LT1 intake....siamese runners?

cutting out the runner divider...
any benefit?
little more volume?
anyone done it?

some TPI setups seem to benefit from it.....would the LT1?
wouldnt be hard too do! would make porting a bit easier

Cutting out what? The space between the Intake ports?

cutting out the runner divider...


yes

That's an interesting idea! It seems like you wouldn't want to take out the whole divider, but I wonder how much of it would be optimal (if it would show a gain) to take out. This would be a good advanced tech topic, in my opinion.

do it and tell me how it works out :D

That's an interesting idea! It seems like you wouldn't want to take out the whole divider, but I wonder how much of it would be optimal (if it would show a gain) to take out. This would be a good advanced tech topic, in my opinion.


what part of the divider being left in would be beneficial, at the beginning of the runner (entry) or end of the runner (exit)? and why?

what part of the divider being left in would be beneficial, at the beginning of the runner (entry) or end of the runner (exit)? and why?

I really have no idea. Most of the ideas I've heard for improving the LT1 intake involve adding more volume to the plenum.

If you took out the whole divider wouldn't you have cylinders fighting eachother for air? With the runner you are simply setting aside more of a volume of air for whenever the cylinder draws it in right?

the cylinders that would be siamesed, wont be the ones firing at the same time or firing in sequence...

with the divider completely removed, a gain in volume would be there but how much and is it worth it...?

it seems like only the runners on the back side of the divider would gain from the removal tho since there wouldnt be any change too the intake for the cylinders that are on the front side of the divider....altho the added room with the divider removed might aid in porting of that area for those cylinders...??

Keep in mind that a gain in volume takes away from velocity of airflow, holding all things else equal. I'm not necesarily talking about plenum volum, but you're turning two runners into one, and I'm honestly not sure how they'll react. I have seen siamesed runners for the TPI like you were talking about, but that's a vastly different set up to start out with.

and thats why i'm hoping some of the more experienced fellas will chime in and shoot down any hope i had of this gaining anything at all :D :death:

Keep in mind that a gain in volume takes away from velocity of airflow


My thoughts exactly. By removing the majority of the divider would that not cause a whole lot of turbulance at the intake/head transition point?

I would think that the amount of divider you would need to keep to provide velocity and smooth airflow would negate any gains in the first place.

any other takers on this?
Rich, Fred, Bret, Phil, Joe, Mindgame....? :D

i have heard of this...my one buddy did it to his car...if your looking to get your fuel mileage, i wouldnt do it, but for an easy HP mod...its a good idea..

1)You lose intake tuning. LT1 runners are too short now, and you make it worse.

2) Air will have a 3-sided runner with only a 'virtual' wall on one side which might disrupt flow. You could verify this on a flowbench with a modified manifold.My guess is worse flow, not better.

3)Fuel may have a hard time deciding where to go because it will now be sprayed into one side of the siamese port and not directly into an individual cylinder port. The consecutive firing cylinders (5 & 7) will probably be the worst.

I'm trying to think of the up side....nothing much comes to mind.

Siamesed runners for TPI were in the upper portion of the manifold, right? That was done to shorten the overall intake tract length to something around 5-6 inches from more like 16+.

Look around for other modern (post 1950s) intake manifolds for NA engines that use siamesed runners. Study them and how they improved engine performance. BTW, post the list. I'm interested.

My $.02

Ditto....

This is a big big big mistake... Already been tried on SBC intakes years ago and it sucked there too.

Bret

and as a side effect you're shortening the lt1's already too short runners. this is a really really bad idea imho. its right up there with making the runners in a vic jr siamesed. runner length and cross sectional area is a very critical piece of where you make your power at and how much you make because if effects the rpms you can run. just hogging out part of the divider and shortening the runner and would create very negative results if you ask me. tpi's benefit because they have a runer thats way too long and way too small. so you're not really hurting them when you knock down the length of a runner thats 13" long and then the siamesed runner acts like part of the plenum. but keep in mind theres still a good chunk of runner in the base manifold of those a good 6" or so.

tis why i asked before trying :)

so then my other big "can o worms" question arises....
short of converting a carb style or going custom with the intake (including Steve Quinns hybrid type)
what ALL can be done too the LT1 intake on top of removing the injector ramp, porting and polishing the runners too get maximum potential out of it without needing unacceptable rpm (7000+) for a street motor?

time has gone by now since this intake has been available but has the wall of what can be done too it been scaled already?

btw, thanks for answering fellas

Hmmm.... The effect would be like makes the runners even shorter then they are and adding Plenum Volume.

That is my guess lets see what the big boys say ;)

Well plain and simple... not enough. Throw more cubes under it and it all gets worse.

Bret

Copying it didn't work... somebody moved the original from LT1 Engine Tech to "Advanced Tech"..... now we'll try the "merge" option, and delete the duplicates. :rolleyes:

Thanks Fred