I just posted about not getting the larger 1.55 exhaust valves and thanks for the help on that! With my combo I've heard to stay with the smaller primary tubes for enhanced low end. This is solely a street car. I'll list what I have: 68 Lark Custom, 350 .030 over with hyper 10.1 slugs measured 9.7. Stock points dizzy with FAST digital conversion and coil. All oil mods. Heads have TA stage 1 intake valves ported and polished with 3 angle VJ and TA stage 1 springs. Heads are gasket matched. SP3 intake with QF 750 annular boosters. TA290H cam/lifters and TA cam bearings. ST300/2500 stall and 3:42's out back. Which set of TA headers and why please
I think it would work fine with either one. There will be differences in opinion about which one and why, but that's my best summary. Which type of exhaust and mufflers are you using? Any merge pipe? (X pipe) The smaller one won't necessarily make more torque so much as it will move the powerband down a little vs the larger one--which may be desirable with the use of the ST300 transmission. If there was a deciding factor, it would be that (to me). my 2c
1 5/8 The fit is good, and the larger headers aren't really required till you approach 400 hp or so according to TA
The rest of exhaust will be 2 1/2" mandrel bent flow master 40 series. All the way out the back. Thanx for the confirmation on 1 5/8"! H pipe.
What cam do you have? What rear gear do you have? When optimizing a combo you need to consider the above before you even choose a stall converter, plus compression ratio that you already posted. With more gear(numerically higher) you might be able to get away with the bigger tube headers to help bring the power band higher while not killing the low end so much. Although the st300 will kill your off the line with its horrible gearing, even if you stepped up the rear gear I would probably still stay with the 1 5/8" headers with that trans you'll need all the low end torque you can get because of the lack of 1st gear multiplication to help get it moving from a dead stop. The st300's 1st gear would make for a better 2nd gear than a 1st gear with its 1.76:1 ratio. In comparison you would need a 5.40:1 rear gear with the st300 to have the same 1st gear multiplication as a 3.73:1 rear gear with a TH350. Not the best off the line trans but would be a good moonshine runner with a better 1.76:1 passing gear when you're up to speed vs a 1.52:1 2nd gear of a TH350. Which all comes down to personal driving preference. I personally like to be able to take off faster from a dead stop and stay within 10 mph of the speed limit on the freeway so I really don't care for the st300.(to each his own though) So yeah, with that trans you should go with the 1 5/8" headers unless you're going to run a 5.40:1 rear gear or numerically higher. But I don't think your engine is setup to handle the RPM for a drag race car setup like that, unless you add a gear vendors bolt on overdrive to make it more street friendly. GL Derek
Thanx guys. Hey Derek, I listed TA290H cam and 3.42 gears in initial post. I know the ST300 isn't ideal and I may go 200R4 in the future but it is an untouched 68 that I would like to keep fairly close to the way my father in law bought it in 67. Thanx again to all!
Sorry, I got distracted after(and when I was reading it) I read the 1st post and forgot some of the info. But would still say 1 5/8" would be the way to go if you had your heart set on getting headers, for your combo manifolds would be good enough though. I realized that about the car is why I wasn't recommending getting rid of the trans, but he!! ya a 200R4 would be a great upgrade! Derek
The way I see it, 1 5/8" should be fine considering............... https://www.youtube.com/watch?v=azPKIjxmmdU
That's a crazy video!!!! I guess it really doesn't matter. Manifolds would probably not make much difference.
I was going to try and steer clear of the ST300 comments, but it looks like it's unavoidable lol I won't go into details, I'll let the transmission speak for itself. Do us all a big favor and let us all know how well (or bad) that transmission does with the 3.42 gear and 2500 stall. If you plan on swapping it out later for a trans with more gears, record your times/speeds, etc. with the ST300 and then compare it to whatever you choose. It would make for a great addition to the information database we have here. It would be awesome if a chassis dyno could be used with both to see the actual power differences. Maybe a fund could be worked up to contribute to this if the trans swap is seriously planned? Perhaps even some monetary wagers? lol Thanks!
I will be more than happy to give some feed back once I'm up and running. My trans guy explained to me why a lot of drag race only cars run the 2 speeds. It made sense and I stuck with the ST300. He even had three non switch pitch ST400's sitting there that he offered to build one for me and I said no. He said the ST300 should take around 15ish HP to turn compared to 40ish on the ST400. Also said I wouldn't blow the tires off on the street since I won't be running drag radials or anything. All around good match to the legendary Buick torque. Just repeating a few of the things he said. Please don't blaze me:beer! I know this can be a touchy subject
Its rebuilt already, might as well use it. You're either going to like it or you're not. I'm not a fan myself, I like more gearing off the line but that's just me. The 2 speeds are popular for drag racing because the racers will use very steep gearing like 5.13:1 or numerically higher with their engines that are setup to rev to 8,000 RPM before they have to shift. Not real economical to set a car up that way for the street though. Plus with your stock rod sbb 350 you shouldn't expect or even try to spin it to far past 6,000 RPM if you want your rods to not spin on the outside of the block. :shock: (that's all sbb cast iron rods, not just yours) It shouldn't be to horrible with the 3.42:1 rear gear and the 2,500 stall though, let us know how you like it. At speed the st300's 1st gear is slightly better than a 3 speed's 2nd gear so there is that advantage if you like freeway racing starting at over 40 mph or just slightly quicker semi-truck passing. The most important thing to do is make sure you enjoy your Buick. GL Derek
We run 2 speeds when the cars are light (under 2800lbs or so) and/or mega torque and hp (750 or so), in addition to the above mentioned scenario of high rpm and gear. Either way, the 2 speed is preferred when the car can't use the extra gearing.
Maybe it matters, maybe it doesn't. https://www.youtube.com/watch?v=O1bXPNy1Yn4 As always, with a grain of salt.
Well, looks like with 50 less cubes and way less than 500 hp, the 1 5/8" for the Buick 350 is the clear pick! Excellent video, I hadn't seen that one yet. Thanks for sharing.
The reason it's been a bit 'touchy' in the past is because one particular individual seems to think the ST300 is pure garbage and should never, ever be used...but now sings a slightly different tune, which is cool. You won't need crazy gearing (5.xx) for the ST300 to be good on the street. "Slightly better" 1st vs 2nd on a 3 speed has about the same difference as the 2004r's 1st vs the TH350's 1st, but that was harped on over and over on how much better that was... ...sooo, I think we can see clear bias here, but only when there isn't massive support and evidence to the contrary. I, on the other hand, have always said to use whatever you wanted ('you' being whomever), and that there are always pros and cons to everything. So long as everyone gets the real scoop on what it's about, instead of one or two bad experiences with something. Anyways, I seriously doubt you'll be disappointed with a 3.42 gear and 2500 stall on the ST300, unless you're one of those guys who wants his car to be wound out in 1st below 20 mph, or feels like there's something missing without that extra shift. If you still feel like you want a trans swap after you use the ST300 and for some reason don't like it, I'll be happy to take it off your hands for a fair price. Tune it with the 1 5/8" headers and rip some ass. :TU:
The vid after this one with the "stock" sbc 305 to see how much N02 it can handle before it blows up was pretty cool too! Derek
Swap from the 2 speed to a TH 350 will feel like you gained 40hp. Use a TH 200R4 if you have 3.73 or higher gears and will feel even stronger. No blazing, just experience. With a single plane intake use headers. Either size will work fine, don't worry about the size. I'd use the 1 3/4.
