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Old 11-10-2003, 05:38 PM
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400 to a 350 engine swap any tips??

I have a 77 GMC Sierra High, it is my first try at a engine swap. I am planning on taking the 400 out of the GMC and put in a 350 out of a 81 chevy. The GMC is 4 wheel drive and the 81 chevy is not i don't think this posses a problem but i have limited experience with this so not sure, any Tips, or helpful hints on the whole process would be greatly appreciated.........

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Old 11-11-2003, 05:02 PM
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engine swap

The 400 was a torquer, the 350 won't exactly take its place unless you build the 350 a little. They are both sbc engines but the parts will not interchange. I am not sure about the exhaust, may interchange? There are books out there you might want to get to help you plan your project. CK Borders and Barns and Noble, or www.Amazon.com/


Todd


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Old 11-11-2003, 06:47 PM
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The engines will swap with no problem. Heads, intakes, and exhaust will not interchange. Everything else should.

Kevin
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Old 11-11-2003, 08:03 PM
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Sparks,
Be sure to use the flex-plate and vibration dampener that came with the 350, as using either of those parts from the 400 on the 350 will cause serious balance problems. It's O.K. to swap pulleys and use the torque converter that is in the truck now.
You can get plenty of power from a 350 and this is an easy swap.
.
This is a good project to gain experience on. Allow yourself plenty of time and have fun with it.

Kevin45,
Why won't the exhaust manifolds from the 400 work on the 350?
I haven't worked on a 400 for some time. I know headers with the standard bolt pattern fit both engines, is it possible that the manifolds will interchange also?
If anyone else has an opinion on this,weigh in, I'm by far no expert, just curious.

Thanks

Last edited by Wheels427; 11-11-2003 at 08:03 PM.
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Old 11-12-2003, 09:36 AM
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The exhaust manifolds from the 400 will work on the 350.
There is a site in the KB that has the dimensions and weight's of all motor's.
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Old 11-14-2003, 08:19 AM
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Talking

The 400 block and heads are different from a standard SBC configuration, the 400 has a different gasket for mounting the heads and the block has more water/steam holes in it. They do not interchange with all 350 parts. Trust me on this one guys/gals. I Talked with an engine shop/Wallace &DeWitt, for the exact differences, was told the short block is completely different. The heads from a 350 will overheat a 400 but 400 heads will work on the 350?? I am now sure about the exhaust, it will interchange. If you have more questions contact your local engine building shop.......they will be glad to help!

Todd


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Old 11-14-2003, 11:42 AM
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Todd...your right amd I'm wrong on this one. I do know the 400 has the sistered cylinders so whan the head is swapped you have to be sure that the water jacket holes are not covered by the gasket. It's been quite awhile since I've had the 400ci but there are quite a few things that do not swap out. As far as the exhaust, well duh!!! I missed on this all around. Don't know what I was thinking.

Kevin
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Old 11-14-2003, 03:05 PM
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Thats OK Kevin, I will not hold it against you, believe me!! Mistake is my middle name buddy, thats how I LEARNED most of the stuff I know about cars, by making a lot of mistakes!!! These new guy n gals have the benefit of our experience to call on and hopefully learn from OUR mistakes and NOT have to make so many themselves, right guys/gals!!!! Group Hug time....come on....GREAT!!!!



Todd



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Old 11-15-2003, 05:27 PM
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Interchangability is Chevy's middle name. You should be able to just unbolt the 400 and drop the 350 right in place. The year models of these engines will have all the right bolt holes to accomidate the mounting brackets you take off of the old application. The only thing you may have to do is get the right flywheel or flexplate, and harmonic balancer.for the 350, 400's are externally balanced and if you use these parts on the 350 you'll shake rattle-n-roll for sure. All other parts will interchange, even the heads if steam holes are drilled (easy job, match up a 400 head gasket and drill away with a 5/15 bit, done it several times). The sbc is the most interchangable and versitile engine ever built, in my opinion. I currently have a real doozie in this respect, a 305 stroked with a 400 crank, with a .030 overbore makes a 348. I've been plowing snow with it for 7 years now without a single complaint.
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