400/350 swap

tgzzzz · 06-01-2008, 01:46 PM

Sorry to beat a dead horse: I have a 400 engine available to replace my blown 350 in an '86 1 ton motorhome chassis. A couple of local gurus suggest not doing it saying there were head/cooling issues with the 400 which is why Chevy dropped that engine. Any thoughts on that issue or the swap generally? It looks like a direct bolt-in swap except that the oil dipstick is on the other (driver's) side, no small thing with that 4' long dipstick. To me, it looks like another 50 sorely needed cubes and at least 10 hp.

jimbo543 · 06-01-2008, 02:43 PM

you MUST use a 400 dampner and flexplate. otherwise drop it in.
while engine out have radiator cleaned.

PAPA BEAR · 06-01-2008, 06:18 PM

my wife's dad had a 400 in an old service truck went through 3 wrecks 2 different truck cabs finally wound up in a 76 blazer still runs OK

chevyguy · 06-01-2008, 06:33 PM

it will run a few degrees hotter. not a big deal. Probally wont notice it since it wont have to work as hard as the 350 did to move it down the road. The 400 is a fine engine, go for it.

tgzzzz · 06-02-2008, 05:44 PM

Sounds good. Thanks

436'd skylark · 06-02-2008, 05:52 PM

The big about 400s is that they run hot since the bores are so large that they are actually siamiezed. They run steam hole between the bores instead of actual cooling passages. Not a great system but it works. 400s are pretty torquey, you'll like it. I'd do it.

06-01-2008, 01:46 PM	#1
tgzzzz Full Member Join Date: Apr 2008 Posts: 18	400/350 swap Sorry to beat a dead horse: I have a 400 engine available to replace my blown 350 in an '86 1 ton motorhome chassis. A couple of local gurus suggest not doing it saying there were head/cooling issues with the 400 which is why Chevy dropped that engine. Any thoughts on that issue or the swap generally? It looks like a direct bolt-in swap except that the oil dipstick is on the other (driver's) side, no small thing with that 4' long dipstick. To me, it looks like another 50 sorely needed cubes and at least 10 hp.

06-01-2008, 06:33 PM	#4
chevyguy Senior Member Join Date: Sep 2005 Location: ALABAMA Posts: 3,554	it will run a few degrees hotter. not a big deal. Probally wont notice it since it wont have to work as hard as the 350 did to move it down the road. The 400 is a fine engine, go for it. __________________ Some people are like slinkies, Basically useless, But fun to watch when you push them down the stairs.

06-02-2008, 05:52 PM	#6
436'd skylark Senior Member Join Date: Mar 2007 Location: Pennsyltucky Posts: 988	The big about 400s is that they run hot since the bores are so large that they are actually siamiezed. They run steam hole between the bores instead of actual cooling passages. Not a great system but it works. 400s are pretty torquey, you'll like it. I'd do it. __________________ Joe 89 K2500 Chevy, Wee-Oh-five 294K miles 1962 Scout 80 parts I guess 1966 Scout 800 resto job 2005 Chevy 2500HD Short cab long box DURAMAX 1996 P30, 6.5 NA Mac Mobile whole lot of buicks

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06-01-2008, 02:43 PM	#2
jimbo543 Senior Member Join Date: Sep 2007 Location: MN Posts: 208	you MUST use a 400 dampner and flexplate. otherwise drop it in. while engine out have radiator cleaned.

06-01-2008, 06:18 PM	#3
PAPA BEAR Senior Member Join Date: Mar 2008 Location: virginia Posts: 134	my wife's dad had a 400 in an old service truck went through 3 wrecks 2 different truck cabs finally wound up in a 76 blazer still runs OK

06-02-2008, 05:44 PM	#5
tgzzzz Full Member Join Date: Apr 2008 Posts: 18	Sounds good. Thanks