What is the difference in the too i kno how they look is different but what about performance wise what is siamese for and what does ltr improve like rpm range hp and tq.

 

Here is my experience. From stock went to SLP runners and Edelbrock manifold. Horsepower and torque increased. SLP has shorter runners. Then fully siamesed my SLP runners. Horsepower and torque went up again. I have never lost horsepower or torque with any mod I have done. Fixing to up the HP and TQ again. Currently at 330RWHP and 370RWTQ.

 

To really oversimplify, the siamesing allows more overall air. They will improve peak HP, and it will happen at a higher rpm. Same with torque. It'll happen at a higher RPM. Why this can be bad, and this is a TOTALLY general statement, is that "normal" non wide open throttle driving really uses low end torque. Due to siamesing, your peak torque isn't necessarily "low end" anymore.

But realistically, the worst possible intake for this is probably the Mini-Ram/LT1 style intake. Peak torque moves way up the powerband, and there are plenty of people using those intakes who don't seem to have any trouble with "low end"!!!! ....so I can't see any normal driving, or even race situation where siamesing runners could be a bad thing.

 

I'm all for siamesing, but on the LT1 intake and LOW RPM topic I just wanted to throw something in. On both LT1 intake swaps I've done, a 800-1300 RPM "Surge" becomes noticable at times. I'm told from the LT1 crowd that this is due to the disruption in airflow through the plenum. I can't remember, but either the back two or front two cyl.'s will run lean at times at low RPM's, creating the mentioned surge. I always noticed this in my Roadmaster (which has an LT1), but I never knew why until it was explained to me this way, and evidenced by the same event occuring on Gen1 SBC's with the LT1 swap that I've done (2).

Just something interesting - about low rpm performance - upper RPM performance is of course killer, but siames'ing seems llike a better route, IMO.

 

Yep, I've heard that too.

Torque, HP, and where they're made can be REAL tricky if everyone isn't comparing apples to apples. 1989GTATransAm mentioned that he never lost torque or HP. What wasn't mentioned was how it effected the powerband. A perfect example of this was GMHTP's article on "Ram that TPI" where they swapped a Stealth Ram on a built 355 TPI. The Stealth picked up IIRC about 40 or 50 horsepower. BUT-what they don't tell you is that until 4800 hundred RPMs, the TPI made more torque and more HP at EVERY rpm. Now I'm not saying which is better, and we're not talking about driving styles, and where not talking about race or street car, but the point is that the FACTS can be misleading.

 

You also can't go by what people "remember" - It was estimated to be an approximate 38hp difference peak to peak and there IS a comparison chart in the "Ram that TPI" article. However, they left out the graph (below) that was supposed to accompany the numbers (due to space limitations) - no denying the visual differences in the power curves,, which should give an indication of why it was near impossible to hook the TPI/SLP combo with the peak TQ and the torque multiplication of the stall converter hitting so close to peak torque.

To the original poster, I kept taking the SLP runners off grinding away at the divider until the ET and mph leveled off. I ended up at a little short of the halfway point on the runners on the approximate 400 horse 355. As other has said this DID move the power curve up the rpm scale - about 400rpm. I know that any shorter and the car would have slowed down, but that was on this particular application. Larger more powerful engines in cars with low gearing (higher numerical) should want less length and / or larger diameter runners,, smaller less powerful engines in cars with higher gearing (less numerical) might want more length and / or smaller diameter runners. It is all about the application or combination (engine and car).

 

BadSS. Well said.

Let me add that I'm running a 700R4 transmission and the dyno graphs do not start until the motor has reached about the 4000rpm mark. I don't know what the torque is doing below that rpm for sure but I can tell you it is higher with the mods at the 4000 mark. If one were to extrapolate it is most likely higher below the 4000 rpm mark.

I have posted my dyno graphs on this site and they are available for review. Can't wait to get my next motor installed. Should be in by Thanksgiving. You never know about these things but hopefully my siamesed TPI will be well above the 450HP mark at the flywheel.

 

I agree with everything that was said. While the facts of the Stealth Ram swap are available, they conveniently dont really go into too much detail about the "under the curve" power in the article. GMHTP is HORRIBLE for trying to sell products in their articles.

TPIS does this too. Bone stock L98, swap on the mini-ram, pick up 95 horsepower!!!!!! Yeah right. While the fact may be correct, at a certain RPM, if you don't know better, it reads like it's a peak to peak gain. It's not wrong, it's just good marketing.

Again, my ONLY point is that you need to look at the whole picture!!!!