HwyStar

Does LPE still sell those siameased plenums? I've been toying with porting mine...

USAZR1

I'm sure Lingenfelter will still build you one,Rick. Bill Kirchhofer can build one for you,too,for a lot less money.

VetteBabe1

I think Jeal sells them too....heard through the grapevine. Also heard it does not do any good, more like slows it down, unless you have a 415 (too much air flow).

4cefed

Yes he still does them at a clip of around $5,000 each for the full blown version.

USAZR1

Bill Kirchhofer is a Jeal representative. Mine made 5rwhp more on the dyno(395 vs 390) with an A/F ratio of 11.1 at WOT. I think it's safe to say there's another 5-15hp available through chip re-calibration. Is it a cost-effective mod for a stock displacement LT5? No,,but it won't "slow the car down",either.
Clint

VetteBabe1

Oh ok....I only know what I hear....

And I do know that it looks AWESOME...are they really $5000, I heard, again, heard, $2000ish.

USAZR1

I've heard LPE wants as much as $7K for a siamese plenum and injector housings but do not know how accurate that number is. Bill Kirchhofer gets around $1,500 + exchange for just the plenum. The Jeal inscription on the top of mine was done by a friend in OKC with a CNC mill.
Greg Van Deventer Machine built the experimental injector housings for my engine. The bifurcation on them was probably just a little too radical,though.
Something a little more mild would have made even more power and torque.
The cylinder heads on my LT5 were also just Extrude-Honed instead of ported. Pulling them back off for porting to match the new top end would be a lot of work so I was going to wait till later.(402" or 415")
Clint


[Modified by USAZR1, 9:10 PM 7/26/2002]

HwyStar

$5000 for the plenum. :eek: :eek: :eek: I guess porting my plenum and the injector housing plus headers with a tweak on the chip would be a lot more cost effective for a stock displacement motor. Could do all that for less than what Jeal or LPE would charge just for the plenum. I guess there's my winter project this year. :)

USAZR1

I believe a siamese plenum is a waste of good money on a stock displacement LT5 unless you have done all the other necessary mods to compliment it. Even on my car,it was probably overkill. But,I only had around $2K invested in my top end and it did make more power on my LT5,so it wasn't a waste of time. Greg and I learned a lot from the experiment and would do it again,if given the opportunity.
Clint

4cefed

He adds a lot of volume on the full blown versions. Something like 1 to 2 liters more than the stock volume. I heard that in P Smiths car the coils were moved to the firewall because there was no more room under the plemun. There is a lot of work to do this correctly. Labor intensive job.

Rkreigh

moving the coils is a good idea, but it doesn't look like there is much roolm without moving the PCV and the regulator.

I'l like to hear more about how to do this mod and the extreme plenums.

bill does good work, as does Greg V. and Jim.

I would trust any of these guys to do some good work for you. the full boogie siamesed runners are really more for a BIG LT5 and even then, work better at high rpms.

my LPE is tuned to make power at 7500, but at 2k it does feel a little soft in comparison to the stock engines.

porting and cams move the power upstairs, and make the 4.10 gears work well too.

stepping up to the bigger manifolds is a great idea, but don't go crazy or you will lose too much low end. it's flow "quality" (ie velocity & flow) that is more important than just hogging everything out.

cya.

:yesnod:

mvabob

With the siamesed plenum you lose the "stock" appearance. Do all 415's have siamesed plenums? Can a big inch LT5 retain the stock exterior and still pull comparable hp. readings?

4cefed

Mine will not have the siamese plenum. Goerge East has a 402 with a non siamesed plenum and is making really good power with his. 520+ rwhp.
I may break down in a year or two and get one, it probably will not be LPE at $5,000 a pop. The advantage of leaving the stock appearing manifold are: 1. stealth 2. cost 3. regain some (small amount) of low end torque????
my 2 cents


[Modified by 4cefed, 4:28 PM 7/27/2002]

USAZR1

A siamese plenum doesn't eliminate the secondary port throttle system,Joel,and low end torque with a 415" will probably be the least of your worries. :D
On a serious 385",402",or 415" a siamese plenum and matching injector housings will probably be good for another 25-40hp.
Clint

4cefed

I know they don't necessarily required butterfly removal because the upper doesn't have anything to do with the secondaries butterflies. However, I thought LPE did that to the injector housings on his full blown versions. I was sure P Smith was telling me that his did not have the secondary butterflies in the injector housings. Could be wrong, definately don't know much about a LT5 thus Aaron doing the motor. I do fine with small block fords but these are a little more comlicated. :cheers:




[Modified by 4cefed, 10:38 AM 7/27/2002]

xsmph

I think ther are 'two" kind of modifications that we are talking about here.
the siamessed runners remove the divider from the inside of of the runners, and by doing some extra welding the mono runner cross area can be flattened out.
I believe the reason LPE charges $5000 plus, is because on the big motors they do what is called a "Dropped Plenum". this adds about 1-2 inches to the bottom of the intake plenum, so the engine has a bigger box from where to suck air, this means typically relocating the vacuum canister, and in some more extreme cases the coil packs.
I believe Phil DeJohn experimented with just removing the dividers from the stock plenum so they will lookstock from the outside, but siamesed from the inside. he did this on his white Heads and exhaust Zr-1 and picked up 1 mph and .1 in the 1/4 mile (Phil correct me if i'm wrong)

Now my thinkingis the following:
The fastest 415's out there trap in the 135.x mph in the 1/4 with bigger valves ($2000), and the siamesed and dropped plenum ($5000)

Phil's callaway 415 (motor by lpe) has trapped 134 mph with stock valves, std. plenum ported, and the small cams for the 415...
So your call.... but I don't think searching that extra bit of power is worth it.. it can get really expensive in a hurry!....

4cefed

It is a cost benifit analysis. To get 30-60 more hp you spend $7,000 additional. For a poor boy like me thats a lot of doe for a little show.

xsmph

I thinnk the "mild" 415's can do 530's maybe 540's rwhp with the .454" cams, and a cheap porting on the plenum that would just remove the divider inside the runners ( I did this to mine, and Jim Milstead did it to Jeff's car)..
I think the full blown 415's are in the 560's 570's.. so you are really looking at 30 more rwhp for $7000....
If money is no object.. who cares?, but if you are doing a 415 on a budget (if there is such a thing), then it is not worth it to me...

you can always do one of these on top of your mild 415, for 1/2 that and really move, but then you will need a driver :crazy:



[Modified by xsmph, 4:52 PM 7/27/2002]

DDSLT5

xsmph - absolutely stunning looking engine - do i have this right? This is a "mild" 415" with direct port nitrous injection? What kind of numbers are you producing with this monster?

Very Cool!! :cool: :cool: :cool: :cheers:

VetteBabe1

That looks totally bad azz!!!! :cool: :cool: