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Viterbo

Worked 5K problems on 1st start

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On the past months I've been building a worked 5K with the following specs:

+0,5mm oversized pistons

2mm oversized valves

290º camshaft with vernier pulley set to max lift at 103º as indicated by the technical sheet

5K/3F solid lifters with 4K adjustable gear

Ported head to match the 1 piece gasket

Block and head machined, around 10,5:1 compression ratio.

Lightened flywheel and crankshaft

 

In order to have a smooth 1st start, particularly in order to run in the camshaft I used the standard dizzy and carb with the main jet of the carb drilled from 0.96mm to 1.1mm.

This is how the engine ran:

 

 

Audio isn't the best but looks like it's working on 3 cylinders or something like that, that's too many new variables for me to have a clue on what can be wrong.

The car worked around 15 minutes do ensure proper run in of the cam, varying between 2000 and 2500 rpms and it never ran better than this. After that, I took my foot of the gas to see if it would idle and it shut down. The carb was set as it was removed from the engine before the disassembly (apart from the drilled jet). The car is not giving massive pops through the exhaust... Plugs left the engine dry and with a brownish color.

While the engine was running I tried advancing or retarding the dizzy but apart from differences on throttle response it didn't change the roughness...

 

EDIT: is running on 95RON

Edited by Viterbo
missing information

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Hi Francisco,

                      Always a bit of a nervous time, when you start up an engine for the first time, especially when you have put so much time & effort, & money into it. 

Look at it on the bright side.   It does start & run, despite the running being rough.  All we have to do is now find out why it is running, below your expectations, & rough.

The audio is a bit poor, as you mentioned, so that doesn't give us a lot of clues.I'm going to fire a whole lot of questions to you, & after we have your answers, we might be in a better place to offer valid suggestions.

1.   Did you assemble the engine, or was it put together by the people that did the machining ?

2    Was the engine checked with a degree wheel, after assembly, by you or others, to ensure the valve timing was correct ?

3.   I presume you replaced the original single timing chain, with a duplex, which has a vernier adjustment ?  If so, what was the vernier initially set at ?  0 degrees ?

4.   Does the engine feel, or sound like it is starving for fuel ?

5.   Is the engine now in the car, with a gearbox on, or on a test stand ?

6.   Have you got a timing light, that you can check the timing & advance ?

7.   Without spark plugs in, is the engine very tight to turn over ?

8.   Have you got an oil pressure guage attached to the engine ?

9.    In the video, were you revving the engine, or was it surging like that all by itself, with a static throttle setting ?

Fire us back some answers, & we'll go from there.

P.S.   My first best guess is that the dizzy, has been installed 1 tooth out, & the rotor arc'd end is running out of lining up with the distributor cap posts, inside the cap.  At the higher revs, it could be causing it to feel like it is running on 3 cylinders.  If one cylinder was dead, & it was only running on 3, it would show up instantly on the plugs, which I guess, are all brand new.

Cheers Banjo   

 

 

Edited by Banjo

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Hi Banjo, here goes some answers:

 

1- Engine was assembled by me

2 and 3 - Yes, degree wheel was used, I found the true TDC and then set the cam timing with a duplex adjustable pulley

4- I don't think it's starving because in the video it's me who's accelerating and the engine responds to my input very easily

5- Engine is on the car with everything attached to it ready to go for a spin

6- I do have a timing light and that's something I want to check but I need the engine at least to idle which he doesn't do atm

7- it's easier to rotate the engine without the plugs but seems pretty tight

8- only factory dash oil pressure light

9- As said on question 4 it's me who's accelerating, because I was running in the cam revving the engine between 2000 and 2500rpms, it responds rather well to the input despite the roughness behaviour

 

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Is the roughness at the higher revs, or over the whole range ?  Have you looked at the possibility that the dizzy is out one tooth.  Very easy to do, & does often provide a symptoms like you describe. 

What type of Toyota dizzy are you currently using.  Points, Reluctor, electronic ignitor ?

Is this roughness the kind when you are missing one spark plug lead, or is it a shaking kind of roughness ?  The first one is like a hiccup every now & again, where the second one has the engine rocking erratically on it's mounts.

I know you realise, that once you put a 290 deg cam in the 5K, you will never get the smooth idle you enjoyed with a standard curve.  That is the trade off; but I gather, what you are seeing is a lot worst than that.

Get that timing light working.  They can often tell you a lot, just by observing what the flashes are doing.  It may well be too advanced, but the timing light will uncover that.

Cheers Banjo

 

 

 

Edited by Banjo

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It goes till 2800 that was the maximum it went. It misses roughly the engine shakes. I'm using standard points denso Dizzy.

I think there's a possibility the timing is out, I set it according to the belt pulley mark which for some reason seems to be around 15 degrees of (piston is at TDC at 15 degrees btdc on the timing cover) and it was at 0 before.

But the chain was well fitted I can ensure that

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I think you have found your problem.   In my last post I said,  "it may well be too advanced"

Do you know how to make a TDC piston stop tool, & find true TDC ?   Plenty of details on the net, with videos.

https://www.youtube.com/watch?v=PD0ZRc7Dy28

 I made one out of an old spark plug.

What brand of duplex timing chain did you use ?

The small sprocket is keyed to the crankshaft, but the large upper sprocket is aligned with a pin that comes out of the front end of the camshaft. 

Some vernier type TC sprockets have a number of holes, set distances, either side of the TDC location hole, to advance or retard the valve openings.

Are you sure a pin locator was used.   It sounds like the top sprocket might have moved/rotated slightly.

After determining the true TDC, with the  piston stop tool, you may find that the timing chain cover, is going to have to come off, to see where the issue really is.

When you assembled the engine, before fitting the head, did you bring the cylinders 1 & 4 to the top of the block, & check that the crankshaft pulley timing mark aligned with the markings on the timing chain case.

Is there any chance you used a timing chain cover from a different K series engine ?  Their timing marks are not all in the same place. 

I think you are close to finding the issue, but as we are not in Portugal, it's you who will have to try out all these suggestions.

P.S. I was so hoping, the problem would be the dizzy out one tooth, as that is so easy to fix.

Cheers Banjo

 

Edited by Banjo

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Pulley is the same brand as the camshaft: Kent Cams UK

The engine was running in std form before disassembly and everything from it was used so no swapped parts that could lead to error.

Marks were aligned, the timing on these engines seems to be dumb proof. The pulley only has one single hole to insert in the camshaft pin so no chance to error there too...

I'm going to see if the mark on the belt pulley doesn't match the new TDC, if it doesn't my timing must be around 15 degrees retarded which might well be a tooth out on the dizzy

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From your latest test, I can pretty safely say, the issue is one of "timing".  All you have to do is find where the timing error lies.

There are really only two places.  The timing chain & sprockets, or the dizzy alignment with the camshaft centre gear.

Quote

Marks were aligned,

Do you mean by above that the dots on the two sprockets, were both on the outside, & aligned with a line passing through the centres of crankshaft & camshaft ?

DSC02310.JPG.5a11849f2592ee2f047a8929ff5c74c7.JPG

DSC02315.JPG.b3fb0e613755c4a6b3a138eff9138d44.JPG

DSC02315mod.jpg.d6ef14138a4dc0936b905ddd4a5f1d2a.jpg

Even one chain link out in this area, can cause havoc.   Was there any special instructions that came with the Kent camshaft ?

With the keyway in the crankshaft vertical, at the top, that is at TDC for no 1 & No 4 cylinders.

Interested to find out where the error lies.

Cheers Banjo

 

Edited by Banjo

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Yes. Dots oposite to each other, then with the chain I stretched it making a rectangle shape with the links touching each other having a single link on each end (oposite to each other) and I marked them to ensure I place them on the dots on the pulleys. 

I think it's a pretty simple process leaving no room for error.

No special instructions on the camshaft, just the degrees to have it dialed in (103º at full lift).

I maxed out the advanced on the dizzy adjustment and had no time to advance another tooth. Tomorrow I'm going to do it and see how it reacts to more timing.

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Did your KENT vernier large timing chain sprocket look something like this, or was it one with an off-set pin for adjustment ?

image.png.442b5cce12adb5207859cc038f418ccc.png

 

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2 hours ago, Viterbo said:

Advanced the dizzy and got a bit better but it's still like this:

That's pretty normal for a cam that big.

If you degree'd the camshaft there's no way you're off by a tooth.

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14 minutes ago, irokin said:

That's pretty normal for a cam that big.

If you degree'd the camshaft there's no way you're off by a tooth.

Full lift was at 104,5º with the vernier pulley untouched so I advanced it a bit to reach the 103º specified by the manufacturer.

 

The issue is the car doesn't idle, at least below 1800rpms and with the help of the butterfly being a bit opened...

In that last video you can see when I enter the car the idle drops a bit and the engine starts to miss a lot, I had the choke pulled and closed it a bit. Its enough for the engine to shut down...

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Hi Francisco,

                       Have you found that elusive 15 degree difference you discovered, that wasn't there initially ?  This is a bit like a murder mystery.  i can't wait to find out what/who is the culprit.

Did you rotate the engine to TDC No: 1 cylinder exactly, then lift the dizzy cap, & see at what part of the rotor outer end brass arc, the dizzy cap post for No: 1 spark plug was pointing to ?

As you've got a points dizzy, you should also be able to visually see where the lobe & points are positioned at TDC.

P.S.  I always place a white mark, on the bottom base of dizzy, dead opposite No: 1 spark plug lead post.  That way, when you can take the cap off, to look at the rotor position, you have a reference mark directly below it.

Good luck !

Cheers Banjo

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