3.5 V8 Carb Engine Blow Back after cam Shaft replacement

So, new plugs are in. And I tried it wet, same thing, 8.5 bar max on the left bank... Didn't bother with right one. Seems to run better with the new plugs, still not enough power at low rpm so. With an advanced (?) ignition she runs almost acceptable at 1k rpm in idle...

So, just how do I fix a low compression on the old beast?

Good thing so, the blow back from the right carb is almost gone. Oh, I found a loose exhaust manifold screw.

Also, nothing out of the oil filler cap.

I'm still leaning to cam timing
Did you do the compression test with throttle fully open and all plugs out?

All plugs out, but no throttle...

I installed the new ingnition wires, she runs so much smoother with those and the new plugs. In idle that is, did have time for a test drive.

So, tomorrow new compression test on full throttle, test drive. Maybe exhaust if I can use the old nuts and bolts and stuff.

And I discovered something else: I need to fix my windscreen washer pump to pass MOT/TÜV by next Friday (!)...

If it is the cam timing, well, off to the workshop it is then I guess... Not JLR, they botched it once already, and as they were sold to a chain I know, they won't do that free of charge anyway.

But since we can more or less, I assume, exclude valves, there is some budget left, luckily.

Or should I have new valve springs installed when it is in the workshop anyway?

If you're going to take the heads off then lap the valves while you're at it. I would say springs are ok unless damaged. Not like it's a high revving performance engine
But I'd check cam timing first as it's fairly painless apart from having to drop the sump.
If it's wrong then you'll need to loosen the rockers to align it properly

Don't I have to take the front of to chrck the cam timing chain positioning? I'll have a look at the valves with the rocker covers off one of these days, just to be sure. And repear the compression test properly tomorrow! Maybe there wasn't a real problem besides spark pligs and ingnition to begin with. Not that I think I am that lucky, but who knows?

hef19898 said:

Don't I have to take the front of to chrck the cam timing chain positioning? I'll have a look at the valves with the rocker covers off one of these days, just to be sure. And repear the compression test properly tomorrow! Maybe there wasn't a real problem besides spark pligs and ingnition to begin with. Not that I think I am that lucky, but who knows?

Click to expand...

Yes you do, but that means sump off.
Don't forget it takes several cycles to find max compression on a given cylinder min 3-4 blows

I'll give it another go tomorrow and let you know!

Somehow I am still not asleap. Anway, I ordered some exhaust installation paste (I mentioned the new exhaust came without installation kit?). I remembered something so, after I realized the exhaust has one tube per cylinder bank: Before I changed the ingnition leads and spark plugs, the exhaust gas of the left tube was considerably cooler then the right one.

I tried to find it earlier, but couldn't. So I'll just ask: The right hand carb, seen in driving direction, links to which cylinders? If I remember correctly, the carbs each supply two cylinders per bank?

Sooo Almost good news to report! Just took for a test drive on the highway, a section with some hills. She pulls without complaining up to 4.5k rpm in 1-3 rd gear, climbs the hills easily somewhere between 110-120 km/h and achieves a top speed of 130. 0-50 km/h takes arpund 6-7 seconds. That sounds promising, especially woth the old exhaust. No new compression test done yet so.

Two things need to be adressed:

- a perceived lack of high rev power (I didn't recalibrate the carbs yet)

- some blow outs around 2k rpm if load changes happen to fast

Now I wonder, since two spark plugs where full off soot, can the same soot affect the valves? And if so, how can I clean them in-situ, just spray some brake cleaner in the cylinders and give them some oil afterwards?

Anyway, I'll wait until the new exhaust is in begore I touch anything else.

By the way, idle rpm are around the 900 mark now, I'll try to advance the ignition a little bit more to get down to around 750-800, that feels like a good value woth the new cam.

Or am I missing something?

Sounds like you're about there
I don't know the cam but maybe some popping through the inlet can be expected? Could be an ignition timing issue
Are the carbs in good order?
An Italian tune-up should be able to handle a bit of carbon. Put some decent fuel through it

The carbs are more or less fine, as far as I can tell. Not properly calibrated so, and the left one still needs a new temp-sensitive thing (the one that regulates the mixture based on temperature, the right one already has a new one).

Out of curiosity, what is an Italian tune-up?

hef19898 said:

The carbs are more or less fine, as far as I can tell. Not properly calibrated so, and the left one still needs a new temp-sensitive thing (the one that regulates the mixture based on temperature, the right one already has a new one).

Out of curiosity, what is an Italian tune-up?

Click to expand...

Onward!! And don't spare the horses

How low can you get that mpg!?

MPG? I guess fuel economy is something the car is remotely aware of, but doesn't care! I reached the point of enlightment where I don't neither beyond MPG being an indicator something migjt be wrong.

hef19898 said:

MPG? I guess fuel economy is something the car is remotely aware of, but doesn't care! I reached the point of enlightment where I don't neither beyond MPG being an indicator something migjt be wrong.

Click to expand...

Ok well drive it like you stole it

Is there another way?

hef19898 said:

Is there another way?

Click to expand...

Hand me the keys for an hour

Wouldn't that be contradictory in a sense?

hef19898 said:

Wouldn't that be contradictory in a sense?

Click to expand...

I'm not going to actually steal it