissy cap, & see where the distributor rotor is pointing.  If it is pointing towards the distributor cap post with the lead that goes to spark plug no: 4, then rotate the crankshaft another full turn, until the timing marks, line up again.  The engine will then be in TDC No: 1 cylinder.  Now look at where the arc on the brass tip of the rotor button, & see where it is, in relation to post in the dissy cap post, which is attached to No: 1 spark plug (the one at the front of the engine). We have seen distributors installed one tooth out, when it inserted into the block, to engage with the camshaft gear. We have seen them, where users have then rotated the dissy to get it to run, but when the car is running & the automatic advance kicks in, the rotor arm, will not line up on it's arc, to the post in the dissy cap, & the HV can't jump inside the cap, & you get miss firing.  Where are You physically located ?  I tried to look at the number plate in your picture of "Alice", but couldn't read it, at the angle the photo was taken.

Cheers Banjo

[Braydenj]

Hi banjo

located perth Western Australia currently not home atm so haven’t had time to tinker with it but when I head back in about a week or so will have a look and see what I can work out I will take the dizzy cap off ling up my timing marks and send thru some photos on here to see what I can work out and see what everyone recons

[Braydenj]

Alright I have had a brief moment to mess around with everything I found a vacuums line unpluged and have plugged that back in that was for the vac adv on the dizzy did not fix issue I think it’s slightly better but that could be placebo.

 

i replaced the fule filter quickly that was filthy so that should help me a bit

 

now I have lined up the timing marks like you all suggested onto 0 deg taken my dizzy cap of taken a photo and then put it back on taken another photo so you can see where the top of my finger is is about the middle of that brass arc when it is at 0 deg. So it just misses the number one lead at 0 deg

 

i haven’t had time to get a timing light yet as I fly out again tomorrow but from what I can see there it is a little out still am I right in saying this?

 

also the rotor turns to the left (anticlockwise) when the engine is rotated clockwise so does that mean turning the dizzy clockwise will advance it and turning it anticlockwise will retard it.

 

the more I look at it and think about it the more I am led to believe that it has been installed a tooth out so is it as simple as pulling it out rotating it a tooth in a direction then putting it back in?

 

anyway please let me know your thoughts and what I am doing wrong or some other things I should try cheers

[Banjo]

Hi Brayden,

                    You've done well, & everything you do will help.  The timing is out, as if anything; the red mark on the edge of the dissy, should line up with the other end of the brass arc, on the rotor button.  The dissy rotor rotates clockwise, looking down from the top. If the engine is started, it will probably run, but as soon as you rev the engine up, & the auto advance kicks in, & causes the ignition, to spark, before the the brass arc on the button is near to the post inside the cap.   This is where a timing light is so useful.

You may be lucky, & it is only a case of simply unlocking the bolt into the block, that holds, & stops the dissy from rotating; & then turn the dissy a little anticlockwise.  You can do this with the engine running, but it is probably safer to unbolt the clamp as it is in the picture, & rotate the dissy body, until the rotor is pointed towards the other end of the arc.  Then get that timing light, & do it dynamically, at night; & you will see the whole auto advance function, in real-time.

Let us know how You go.  Clean the area around the crankshaft pulley TDC mark, & paint it with a little white out.  It makes it so much easier to see.

Cheers Banjo 

   

[Braydenj]

So if I got this right that red dot on the dizzy should be on the other side (left hand side) of the brass arc and that will be a lot closer timing? Then you think grab the timing light from there and check to see what it does 

[Banjo]

Yep, You got it.  Be very surprised, if it doesn't run significantly better, by just rotating the dissy a little bit anti-clockwise.  Get yourself that timing light, & all will be revealed as you see the automatic rpm advance working dynamically.

Keep us updated, with your progress ! 

Cheers Banjo

Edited July 30, 2024 by Banjo

[altezzaclub]

You can see the pickup here, the vertical strip of metal in the plastic electronics unit. It triggers as the apex of the rotor goes past.