Classic Alfa Forums

Got a couple of iffy valves in my 95 bhp (301.28) engine.

My Haynes manual states valves are "as 1200 engine" for all the later engines (excluding the 1.7)

So, I found some 1200 valves quite cheaply on ebay.

But they are too long....by over 2mm on the inlets, a bit less on exhaust.

Does anyone have the correct lengths for valves my engine?

Dave. I’ve got box full of valves from various engines if you pm me with the following dimensions I’ll see what I can dig out. A) total length b) head diameter c) stem diameter d) distance from top collet groove to top of valve

Lou.

PM sent,thanks Lou
Its just an inlet valve I need, the others lapped in ok.

The 2 inlets on the head I've got off measure 92.1/92.2 mm

Thinking about it, they had allen key tappets, shims, and hydraulic.....so maybe explains why valve length varied.

But the valves I bought for the 1200 engine were 94.5 long.......if anyone has this engine they are a bargain at £3.15 each from Bradford Grinders on ebay!

Had a drive to Justsuds this morning, and got the inlet valve I needed......thanks for digging it out John!

Have replaced the pitted inlet valve on no 2
refitted the head and fired it up

Compression is still low on no 2 at 175.....gulp!

Double checked the valve timing after doing the comp test, and its ok.

The other three are over 200.

I can only think the rings need looking at.

The moral of the story is ....don't jump to conclusions, I suppose !

Have you tried a wet test on that cylinder? A little oil in there will tell you if you have worn piston rings.

Good idea!
But I wondered if it worked on horizontal pistons......will the oil seal right round the rings?

To answer my own question.....yes the oil will seal round the rings!

Warmed it up again, put a few shots of oil into no 2.

Compression has gone up from 175 to 210.

So its a piston out job.....and check the rings.

The block is a 301.24 from a 1.5 SC.....not sure if rings are available?

Or maybe a used piston and rings.....not perfect engineering, but I've done it before.

Rings are still around Dave, not that long since I needed some and had no trouble at local motor factors. I'd assume all 1.5's have the same rings.

https://www.autodoc.co.uk/car-parts/pis ... 522-1-5-ti

Blimey Dave, you certainly aren’t getting it easy mate.

Really, really hope this sorts it...you deserve a break!

Took the head off this morning, dropped the sump, and took the piston and rod out.

Piston and rings look perfect, big end shells are fine. Pistons are AE 84mm.

The problem seems to be some corrosion in the bottom of the bore. Approx 20mm wide x 50mm deep from the face of the block. Perhaps a bit of water sitting there whilst its been in storage.

Maybe why oil sitting in the bottom improved the comp figure so much?

I've asked the local engine guy to call here, and give me his opinion in the morning......I hope some fine emery paper will improve it. I asked about honing in situ, but seems the kit is too big.

As an aside, getting the sump off with the AR bar in the way is a pain!
I undid the ends on the front suspension arms for a bit of movement.
Am I right in thinking some cars didn't have an ARB........should I get rid of it? Wondered what the informed thinking was?

Think Ted has removed ARB on both of his racers.

The guy from the local engine shop, measured the piston I took out.
84.57 mm.

So, looks like the engine has been rebored.
The big end bearing looks perfect, so maybe a crank regrind has been done.

Got both heads off and cleaned up and relapped valves ok now.

So, looks like I'll buy a bare 1.5 block, and have it rebored to suit the pistons.

Will also let me put in the new clutch kit I got on ebay for small money!

Bit of a pain I know, but at the end of the day, I'll have a nice engine I hope.

Justsuds to the rescue!
Got a rebored block from John 84.6mm.
And a set of rings to match.

Top job!

Gulp!
Got a call from the engine guy (40 yrs exp)

He's fitted the crank and bearings into my new block......and the crank is moving about.

He's asked the question.....did they ever line bore the housings?

A bit odd it seems, I presumed one crank, and its bearings would fit in any block

I think there is a choice of 3 different shell sizes from the factory I think they had a colour code

Got a standard 1.5 block today from Justsuds.

Took it to the engine guy, and the crank and bearings fit perfectly.

So,its having a plus 0.6mm rebore and hone , and the plus 0.6 pistons with new rings fitted.

Unsure why the other block had oversize housings.....it had been in a Rally car.....maybe they fitted special heavy duty bearings?

I've heard that they sometimes remachine to take bearings for Cosworth BDA engines. They are more readily available for high performance use.

Rsfruitbat

So,if someone wants a block, rebored to 84.6mm, and line bored to take Cosworth mains........ring John at Justsuds!

The engine guy gave me an interesting tip
To check the valves are lapped properly,after they are fitted in the head, fill the inlet/exhaust ports with diesel/paraffin or similar and check for leakage.

Good tip, as one of my inlets was weeping slightly, so took the valve out, re lapped it, and all was ok.

Had the block rebored plus 0.6mm, and honed.
Then cleaned out in the parts washer, and with the air line.

He checked the crank journals which have not been ground, but the journals and bearings are all in vgc.

For peace of mind I had the guy fit the crank, pistons and rods with new rings, and torque everything up.All nice he said.

Got the block home today, and gave it a coat of black paint......will fit it up and install it next week.

What could possibly go wrong now?

Watch this space!

Hi Dave . Sounds like good progress . I’m sure your engine guys are well aware of the boxer engine but it’s worth just checking one small thing.
The pistons have arrows stamped in to the crown . Make sure that they are facing UP on 1 & 3. (R/H)
& DOWN on 2 & 4 (L/H)

Lou

Yes Lou, he told me that.
Arrows point in direction of rotation I think

See pic

Do all pistons have offset pins or is it just flat engines?
What's the purpose of it?
What happens if they are fitted the wrong way round?
What happens if the pistons are made with the wrist pin central?
Sorry for so many questions

Rsfruitbat

Have a look at P 24 of Burton Power on line catalogue.
Tech tip there re offset pins.
Seems to relate to Ford engines as well as suds

We did about the effects of offset gudgeon pins at college mate, that was about 30 years ago though so the memory is fuzzy about why,.
Is to do with thrust angles if I recall, if the pin was central then the natural force of rotation tends to wear one side of the piston/bore. Offsetting it slightly counteracts this.
Something like that anyway.

You've got the thrust of that dead right Kev!

Cheers guys, what an interesting thread.

Got the rebored engine fitted and fired it up today.

Compressions are 1. 190
2. 185
3. 195
4. 200


a bit low on no 2 perhaps....but not too bad overall.

Also there is evidence of slight coolant leaks at the top of each head (not at the bottom though)

I torqued up the head bolts to 9 kgf m with the engine out, used new AR gaskets, cleaned and oiled the head bolts.

Will re torque the head bolts tomorrow, and maybe increase the figure a bit.....the bolts are well used!