What is the biggest restriction of these two, and is there any way I can siamese the stock runners?

 

I think it's a combo of both but I can tell you that a stock base is only good for 4500rpms. After that the fuel flat lines and there is no more power.

 

I would say stock runners. The base can be ported and siamesed. runners can not.

 

It's true that the base can be ported etc. but that's not what I thought he was asking. He was asking which of the two was the most restrictive. In my opinion, it's the base. When I had tpi I had my base ported and it didn't show much improvement at all.

 

The stock runners can be siamesed, but I wouldn't recommend it unless you're a expert DYIer. There is a thread on here that a guy cut out the centers of the tubes and weld in sheet metal rolled to fit the contours.

The runners and base both have ~1/8" tapers on the radius of the passages. So I imagine if you clean both those up and port match them you'll be better than stock.


--EDIT--

Dug out the post for you..

https://www.thirdgen.org/techbb2/sho...threadid=96858

 

I thought I had some information that would answer your question. Here is what I do have.

In one test the stock runners flowed 203.17 CFM. In the test with both the runner and stock base the flow was 198.72 cfm. I could not find a stock base only test. From these numbers the flow is about the same for both.

Like was said above the base would be easier to open up than the runners.

 

A good set of runners on a stock base will flow about the same as the stock runners on an aftermarket base.

What if any benefit you see from changing the base and / or runners will depend on the engine combination. If you’re basically stock you won’t see a lot from doing either or both,, at least not for the money you spend. If you have a hot combination, you should see enough gains that you shouldn’t feel like you’ve wasted your money.

If you’re going to buy one or the other,,,, if your heads are stock, I’d do a minor clean up on the stock base and go with a set of runners. If you don't mind using a grinder, SLPs are good for the money,,, but I wouldn't consider them "bolt-on". Plus, you can siamese them further for a little more upper RPM. If you have aftermarket heads, I’d recommend buying a good used aftermarket base and saving money for the runners later.

 

So according to the thread about siameseing runners. If I do this to my stock runners, or buy a set of siamese runners I will have shortend my runner length to approx 7" which is approx the same length as a dual plane manifold therfore I should be able to get around 5500 rpm out of my 305 without it fallin off with the right cam and head combo. Correct?

 

That also depends on the exhaust system. Seeing as you have the 305 you should be ok on the rest of the intake system. I would have to say yes to your question. The SLP runners are a good source if you are modifying the runners.

As you have probably read elsewhere I'm shifting at the 6000rpm point on the 1-2 shift and 5600rpm on the 2-3 shift. Next time at track looking for the 12.6's and 106mph.

 

Are the SLP's fully siamesed or just part of the way? Would box stock SLP's flow as well as the modified stockers and if they are not fully siamesed would they still pull above 5000 rpm?

BTW I do have a 3" cat back and 1 5/8 headers plus all of the free mods including a Adjustable Fuel Pressure regulator just for your information.

 

ttt

 

delete

 

[QUOTE]Originally posted by fireturd350
[B]The stock runners can be siamesed, but I wouldn't recommend it unless you're a expert DYIer. There is a thread on here that a guy cut out the centers of the tubes and weld in sheet metal rolled to fit the contours.

The runners and base both have ~1/8" tapers on the radius of the passages. So I imagine if you clean both those up and port match them you'll be better than stock.


Isnt that a ferrous on non-ferrous metal?
sheet metal and aluminum? howd did he weld that?

Ive been tig welding for some time; cant say Ive ever welding sheet metal unto aluminum?

sorry for being off topic

 

I think he brazed it on. I might be wrong. It says somewhere in the linked thread.

 

[QUOTE]Originally posted by fixin87formula
[B]Are the SLP's fully siamesed or just part of the way? Would box stock SLP's flow as well as the modified stockers and if they are not fully siamesed would they still pull above 5000 rpm?

Well anybody

 

Box stock, SLP runners now come siamesed about 1.25" or so into the runners. At one point, I believe they used to offer the fully siamesed ones... but that was long ago.

 

But they can be fully siamesed easily. Correct?

 

Tons of meat on them from the looks. If you can port for $250 it wouldn't be a bad deal. AS&M offers large tube siamesed runners also but they're $475.

 

As you can see from the above picture the SLP runners are partially siamesed at the top. I have the early style SLP runners which came from the factory with one pair fully siamesed from top to bottom and the other pair siamesed in about an inch at both top and bottom.

I did some heavy duty modifications to my SLP runners as seen in the attached photo. If you siamese the runners at the bottom about 1 1/2" it will raise the rpm band on your engine. Be sure to port match top and bottom. I would also highly recommend the Edelbrock TPI base. Allen

 

what'd u use to port?

alil pneumatic die grinder?

 

Mainly sanding drums but some with an electric die grinder. Allen

 

nice, ill be doing the same to mine
except pneumatic style

 

hey fireturd, u can tig weld sheet metal and aluminum, i was spacing out .. just dont use any filler rod and your set!

 

Good to know, too bad I can barely stick weld anything.

 

stick welding is Arc welding, hardcore stuff .. strongest form of welding.

whoever welded them use a Tig torch. Using a foot pedal
to adjust heat and the rod to add metal when needed.

 

[QUOTE]Originally posted by 1989GTATransAm
If you siamese the runners at the bottom about 1 1/2" it will raise the rpm band on your engine.

But would 1 1/2" be enough to get it to pull to 5500?

 

Both cylinders would be able to use both runners which in a way doubles the runner size. The effective runner length would be shortend to the length of the manifold and whats in the heads. Maybe 11 inches.

Mine does quite well to 5500 on the dyno. In fact I have mine trans set up to shift at 6000rpm on the 1-2 shift and 5600 on the 2-3 shift.

Of course there is more to it than just the runners. That is only one piece of the puzzle. You need a good free flowing exhaust system, a good cold air intake system, at least a ZZ4 cam and number one good heads. Allen

 

I dont know where my brain was. I just realized after reading the last post that I don't have to fully siamese the runners to get that effect (one cylinder pulling from both runners). Fully siamesing the runners just adds a little more volume. Sorry bout the brain fade.

1989GTATransAm
So you think an LT1 cam would fall off before 5500 rpm even in an LB9.? Wouldn't a ZZ4 be a little much for a 305?

 

I don't know about the zz4, but the LT1 cam would fall off way before 5500.