1 5/8 or 1 3/4 headers

x2

 

x3

 

Thanks for your input, Steve. Which ST300 did you swap from, the one with switch pitch, or without? Was it a direct swap with no other parts changed? Was it in the same car?

According to the facts, the TH350 uses twice as much power to turn (36 vs 18 (vs 44 for the 400)), so I find it very interesting that experience shows a gain of 40 hp. With all the ranting and raving about how the 'butt dyno' can't be trusted, telling someone it 'feels' like something sends a double standard message. Are you sure it didn't feel more like 50 or 60 hp gained?

My experience shows that the only place you'll 'feel' an improvement swapping from the ST300 is at a dead stop take-off, and that's if you have the proper traction. Once you shift into 2nd gear on a 3 speed tranny, your gain is negated and overcome with the extra parasitic loss.

I suspect this is whole thing is merely an attempt to goad me into a response...

I'll look forward to the test results the OP reports after he gets things going. If he decides it's as terrible as everyone else here seems to think with their extensive experience using the ST300, I'll happily buy it off the guy for a fair price. PM me for details on how I can be personally contacted to do so.

 

Relax Gary, I said feels like, no actual numbers that I usually supply. Yes I pulled 40 out of thin air. While I am not a fan of the butt dyno this is a change you can feel and back up. Good memory by the way. LOL
I would not be surprised to see a decrease of .400 seconds on the track making this switch.

The only drag cars that are using them are very light cars that turn lots of RPM.

I've never had a switch pitch and its been years since I've played with a 2 speed nor would I ever want to. They were terrible. Theres a reason modern transmissions have 8 and 9 speeds.

Oh and I never Goad, I leave that up to my minions. Thats a joke guys.

 

Haha, thanks Steve!

The header video suggests that the 1 5/8" header would be the optimal choice for a 350ish CID engine running less than 500 hp.

Any reason you chose the larger one? Just curious.

 

Looks impressive!

Also might be a help with that 200 shot as mentioned elsewhere.

 

I was thinking about this build and was wondering why he is using such a mild cam with the new SP3 intake(let alone using factory rods), a 200 shot would probably explain it? If that is the case then yeah the 1 3/4" would be better when using that much juice. Would be able to increase HP without having raising the RPM to high with the N0S, cool.



Derek

 

TA helped in this combo. I was told that was about the most Lift you want to run on factory valve train ".500" or so. This build is for the street and pretty mild. The testing, which isn't a lot, has shown the SP3 to have solid low end support due to the long narrow runners. Kinda like the heads. The TA dual plane hasn't really been shown to help low or high sooooo I'm taking a bit of a chance. I know it's on the edge but hopefully it's not the same traditional Victor Jr small block chevy single plain.
If it absolutely kills bottom end, it's easy to change and hopefully sell! At least it will be some more info on this elusive intake BTW, I'm having this combo dynoed at Brannon's Performance in Madisonville KY. At least that part won't be conjecture. Maybe we could start a betting pool on closest HP n Torque numbers!

oh yeah, the factory rods have been shot peened and smoothed to alleviate stress risers. ARP hardware was installed and ends resized. I was told these would spin to 7000ish a few times and be OK. The TA290H is 1500-5500 and my rev limiter is set at 6K. Is this not safe?

 

It should be fine. I would trust TA.

I'd like to see a comparison on the dyno of the ST300 vs a 3 or 4 speed auto to compare the parasitic loss.

As far as the headers go, the occasional shot of juice isn't really going to warrant running the large headers unless you're trying to milk the most out of it at the strip, which it doesn't seem like you are.

Would you use one part over another that would benefit the car only every now and then, or one that would work best most of the time?

Pros and cons.

On that header video, using the larger 1 7/8" headers actually hurt performance, so bigger is not always better.

With 50 less cubes and way less than 550 hp, it's fair to say you could step the header sizes down one, so the 1 3/4" that was best for the 550 hp, 6500 RPM 400 CID engine would make the next size down better suited for the Buick 350 combination you have.

That's just logical, don't you agree?

 

With that cam and hyperutectic Pistons at near 9.9 compression I don't think low end torque should suffer much at all. Just make sure cam is degrees per cam card not just line up per timing chain.

 

Hey Derek, cool name by the way. LOL

I wouldn't believe that if I were you, maybe if they were sbc factory rods prepped that way seeing how those are forged while the Buick rods are cast.

Not sure if you read post # 8 in this thread that Sean posted;

http://www.v8buick.com/showthread.p...00-2-speed-transmission&p=2641243#post2641243

Its about a race team that used the sbb 350, and they talked about how the rods would fail right around 6,500 RPM among other things discussed.

Your rev limiter at 6,000 should be safe, you might even be able to get away with 6,200. When you have it dynoed it'll probably max out on HP around 5,700 RPM or perhaps a couple hundred RPM more with the SP3? So no real need to rev any more than 6,200 anyway.

If you plan on spraying N02 a lot then the 1 3/4" headers would be the ones to get. But if the N02 is only for special occasions then the 1 5/8" headers would be a good idea. It should be a good runner, I can't wait to see how it turns out.




Derek

 

Cool combo this should be really good... In the future I plan to do a 3 way intake manifold dyno test with the Ta dual plane, Ta single plane, and my custom single plane. Engine or chassis dyno?

 

You guys are great!!! I can't wait either
Thanx again for everyone's input. Merry Christmas

 

Sorry I missed your question Sean. It's an engine dyno. I guess I could do a chassis dyno after install and compare the two.

 

Engine dyno is nice as its way less variables, that will be fun! Not many dyno tested builds on here. I will dyno test my good engine without boost then put it in the car and do a chassis dyno with the turbos.

My guess on the Hp and TQ is:

370 HP at 5900 RPM
425 TQ at 3800 RPM

HP will stay over 350 hp all the way to 6200 RPM but peak at 5900....

 

I will be very happy if it hits those numbers for sure!!!! TA said between 350-400 depending on how well the heads are massaged.

 

http://i349.photobucket.com/albums/...B-F64A-4A0F-8E62-7E5124549A01_zpsyqvpklo8.jpg

just seeing if this works

 

Go to "share" then "get links" then copy and paste the one that looks like this:

http://i349.photobucket.com/albums/q397/derekv3/Mobile%20Uploads/2016-12/71E8806B-F64A-4A0F-8E62-7E5124549A01_zpsyqvpklo8.jpg[/IMG[/URL

And the pics will show like this:

[URL=http://s349.photobucket.com/user/derekv3/media/Mobile%20Uploads/2016-12/71E8806B-F64A-4A0F-8E62-7E5124549A01_zpsyqvpklo8.jpg.html][IMG]http://i349.photobucket.com/albums/q397/derekv3/Mobile%20Uploads/2016-12/71E8806B-F64A-4A0F-8E62-7E5124549A01_zpsyqvpklo8.jpg

 

I would pull the 2 speed and put in a 2004 trans. the 60 fts will suffer with the 2 speed and then you will lose the off the line performance. With 455 that would be different but not with a 350. The low first gear with the 200 trans will get you going right now and not later. I run 1 3/4 headers. The difference between a 1.80 60ft and a 2.00 60 ft is a car length... you just lost.

Soon as you put a cam in the engine will not get going till 3000 rpm. .

 

I wouldn't recommend the ST300 for maximizing drag strip results either (I've said this before).

Geeze that trans is a hot topic, isn't it? lol