Re: "French" PRV

[abbotts@xxxx]

The PRV's poor reputation is only partially deserved IMHO. My feeling 
is that the early versions had some design and manufacturing flaws 
which can be overcome with a bit (a lot?) of work. One of the worst 
flaws is the engine's propensity to leak coolant into the oil when 
the cylinder sleeve seals fail. I have a strong suspicion that the 
sleeves did not have enough protrusion above the block when these 
engines were first assembled at the factory. This could contribute to 
blown head gaskets also. The fix requires a full rebuild. Check the 
sleeve protrusion. I bet its nowhere near enough even with the 
thickest available seal fitted to the base of the sleeves. Cure? 
Simple (relatively!). Have the block decks machined to achieve 9 
thou protrusion with the thickest seal (yellow one) fitted. Only 
needs about 3 thou or so taken off on average, so doesn't measurably 
affect cam chain tension. So long as the protrusion is the same for 
all 3 sleeves on each bank and they are square with the block and 
each other, that *should* hopefully take care of any future concerns. 
The other problem I have suspicions about is low oil pressure due to 
faulty oil pump relief valve springs. My engine showed precious 
little oil pressure on a gauge, but the idiot light on the dash 
rarely came on. Geez, what are those switches set at, about half a 
psi? When I disassembled the oil pump the spring was in 8 bits. 
That's not a one-off failure, that's a badly made spring. Early V6's 
were known for hacking up valve train components due to a lack of 
lubrication. Haven't got proof, but my gut feeling is that the cause 
could be primarily due to bad oil pump springs leading to oil supply 
limitations to the top end of the engine. Don't know for sure, just a 
hunch. How many folks would bother to routinely pull the oil pump 
(not an easy job) just to check it out?
Otherwise (French design quirks excepted) its a nice little engine. 
The later B280 version fixed the odd firing sequence by offset 
grinding of the crank throws to even things up. Heads were modified 
and given oil 'wells' for the cam lobes to dip into each revolution. 
Cams were re-designed to give a bit more grunt and a little better 
fuel consumption, the silly distributor position of the early 
versions was altered. My B28 had covered over 200,000 km when I 
pulled it apart due to the busted oil pump spring. The bottom end, 
including the bores, showed virtually no wear at all. A quick 'glaze 
break' and a set of new rings and bearings just to be on the safe 
side and it should be good for another several hundred thousand km. 
Hopefully :)
Our local machine shops and Volvo dealerships have never yet had a 
B280 apart. Some of them must have accumulated pretty high mileage by 
now. Must say something for the longevity of those engines I guess. 
And for a V6 they are remarkably smooth. Considering the modest power 
output, it'd be nice if the fuel consumption was a bit better though.

Cheers
Steve Abbott

--- In dmcnews@xxxxxxxxxxxxxxx, brobertson@xxxx wrote:
> Factory was in France, but Swedes have their fingerprints on design 
too.
> 
> To be honest, Volvo's final rework of original design (B280) is very
> nice engine, EFI not withstanding.
> 
> I was very leery about PRV before actually getting my hands on one
> (original posts to DML regarded Vortec conversion). Now, am rather
> fond of the little powerplant. Has its weaknesses: "Internal" water
> distribution pipe is assinine. Ignition distributor would have been
> better relocated by cylinder #3 (as it is on B280). Clearance is 
tight
> among injectors and spark plugs. But in all PRV is surprisingly 
smooth
> running (given odd fire sequence) with good bottom end torque and
> projected long life span -- Bertone I saw in Hagarstown junkyard had
> 180,000 miles on odometer.
> 
> JZD could have chosen worse.
> 
> Bill Robertson
> #5939