Re: [Cadillac_Performance_Association] Digest Number 668
- 2" is almost certainly too big. 2" primaries on headers are enormous, and
intake runners need to be smaller than exhaust runners owing to the
smaller volume of intake than exhaust.
The LT1 style intake won't cost you any low RPM torque if you chose your
cam correctly. At RPM below the primary resonant frequency, the runner
acts like a non-resonant dump and neither enhances nor detracts from flow
volume at different frequencies. That's why LT1's have virtually flat
torque curves from almost off idle right up to the RPM at which the torque
curve noses over. The runners are so short that the stock engine barely
gets into the RPM range at which the runners have resonant effects, so the
runners are straight dumps for most of the RPM range. No part of the range
is enhanced or detrimented relative to the rest.
Compare to TPI with 26" runners, which enhances low RPM torque heavily at
the expense of upper RPM torque and the LS1 with ~14" runners that enhance
upper midrange at the expense of extreme high RPM and extreme low RPM.
(despite shorter runners, LT1's pull harder off idle than LS1's, but the
LS1's power to 6 or 6.5K really runs away from that of the LT1).
> From: Jacob Vogelpohl <vogey@...>
> Subject: Re: Re: building your own intake
> what do you mean by dry?? it sounds like it is, i want a multi port fuel
> injection, not tbi, wont suport enough HP barly 400 im told and i want
> the look of the lt-1 or TPI that would be suficent, so how do i figure out
> runner size? i was thinkin 2'' runners, i don't want to kill low end
> tourque, but i don't want to choke it on the top end either, it will need
> to breath to 5500-5800 RPM
> david brode <dbrode@...> wrote:Jacob,
> You talking dry intake with port injectors? If so, you could cross the
> runners from side to side, even U-turning them back around, into the
> side of the plenum, on the opposite side. Like an tuned port chev
> intake. I'd make the runners as long as possible.
> --- In Cadillac_Performance_Association@yahoogroups.com, Jacob
> Vogelpohl <vogey@y...> wrote:
>> what would it take to build your own intake for a 500 cad? i want to
> build a lt-1 style intake for my engine (want it to look stock in my 94
> buick roadmaster estate wagon) i was thinkin a short tunnel ram style
> with a throttlle body on the end? is it possible? its really a street
> engine. so how would i build the intake so im not killin low end torqe?
Don't bet on it. Unlike the exhaust side, the intake has only the
atmosphere pushing it.
If you don't believe me, do some looking out there for intake
manifold design, and you'll see.
btw - off topic, but 2" headers aren't enormous on a 500", esp a 5500-
5800 rpm one.
--- In Cadillac_Performance_Association@yahoogroups.com,
> 2" is almost certainly too big. 2" primaries on headers areenormous, and
> intake runners need to be smaller than exhaust runners owing to the
> smaller volume of intake than exhaust.