Primary Differences in 400E and 400G engines
September 21st, 2012, 12:35 PM
#1
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Primary Differences in 400E and 400G engines
I didn't want to hijack an existing thread about the 400G vs a 455, so I am starting a new one. Can one of you experts school me on the main differenced between the 400E and 400G engines?
Thanks,
Randy
Thanks,
Randy
September 21st, 2012, 12:44 PM
#2
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E is closer to a square block meaning bore & stroke are about the same. A G uses a 455 crank but has a much smaller bore so it is actually less than the stroke. E's will rev better and are considered more desirable & better to build. G's can run good in close to stock form (I like mine at least) but aren't considered good engines to build because they won't rev.
September 21st, 2012, 06:09 PM
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Thank you professors!!
I just bought a completely stock 66 L69, and am wondering about engine potential. Is/was there anything special done to the L69 engine to enhance the performance?
Thanks again.
I just bought a completely stock 66 L69, and am wondering about engine potential. Is/was there anything special done to the L69 engine to enhance the performance?
Thanks again.
September 22nd, 2012, 07:02 AM
#6
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Here's a real good thread on the differences between them:
http://www.realoldspower.com/phpBB2/...ighlight=truck
This part is my favorite:
http://www.realoldspower.com/phpBB2/...ighlight=truck
This part is my favorite:
Originally Posted by 468Calais
What's the difference between an early and late 400?
4.00" bore x 3.975" stroke vs. 3.875" bore x 4.25" stroke
forged crank vs. cast crank
7" rod vs. 6.735" rod
performance potential vs. truck engine
4.00" bore x 3.975" stroke vs. 3.875" bore x 4.25" stroke
forged crank vs. cast crank
7" rod vs. 6.735" rod
performance potential vs. truck engine
Last edited by allyolds68; September 22nd, 2012 at 07:09 AM.
September 22nd, 2012, 11:47 AM
#7
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For those who haven't heard this story before...
The 400 motors were relatively low production rate items, since they were primarily used only in the 442s. To save money, Olds designed the 400 to use the same crank (and thus the same stroke) as the 425. This resulted in the short-stroke 400 used from 1965-1967. When the 425 was stroked to the 455 in 1968, Olds again wanted to use the same crank to save money. Unfortunately, the GM mandate of a 400 cu in max displacement in the A-body line was still in force, so Olds had to reduce the bore to keep displacement at 400 cu in with the longer stroke. The advertising BS at the time claimed that the smaller bore was intended to reduce combustion chamber surface area to reduce NOx emissions or some such crap, but this was purely a decision driven by the bean counters.
The 400 motors were relatively low production rate items, since they were primarily used only in the 442s. To save money, Olds designed the 400 to use the same crank (and thus the same stroke) as the 425. This resulted in the short-stroke 400 used from 1965-1967. When the 425 was stroked to the 455 in 1968, Olds again wanted to use the same crank to save money. Unfortunately, the GM mandate of a 400 cu in max displacement in the A-body line was still in force, so Olds had to reduce the bore to keep displacement at 400 cu in with the longer stroke. The advertising BS at the time claimed that the smaller bore was intended to reduce combustion chamber surface area to reduce NOx emissions or some such crap, but this was purely a decision driven by the bean counters.
September 23rd, 2012, 10:39 AM
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For those who haven't heard this story before... The advertising BS at the time claimed that the smaller bore was intended to reduce combustion chamber surface area to reduce NOx emissions or some such crap, but this was purely a decision driven by the bean counters.
There may have been some truth to Oldsmobile's claim. The smaller surface to volume ratio of an undersquare engine does contribute to less emissions.
I do agree that keeping parts interchangability at a maximum was an important, if not greater part of the decision.
Last edited by turbobill; September 23rd, 2012 at 10:42 AM.
September 23rd, 2012, 04:35 PM
#9
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Yeah, but if you REALLY cared about emissions, you would have done this on the 350 and 455 that were produced in much higher numbers than the G-block motor. Just sayin...
September 24th, 2012, 07:08 AM
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For those who haven't heard this story before...
The 400 motors were relatively low production rate items, since they were primarily used only in the 442s. To save money, Olds designed the 400 to use the same crank (and thus the same stroke) as the 425. This resulted in the short-stroke 400 used from 1965-1967. When the 425 was stroked to the 455 in 1968, Olds again wanted to use the same crank to save money. Unfortunately, the GM mandate of a 400 cu in max displacement in the A-body line was still in force, so Olds had to reduce the bore to keep displacement at 400 cu in with the longer stroke. The advertising BS at the time claimed that the smaller bore was intended to reduce combustion chamber surface area to reduce NOx emissions or some such crap, but this was purely a decision driven by the bean counters.
The 400 motors were relatively low production rate items, since they were primarily used only in the 442s. To save money, Olds designed the 400 to use the same crank (and thus the same stroke) as the 425. This resulted in the short-stroke 400 used from 1965-1967. When the 425 was stroked to the 455 in 1968, Olds again wanted to use the same crank to save money. Unfortunately, the GM mandate of a 400 cu in max displacement in the A-body line was still in force, so Olds had to reduce the bore to keep displacement at 400 cu in with the longer stroke. The advertising BS at the time claimed that the smaller bore was intended to reduce combustion chamber surface area to reduce NOx emissions or some such crap, but this was purely a decision driven by the bean counters.
October 2nd, 2012, 06:11 PM
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Guys all I can tell you is I had a 69 442 bench seat 4-speed (in 70) and that poor car could not get out of its own way. I was embarrassed, kept the car for a year traded it for 69 Grand Prix SJ.
February 6th, 2013, 01:02 PM
#15
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I have a 68 442 with the g block 400 rebuilt the top end new cam,lifters,timming chain,big valve c heads,edelbrock 750 carb and intake. Had decent power but ran it past 5000 rpm 1 to many times and spun a connecting rod bearing,in the process of building a 455. I did have to keep my foot in it to get it to move......
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