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#21
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2X Bman,run the right CR and pull into any gas station and not worry about detonation.Tom
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The Following User Says Thank You to tom s For This Useful Post: | ||
#22
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All great advice from everyone. My vote is go with the 428 and 670s. This will make your 2+2 clone so much better and you won't regret the 428 when done.
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DragStarLeMans |
#23
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If I was trying to clone a 67 2+2 the first thing I’d be worried about is the front fender/louvers. Do you have those already?
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#24
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Jeff |
#25
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In more than more than 50 years with Pontiacs I have never found a issue with street driving large J cranks.Tom
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#26
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You said "6X with the vertical boss" - what does that mean? 6x-4 and 6x-8 are identical castings, the only difference is the chamber size and the little number stamped on the machined pad (Secondary Stamping in the attached picture). If you're referring to the presence of the machined pad where the number is, the existence of that pad doesn't mean anything. The number stamped on it is what you need to look at.
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---------------------------- '72 Formula 400 Lucerne Blue, Blue Deluxe interior - My first car! '73 Firebird 350/4-speed Black on Black, mix & match. |
The Following User Says Thank You to Will For This Useful Post: | ||
#27
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PM if you have some for sale
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Mark Las Cruces NM ___________________________ Current Project: '67 Catalina Convertible 400 4-spd |
#28
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So for now they're 6x mystery heads....
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Mark Las Cruces NM ___________________________ Current Project: '67 Catalina Convertible 400 4-spd |
#29
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Many thanks for all the insight and excellent comments. I was leaning towards the 428 at the start, and have just told the seller I'll take it! Looking forward to the build!
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Mark Las Cruces NM ___________________________ Current Project: '67 Catalina Convertible 400 4-spd |
#30
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Something is really amazing with some folks on this site!
They give a big Thumbs up to someone who as dropped a 535 cid motor in there PONTIAC , yet when a guy can’t decide between yanking his 400 out to drop in a 428 he gets all sorts of crap thrown at him from the never over a 400 crowd, lol!
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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! |
#31
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all these posts and still no one has given you the correct answer - put the 428 in your current car, keep the 400, buy another Pontiac, and put the 400 in that one.
COME ON PEOPLE! |
The Following User Says Thank You to i82much For This Useful Post: | ||
#32
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I like the 428 best, had a few 400 and 455, but like the bore/stroke ratio of the 428. Built two 428 and they have been the most responsive engines. Might be the combination of parts too, but really like my 428 matched to my TKX.
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#33
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Building a 428 from pieces is painful at times but he has the majority of parts in a complete engine with needing a compression ratio drop to run today's pump fuel. GOOD pistons are available from Ross, Diamond, JE, among others. I have a set of custom WISECO Forged Pistons with a custom Compression Height. (Also known as a "Dial in your own Compression Ratio") and I have plenty of valve to piston clearance with the camshaft I run. Good rods, custom pistons and rings for a minimum bore job on the 428 block and 670 heads and you are good to go. Tom V.
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#34
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I’d do this. You can always just tell people it’s a 428.
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1965 Pontiac LeMans. M21, 3.73 in a 12 bolt, Kauffman 461. |
#35
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I’d do this.
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"If the best Mustang is the Camaro, the best Camaro is actually the Firebird" David Zenlea |
#36
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I would build the 428 for the added torque/hp but if you’ll use those 670 heads(Rated factory at 10.75 compression)they are no fun for todays pump gas. I would install custom dished pistons and aim for a true 9.1-9.5 compression. You can then use normal pump gas instead of octane additives and race fuel. Either way it will cost you money but less grief at the pumps later on.
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#37
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Wouldn't a 428 with flat pistons and 6X's do better on quench, flow and compression?
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#38
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Quench, I would say that the 670 heads would have far more of that vs the open chamber 6X heads.
Flow, the 670 heads for several years (with a good valve job) were assumed to be better flowing vs the #16 casting 1968 GTO heads, the "later" Emissions heads, and the non early SD 389/421 heads. Only the 455 SD heads and the RA-IV heads were better. As posted before, easy to get a piston made that would have a 9.1 to 9.5 compression ratio with the 428 cid engine. Tom V. The emissions heads are good for emissions. But do what you want. 10 or 15 cfm difference in port flow is not going to do much on a street engine. Now a Boosting device!!!!!!!!!!!!!!!!!!!!!!!!!!!
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"Engineers do stuff for reasons" Tom Vaught Despite small distractions, there are those who will go Forward, Learning, Sharing Knowledge, Doing what they can to help others move forward. |
#39
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The 428 is my favorite for street driving: more torque than a 400, but not so much that street tires have no chance off the line. And it still likes to rev. I'd make a template of the 670 combustion chamber outline and digitize that to mill a dish exactly that shape into the pistons which will maximize quench, which in turn reduces octane dependency. |
The Following User Says Thank You to hgerhardt For This Useful Post: | ||
#40
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I think you could make a clay of the combustion chambers and give it to the piston maker to make exactly what you would want?Tom
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