Compression & Blue Smoke Issues

[Yozza]

Hello
I had to do a top end re-build on my 2.1iDJ due to a cooked engine. This involved new pistons and barrels from GSF and replacing the cracked cylinder heads. I couldn't afford £200x2 for new heads so I got hold of a pair of good(ish) heads, however, some of the valves weren't in great condition so I did some swapping around and lapped all the valves.
I've been using the van for over 12 months and ever since she has always blown out a bit of blue smoke on start up, and the compression (dry) isn't great either (No.1 8.5bar, No.2 9.25bar, No.3 8bar, No.4 9.25bar). Ideally I should of done some form of leak test on the heads before installation. I suspect the heads are the reason for the low compression as the pistons and barrels were new.
Could any of you technical gurus please point me in the right direction...
What is best practice for rebuilding/refurbishing cylinder heads?
How can I determine if the heads are the root cause of the problem?
How do you do a leak test on the heads?
(Apologies for all the questions - I'm hungry for more knowledge)

Thanks

[Fritz]

Gordon Ramsey will always tell you if it's Brown it's cooked, if it's Black it's F**ked,,,,,,,,But in your case it is Blue so I wouldn't worry about it.

Sounds like a case of worn valve guides/valves which you have mentioned all ready, you will have inherited this with the purchase of second hand goods .

I am sure you don't need me to tell you that,,,,,,,,simply stay off the beer/fags/food and petrol for a month and hey a new pair of heads will appear at the foot of your bed one sunny morning.........





Regards


Fritz,,,,,,,,

Unless you throw your wallet at it , it will have to stay as it is,,,

[Yozza]

Thanks for the reply, I needed a second opion as I suspected he worse case. Would it no be cheaper to service my existing heads, new valves, guides, springs, etc?? Thanks

[Mr Bean]

Thanks for the reply, I needed a second opion as I suspected he worse case. Would it no be cheaper to service my existing heads, new valves, guides, springs, etc?? Thanks

The classic signal for worn valve guides (I think you will find no rubber seal gismo's on these engines) is a puff of blue smoke when coming off the overrun. I don't know if you can get valves with oversized stems or how you would go about getting the heads machined to accept them but just look into the efficacy of putting new valves into a head with worn guides. It could be a lot of work for not much success! Others will have a view
Cheers
Wolfie

[dave friday]

Do you park on a slope, my air cooled van used to smoke badly when parked on a large camber [oil trickling along the boars and through the piston ring gaps].

[Laurie]

The clue is in the 1 and 3 = 8 Bar and the 2 and 4 9.25 bar.
It might be a good idea to measure the valve lift and compare 2 and 4 with 1 and 3. Just in case you have a worn cam.

Before that, just try winding back the valves half a turn.

As far as the puff of oil is concerned, a tiny amount makes a lot of smoke.
It will sit on the inlet guide and just get sucked through on fire up. Looks bad, but provides a little upper cylinder lubrication.

The only danger you have there is in the exhaust valves and guides. Worn valves and guides (exhaust) causes dropped valves. Guides are available (type4 do the job) and exhaust valves are about 7 quid each.

Failing that, take your heads off and take them to any local reconditioner who does the guide inserts. New heads aren't all that good, unless you can find genuine and ones that have been re-faced and re bored often need shims under the rockers to get valve adjustment. Use what you have.

Boxer heads often crack between the seats as early as 20,000 miles, just like VW diesel heads the inspection procedure is to check that the crack doesn't extend below the seat, in the ports. VW allow 1mm between the seats on diesels!

As far as compressions are concerned, most gauges are inaccurate so you look for parity, meaning that yours don't sound bad at all.

[Yozza]

Thanks for the replies fellas, I'll check the valve lift but I'm not sure what "wind the valve back half a turn" is about. Do you mean the tappet?
Thanks

[toomanytoys]

Yes Laurie means the "tappet"... we will presume you still have the hydraulic lifters... worth resetting to 1/2-1 turn of preload in any case.. (at TDC for each cyl)
Does it use much oil and smoke on overrun on a big hill???

[Yozza]

Yes, it has the hydraulic lifters. I originally set the valves with 2 turns of pre-load (as recommended by Mr Haynes). Is 1/2-1 turns more suitable? She does like her oil but I haven't noticed excessive smoke on big hills.
Thanks.

[kevtherev]

I prefer the two turns
there is a debate on this

from the wiki

The lifter will pump up to the correct oil level no matter what you set it to but a sufficient initial setting is important in order to prime the lifter: two turns of the 10mm valve adjusting screw with 1mm threads will preload the lifter ~1.5mm .
This is about half the distance that the piston inside the lifter can travel. If you use too little preload you will be stressing the lock ring that holds the lifter together. If you use too much preload, the plunger may bottom out at first, then if the lifter pumps up the valve may not close properly and compression, performance and valve life will suffer.

How about 1.5 turns instead of 2? In practice, this seems to be as acceptable as the factory recommendation and a feel good insurance against the ills that other people have experienced over the years following the factory recommendation. In my experience, 1.5mm of adjustment after the engine has run for a while ends up as 2mm. This is good news because it continues to support the ease of valve adjustment vs. solid lifters.

What happens if you only adjust them 0.5 turns? The lifter won't achieve 2mm of travel and you then upset the rocker geometry accelerating valve train wear.