Hi, I am from Canada and new to the Forum. I am having a Rudy inspired hot rod pick up build and bought a 1958 - 348 bbc motor for it. I have done as much research as I possibly can on the subject. I am now looking at how to dress the motor which will be professionally rebuilt. My questions for which I am having trouble finding material on, are: 1) For that motor ('58-'61), what was the more period correct modification with regards to carburetion? 2) Dual quads or Tri-power? 3) What are the major differences? Thank you
Tri-power was available as an option on the 348 from the factory. A friend of mine had a dual quad, 4 speed, Impala that was supposedly built as a "test mule" for the upcoming 61 SS Impala. That car had a hotter cam, and some free flowing cast iron headers, along with the dual quad 348, go figure! KK
have you checked for this over on the 348-409 site? I assume you know about the early 58 348's and their cooling issue with the early heads???? All that info can be found over there. good luck with the build. You could check with Dickster on here as he sells a lot of dress up kits for induction systems.
I'd guess the tri power set up was seen more, since you could probably pick up a complete set up at the local bone yard. Bolt in on and be ready to go. BTW - 58 348s were a one year only deal. Later heads won't work on the block without plugging some water passages. Same thing with 58 heads on later blocks.
Thank you for the info. I was recommended Edelbrock aluminum heads. I do prefer visually the look of the tri power over the dual carbs myself. Thx
I had a 58 Impala 348 with factory vacuum operated tri power and three on the column. The car was not bad for what it was. Seriously doubt you could ever locate an original factory tri power set up in a bone yard. They weren't that common back in the day. Something after market would be your best bet. Wish I just had the factory air cleaner it would be worth something. Gary
I was actually talking about back in the 60s when wrecking yards actually had parts for old cars. Lots of high po stuff around here back then. I had a guy swap me a complete tri power set up for a 4 bbl intake and carb because he didn't want to mess with keeping them in tune. That set up is long gone, but I do have a factory tri power intake if anyone is interested in one. Got some early Pontiac cast iron tri power manifolds I'd get rid of too.
The guy that was fast back then may have been running big heads with a single 4 and a 409 crank in it. And they are not big blocks....
Hey Gman, Similar minds, similar cars. Ours was a black 58 Impala with 348/3 carbs +280 hp/posi... We wanted the most powerful motor, the 315 with 11 to 1 pistons, but the cost was so much more. At the time, my brother thought if we needed more hp, we could always add a cam and lifters, plus other internal mods. Later, when I owned the car outright, I had that factory air cleaner top plate chromed. It stood out quite well when the hood was raised in the drive-in restaurant parking lots during motor talks and showtimes. Those funky orange, valve covers looked alright, but we also chromed them and that made a huge difference, along with the Moon Breathers. For 37 4d: In my neighborhood, there were more 4 barrel carb set ups on the Impalas and Biscaynes. But, the factory 3 carb set up was almost trouble free...Except for my one narrow loss in racing when the vacuum hose popped off and I was only running the center carb. The outside two certainly made a difference. 30+ hp difference was a lot of wins vs losses. But back then, unless you had racing in mind, the dealers had plenty of 4 barrel carb, 348s in stock for immediate sales and the drive off. We had to wait for our car on order because of the 280 hp/4:11 Posi/HD everything, plus being black/red upholstery. The wait was worth it. The funny thing was that we never actually raced a 315 hp in another Impala in A/Stock until 59-60, when those 59's were the commonplace cars on the lots. By then, the top of the line 335 hp models were the special order Impalas. Once those 315 hp cars were at the dragstrip, it was hard to keep up with them with 35 hp less. When those special order 335 cars showed up, we were doomed for sure, there was no way to keep up with 55 less horsepower. Unless of course, we added our own cam/lifters/head mods, etc. which we did, but we were no longer in the stock class. One complaint during those times was that our 280 hp models should have been dropped down to the B/Stock class just because we were outgunned from the factory. We dropped out of stock class racing and built a 671 SBC in a 40 Willys for the C/Gas class competition. jnaki from Super Chevy: The Offerings Two new 348 engines were initially offered. The 250 horsepower "Turbo Thrust" version had a Rochester 4GC four barrel carburetor and produced a maximum of 355 foot pounds of torque at 2,800 rpm. The other was a "Super Turbo Thrust" and had three two-barrel carburetors. It produced 280 horsepower at 4,800 rpm and 355 foot pounds of torque at 3,200 rpm. Under normal driving, only the center carburetor metered fuel and air to the cylinders. When the throttle (also known as "foot feed" in 1958) was opened 60-degrees, a vacuum switch opened the front and rear carburetors. Each two barrel carburetor flowed around 225 cfm while the Rochester 4GC four barrel carburetor flowed about 450 cfm. The extra 225 cfm "tri-power" air flow equaled 30 horsepower. Both engines featured the same heads and hydraulic lifter camshaft. Chevrolet publicly limited engine rpm to a respectable 5,400. Most of the Brand-X engines generally peaked out at 5,000 rpm.
Jnaki Great story!!!! Thank you for all the information. A lot for a guy who knows little on motors but enough for me to understand. I most likely won't be racing it...Lol But would like to have a cool 350hp at my disposition and considering the car will weight nothing, I'm assuming that it will feel like having 400hp in a modern car. Found a video with a face-off on dual vs tri on sbc but it delivers the principal and at the end it came down to aesthetic preference for street drivers. I love the look of the tri-power and wanted input from seasoned guys on the matter which so far is great!!! and as members said before the tri looks cool and the dual says race more. Either way....the power difference is probably not something I will truly notice unless I took up racing! if I'm correct.... Here is that video which I hope touched on the subject even though it's not a late motor: Thank you!!!
Early heads used AC 44 plugs same as a 283 threads about 1/2" long Later heads used AC44N plugs about 1" from the end of the plug to the gasket seal. The 44N plugs may or may not be threaded all the way up.
Hey 37, Here is an example of the stock, three carb, air cleaner and filter from the GM 348 motor. It was a neat system and to top it off, I had the top plate chromed and that gave the giant air cleaner a nice contrast in the motor compartment. It seemed like it did not make much difference racing at the drags, but everyone in the A/Stock class took theirs off to race. But, on the street, it was usually on unless, a match race was set up and the date/time was given in advance. Every little thing helped on the street. (Even changing the stock 4:11 gears to the special order 4:56 gears.) I tried three individual chrome carb covers, but they just did not do anything as far as filtering anything out, for daily use. The stock chromed/black air cleaner looked much better. In the higher elevations around 10000 foot level, we always took the huge air cleaner off and put on the three small chrome covers for looks. We also adjusted the carb to make it run better at the higher elevation. Plus, the three chrome covers made the carbs sound racy with the hiss sound. Jnaki The 348 was an unusual engine, but working on it during my teenage years gave me tons of experience on what worked and what did not. after a few years, we added a Racer Brown Cam and solid lifters. I was responsible for adjusting the whole system every week to get it running perfectly. Now, we had enough HP to compete with the bigger 315 and 335 hp motors, but then, we were not in the stock class anymore. Customizing, racing, and cruising were so much fun with this impala. Those times in So Cal will last forever.
I like your choice of engine color. I cant explain why I feel the way I do but to me an engine should just be a metallic color such as copper, silver , gold etc.
Haha...I'm still trying to decide what color I want my block. I do like the gold but for an easier maintenance and not see dirt, I'm pulling for black or silver!!!
...decisions, decisions... Glad to see W interest! Keep us posted with whatever-the-heck You decide (complete with photographs) k? Sent from my iPhone using The H.A.M.B. mobile app
Looks like it came without a distributor, just so you aware the 348-409 uses a distributor with a different length than a small or big block. Also, is the oil pump drive shaft there?
Stock 3X2 intakes are still reasonably plentiful and usually go for $100-$150 range. Carbs ar still out there as the 2G was used on tons of GM vehicles. There are some pretty good how to's on line as far as rebuilding and setting up triple systems. I run stock intake on my 348 powered T, '58 block and later heads (water ports plugged).
Fordors, thank you for mentioning these details...however as mentioned in my op, I am not very motor savvy and am having a pro shop deal with it for me all the while having the final decision in the direction it will go. Hence my presence here, above and beyond my personal research, to gather as much knowledge as possible so that I may not be clueless while conversing with the shop And I hope to walk away from this experience with enough knowledge to tinker on my own if need be...
Thanks, I have found intakes, unfortunately items purchased in the U.S for us Canadians is subject to almost a 34% surcharge plus duty and shipping due to the current exchange Like so many parts for this project, sometimes it just makes more sense to buy brand new for the difference in price and start fresh. Not going to be a budget motor but heck!!!
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