HEY TPI Guys,

I came across these pics in a "Madmax" thread. It is a siamesed TPI intake. Madmax is some kind of 3rd gen guru on the engine/tech board. He sure does some interesting mods from what I have seen so far. This is one of them. Last month I was about to jump into an eBay bid on some after-market intakes but then I came across this thread and couldn't resist the opportunity:

https://www.thirdgen.org/techbb2/sho...siamese+intake

It seems there is (modest) hope for the stock TPI intake through siamesing the ports. IMO a pretty interesting idea and eminently doable -- seeing as I have carbide bits and a dremel. My intake will be off for a few months while my heads get done. Seems like a no brainer.

I've already got SLP siamesed runners I think I will grind/siamese the lower portion of the runners to maintain the siamese for as long as possible for the tuned port.

From what I have read sofar (plus various PMs) I can expect to see minor loss at low end rpms and big gains at high end (relative to the factory setup of course). As you can read from Madmax his peak went from 4800 to 5400rpm and gained 18hp on his stock 305 (not sure if those dynos are in the link ?).

a grinding I will go... a grinding I will go... hi-ho-the-derryo a grinding I will go...
RP.

 

Now this is a Siamese. My TPI's body guard! I too am about to do this to my other intake. Should be profitable (HP wise) Nice link and thanks. gives me a better perspective. Watch out my baby may eat your Siamese

 

Accel or Daz can clear this up better.. but wouldn't the low rpm drop in torque be a problem due to the fact the earlier firing cylinder would be taking in the reserve air for the other cylinder before the other cylinder in the siamese draws the air?

Couldn't this be fixed by decreasing the runner length and increasing the reserve air in the plenum? This would in turn help in the upper rpm ranges as well too wouldn't it?

 

Interesting point Slade. There is no shortage of debate on the siamese-the-TPI threads out there.

Some say cyl pair 5-7 will starve, some say no problem. Some talk about loss of bottom end, gain in top-end. I found enough posts from people who have done this mod to free me of worries about what it will do. Besides if it really screws up well, I was going to buy a Lingenfelter or ASM unit anyway...

I will be using SLP runners and these will be siamesed on the bottom as well as the top then I am going to siamese the plenum to match the runners. Once air has entered the TB there will be two dividers for each pair between the TB and the head. Each divider will be about 3-4 inches long, one in the runner itself and the other in the non-siamesed portion of the TPI intake (closest to the head).

I am expecting to see some drop in lower rpm torque and some gain in upper rpm torque. I'll find out on dyno day.

RP.

 

I'd take a gain in upper rpm torque anyday.

The goal is to make the torque curve as flat as possible isn't it?

hmm 275 ft/lb peak dropping to 200 ft/lb by 4500 or holding 250 ft/lb till 4500?

I'd choose the 250 ft/lb flat curve...

 

I really dont see the point in siamesing the ports at the top, at the plenum sides and down into the runners, having them seperate again in the middle of the runner, and then siamesing them again at the intake manifold, into the bottom of the runner, and the intake base. What is the effeictive point of going from siamesed to seperated, back to siamesed and then to sperated ports agian???? Seems like alot of time wasted to me. If your planning on buying and aftermarket intake anyways, then i would go ahead and do it right now. Spend your time where it will be more worthwhile....

Stang Eater

 

Didn't he say he will be siamesing the SLP runners too???? I need to get me a set of those SLP runners.

 

how are you going to FULLY siamese the runners???

 

Or spend my money -- an ASM or Lingenfelter intake is over $500 CDN.

RP.

 

Mattsgarage has a set for $217 US on eBay right now.

RP.

 

I am not going to fully siamese them. There are those who have and they are running big cube hi-po outfits so it works for them. Waste of time on my current setup.

I planned on siamesing into the base of the runner about 1 inch there are those who have done this and seen positive dyno results. The top of the runner is, of course, already siamesed several inches by SLP.

RP.

 

palric

i too have been watching this mod of his for some time. as well as some others that have tryed it.

there is one guy(i cant remember his name) had to rebuild his engine 3 time. for what he said was a direct result of the base being siamesed. each time it was the #7 running so lean that it just burnt it self up. if i ever fine the link i will send it too. if its not to late.

you are braver than i. that is one mod i just will not do.

 

Cool that you are checking it out. I did some research on this too.

I found 3 threads with references to the 5-7 starvation issue and in each case it was posted by someone who knew someone who had blown the #7 piston due to leaning out as a result of the firing order vs. fuel starvation, etc.

The earliest post that I could find was from spring/2001 the guy later posted that as far as he could tell the blown engine had in fact nothing to do with the siamesing rather it had failed due to other reasons.

So I started pestering some of the other people who had posted about people that they knew whose siamesing had led to a blown #7 piston. The responses I got were pretty much just more hearsay and non-facts. I could not find anyone with direct experience on this subject (eg: had actually blown #7 due to siamesing).

On the other hand Madmax and several others have been running siamesed intakes on their car for several years now with no reported issues.

I understand your reluctance to do this mod on a new engine there is alot we don't know about it. But I have an old 305 with eyes on a 400 -- so am not really worried about it.

adious,
RP.

 

haha...yeah, here's my siamese for ya! A real terror!