My '91 744 B204GT project

[tomasss]

Also getting ready for the cruise control integration

Before


After

[ZVOLV]

I enjoy the thread!

Please document the cruise install. I wanna do this on my 1991 740 T. I think I have the bits from an 89 740 GLE

[tomasss]

Originally Posted by ZVOLV

Please document the cruise install. I wanna do this on my 1991 740 T. I think I have the bits from an 89 740 GLE

I will
During one of the trial warmups, the old tired radiator gave up and started leaking badly, so next week new Valeo unit is to be fitted. Also I have replaced the two-piece air guides behind the front grill with the updated one-piece version from 940 (better design). The corner lamps has been replaced, trims under headlamps has no holes for the wipers anymore and are repainted, and I started playing with idea of fitting the 2din black face SC805 radio that I coincidentally bought.
The >plastic radio frame from 780< is NLA, but fortunately there is a >guy< in Norway that makes a 3D printed equivalent. I just need to check how the SC805 fits the universal 2din metal frame, if it does I am going that route (and combine it with the Yatour to have the convenient support of the mp3/usb/bluetooth).

[tomasss]

Leaky Blackstone out, new Valeo in

[ZVOLV]

Take out the frame weights next time the bumper's off. The weight is probably 5 Kg each side.

[tomasss]

Originally Posted by ZVOLV

Take out the frame weights next time the bumper's off. The weight is probably 5 Kg each side.

I was checking with the endoscope today and I can't find it. If I understood correctly, these weights are not present on the engines equipped with balance shafts (b234f and b204ft/gt).

[tomasss]

Oh, and in the meantime...based on some my suspicions and long talk with a friend of mine who is a mechanic, I've decided to do a dry and wet compression test on the cold engine again.

The dry measurements were similar to what I've got last time:

#1 135psi (9.5bar)
#2 130psi (9bar)
#3 138psi (9.6bar)
#4 119psi (8.2bar)

then I injected teaspoon of oil and measured the same thing again per cylinder:

#1 148psi (10.2bar)
#2 148psi (10.2bar)
#3 144psi (9.9bar)
#4 126psi (8.7bar)

So while the #1, #2 and #3 responded to the wet test by increasing the compression as expected, the #4 stayed almost the same. Seems I have a leaky or burnt valve
I have already started disassembling it again, and I need to find a shop that is open for head resurfacing these days

[tomasss]

Alright, head is removed.

The good news...head looks good from the other side, no cracks or damaged valves on the first sight. Some carbon build up but nothing serious.

The bad one - and correct me if I am wrong - all the pistons have quite some play in the bores
According to the greenbook the allowed used piston clearance is up to 0.08mm. The worst piston in my engine has around 1.1mm play, the other ones around 0.9mm. When I push on it with my thumbs (see the video below) it makes the clicking noise that I would swear is the same that I've heard when the engine was idling.

Other than that the walls are smooth without any scoring. The engine officially has 220tkm by the way.

[Cwazywazy]

I'm not sure piston slap would cause uneven compression. Have you checked for valve leakiness?

[ZVOLV]

That's normal.

[tomasss]

Originally Posted by ZVOLV

That's normal.

Normal for what? For a good engine? Or for a worn redblock? The excessive play is by the way almost the same at the TDC and BDC.
The point is that I am building this car for fun, so although I believe it could still run for some time, I don't want to assemble it back if there is already an apparent issue. And the knocking I've posted in one of the youtube videos I didn't like at all...

What are my options here, sorted from $ to $$$?

- resurface the head, grind the valves and put it all back together
- get a known good b200f/ft 8v bottom end and cut the valve reliefs? Not sure if this is possible
- get a good known b230 8v bottom end and b234f head and make it b234gt
- rebore it and get custom pistons & rings (Volvo doesn't supply them anymore)

I am almost certainly not going the fourth way. How much work it would be to have the second/third option working? Different crossmember? Different engine mounts? And then of course the timing belt changes...

Oh, by the way...>Volvo< webpage shows the same number for the B204gt/B234f head...is that correct? As these engines have different bore, I doubt the head is the same, or am I wrong?

[tomasss]

Originally Posted by Cwazywazy

I'm not sure piston slap would cause uneven compression. Have you checked for valve leakiness?

Yes I have checked that. The valves are all sealing perfectly.
My theory is that the worst cylinder reacted so poorly to the oil during the wet compression test because the gap between the piston and bore is already so large that the oil just went through giving barely any resistance...not sure if that makes sense.

[Sjeng]

That's a lot of movement. I had a worn engine (0.1mm measured bore wear) that had less movement than that.

I would see if you could get a good b230 turbo block and cut the recesses in the pistons.

[tomasss]

Some more pics...the worst one is on the last picture, the scoring of the cylinder wall by the wiggling piston is already visible at the top...

[ZVOLV]

You are going deep down the rabbit hole.

You could pour some ATF in the holes and see if any is left overnight.

A leakdown test while it was all together would've been a good place to start.

Maybe put new rings, do the valves and then continue on with boosting.

[tomasss]

Originally Posted by ZVOLV

You could pour some ATF in the holes and see if any is left overnight.

Well I did that with a white spirit and I could see the liquid disappearing from the two outer cylinders much faster than the two inner ones...

Originally Posted by ZVOLV

Maybe put new rings, do the valves and then continue on with boosting.

Yeah, I've ordered new rings yesterday. I'll fit them and see how much it helps. Considering how much work it is to put it all back together, I want to do it right this time

[tomasss]

Engine is out again, I've got the piston rings, this week the engine stand should arrive too...
This time the whole extracting procedure took less than half of the time...learning curve

[tomasss]

Today all the tools arrived

Valve compressing tool; all valves are out, head is ready for resurfacing. By the way, do you do the valve lapping before or after the head resurfacing? I am thinking it would be more convenient to do it before, as the shop does thorough cleaning after the skimming and I'll be sure that all the lapping compound is gone then.



Engine stand, so it immediately received an engine to hold tomorrow the pistons go out and I'll see if the new rings stabilize the pistons in the cylinders enough or not.

[tomasss]

Some more disassembly...the conrod bearings looks good to me, equal wear over the surface, no spots...




The head is resurfaced & ready for reasembly


Testing the valve sealing properly after lapping with white spirit


And also some new stuff arrived

[ZVOLV]

Hi

Originally Posted by tomasss

I was checking with the endoscope today and I can't find it. If I understood correctly, these weights are not present on the engines equipped with balance shafts (b234f and b204ft/gt).

Interesting. Check for four nuts on the inside of each frame rail. About half way back.

I wanna do a similar build as you, but with a B234F I have on the stand. I have done some engine rebuilding classes and got to play around with the micrometers. I wanna get some. I liked the Starrett ones.

Now would be the time for you to mic the bores, pistons, crank, rod journals, etc.

[rijk]

Oh, by the way...>Volvo< webpage shows the same number for the B204gt/B234f head...is that correct? As these engines have different bore, I doubt the head is the same, or am I wrong?

B234F has different camshafts. More lift, different duration. Did wonders in my B204FT (together with ported head) before and after I dumped the stock shortblock with those stupid, heavy balance shafts for a newly build up B230FK.

[tomasss]

Originally Posted by rijk

B234F has different camshafts. More lift, different duration. Did wonders in my B204FT (together with ported head) before and after I dumped the stock shortblock with those stupid, heavy balance shafts for a newly build up B230FK.

Yeah, later I've also found some topic describing the different volume of the combustion chambers...

[tomasss]

Head is reassembled Everything cleaned, new valve stem seals.

[tomasss]

Originally Posted by ZVOLV

Interesting. Check for four nuts on the inside of each frame rail. About half way back

That's what I did. There are four holes in the rail on each side prepped for the nuts, but nothing is mounted there

[tomasss]

Originally Posted by ZVOLV

You are going deep down the rabbit hole.

Seems I am not going deep down the rabbit hole anymore. I've started digging a brand new hole

Lots of updates
After dismantling the pistons and checking the wear of the cylinders and pistons and lots of consultations and measurements, it has been decided that re-ringing would help maybe for a while, but definitely not in the long term, as the wear was already too serious.

That led to sequence of other actions...the block has been stripped down entirely, pressure-washed, rebored to 2nd oversize and honed. The next thing are the pistons (that are NLA from Volvo for a long time), so custom pistons from Josh - Yoshifab needs to be made

Old worn piston


Engine block stripped down & ready for the shop


Engine block being re-bored


Engine block being honed afterwards