Amazon: tuning a b18a

[Burdekin]

Hi Gareth,

Here's some more reading from a Swedish guy on tuning a B18 etc. It's 12 years old the website and I contacted Johan the guy who wrote it a while ago and he doens't really work/play with old Volvos anymore but some of the info will be helpfull.
http://legolas.mdh.se/~mas95jed/volvo/b18.htm
http://legolas.mdh.se/~mas95jed/volvo/tips.htm

[asneddon]

From the tips page above, it says this:
"
All B20 and B19-B21 before 1980 (with 8-bolted flywheel) have trouble with low-strength rods,
they are useless if you use the engine above 6000RPM. If you have this engine, rebuild it to a 6-bolted
crankshaft whit corresponding flywheel.
"

Thats the exact opposite of what I haev read elsewhere. ie, the 8 bolt engines are the better ones if you are going for max HP. Is there any other info on this?

[B20F]

The heads from the metric 8 bolt flywheel B20's ('75 and onwards) flow better. The rods from these engines are beefier but a weaker alloy is used, the're from the B21 engine. The're crap and break easier in the higher revs then the original ones which never fail. So use a pre '75 6 bolt engine and combine this with the fuelinjected head from '75 onwards for tuning. I think that is where the confusion is about.

[B20F]

Here are some more informative B18/20 tuning sites:
http://www.buvic.com/car/repairs/b20.html
http://www.1800philes.com/
http://www.vclassics.com/archive/index.html
http://www.v-performance.com/

[redcar]

evening gents..it's been a while, but work has been getting in the way..

well, as a start to my summer project part collection, some bits have arrived

From a p1800e (B20) in Scotland, i have a lovely twin downpipe manifold and aluminium inlet manifold set. And from California, i received a fairly tidy pair of SU's off a 142 (B20B), which I'm going to play with over winter..

Now to prioritise the order of events..

1. i've been reading around, as one does, and think i should probably do the head and cam first now, before putting on the carbs and manifolds. i.e. skim 2mm and unleaded conversion. This way, i can see that what has gone in is good. drive around for a week or so.

2. apply carbs, and manifolds and if i can, mate the current exhaust to the 2-1 downpipe and the following week get the exhaust done.

anyone else gone this route, or suggest a better way to go? Should i just go and get a b20 head instead of messing with the b18a? if so which one?

any thoughts?

regards,

Gareth

[classicswede]

Unleaded conversion? I asume by that you are talking about alloy bronze valve guides. If you are aslo wanting to fit hardened valve seatsony do the exhaust side not the inlet. If you are having headwork done go to B20 style valves and at least fit E size valves.

[Burdekin]

Hi Gareth,

My understanding is that if you are going to stay with the stock size pistons then you should stick with the B18 head due to the combustion chambers sizes, do the mods like classicswede suggets and port and polish the head with a cam to match and this will give you a nice increase in performance. If you want to go for extra performance bore the cylinders to a B20 then a nicely ported and polished B20E head will give you good gains with minimal mods to the head. If you want to go to town with head work then go for a B20F or the late B20 carb head.

Apparently the casting quality wasn't that great for the B18 and you can get voids which may hole when boring the cyclinders.

One thing for sure is if you are paying someone to do your head work then you need to decide up front what way you want to go as it isn't cheap.

The difficult thing is deciding how much power you will be happy with before you start, how far from stock you want to go and how much you want to spend.

[Steve121]

just out of interest, what size valves would it be worth going to in a B18 (if at all) and unleaded exhaust seats are to be fitted?
Just asking as I've got hold of a standard B18B head and am thinking of putting the unleaded seats in... and if the thinner stem B20 valves would make an improvement, maybe its worth a go.

[Burdekin]

The B20E valves are 44in and 36ex.
My understanding of when you do porting and polishing it's normally best to enlarge the intake valve and keep the exhaust valve the same. The reasoning behind this is that the smaller (standard size) exhaust valves will help draw the air/fuel mixture in through the intake valves and as it's harder to get fuel/air to flow into the engine than it is to get the exhaust gases out, then improving the flow in will reep the greatest improvements. This is a general rule so whether this works with the B18 I don't know.

But saying that V-performance use larger exhaust valves on their B20 upgrade head rather than increasing intake valve size.

My B20 upgrade I've purchased 46 and 38mm valves. This is what KG Trimning recommended so I'm trusting his experience. But my engine is a long way from being completed so I can't comment whether this combination and head work works or not.

[Derek UK]

A B18 should use a B18 head, the width of the combustion chamber on the B20 head is bigger than the B18 bore unless bored to B20 size. It will work as a low compression engine but not advised for tuning a standard B18. Unfortunately with the B18, the valves are already very close together as standard so increasing the inlet size is limited. B20 guides are wider apart so it's easier to fit bigger valves. Big valves and big ports can mean slow gas flow, not really the best for a responsive street engine. If you can afford to spend a lot of money on a B18 you might as well start with a B20 and upgrade that.
Quoting the old saying, "speed costs, how fast do you want to go?"
A properly built B18 with a D cam and minor headwork, dual outlet exhaust and Simons should net 120-125bhp. Not too shabby and won't annoy your bank manager too much,