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Need a measurement please - solved

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MGB567 Avatar
MGB567 Gold Member Barrie Braxton
Sunshine Coast, Queensland, Australia   AUS
1966 MG MGB MkI "Money Guzzler"
1979 MG MGB GT V8 Conversion "Darkside"
Anyone have at hand the measurement from the back of the valve to the cylinder head face on Rover V8. It's evening as I type so I can't measure until I'm back at the car tomorrow. Dr G doesn't seem to have or if he does he won't give it up. smiling smiley



Convertible: CKD 11/66 first registered 8/5/67. Owned since 3/77. 90% original sheet metal. 18GB +40 balanced with almost all new internals. Peter Burgess big valve fast road head. Piper 285. Fidanza FW. Basil's followers and pushrods. TR7clutch. TT exhaust. ARP everywhere. 123 ign. Needham 4synchro c/r box.. Stock rebuilt/replaced suspension. Superpro bushes. New brakes all round including all pipes in SS flex. Interior redone. CAMS approved roll bar and side bars. Lots more. Hybrid of o/e and show/fast road car. Not for sale - it's my toy!

GT: UK car built/sold December '78. Stripped back to bare shell with VW Golf flared guards, flush fit front and rear valances with front guards immovable. Front and rear seams removed,Torana XU1 vents, frenched indicators front & Mk1 rear lights. Powered by 'worked' Rover 5 litre V8 (ex TVR Chimaera) with efi. T5 box. FC IFS. CCE rear attached to Salisbury axle with Quaife. All new interior with MrMikes covers on MX5 seats. Retro4 7x15 rims (zero offset) and 205/55 rubber. Colour: Jaguar Storm. Not for sale - it's my sanity!



Edited 1 time(s). Last edit at 2019-02-25 02:07 AM by MGB567.

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Walrus1954 Avatar
Walrus1954 Neil Peniston
Calgary, AB, Canada   CAN
Hi Barrie,

I measured the distance from the valve face to the cylinder head face as 7.65 mm. Hopefully that was the distance you were looking for. I have cylinder head on the bench at the moment so I can get any measurement you require.

Cheers Neil.

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MGB567 Avatar
MGB567 Gold Member Barrie Braxton
Sunshine Coast, Queensland, Australia   AUS
1966 MG MGB MkI "Money Guzzler"
1979 MG MGB GT V8 Conversion "Darkside"
Thanks Neil but that's not the one and I realise they're probably different depending on the head being used - I just thought someone might have done this so when I do it I know if I'm in the ballpark.

The measurement I was after is called "from the back of the valve" and is actually from the backside of the valve aka valve face as opposed to the valve head so way down on the back of the valve near the piston and then all the way up the valve stem and out to the head's face. You measure the nearside and farside add together and divide by 2 and that gives you the length of the runner from the back of the valve to the head face. Then you add that to the length of the manifold runner (measured in a similar way) add on the thickness of the plenum and any gasket and that gives you the total length of each runner. From that with the help of the cam's specs you can plug it into a program and it'll give you the optimum height to set each trumpet depending on whether you're after HP or torque.



Convertible: CKD 11/66 first registered 8/5/67. Owned since 3/77. 90% original sheet metal. 18GB +40 balanced with almost all new internals. Peter Burgess big valve fast road head. Piper 285. Fidanza FW. Basil's followers and pushrods. TR7clutch. TT exhaust. ARP everywhere. 123 ign. Needham 4synchro c/r box.. Stock rebuilt/replaced suspension. Superpro bushes. New brakes all round including all pipes in SS flex. Interior redone. CAMS approved roll bar and side bars. Lots more. Hybrid of o/e and show/fast road car. Not for sale - it's my toy!

GT: UK car built/sold December '78. Stripped back to bare shell with VW Golf flared guards, flush fit front and rear valances with front guards immovable. Front and rear seams removed,Torana XU1 vents, frenched indicators front & Mk1 rear lights. Powered by 'worked' Rover 5 litre V8 (ex TVR Chimaera) with efi. T5 box. FC IFS. CCE rear attached to Salisbury axle with Quaife. All new interior with MrMikes covers on MX5 seats. Retro4 7x15 rims (zero offset) and 205/55 rubber. Colour: Jaguar Storm. Not for sale - it's my sanity!

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MGB567 Avatar
MGB567 Gold Member Barrie Braxton
Sunshine Coast, Queensland, Australia   AUS
1966 MG MGB MkI "Money Guzzler"
1979 MG MGB GT V8 Conversion "Darkside"
Anyone? I'm measuring 4" give or take. If not a Rover I'm assuming any BOP would be the same. I'm just trying to see if I got close with my measuring.



Convertible: CKD 11/66 first registered 8/5/67. Owned since 3/77. 90% original sheet metal. 18GB +40 balanced with almost all new internals. Peter Burgess big valve fast road head. Piper 285. Fidanza FW. Basil's followers and pushrods. TR7clutch. TT exhaust. ARP everywhere. 123 ign. Needham 4synchro c/r box.. Stock rebuilt/replaced suspension. Superpro bushes. New brakes all round including all pipes in SS flex. Interior redone. CAMS approved roll bar and side bars. Lots more. Hybrid of o/e and show/fast road car. Not for sale - it's my toy!

GT: UK car built/sold December '78. Stripped back to bare shell with VW Golf flared guards, flush fit front and rear valances with front guards immovable. Front and rear seams removed,Torana XU1 vents, frenched indicators front & Mk1 rear lights. Powered by 'worked' Rover 5 litre V8 (ex TVR Chimaera) with efi. T5 box. FC IFS. CCE rear attached to Salisbury axle with Quaife. All new interior with MrMikes covers on MX5 seats. Retro4 7x15 rims (zero offset) and 205/55 rubber. Colour: Jaguar Storm. Not for sale - it's my sanity!

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Denis Avatar
Denis Denis Hill
Bearii, Nth Victoria, Australia   AUS
Barrie I cant see how valve length can relate in any way to runner length?? Just wondering. The way we used to check runner length was with a thin sticky tape. Run it along the roof of the runner, making sure it follows the shape, from the valve seat to the mouth. Do the same on the floor of the runner, add together then divide by 2. Your cam design should play a big part in your overall torque/power result. Going larger in diameter with your trumpets has the same effect as cutting them short, but it also means you need more room above them for efficient flow. I would try to keep the length the same but not be concerned about what the length is. You will have heaps of torque anyway with that engine, and soon looking for better gearing.

Denis



68 B roadster, Daffodil yellow, supercharger, Burgess SC head, SC cam, Mikuni HSR 48 carburetor and engine built for supercharging.

73 BGT V8 conversion starting with a bare shell. Built the engine "3.9L Rover" early in 2016 with high comp pistons and a few other nice bits, plus a T5 ford trans. Started on the body late 2016 and complete late 2017, Did all the work myself, mechanical, body. paint etc.
Finished and going well, great to drive and quick. Now has a nice 3.23 LSD.



Edited 2 time(s). Last edit at 2019-02-23 12:30 AM by Denis.

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MGB567 Avatar
MGB567 Gold Member Barrie Braxton
Sunshine Coast, Queensland, Australia   AUS
1966 MG MGB MkI "Money Guzzler"
1979 MG MGB GT V8 Conversion "Darkside"
"The way we used to check runner length was with a thin sticky tape. Run it along the roof of the runner, making sure it follows the shape, from the valve seat to the mouth. Do the same on the floor of the runner, add together then divide by 2."

Denis it's beyond my paygrade to fully understand but it seems the computerised programs work on optimising the runner length for a particular harmonic. The program needs to know the runner length from the back of the valve. Then with the other info as outlined in #3 you can calculate the sweet spot for the height of the trumpets for either HP or torque. I can go back and measure as you suggest which was also what the programmer said but I am able to see the back of the valve where the neck and face meet and I was able to shape a soft wire that went from that spot up the neck and out the head port's centreline. I know I have plenty of room inside the plenum chamber for airflow and while it might seem crazy I figured given the heads have been worked and the roller cam/rockers are in there I might as well see it through to the ultimate.



Convertible: CKD 11/66 first registered 8/5/67. Owned since 3/77. 90% original sheet metal. 18GB +40 balanced with almost all new internals. Peter Burgess big valve fast road head. Piper 285. Fidanza FW. Basil's followers and pushrods. TR7clutch. TT exhaust. ARP everywhere. 123 ign. Needham 4synchro c/r box.. Stock rebuilt/replaced suspension. Superpro bushes. New brakes all round including all pipes in SS flex. Interior redone. CAMS approved roll bar and side bars. Lots more. Hybrid of o/e and show/fast road car. Not for sale - it's my toy!

GT: UK car built/sold December '78. Stripped back to bare shell with VW Golf flared guards, flush fit front and rear valances with front guards immovable. Front and rear seams removed,Torana XU1 vents, frenched indicators front & Mk1 rear lights. Powered by 'worked' Rover 5 litre V8 (ex TVR Chimaera) with efi. T5 box. FC IFS. CCE rear attached to Salisbury axle with Quaife. All new interior with MrMikes covers on MX5 seats. Retro4 7x15 rims (zero offset) and 205/55 rubber. Colour: Jaguar Storm. Not for sale - it's my sanity!

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Denis Avatar
Denis Denis Hill
Bearii, Nth Victoria, Australia   AUS
So what ultimate are you looking for max HP or torque? Remember your "maximum" torque will be around"3500 revs . Your max HP might be in the 6000 rev area, The rest of your engine seems to be setup for HP
Denis



68 B roadster, Daffodil yellow, supercharger, Burgess SC head, SC cam, Mikuni HSR 48 carburetor and engine built for supercharging.

73 BGT V8 conversion starting with a bare shell. Built the engine "3.9L Rover" early in 2016 with high comp pistons and a few other nice bits, plus a T5 ford trans. Started on the body late 2016 and complete late 2017, Did all the work myself, mechanical, body. paint etc.
Finished and going well, great to drive and quick. Now has a nice 3.23 LSD.

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MGB567 Avatar
MGB567 Gold Member Barrie Braxton
Sunshine Coast, Queensland, Australia   AUS
1966 MG MGB MkI "Money Guzzler"
1979 MG MGB GT V8 Conversion "Darkside"
Probably torque but I need to see what the computer program says.

BTW the measurement is 4.5" using the long + short/2 measurement.



Convertible: CKD 11/66 first registered 8/5/67. Owned since 3/77. 90% original sheet metal. 18GB +40 balanced with almost all new internals. Peter Burgess big valve fast road head. Piper 285. Fidanza FW. Basil's followers and pushrods. TR7clutch. TT exhaust. ARP everywhere. 123 ign. Needham 4synchro c/r box.. Stock rebuilt/replaced suspension. Superpro bushes. New brakes all round including all pipes in SS flex. Interior redone. CAMS approved roll bar and side bars. Lots more. Hybrid of o/e and show/fast road car. Not for sale - it's my toy!

GT: UK car built/sold December '78. Stripped back to bare shell with VW Golf flared guards, flush fit front and rear valances with front guards immovable. Front and rear seams removed,Torana XU1 vents, frenched indicators front & Mk1 rear lights. Powered by 'worked' Rover 5 litre V8 (ex TVR Chimaera) with efi. T5 box. FC IFS. CCE rear attached to Salisbury axle with Quaife. All new interior with MrMikes covers on MX5 seats. Retro4 7x15 rims (zero offset) and 205/55 rubber. Colour: Jaguar Storm. Not for sale - it's my sanity!

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MGB567 Avatar
MGB567 Gold Member Barrie Braxton
Sunshine Coast, Queensland, Australia   AUS
1966 MG MGB MkI "Money Guzzler"
1979 MG MGB GT V8 Conversion "Darkside"
FWIW I am now equipped to set the distance from the back of the valve to the top of my trumpets at 12.95" as determined by the computer program. That's according to the 3rd harmonic but as my calculations were done for free I didn't pursue what that really means. Anyway it is what it is now so onwards and upwards.



Convertible: CKD 11/66 first registered 8/5/67. Owned since 3/77. 90% original sheet metal. 18GB +40 balanced with almost all new internals. Peter Burgess big valve fast road head. Piper 285. Fidanza FW. Basil's followers and pushrods. TR7clutch. TT exhaust. ARP everywhere. 123 ign. Needham 4synchro c/r box.. Stock rebuilt/replaced suspension. Superpro bushes. New brakes all round including all pipes in SS flex. Interior redone. CAMS approved roll bar and side bars. Lots more. Hybrid of o/e and show/fast road car. Not for sale - it's my toy!

GT: UK car built/sold December '78. Stripped back to bare shell with VW Golf flared guards, flush fit front and rear valances with front guards immovable. Front and rear seams removed,Torana XU1 vents, frenched indicators front & Mk1 rear lights. Powered by 'worked' Rover 5 litre V8 (ex TVR Chimaera) with efi. T5 box. FC IFS. CCE rear attached to Salisbury axle with Quaife. All new interior with MrMikes covers on MX5 seats. Retro4 7x15 rims (zero offset) and 205/55 rubber. Colour: Jaguar Storm. Not for sale - it's my sanity!

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