B20 rebuild

[AmazonMatt]

The B20B in my 1970 Amazon is going to need a rebuild soon as the compression is low in two cylinders (quite a bit lower in one), it is burning oil and has low oil pressure. It is at least going to need a hone and new rings, more likely a rebore and crank regrind. The compression test suggested that it was the rings or bores at fault but I will test the cylinder head as well.

What would be recommended that I change at the same time?

It is fitted with a 123ignition distributor, rebuilt SU HS6 carbs and all the ancillaries are good.

According to the records I have from previous owners, the engine was rebuilt in 1988 and has done around 100,000 miles since then. At the time it was fitted with new fibre timing gears, a new 'C' camshaft and followers and the head was converted to unleaded.

What is the lifespan of fibre timing gears? Are they likely to need replacing? If they do is it a good idea to go to steel gears?

I know the camshaft is unlikely to have much wear but are there performance improvements to be made by fitting a different profile? I will only be using it on the road, not for competition. I see mention of the 'D' and 'K' cams on the forum but I have no idea how these differ from the 'C' cam. Would I need to change anything else if I went this route?

I will be replacing the oil pump as a matter of course especially as the oil pressure is currently low. I will also replace the clutch and do the rear crank seal conversion if it hasn't already been done, if it has then of course I will replace the seal. I recently fitted a new felt seal to the timing cover as it was leaking, is the seal conversion possible to do with the engine in the car? I might leave that conversion to later if possible to save a bit of money just now.

Thanks
Matt

[Quarterless]

Whats your budget?
I'd recommend steel gears after shredding my fibre ones.
Other cams will give more power.
Yes you can change the front seal in a he car. But if you are taking the car out for work do it then.

[northNH]

Hope this helps:

-A lot depends on $, enthusiasm, and who's doing the wrenching (you or a hired hand).
-Replacing fiber gear makes perfect sense, but if totally uncracked/unchipped I'd reuse it. I've always been satisfied with Volvo's OEM fiber, but don't know the quality of what's out there now. I never saw the need for metal gears for the type of power you're talking about, and neither did Volvo. And I like hearing the valves and not the gears...
-If your C cam and lifters are good, with only slight wear, I'd reuse 'em. If not, K (Volvo's most "modern" B20 cam) has been my choice, especially with OD, with new lifters/pushrods of course, but no other changes needed.
-Consider CR. I like ~9.5:1 for my available premium gas.
-Biggest bang for the buck no one seems to consider? Have 5-7 lbs expertly removed from that ~20 lb flywheel, and have it balanced with the new clutch cover attached. Feels like 15 extra HP.
-Rear main seal conversion, most def...Front +/-, not that hard to get a felt one right for 100K miles.
-123 distrib no experience, but I've always been happy playing with Bosch stuff.
-Keep the SUs, learn what makes them behave.
-Paint it the correct Volvo red, not just some stuff you find that looks close.

Others with more to add I'm sure...

[Amazonjulian]

Morning I'm currently doing exactly the same job.. Picking up my re bored block this morning. Mine already has metal timing gears but I'd be adding them to the shopping list if I didn't. A friend who runs a historic motor sport engineering company is working on my e head and once we see how that's flowing I'll be making the cam choice. K G trimning is currently favourite. Simon does an exchange timing cover converted for neoprene seals. I was planning to retain my oil pump as it seems unworn. Is that a false economy?

[Burdekin]

Also maybe an option, don't Volvo still sell new B20 engines? It maybe a cheaper option if they do.

My engine specs and new parts:
Lightened flywheel
Clutch assembly
Polished crank and new bearings
Balanced clutch/flywheel/crank and con rods assembly
Bored 30thou over cylinders
Pistons and rings
Skimmed and worked E head with hardened exhaust seats - CR 10:1
Inlet & exhaust valves and valve springs
KG10 cam, followers & push rods
Oil, fuel and water pumps
Front and rear crank covers with modern seals
Rocker assembly
Gasket, seals and bolts etc.

[Burdekin]

Matt, I'd say your cam will be quite worn after 100k so I'd be changing it.

[123GT-AMAZON]

Hi ya

Ok 100, tho miles is nothing to these engines I would say its just run in in my honest opinion , no wear should be present to worry about if serviced correctly naturally it will not be like brand new but with that cam wear will be very miner


nOT a lot of people know this but K cams r only gd for 25,000 miles thens it's all down ! Hill I'm affraid and I have seen it and had this confirmed by engineers who do this for a living due to excessive load to gain extra power naturally wear happens ten fold so basically your getting the most out but with the suffering of parts under major load so I would never ever fit a K cam to any of my cars but if I wanted a track car then yes as it's power for course .

You research if u don't believe me but 25,000 thousand miles then it's down hill with lots of wear happening compared to a nice d cam that lasts way way longer and in long run will have just as much power as the k once it's worn out

So if u want value for money and don't want to be in this situation few years down line forget the k cam but it's your money folks spend it any which way you want as you have earned your money .


Once you have had the work done I highly recommend poppin your car on a rolling road for a full setup they will get the best optimum result for you.

Kind regards
Robert.w

[Burdekin]

Yeah Robert the higher the lift, sharper angle the faster the wear on the cams.

Cam chart and info:http://www.1800philes.com/ianr/_superlist_grinds.html

[northNH]

Re: K cam...Must be a your-side-of-the-pond thing. Inferior metallurgy?

I know of several >100K mile K cam motors that don't seem to know they should have been worn out by now. Unlike D cam (max power at high RPM), K cam is best for prodigious torque at lower RPMs (like a better A cam)...nothing "radical" about it.

[Burdekin]

I thought there was very little difference between k and d cams?