Low Rise Inlet Manifold?
Discussion
A high rise manifold, often has an air gap- which means the lower part of the inlet manifold stays cooler-better for Volumetric Efficiency.
In addition it often has less bent or bendy runners into each cylinder-which is better in terms of less losses- again better for power.
You want it to sit low in the chasis- presumably for a lower C of G- I can tell you the inlet set up of a cast iron American V8 will make sod all difference to C of G, however you WILL feel the loss of power and torque due to a poor inlet/carb set up.
In addition it often has less bent or bendy runners into each cylinder-which is better in terms of less losses- again better for power.
You want it to sit low in the chasis- presumably for a lower C of G- I can tell you the inlet set up of a cast iron American V8 will make sod all difference to C of G, however you WILL feel the loss of power and torque due to a poor inlet/carb set up.
divetrucker said:
Nuthin whatsoever to do with CoG. I aint that daft.
It's to do with body clearance and the desire to avoid havin a huge hump / scoop in the bonnet.
Well it's your choice then, for good power and torque- you need space.It's to do with body clearance and the desire to avoid havin a huge hump / scoop in the bonnet.
Edited by divetrucker on Thursday 30th October 18:11
Edited by divetrucker on Thursday 30th October 19:03
Nothing to do with americans opinions and suchlike.
Engineers get it wrong, and stylists are the worst.
When the X600/Jaguar roadster was on the drawing boards, some idiots penned it with barely enough rooms to fit two exhaust log manifolds as intake manifolds and expected a target output of close to 90 BHP/litre. The tighter the R/d ratio (the radius over the diameter of the runner) combined with a high intake runner velocity- the worse. Even bolting on gizmos such as cam profile switching and hogging out the ports didn't help matters. I fought this decision.
Ferraris get it right, quite often you'll find them with as much space above the engine again as the engine itself almost- just look at a 355 or 360.
Edited by Marquis_Rex on Thursday 30th October 23:45
divetrucker said:
hmmm....dont think that quite works. The car involved is a sports libre racing sports car, where the body height is just below knee level!
Still,thanks fo the idea.
Ahh... then yes, it isn't really applicable... (love to see pic of said Libre ... !)Still,thanks fo the idea.
Edited by divetrucker on Thursday 30th October 19:02
divetrucker said:
Why are americans so single minded about downdraught carbs?
I want a low rise inlet manifold (like the ones they use for EFI setups on current models) but with a side draught carb stuck on the end so it sits low in the chassis!!
Anyone ever heard of such a thing??
What engine is it for ? only IIRC there was a racing manifold for the SBC where the carb was sunk in the middle of the manifold, would be very hard to find one now.I want a low rise inlet manifold (like the ones they use for EFI setups on current models) but with a side draught carb stuck on the end so it sits low in the chassis!!
Anyone ever heard of such a thing??
4 x twin choke Webber type side draft set up's used to be made for the more popular engines SBC & SBF, hot rodders would be your best bet to find one now. Are you running a dry sump set up ?, as that can drop the engine approx 5" in the chassis.
Marquis_Rex said:
divetrucker said:
Nuthin whatsoever to do with CoG. I aint that daft.
It's to do with body clearance and the desire to avoid havin a huge hump / scoop in the bonnet.
Well it's your choice then, for good power and torque- you need space.It's to do with body clearance and the desire to avoid havin a huge hump / scoop in the bonnet.
Edited by divetrucker on Thursday 30th October 18:11
Edited by divetrucker on Thursday 30th October 19:03
Nothing to do with americans opinions and suchlike.
Engineers get it wrong, and stylists are the worst.
When the X600/Jaguar roadster was on the drawing boards, some idiots penned it with barely enough rooms to fit two exhaust log manifolds as intake manifolds and expected a target output of close to 90 BHP/litre. The tighter the R/d ratio (the radius over the diameter of the runner) combined with a high intake runner velocity- the worse. Even bolting on gizmos such as cam profile switching and hogging out the ports didn't help matters. I fought this decision.
Ferraris get it right, quite often you'll find them with as much space above the engine again as the engine itself almost- just look at a 355 or 360.
MartinD said:
Marquis_Rex said:
divetrucker said:
Nuthin whatsoever to do with CoG. I aint that daft.
It's to do with body clearance and the desire to avoid havin a huge hump / scoop in the bonnet.
Well it's your choice then, for good power and torque- you need space.It's to do with body clearance and the desire to avoid havin a huge hump / scoop in the bonnet.
Edited by divetrucker on Thursday 30th October 18:11
Edited by divetrucker on Thursday 30th October 19:03
Nothing to do with americans opinions and suchlike.
Engineers get it wrong, and stylists are the worst.
When the X600/Jaguar roadster was on the drawing boards, some idiots penned it with barely enough rooms to fit two exhaust log manifolds as intake manifolds and expected a target output of close to 90 BHP/litre. The tighter the R/d ratio (the radius over the diameter of the runner) combined with a high intake runner velocity- the worse. Even bolting on gizmos such as cam profile switching and hogging out the ports didn't help matters. I fought this decision.
Ferraris get it right, quite often you'll find them with as much space above the engine again as the engine itself almost- just look at a 355 or 360.
The only thing I have ever found that offers an alternative to the normal holley downdraught arrangement is the quadruple dellorto crossover manifold set, which is very nice but very very costly.
Fuel injected american V8s (such as the one in my Chevy Avalanche 8.1) often use a (plastic) manifold that sits in the middle of the V with the mass flow meter projecting forwards over the top of the water pump. What I wish for, is a single big side-draught carb that would be able to operate in that position. If such an arrangement existed, it would combine the simplicity of a holley carb with the convenience of much reduced engine height.
The engine in question is a chevy big block 502c.i. and it is not dry sumped, again because of the cost (dry sump kit + smaller flywheel/clutch + special bellhousing + special starter motor...), even though I accept that this would lower the engine by the desired amount.
It seems very strange to me that no-one has ever seen the advantage in this.
Fuel injected american V8s (such as the one in my Chevy Avalanche 8.1) often use a (plastic) manifold that sits in the middle of the V with the mass flow meter projecting forwards over the top of the water pump. What I wish for, is a single big side-draught carb that would be able to operate in that position. If such an arrangement existed, it would combine the simplicity of a holley carb with the convenience of much reduced engine height.
The engine in question is a chevy big block 502c.i. and it is not dry sumped, again because of the cost (dry sump kit + smaller flywheel/clutch + special bellhousing + special starter motor...), even though I accept that this would lower the engine by the desired amount.
It seems very strange to me that no-one has ever seen the advantage in this.
Motown Junk said:
Now that's nice... !I have an idea what you mean.
Take the inlet on a LS1, but not have a bottle throddy on the end of it, but a sodding great side-draught carb.
There is a big issue here. Due to the difference in lentgh of the tract to each cylinder, you'll find the front ones rich, and the back ones weak.
Came across this first when one of my friends looked to work on a certain pre-war mental Bentley with a Supermarine W12 engine in it. That was the case - where the carbs had to be set so rich to keep the rear cylinders running right that the front ones washed the bores!!
Would you not be better off using the aforementioned LS1/LS7. Nice alloy lump, the latter being available in a crate producing 505bhp from the factory.
It is very compact indeed.
Going back to the old type SBC, ever extra inch of inlet = more torque. It's common to fit a 1" spacer to help improve grunt, and also improve charge cooling/reduce carb heating.
Someone made a swan-neck manifold system which took the carbs outboard, but requires width under the bonnet to do it. Can't remember who did it though.
Take the inlet on a LS1, but not have a bottle throddy on the end of it, but a sodding great side-draught carb.
There is a big issue here. Due to the difference in lentgh of the tract to each cylinder, you'll find the front ones rich, and the back ones weak.
Came across this first when one of my friends looked to work on a certain pre-war mental Bentley with a Supermarine W12 engine in it. That was the case - where the carbs had to be set so rich to keep the rear cylinders running right that the front ones washed the bores!!
Would you not be better off using the aforementioned LS1/LS7. Nice alloy lump, the latter being available in a crate producing 505bhp from the factory.
It is very compact indeed.
Going back to the old type SBC, ever extra inch of inlet = more torque. It's common to fit a 1" spacer to help improve grunt, and also improve charge cooling/reduce carb heating.
Someone made a swan-neck manifold system which took the carbs outboard, but requires width under the bonnet to do it. Can't remember who did it though.
Motown Junk said:
Seen that before - had an idea of fitting throttle bodies on it - but I dont think you could machine fuel injectors onto the runners.Gassing Station | Yank Motors | Top of Page | What's New | My Stuff