So, what was the general consensus on siamesing the tpi base? Is it a good mod only for all out motors or would a stock 350 gain anything noticeable?

 

So, it's that good!! Surely someone has some info on this!

 

with 80 something views nobody has any comments about this?? Did i forget to say please or something...lol.

 

I think the lack of responses is related to the lack of information on that setup. I'm still not sure yet about a stock 350 if porting will do just as much, thats quite likely. I will have 305 results hopefully before August and that should take care of that issue.

 

In theory, on a stock motor, it will kill bottom end power.
At low to mid rpm's on a stock motor it will kill port velocity since
you have two ports bleeding back and forth. In the time between
when the intake valve closes and opens again, the air in the
runner is still moving and actually compressing into the valve
pocket. When the valve opens again, the air is still moving down
the runner and can fill the cylinder more effectivly.

In a long narrow port (like the stock TPI intake) the air has a
great deal of speed to it which is great for low to midrange power.
As the rpm's and required air supply increase, you need to use a
larger port for more air and can get away with a shorter port
because at higher rpm's (4000-7000) the air is already moving
fast enough to fill the cylinder effectivly. But the larger, shorter
port kills low speed driveability.

A siamesed base may work well on a 400+ hp motor on a track
but would not work well on 350- hp street motor.

 

I'm wanting to have ~350 HP on my street motor..if I buy the Super Ram base and have it siamesed, how will that affect my low-end torque curve? Should I just leave the base unmodified and bolt it right in, if I'm wanting to keep the lowend? I don't plan on replacing the stock TPI plenem

 

The car is all stock except for the mods in my sig. I was just wondering if there would be any gains for me with a setup like this but it's looking like there wouldn't be much except maybe above 4000? Would switching cams help? I'm looking to upgrade my intake in some way and this method appeared to be the most cost effective if it worked. Would switching to a mini ram do the same? (drop velocity and low end considerably) Later on I'm planning on doing some form of abnormal aspiration but i want to still be able to drive the car until then.

 

The stock intake will make 350hp with a good porting/cleaning
and a 52mm throttle plate. I would not spend the money on a
Super Ram base just to make 350hp, just port match the stock
base then run a sandpaper hone through the ports for a few
weeks and it will flow with the best of them, well almost. But
it will flow a lot of air with just a little attention. I run the stock
runners and they make a tone of tourqe but I don't go much past
5,500 rpm either. I am setup with 2.88 gears in a 4890lb car so
I need tons of tourqe, well past the 425 ft lbs range. The upper
is easy. Hog the **** out of it. Port match "all" gaskets, nuf said.
The 52mm throttle body is a bit overkill under 350 hp but the
stock one is way too small so go with a 52mm. I made mine for
just a few dollars in materials, but it wasn't easy.

I run a 1996 Vortec cam with 1.6 rockers and 1994 350 high
swirl truck heads with mild bowl work and port matched, stock
base bored and honed till the cows came home to match head
runner cross section, stock runners with the openings cleaned
up, upper with egr walls removed and port matched to the
gaskets, throttle bores opened up to gasket size and 52mm
throttle body. With this camshaft this motor will pull tree stumps
out of the ground but stops making power just before 5,500 rpm.

 

I dont really agree with this. My 305 on a g-tech (yea yea I know) was faster with the siamesed intake than without, and although it had lost some power in the lower end there was still plenty left to break the tires loose. The car I did the testing on with dyno sheets and stuff is making less than 350hp at the crank and I still picked up power everywhere from 3150rpm up. The car feels stronger across the entire powerband although I have no proof of that on paper. Picked up 1.5MPH at the track with no other changes.

 

Mt favorite part of the whole 'siamesed base kills all torque' debate is: what about carbs? Nobody uses a carb intake with much more runner length than a mildly siamesed base and they seem to do ok, eh? And EFI can do one better than that since it has better fuel control on the low end it still tend to make more torque.
Sure, you might lose 'a little' low-end. But that was all overkill anyway. I'd much rather give up a little power on the bottom, especially considering my torque converter and timing curve will make it a wash, for real measureable power off the top.
I know, i know, i'm talking about actually modding a car as a system to go fast nstead of worrying about maintaining torque and staying slow. What the hell is wrong with me, i must be crazy?

 

As I said, in theory, on a stock motor, it will kill bottom end
power. Which in your case it did but you gained enough on the
top end to make up for it by the end of the 1/4. This is good
information to know. Does anyone else have motors they have
done this to? If so how far down the runners did you go?

If this is a good mod I may try it myself, I have a few extra
bases and wouldn't mind cutting one up for a good cause.

 

See. There's the flaw. Whats this 'kill' chit? I had an 85 LG4 (carb) w/ 3.08 gears that could burn the tires off the rims w/o power breaking. Short runners didn't 'kill' it, did they?

Yes, no doubt you'll make a little less low end, and a little less on the peak. But the gain across the board already seems to more than make up for it, even on madmax's high 14 second 305.

I hate talking too much smack here though. I actually should be track testing my siamesed base this weekend but my tranny is living on borrowed time after my last outing 2 weeks ago. My plan was originally to track test the siamesed intake before the converter goes in. My heavy 305 vert uses all of it's available torque to get out of the hole, and i have enough runs and practice in it that i could see the smallest change clearly in my 60' and 330' (to get an idea of what i call consistency. Last session at the track. 5 runs. ET all within 0.06 at the 1/4 and 0.02 at the 60')

Anyhow, now the plan is to see what a vigilante does w/ a stock 305 w/ headers first instead. Like i said in my other post, i'm sure any torque lost with the new base will be a wash w/ the stall i'm running. And if it isn't, i can move torque around in the bin w/ the spark curve.

If you're sitting on some spare bases, i'd definitely go for it. So far i don't think anyone can actually prove any ill effects, and there's a few out there who are running killer on siamesed bases. Your chance to get in on the ground floor of a new movement of fast 'LTR' cars.

 

Ok, stop beating me up. If does work without loosing too much
off the bottom end then I might think about it for my application.
I am running mine in a Jaguar sedan that weighs just under
5,000lbs, yes that's 2 and 1/4 tons of iron, leather and oak.
My best time is 13.89 @ 96 mph with 2.88 gears.

I would not want to upset the ballance I have now by shaving
too much off the bottom. This car is heavy and takes alot to
get it moving just driving around town.

Come on guys we need some more info from people who are
running a siamesed base.

 

What kind of converter / etc you running to get that tank moving so fast. That's flyin ET for that MPH. With any luck i'll be running pretty similar to that once i get my next round done as long as i can keep hooking. Only a 305, but a little lighter too (still a helluva lotta metal, leather and cloth though)

I expect by the end of the summer we'll see a lot more people with definitive results. Thats why i'm trying to encourage you and others to do it. The folks who have done it so far all like it and have shown gains. If you have a spare base, what can it hurt. Worst case, someone will buy it from you, lol.

Think about it. As nice as it is to holeshot everyone, wouldn't it be nice to not get passed at the 1000' mark by some punk in a new Z28 his dad bought 'em. A siamesed base on a stout combo should be good for at least a few mph.

 

It has a 700R4 with a stock converter and no shift kit. The car
hooks hard when all that weight transfers to the back on the
launch, I keep expecting something to break. It's as if you can
feel the cylinders firing like you can when you are lugging down
a 454 in a truck pulling something heavy.

I have had 2 encounters with 4th gen cars. A new T/A tried to
pass me on a highway running at 65 and I walked away from him
like he was sitting still. On a Sunday ride on the old river road
with lots of hills and twists I cam up on a newer Z28 while at a
high rate of speed. He saw me comming and would not let me
pass until we hit a 1 mile straight section then I got around him.
He stayed with me right on my *** at about 80mph until the road
straightened out heading into the country. He tried to pass me
but gave up at about 140mph and I just kept pulling away from
him. The Jag speedo goes to 140 and it was burried and the car
was still pulling pretty good. After about 10 miles we came to a
stop sign on a highway and I went one way and he gave me a
honk and a wave as he went the other way. I felt pretty good
on my 30 mile trip back home to where this encounter began.

 

...

2.88 gears, 13.8 ET's w/ 96 mph trap speed and 5000 lbs dosent sit well For me. Not without a LOT of power... Not to Mention a stock Stall speed and Transmission.

Im callin




Prove me wrong..

 

The time and speed are the best of 5 runs on a good road
using a G-Tech, I don't know how accurate the G-Tech is
but that's what I am going by. I have not had it to a strip to
get a real time on it yet, the strip is a long ways away.

The motor started as a 96 Chevy PU 350 Vortec. I pulled the
heads (I know, I know) and cleaned up the ports on a set of
94 Chevy PU 350 high swirl heads, the intake runners have
a swirl action to them and are designed promote more even
and complete combustion. I did not have them flowed but
looking through the intake port the valve guide is floating out
in the middle of the roof with a ramp that swirls around the
back side of the giude to set the air in motion. The guy that did
the valve job said the local dirt track guys use them for midrange
power. It is also setup with 1.6 rockers on the Vortec cam and
the stock intake which has been ported for all it's worth and a
reworked throttle body with airfoil. Yellow top injectors and an
AFPR set at 52lbs and an 88 Vette prom. Ported ramhorn
manifolds with no catalytic converters and 2 1/2 Mandrel bent
duals out the back.

 

Why so quick to call BS? So if the G-tech is off and say he's running a 14.0@91 that's still pretty good for that tank. Honestly man, if you lose any low end what's it gonna hurt, your smokey show off the line? The midrange and high end you gain more than offsets any lowend loss and maybe you can leave harder. If all you want is a pleasant cruiser then be happy with what you have, it sounds like you are doing real good with it. Sounds like a nice ride.

 

Is that 14.55 at 98.6, bort?? That's a really high mph for that time.

By the way, g-techs report pretty accurately 1/4 mile times, but a little higher on the mph because it is calculated differently at the track. That would be like 13.89 @ 94 at the track, which is amazing for such a low mph.

 

I read this post and had to make a reply. You guys got me worried that I made a mistake with Siamising the base. I cut in exactly 3" deep on both sides of the base, and gasket matched EVERYTHING. My intake is going back in the car sat. I am running stock 350 block, heads and exhaust manifolds. I have done all the normal easy first cheap basic mods so far. I run in the 14.4's with 2.77 gears. I did some tranny work last fall, and haven't run since then. I want to make it to the track this spring, BEFORE the 3.73's go in. I am very anxious to see how it runs. My goal is to get into the 13's.

Wish me luck!!

 

Here she is.

 

Another shot.

 

Another shot. I like to think of it as a 4dr Corvette with all the
Brittish electrical bull****. It launches hard, REAL HARD. It don't
get much tire spin at all when all the weight transfers to the rear.
Just bites the ground hard and pulls hard. Sooner than later I
just know something under the rear of it is going to break and
it ain't going to be cheap.

 

Mike, when you get the new intake to the track let us know if it
helped the stock motor without the gear change.