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Burdekin · May 8th, 2011, 07:57

Forgot to say Darren's organised the engine machining and it should be done this week. Boring the block, crank only needs a polish, hardened seats, skim the head and we still need to see about balancing the crank with the lightened flywheel on. At this stage looking at maybe building the engine first weekend of June. The resto guy is saying end of June / mid July for the bodywork so plenty to get sorted before then. I've ordered a rebuild kit for the SU carbs so hopefully that will be here this week so I can get that done and I'll look at building up the megajolt harness and wiring in the meantime as well.

Burdekin · May 10th, 2011, 09:42

I started porting the aluminium inlet manifold I have. Darren measured the E head inlet ports and they are 40 to 41mm diameter so I measured the inlet ports in the inlet manifold and they are down to 35mm at one section and typically probably about 36mm. It may not sound much but the difference between the area of a 35mm diameter hole and a 41mm hole is 37%. Therefore the manifold as it is will quite restrictive in comparison to the head so not much point having a better flowing head if the manifold is restricting flow into it. At this stage I’m intending on taking the curved section of the inlet manifold out to 40mm (41 if enough material) and slightly over 41mm in the thicker end section where it meet the head. I didn’t get much done last night as a mate came over for dinner but I thought I’d give a heads up and will post some pics when I get some more done. It is really obvious what needs to be done if anyone else out there wants to give it a try and port their manifold.

Derek UK · May 10th, 2011, 11:16

Apparently, this mismatch, i.e. inlet manifold smaller than the head port size, does have advantages. When the inlet valve closes there is a back pulse, and this lip helps to keep the charge in the head, rather than it going back into the manifold. The smaller manifold bore also helps keep the gas speed up.

Burdekin · May 10th, 2011, 12:17

My understanding Derek is that is more the design of the head intake ports. The lower pressure due to the increased size in the inlet mainfold would allow for more air to flow faster into the head. The inlet should match the head intake ports and even preferrably be the same size as the intake valves is my understanding of what would be optimum for the B20. I stand to be corrected though.

Burdekin · May 10th, 2011, 14:17

That’s the lightened flywheel arrived. Lookin good!

classicswede · May 10th, 2011, 22:30

For good advice on general engine tuning take a read of David Vizards material. His finding are all backup with flowbench testing and dyno results.

His adice is the inlet manifold should be slightly smaller than the ports in the head.

To find out if the manifold does need opening up the only way to know for sure would be with a flow bench. You would be looking for similar flow from the head with the inlet at full lift and the manifold does not want to be much more. Over sizing the manifold will result in reduced air speed comprimising the low end.

The area of the port near the flange of the cylinder head does not want opening up as the restriction in the head is in the valve area.

asneddon · May 11th, 2011, 02:14

It would be interesting if someone could measure the dia of the inlet manifold off an 'E' model, as that is what was on the E head from the factory. Also, are B18 inlet manifolds different to B20 ones?

The interesting thing is that I am (very) slowly doing the same kind of build at the moment (building a 2130cc with B20E head). I was just going to port match the manifold to head, but now you have me thinking.

David Vizard is great, but most of his testing is from the A series BMC engine. The 5 port design on that probably doesn't flow over to the volvo heads much I would guess.

Somthing else to look at if you are into porting at the moment. The SUs have some very sharp edges in the throat. I managed another 3HP on my mini by cleaning those up! Made more power than the trumpets and K&Ns together, and cost nothing. Don't touch the venturi, but when you look you will see the sides (comming up to the venturi) are pretty badly cast then machined. Just touch that up a bit.

Burdekin · May 11th, 2011, 06:46

Thanks guys. I was wondering the same thing myself. The inlet manifold is from a B18 so I assumed a B20E would be larger, but could be wrong. The head won't get much work done, hopefully just tidy up any obstructions and polish the exhaust ports. Match the manifolds to the head. I hope to dyno the car when finished so will see in the end, but nothing ventured nothing gained and by doing is the best way to learn. I'm using a KG10 cam so getting the head to flow a bit better should be worth the effort.

I'm not doing anything drastic and following the principles which Des Hammill recommends in his SU and Head tuning books, and also reading what has worked for John Parker and others in the B20.

Burdekin · May 11th, 2011, 08:00

Quote:

Originally Posted by asneddon

It would be interesting if someone could measure the dia of the inlet manifold off an 'E' model, as that is what was on the E head from the factory. Also, are B18 inlet manifolds different to B20 ones?

The interesting thing is that I am (very) slowly doing the same kind of build at the moment (building a 2130cc with B20E head). I was just going to port match the manifold to head, but now you have me thinking.

David Vizard is great, but most of his testing is from the A series BMC engine. The 5 port design on that probably doesn't flow over to the volvo heads much I would guess.

Somthing else to look at if you are into porting at the moment. The SUs have some very sharp edges in the throat. I managed another 3HP on my mini by cleaning those up! Made more power than the trumpets and K&Ns together, and cost nothing. Don't touch the venturi, but when you look you will see the sides (comming up to the venturi) are pretty badly cast then machined. Just touch that up a bit.

Re-building the carbs this weekend is the plan so I'll check out the throat. The inlet manifold is nearly finished. Will finish it off tonight or tomorrow night. Lidl will be selling a port and polish kit from Thursday for £13. I'll go down and pick one up if they look okay.

Derek UK · May 11th, 2011, 11:40

David Vizard is great, but most of his testing is from the A series BMC engine. The 5 port design on that probably doesn't flow over to the volvo heads much I would guess.

He also does a book on the Ford Pinto (2l OHC). That might be more relevant even if it is crossflow.
Waaaaaaaay back I did some work on the carbs on my B16B according to a book you could get then from CCC mag. One of the mods was radiusing the front/intake side of the piston to smooth the flow. Seems reasonable but there might equally be logic against it. I've not seen this mod mentioned anywhere other than in this book. Car ran very well but I don't know if it actually made any difference.

May 10th, 2011, 11:16	#43
Derek UK VOC Member Last Online: Today 15:13 Join Date: Jul 2006 Location: Chatham	Apparently, this mismatch, i.e. inlet manifold smaller than the head port size, does have advantages. When the inlet valve closes there is a back pulse, and this lip helps to keep the charge in the head, rather than it going back into the manifold. The smaller manifold bore also helps keep the gas speed up. Last edited by Derek UK; May 10th, 2011 at 11:18. Reason: Extra.

May 10th, 2011, 22:30	#46
classicswede Trader Volvo in my veins Last Online: Apr 26th, 2024 23:53 Join Date: Dec 2004 Location: Anglesey	For good advice on general engine tuning take a read of David Vizards material. His finding are all backup with flowbench testing and dyno results. His adice is the inlet manifold should be slightly smaller than the ports in the head. To find out if the manifold does need opening up the only way to know for sure would be with a flow bench. You would be looking for similar flow from the head with the inlet at full lift and the manifold does not want to be much more. Over sizing the manifold will result in reduced air speed comprimising the low end. The area of the port near the flange of the cylinder head does not want opening up as the restriction in the head is in the valve area. __________________ http://www.classicswede.org www.classicswede.co.uk

May 11th, 2011, 06:46	#48
Burdekin Chief Bodger Last Online: Today 14:36 Join Date: Oct 2009 Location: Aberdeen	Thanks guys. I was wondering the same thing myself. The inlet manifold is from a B18 so I assumed a B20E would be larger, but could be wrong. The head won't get much work done, hopefully just tidy up any obstructions and polish the exhaust ports. Match the manifolds to the head. I hope to dyno the car when finished so will see in the end, but nothing ventured nothing gained and by doing is the best way to learn. I'm using a KG10 cam so getting the head to flow a bit better should be worth the effort. I'm not doing anything drastic and following the principles which Des Hammill recommends in his SU and Head tuning books, and also reading what has worked for John Parker and others in the B20. Last edited by Burdekin; May 11th, 2011 at 07:19.

May 8th, 2011, 07:57	#41
Burdekin Chief Bodger Last Online: Today 14:36 Join Date: Oct 2009 Location: Aberdeen	Forgot to say Darren's organised the engine machining and it should be done this week. Boring the block, crank only needs a polish, hardened seats, skim the head and we still need to see about balancing the crank with the lightened flywheel on. At this stage looking at maybe building the engine first weekend of June. The resto guy is saying end of June / mid July for the bodywork so plenty to get sorted before then. I've ordered a rebuild kit for the SU carbs so hopefully that will be here this week so I can get that done and I'll look at building up the megajolt harness and wiring in the meantime as well.

May 10th, 2011, 09:42	#42
Burdekin Chief Bodger Last Online: Today 14:36 Join Date: Oct 2009 Location: Aberdeen	I started porting the aluminium inlet manifold I have. Darren measured the E head inlet ports and they are 40 to 41mm diameter so I measured the inlet ports in the inlet manifold and they are down to 35mm at one section and typically probably about 36mm. It may not sound much but the difference between the area of a 35mm diameter hole and a 41mm hole is 37%. Therefore the manifold as it is will quite restrictive in comparison to the head so not much point having a better flowing head if the manifold is restricting flow into it. At this stage I’m intending on taking the curved section of the inlet manifold out to 40mm (41 if enough material) and slightly over 41mm in the thicker end section where it meet the head. I didn’t get much done last night as a mate came over for dinner but I thought I’d give a heads up and will post some pics when I get some more done. It is really obvious what needs to be done if anyone else out there wants to give it a try and port their manifold.

May 10th, 2011, 12:17	#44
Burdekin Chief Bodger Last Online: Today 14:36 Join Date: Oct 2009 Location: Aberdeen	My understanding Derek is that is more the design of the head intake ports. The lower pressure due to the increased size in the inlet mainfold would allow for more air to flow faster into the head. The inlet should match the head intake ports and even preferrably be the same size as the intake valves is my understanding of what would be optimum for the B20. I stand to be corrected though.

May 11th, 2011, 02:14	#47
asneddon Master Member Last Online: Nov 29th, 2021 23:46 Join Date: Jan 2009 Location: Dunedin	It would be interesting if someone could measure the dia of the inlet manifold off an 'E' model, as that is what was on the E head from the factory. Also, are B18 inlet manifolds different to B20 ones? The interesting thing is that I am (very) slowly doing the same kind of build at the moment (building a 2130cc with B20E head). I was just going to port match the manifold to head, but now you have me thinking. David Vizard is great, but most of his testing is from the A series BMC engine. The 5 port design on that probably doesn't flow over to the volvo heads much I would guess. Somthing else to look at if you are into porting at the moment. The SUs have some very sharp edges in the throat. I managed another 3HP on my mini by cleaning those up! Made more power than the trumpets and K&Ns together, and cost nothing. Don't touch the venturi, but when you look you will see the sides (comming up to the venturi) are pretty badly cast then machined. Just touch that up a bit.

May 11th, 2011, 11:40	#50
Derek UK VOC Member Last Online: Today 15:13 Join Date: Jul 2006 Location: Chatham	David Vizard is great, but most of his testing is from the A series BMC engine. The 5 port design on that probably doesn't flow over to the volvo heads much I would guess. He also does a book on the Ford Pinto (2l OHC). That might be more relevant even if it is crossflow. Waaaaaaaay back I did some work on the carbs on my B16B according to a book you could get then from CCC mag. One of the mods was radiusing the front/intake side of the piston to smooth the flow. Seems reasonable but there might equally be logic against it. I've not seen this mod mentioned anywhere other than in this book. Car ran very well but I don't know if it actually made any difference.

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