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#1
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350 vs 400 rebuild
I found a good video on YouTube of a Pontiac 350 rebuild.
https://youtu.be/TnyrvGtMIfA The link is actually putting it back together. There is another one showing tear down. Anyway question is: Is rebuilding a 400 pretty much the same deal as the Pontiac 350? I've got a couple 400's pre 75 and I might try building one just for cruising and to check it off my bucket list. Thanks |
#2
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Other than bore size (3.875” vs 4.120”) they’re essentially the same engine.
Build it.
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1964 Tempest Coupe LS3/4L70E/3.42 1964 Le Mans Convertible 421 HO/TH350/2.56 2002 WS6 Convertible LS1/4L60E/3.23 |
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#3
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With the way competent auto machine shops are falling into the Abis these days, no less shops in general then, go forth and build the 400.
Both motors basically weigh the same and It’s a lot easier to find good pistons for the 400 and unless about 12% higher fuel cost matter to you, once again do the 400. What year heads do you have to with these motors?
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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
#4
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Steve, I've got a 69 XH w/ 62 heads complete. And a 73 Y4 block with mains and a pair of 7k3 heads. Thanks |
#5
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A 400 will get the same gas mileage as a 350 +- 1 MPG. The extra bore size and 50 cubic inches make more "smiles per gallon".
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#6
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Thanks, yeah I definitely want to build a 400.
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#7
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Nothing wrong with a well built 350P. DSS is now producing quality forged pistons for the 350P, along with the 326 and 389.
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“It takes considerable knowledge just to realize the extent of your own ignorance.” Dr. Thomas Sowell |
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#8
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Agreed, I kept my original 350 in case someone ever wants the car back as it left the factory. I currently want to rebuild a 400 to swap out a YS block 400 that's in my car now. |
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#9
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I’d consider building a 350 for 2 reasons.
The first one being if I owned a 350 HO car. The second would be when all the big-bore blocks have disappeared, and they haven’t yet. Come to think of it I’d build a 350 instead of a 400 if all I could find was a 557 casting 400 block. The beauty of owning a Pontiac is all the engines are physically the same size and weigh within pounds of each other no matter the displacement. The 455 is the best bang for the buck hands down, the 400 is an awesome performance engine as well with an edge on fuel economy. To me it makes little sense not to maximize your cubic inches, within reason. Sometimes the 455 is a little too thirsty and the massive torque is hard to harness so the 421/428 or 400 makes sense depending on how you set up your car. A 350 or 326 just isn’t in the cards for the majority of us, unless we’re restoring a 326 or 350 numbers matching car.
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1964 Tempest Coupe LS3/4L70E/3.42 1964 Le Mans Convertible 421 HO/TH350/2.56 2002 WS6 Convertible LS1/4L60E/3.23 |
The Following 2 Users Say Thank You to b-man For This Useful Post: | ||
#10
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Quote:
__________________
“It takes considerable knowledge just to realize the extent of your own ignorance.” Dr. Thomas Sowell |
#11
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They run great with 4" cranks in them. Does anyone even sell the cheap cast 4" crank with 3" mains anymore.
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#12
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Quote:
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#13
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A 326-350 can be built to make very reliable power and last a very long time. I equate these engines to a SBC 305-307. They too can be built to make reliable power and last a long time. But why do that when 350 Chebby's are still around and a dime a dozen. Unless a factory HO engine, hard to make a case to build one. Bill Rink was a long time friend of mine, (RIP), he and a few others proved the 350 Pontiac was no slouch if you were willing to invest allot of time, energy and $$$$ into making it the little engine that could. IMO the saying "No replacement for displacement" really applies to an engine family designed to make low RPM torque.
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#14
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Trying to recall what the usual items to consider when using a 350 block, will take a shot at it strictly from memory for amusement:
* Large valve heads may have issues with the smaller bore, chamfer needs to be scrutinized * Piston selection may be minimal * 350P blocks have thick bore walls (can't recall specifics) * Care needs to be taken on block inspection/prep, cap fitment, line bores, deck, etc (core shift) My first engine build was a 350P, and went big on the bore because of piston availability. I think it was like +80 or maybe even +100, would have to dig thru notes. I abused that engine, RPM-wise especially, rod let go fairly early on in it's life. OE prepped rods with good bolts. My intro into Pontiac engines! .
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. 1970 GTO Judge Tribute Pro-Tour Project 535 IA2 http://forums.maxperformanceinc.com/...d.php?t=760624 1971 Trans Am 463, 315cfm E-head Sniper XFlow EFI, TKO600 extreme, 9", GW suspension, Baer brakes, pro tour car https://forums.maxperformanceinc.com...ght=procharger Theme Song: http://www.youtube.com/watch?v=7zKAS...ature=youtu.be |
#15
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Quote:
__________________
“It takes considerable knowledge just to realize the extent of your own ignorance.” Dr. Thomas Sowell |
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#16
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I know of one 557 based 400 that made 500+hp, but you’ll have to contact Tom S to find out exactly he had done to the block so it would survive at this power level. Replacing the main cap roll pins with solid dowel pin would be the first thing I would do along with a thorough NDT examination. A very light reciprocal mass would lower the stress on the bulkheads. Pontiac went to the 481988XX blocks in the later W72 400s for a reason.
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“It takes considerable knowledge just to realize the extent of your own ignorance.” Dr. Thomas Sowell |
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#17
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It ran really well, beating my 455 for a bit and he let me know about it. Then it broke every main bulkhead in the block. Stock-ish only blocks as far as I am concerned. He has moved up to a good 400 block with Butler Scat 4" crank and rods with the same heads. Car runs 10.50s now. |
#18
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Butler is doing what any smart business would do now that the good 400 blocks are becoming scarce.
Using up that pile of 557 blocks that otherwise would be getting scrapped and capitalizing on them. Personally there’s absolutely zero chance I’d invest 8 to 12k or whatever to build an engine off of a questionable foundation. For those of you who are willing to roll the dice on a 400 - 500 hp 557 block build be my guest.
__________________
1964 Tempest Coupe LS3/4L70E/3.42 1964 Le Mans Convertible 421 HO/TH350/2.56 2002 WS6 Convertible LS1/4L60E/3.23 |
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#19
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Quote:
http://www.krepower.com/Pontiac%20MR-1%20Blocks.htm Considering the $$$$ spent, the MR-1 iron block starts to look good. FWIW
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"No replacement for displacement!" GTOAA--https://www.gtoaa.org/ Last edited by 1968GTO421; 07-31-2023 at 06:18 PM. Reason: twitchy fingers here |
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