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B20 Engine Build

mitch1971

mitch1971

Member
Joined
Sep 11, 2009
Location
Aberdeen, Scotland
I?ve bought a mate?s 131 and the car still is original with the B20A. The engine is in very good condition and runs a single Stromberg. He was planning on building a stronger engine so the car also comes with a; KG17 cam, E head, big valves (not sure what yet as haven?t gone through the parts), high lift rockers, heavy duty springs, 4 branch, lightened flywheel etc. I also have a spare big valve head, pair of HIF44s and parts for a FI conversion. Not decided on how I will fuel the car; SUs or FI.

Low to mid torque is more important to me as I won?t be flogging the car high up in the revs. So not looking for a car that really only produces HP high up in the rev range. Want a car that pulls from low down to say 5000rpm. At a guess something like 150hp at 5500 would be the ideal in my head at the moment, whether that is realistic not sure. Last two B20s I?ve built have been built as per the instructions from the vendors; KG Trimning and Tinus Tuning. I told them what I wanted and they advised me what I needed so this is a little different as not really sure what I will get when assembled. The engine bottom end is in good condition as my mate actually had taken it apart and measured and inspected it all so I wasn?t planning on doing anything to the bottom end. I thought I?d stay around the 10.5:1 CR and a wee tidy up port of the e head. I run premium 99 fuel here in the U.K.

How?s the above sound for a torquey B20?
 
You'll be looking for a tractor cam, so the normal suggestion of a D or K cam wouldn't work for you, they just move the power band up some.

I'd be curious on the specs of the Penta P cam, sounds like it might be good for this application(vaguely), but I didn't see any info on what it actually was.

Otherwise, A or C grind? The fuel injection might work better - the D-Jet manifold has nice long unobstructed runners which helps (I think) with low-mid range torque.

You don't want to touch the bottom end, so the usual trick of adding displacement with B21 pistons won't do, but that's a GREAT way to add low/mid range torque, without changing much else.
 
A C grind would probably be a good compromise. Not sure how that would play with the larger valves of the E or F heads though. Or if the difference would even be noticeable.

Long intake runners are generally recommended for low end torque.
 
I wasn't sure what RPM the D-Jet mani helped out at vs. the SU's.

And I was just curious about the P cam because there's a possibility it's a lower duration (like an A or C cam), but possibly higher lift? But you might not need that with 'high lift' rockers.

What sort of rockers are those, Mitch? I have a set of KgTrimning roller rockers on my PV's motor, along with their 'bridge' mount that repositions/stiffens the rocker shaft:
LliXWptl.jpg
 
JohnMc said:
You'll be looking for a tractor cam, so the normal suggestion of a D or K cam wouldn't work for you, they just move the power band up some.

I'd be curious on the specs of the Penta P cam, sounds like it might be good for this application(vaguely), but I didn't see any info on what it actually was.

Otherwise, A or C grind? The fuel injection might work better - the D-Jet manifold has nice long unobstructed runners which helps (I think) with low-mid range torque.

You don't want to touch the bottom end, so the usual trick of adding displacement with B21 pistons won't do, but that's a GREAT way to add low/mid range torque, without changing much else.
Click to expand...

I have a Tinus Tuning TT3 cam in the 142 which is definitely an improvement over the original A cam and pulls nicely. It?s only 90hp so only 5 more than original but with the ignition and Stromberg properly sorted pulls nicely for a single carb but want more for the 131. Will have a chat with Ben from Tinus Tuning. I don?t want to spend much on the engine though as I am getting the 142 repainted and also have my estate to finish now I?ve finished the welding and also paint the 131.
 
Low and middle range torque affects the drivability far more than it does the 'peak HP' number, since the torque drops off at higher RPM's where, because of the maths, the peak HP is usually generated. So yeah, don't worry about that HP number.

Adding displacement without other mods will similarly make more grunt that you'll def. notice while driving it around normally, but barely affect the peak HP.
 
JohnMc said:
Low and middle range torque affects the drivability far more than it does the 'peak HP' number, since the torque drops off at higher RPM's where, because of the maths, the peak HP is usually generated. So yeah, don't worry about that HP number.

Adding displacement without other mods will similarly make more grunt that you'll def. notice while driving it around normally, but barely affect the peak HP.
Click to expand...

I know how expensive it gets once you start on the bottom end with machining and parts cost these days. 😁
 
Yeah, if you're not rebuilding the bottom end anyhow, where B21 pistons/machining would just be a modest increase over rebuilding it with new B20 parts, don't worry about it.
 
I've found D and K cams are perfectly drivable at low to mid RPM. The K giving a bit more on the low end, but barely noticeable. My B20F with dual HS6s is pretty peppy around 2000-3000 rpm when driving in town. There are probably other choices you can make that will help boost low to mid rpm performance.

If you want it to be cheap then I'd just slap those HIF carbs and the E head on it with the right needles and a cam of your choosing. IIRC that should get you in the neighborhood of 130hp.

Minimal effort to get it running and then you can fine tune it as you want later when you don't have the current financial and time limitations due to the other cars.
 
Emailed Ben from Tinus Tuning so will see what he comes back with, so much easier when someone like Ben can just tell me what is needed to meet my goals.

? I?ve just bought another old Volvo from my mate, this one is a 69 131 with a good original B20A. The car comes with engine parts as he was planning on building a stronger engine. I want to build this engine to be a strong street engine that pulls from low down. The parts with the car are; E head, KG17 cam, big valves (not sure what size at this stage), high lift rockers, heavy duty springs, 4 branch, lightened flywheel etc. I have the parts to make a fuel injected engine and also have a spare pair of HIF44carbs so will use whichever will be best? I also have a big valve B20 carb head in my spares.

Will the above give me a good strong street engine, if not what would you recommend for a good street engine build??
 
Heard back from Ben and he would recommend his TT3 cam or possibly the TT4. For best torque the 2.5l stroker kit, that would be awesome but not cheap so will need to see what the finances are like when I?ve finished the painting. He also recommends FI but said it?s quite a project in itself to install. Would also like some pics and details of the head. So I?ll at least change the cam as a minimum.
 
Yeah, with the fuel injections I'd use some of the D-Jet parts like the injectors/fuel rail, intake/throttle body. But not really much else. Not the ECU, not the MAP sensor, not the throttle sensor, not the fuel pump or even the fuel pressure regulator. Just wire all that stuff from scratch to a Megasquirt/Microsquirt programmable ECU. And use modern cheaper/easier to find/more reliable components for the fuel pump and regulator. And a real TPS (the D-Jet throttle sensor isn't a position sensor). And use it to run the ignition as well.
 
I put together most of the parts a few years back for FI; B20 intake plenum, injector holders, throttle body, TPS etc even bought a megasquirt ECU but sold that so doing a FI conversion is doable and the hard to find parts I have already. Getting ahead of myself but good to plan this stuff out. I need to paint the car first.
 
KG Trimning also got back to and recommended the KG10 cam as they thought the KG17 would be a bit too aggressive. I have a KG10 in my Amazon estate and a TT3 in my 142, think I will go a TT3 when I do the 131 engine and sell the KG17 cam. I like the service you get from Ben with the help and advice.
 
If you don't want to pursue higher RPM operation or more displacement, compression ratio is your primary variable. This assumes that the head is not presenting a significant flow restriction.

If your target RPM is 5000 RPM the OEM E head is probably not going to present a flow restriction and I would not be thinking about bigger valves. Any port work should be reserved for addressing the deficiencies in the exhaust port. Raising the port floor is ambitious. Removing the restrictions around the valve guide is easier to do. Don't fit 'heavy duty' valve springs. Higher spring rates just increase parasitic losses and potential wear on the valve train. Higher lift rockers or a cam with higher lift may require that you select different springs if coil bind becomes an issue. I seem to recall that the stock springs may approach bind at a valve lift of 0.43".

Don't fit a 4 into 1 header. If you can access an original 4 - 2 B20E exhaust manifold that is an excellent choice. If not, I think KG and Tinus make 4-2-1 headers. Just make sure to get the correct tube sizes for a lower RPM engine - I think there are two or three tube size options.

Your primary modification tool is compression ratio and you will want to ensure that your piston - head clearance is correct to minimize detonation. Measure piston height in the bore and have the block decked to establish pistons crowns flush with the deck. The low cost way is to deck the block so that the highest piston is just flush with the deck. The anal retentive way is to deck the block so that the lowest piston is flush with the deck and then machine the crowns on the high pistons to bring them flush. Depending on what your target clearance / quench clearance is you may want to have the piston crown slightly proud of the deck surface. Use a B20B or Cometic gasket. The B20E gaskets are B20F gaskets which are too thick to establish a proper quench zone. You can do the research on what a good target is. Google David Vizard for details. 10.5:1 is a realistic CR goal. With a correct quench clearance you may be able to push it a nudge higher. This will depend on the duration of the cam you choose which will determine your dynamic compression ratio. Ben from Tinus should provide guidance on CR and cam mixes.

For a 5000 RPM horsepower peak, dual SUs are probably just as good as fuel injection. However, once it is configured fuel injection is much easier to fine tune with your laptop than fiddling with carb jetting. Full on sequential injection with spark control is significantly more involved; but, having spark control does allow you to easily modify advance in problem areas to tune out detonation. EFI with the original D jet manifold (dampens MAP pulses nicely) will probably idle better than SUs because SUs seem to be very sensitive to a lack of manifold vacuum. My E head with a D cam has an idle MAP of about 55 kPa at around 850 RPM. That is probably a problem for an SU, of course cranking the idle speed up to 1050 RPM nets you a drop in MAP which is one way to fix that problem.
 
142 guy said:
If you don't want to pursue higher RPM operation or more displacement, compression ratio is your primary variable. This assumes that the head is not presenting a significant flow restriction.

If your target RPM is 5000 RPM the OEM E head is probably not going to present a flow restriction and I would not be thinking about bigger valves. Any port work should be reserved for addressing the deficiencies in the exhaust port. Raising the port floor is ambitious. Removing the restrictions around the valve guide is easier to do. Don't fit 'heavy duty' valve springs. Higher spring rates just increase parasitic losses and potential wear on the valve train. Higher lift rockers or a cam with higher lift may require that you select different springs if coil bind becomes an issue. I seem to recall that the stock springs may approach bind at a valve lift of 0.43".

Don't fit a 4 into 1 header. If you can access an original 4 - 2 B20E exhaust manifold that is an excellent choice. If not, I think KG and Tinus make 4-2-1 headers. Just make sure to get the correct tube sizes for a lower RPM engine - I think there are two or three tube size options.

Your primary modification tool is compression ratio and you will want to ensure that your piston - head clearance is correct to minimize detonation. Measure piston height in the bore and have the block decked to establish pistons crowns flush with the deck. The low cost way is to deck the block so that the highest piston is just flush with the deck. The anal retentive way is to deck the block so that the lowest piston is flush with the deck and then machine the crowns on the high pistons to bring them flush. Depending on what your target clearance / quench clearance is you may want to have the piston crown slightly proud of the deck surface. Use a B20B or Cometic gasket. The B20E gaskets are B20F gaskets which are too thick to establish a proper quench zone. You can do the research on what a good target is. Google David Vizard for details. 10.5:1 is a realistic CR goal. With a correct quench clearance you may be able to push it a nudge higher. This will depend on the duration of the cam you choose which will determine your dynamic compression ratio. Ben from Tinus should provide guidance on CR and cam mixes.

For a 5000 RPM horsepower peak, dual SUs are probably just as good as fuel injection. However, once it is configured fuel injection is much easier to fine tune with your laptop than fiddling with carb jetting. Full on sequential injection with spark control is significantly more involved; but, having spark control does allow you to easily modify advance in problem areas to tune out detonation. EFI with the original D jet manifold (dampens MAP pulses nicely) will probably idle better than SUs because SUs seem to be very sensitive to a lack of manifold vacuum. My E head with a D cam has an idle MAP of about 55 kPa at around 850 RPM. That is probably a problem for an SU, of course cranking the idle speed up to 1050 RPM nets you a drop in MAP which is one way to fix that problem.
Click to expand...

I know the theory says increase CR for extra torque but when I fitted the TT3 cam in my 142 B20 Ben recommended against it as he said something along the line of it will hurt the chamber filling. I?d need to dig out the email but with the B20A head he recommended fitting the thin head gasket only with a minimal skim. So a slightly increased CR. I?ll find out when doing the next engine what CR he recommends for dual SUs or FI if it makes any difference. I run the cars on 99 octane fuel.

I?ve been thinking and talking about doing a FI conversion for years so probably need to do it. I like SUs and Strombergs as I know them pretty well and the one downside with a bespoke FI system is it?s bespoke, I?d always need a laptop with the program and if the ecu broke what would that mean in years to come.
 
mitch1971 said:
I know the theory says increase CR for extra torque but when I fitted the TT3 cam in my 142 B20 Ben recommended against it as he said something along the line of it will hurt the chamber filling. I’d need to dig out the email but with the B20A head he recommended fitting the thin head gasket only with a minimal skim. So a slightly increased CR. I’ll find out when doing the next engine what CR he recommends for dual SUs or FI if it makes any difference. I run the cars on 99 octane fuel.

I’ve been thinking and talking about doing a FI conversion for years so probably need to do it. I like SUs and Strombergs as I know them pretty well and the one downside with a bespoke FI system is it’s bespoke, I’d always need a laptop with the program and if the ecu broke what would that mean in years to come.
Click to expand...

Just for context I thought I'd throw up the cam specs for the TT3.

Intake: 10.4mm (0.409") and 259 degrees
Exhaust: 11mm (0.433") and 267 degrees
LSA is 111 degrees with a total overlap of 40 degrees.

More duration and lift on the exhaust to account for exhaust port restriction? Giving a bit more time to get the gases out?

For comparison the ever popular D cam is symmetrical with .420" of lift, 280 degrees of duration, and an LSA of 111 advertised (listed by IPD at 0.424" and 262 degrees) but seems to vary by who is making it.
 
spock345 said:
Just for context I thought I'd throw up the cam specs for the TT3.

Intake: 10.4mm (0.409") and 259 degrees
Exhaust: 11mm (0.433") and 267 degrees
LSA is 111 degrees with a total overlap of 40 degrees.

More duration and lift on the exhaust to account for exhaust port restriction? Giving a bit more time to get the gases out?

For comparison the ever popular D cam is symmetrical with .420" of lift, 280 degrees of duration, and an LSA of 111 advertised (listed by IPD at 0.424" and 262 degrees) but seems to vary by who is making it.
Click to expand...

From what I've read the old cam profiles aren't comparative to new profiles. A new profile of 260 duration apparently equivalent to a old profile of 278. I
'm happy now that I'm ditching the KG17 and guessing at what is best and just go for a Tinus Tuning cam etc and let the designer and expert tell me.
 
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