My 122S

[classicswede]

B21 pistons come in 3 types
Dished - low compression
flat - high compression
and B21ET - turbo pistons

[Rick269]

Originally Posted by Derek UK

Pistons are all the same. CR is set by how much is skimmed off the head for the B20E and B20F. It's possible to measure the height on the car with the valve cover off, at least, accurate enough to tell which one you have. B20E is 85.5mm and B20F is 87.0mm. This equates to 10.5 and 8.7:1 cr respectively. Assuming you have the latter and the 8.5 cr is correct it'll be due to the clean up around the valves or the bore increase. Valve clearances should be 16-18 thou for both valves with the D cam.
Ignition is best set after the basic set up. If you have no pinking that sounds good, you might even be able to go up another degree or so but max ignition advance is about right, again maybe 36º might be OK. The engine will be running at this over about 3500rpm so too much can burn holes in your pistons.
I believe that ignition timing with supercharging can be a bit of a nightmare.............

At the moment I only have the B20B head on. It measures over 87mm with my ruler. The B20E head I have done up measures less than 84mm over the same measurement so it will be a lot higher compression than the current 8.5. I guess the only way to be sure is to measure the cc of the chamber and go from there.
At least with the Megajolt you can adjust the timing at any one point of the rev/vacuum range so I think it has to be easier than a distributor to avoid detonation. Either way, I have spent too much getting the 'E' head how I want it so I think it will go on N/A for now. Later when I get more cash I'll look at the CR and get dished pistons or take some out of the chamber before fitting the supercharger.
May have to look at increasing the tappet gap though from 14 to 18.
Here's a picture of the supercharger on a mockup. I can't take the credit for the machining and it will have a better gilmer belt setup when finished too. I may even move it over to the other side of the engine to make use of a front mount intercooler. It did run well but there was some mixture problems with the front cylinders getting more than the rear and these Toyota superchargers don't like fuel going through them as it ruins the seals, hence the move to EFI.
Cheers,
Rick

[Burdekin]

Hi Rick,

You can work it out here: http://www.csgnetwork.com/compcalc.html

If it is 2.1l then from memory the bores will be about 90mm but check on this.

Just did some looking and B CR standard is 9.5:1 so boring to 2.1l has lowered the CR to 8.5 so just need to measure combustion chamber volumes on the E and you should be able to work things out. http://www.v-performance.com/article...ification.html

[Burdekin]

A bit of info for you if you haven't seen it before: http://www.1800philes.com/supercharged_volvo.html I e-mailed Steve a while back and I think his B20 is now running at about 280Hp but I could be wrong. Steve is another helpful guy and as he's done it then don't be shy sending him an e-mail.

Increasing combustion chamber volume and dished pistons like you wrote will reduce CR no problem but also depends on what boost you want to run. So work out what the CR is with the E head and what boost you want to run. Another member Mark (oilline) has a good build going so maybe ask him for advice as well. Also with a good worked head, good cam, bored to 2.1l (keeping 10.5:1 CR), lightened flywheel, good intake and exhaust you'll get well over 150HP and closer to 200Hp is easily possible.

I'd suggest giving KG at http://www.kgtrimning.com/ a call if you want to talk to someone with real experience in tuning these engines. The Swedes are way ahead in their experience at extracting power from this engine.

[Rick269]

OK, well according to the pictures on the VPD website, I have an early '72-'73 'F' head, not an 'E' like I thought as it has a single flat over the No. 2 exhaust port. There must have been a lot taken off the face previously, about 3mm! according to my rough measurements.
Thanks for the links and advice

[Burdekin]

If you read more that's the head he recommends for tuning so sounds like you're well on your way to a fine setup. Keep us posted, I like reading how people are getting on with their projects. Good luck...

[Rick269]

Some pics of the head. I think the valves are standard size.

Got a question for the guru's. Is there an easy way to convert the 122 to a cable accelerator pedal?

I've also been thinking hard about going straight LPG instead of EFI. Probably less work, similar cost but less than half the price for gas compared to unleaded here. Would work better with the high compression too.

[Burdekin]

Hi Tony,

Classicswede (Dai) http://www.classicswede.com/ does LPG conversions over here so he may be able to help with answers on that so maybe drop him a PM or e-mail.

Cheers,

Mitch

[Burdekin]

Rick, just noticed I called you Tony. Sorry about that.

[Rick269]

I got a bit carried away the other day and decided to fit the new steel timing gear. There was some noise from the front of the motor, but I wasn't expecting to see the fibre gear in the condition it was and I'm surprised it lasted so well at 6500rpm! It looks like it wouldn't have taken much more abuse before letting go.

Then I decided to fit the head at the same time. It only took me a couple of hours but then I could not get the motor to start. I found the problem. The valve springs in the new head are so much bigger in diameter that the rockers were touching the retainers slightly, preventing the valve from closing. After some careful grinding of the underside of the rocker, I got them all to close as they should and the motor finally started. I haven't driven it yet as I got called away for a couple of days with work. I'm thinking I will have to do some tweaking with the ignition timing and mixture. Job for tomorrow.

Oh, and I roughly measured the cc of the chamber before fitting the head. It was about 35cc