72mm plenum, how?
Discussion
Basically you need to put a collar on the very end first, then bore down to make the hole. After you need to make a new butterfly & open up the slot in the spindle so the butterfly will fit.
Typically the bit underneath (throttle water heater jacket cavity) is the limiting factor of meat, also the idle base screw can get in the way. I currently have for sale on a V8forum a 75.5mm plenum, which must be a very rare casting to be able to be taken out so far ~ it did require removal of the air idle insert & new insert making with tapping for a screw valve.
Normally only 71/72mm is the safe limit of the casting, but the castings do vary much like the rest of the engine ~ and sometimes the most horrible looking rough castings happen to have more meat in them...
Typically the bit underneath (throttle water heater jacket cavity) is the limiting factor of meat, also the idle base screw can get in the way. I currently have for sale on a V8forum a 75.5mm plenum, which must be a very rare casting to be able to be taken out so far ~ it did require removal of the air idle insert & new insert making with tapping for a screw valve.
Normally only 71/72mm is the safe limit of the casting, but the castings do vary much like the rest of the engine ~ and sometimes the most horrible looking rough castings happen to have more meat in them...
rev-erend said:
Before you get too carried away - you should ask the question : where is the biggest restriction in the inlet system.
No.. Bosch MAF.... ACT pipe.. and opened up air box ... all above 75.5mm 
BTW.. who's the girls on your pic.. reminds me of one of my old girlfriends... 'for nut's'.. them were the days!!!! also had a KH
Remember diameter is not purely the CSA, you have to subtract D * @5mm as the spindle is in the way (@5mm as I tend to skinny them a wee bit whilst they're out).
The bend and all the turbulence around it (AFM > Bend > reducing dia > throttle) is not ideal, making the bend dia larger always seems a positive step IMHO. Just looking at X sectional areas won't give the whole story.
The bend and all the turbulence around it (AFM > Bend > reducing dia > throttle) is not ideal, making the bend dia larger always seems a positive step IMHO. Just looking at X sectional areas won't give the whole story.
anonymous said:
[redacted]
not at all.. thats why they never lasted The ignorance of youth!.. if you only knew then what you know now and all that ……
I’d have to have a look through my old photo album for a pic… they didn’t have digital cameras in those days LOL…. In fact the one I think I might have is black and white (but that’s for effect honest
) … 
!!!!!!! TVR Beaver said:
rev-erend said:
Before you get too carried away - you should ask the question : where is the biggest restriction in the inlet system.
No.. Bosch MAF.... ACT pipe.. and opened up air box ... all above 75.5mm BTW.. who's the girls on your pic.. reminds me of one of my old girlfriends... 'for nut's'.. them were the days!!!! also had a KH
The 8 manifold runners to the cylinder can be ported - worst part is they have tight bends.
rev-erend said:
The 8 manifold runners to the cylinder can be ported - worst part is they have tight bends.
That maybe, but even with 72mm plenums we have seen quite dramatic hikes in RR power with 'big pipe over wing' technique which certainly suggests that the manifold is not the only induction restriction.rev-erend said:
Girl is 7 of 9.
The 8 manifold runners to the cylinder can be ported - worst part is they have tight bends.
7 of 9 ??? The 8 manifold runners to the cylinder can be ported - worst part is they have tight bends.
I've only ever had 3 on the go at the same time so respect!!... And yes, ported manifoulds and enlarged base and trumpet's etc etc.. and on a good day, 318 BHP... was it worth it?... probably not
Hi Peter.. hows it going.. I see you're getting to grips with your car now and have you sorted the rattle ? 
I'll give you 'bore scope' next time I see you... Old Blimp!!
you need more air... air box and feed is the big restriction IMHO
spend said:
Basically you need to put a collar on the very end first, then bore down to make the hole. After you need to make a new butterfly & open up the slot in the spindle so the butterfly will fit.
Typically the bit underneath (throttle water heater jacket cavity) is the limiting factor of meat, also the idle base screw can get in the way. I currently have for sale on a V8forum a 75.5mm plenum, which must be a very rare casting to be able to be taken out so far ~ it did require removal of the air idle insert & new insert making with tapping for a screw valve.
Normally only 71/72mm is the safe limit of the casting, but the castings do vary much like the rest of the engine ~ and sometimes the most horrible looking rough castings happen to have more meat in them...
Thanks for that Spend, informative as always! Did you come across those tapered manifold studs by any chance? They're coming off again shortly.Typically the bit underneath (throttle water heater jacket cavity) is the limiting factor of meat, also the idle base screw can get in the way. I currently have for sale on a V8forum a 75.5mm plenum, which must be a very rare casting to be able to be taken out so far ~ it did require removal of the air idle insert & new insert making with tapping for a screw valve.
Normally only 71/72mm is the safe limit of the casting, but the castings do vary much like the rest of the engine ~ and sometimes the most horrible looking rough castings happen to have more meat in them...
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