What's The Diff?
May 28th, 2007, 04:56 PM
#1
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Join Date: Oct 2006
Posts: 45
What's The Diff?
Can someone explain the pros and cons of the 350 vs. 403
I have both and plan to rebuild one or the other and put in my '87 cutlass. I'm just not sure which one to use. I'm not looking for a lot of HP, its a daily driver, around 250-275 would be fine.
I have both and plan to rebuild one or the other and put in my '87 cutlass. I'm just not sure which one to use. I'm not looking for a lot of HP, its a daily driver, around 250-275 would be fine.
May 28th, 2007, 05:06 PM
#2
395558 block of the 350 is the best. These were made from 1968 to 1976. Up to about 73 to 74 they had soild mains. The 403 and all 350's in the mid 70's and up had windowed mains.
The newer 350's and all the 403 aren't made of mush, but the older ones are stronger. From 1968 to 1971, the 350's were rockets motors, so they had more power and more toqure, but they usually run on leaded gas. After '72, most of them were unleaded motors
All the SBO's are externally the same.
If your looking for a daily driver, whatever floats your boat, but to build one up for street and strip use, you want an older one. I've heard the 350 block is overall better than the 403
The newer 350's and all the 403 aren't made of mush, but the older ones are stronger. From 1968 to 1971, the 350's were rockets motors, so they had more power and more toqure, but they usually run on leaded gas. After '72, most of them were unleaded motors
All the SBO's are externally the same.
If your looking for a daily driver, whatever floats your boat, but to build one up for street and strip use, you want an older one. I've heard the 350 block is overall better than the 403
May 28th, 2007, 08:46 PM
#3
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Join Date: May 2007
Location: Chatham-Kent, Ontario
Posts: 117
Take a good close look at your 403. If the cylinder walls are rough, it's a paperweight. The 403's huge bore and thin walls hardly leave any room for boring. If everything looks good on it, give it some serious thought. A friend of mine had a '79 Trans Am with the 403 - that motor went through a ton of punishment and kept on going (make sure your car has a good water temp gauge, though). The extra 53 c.i. are an obvious advantage, but find some better heads if you choose the 403; the original heads on it have HUGE combustion chambers, which of course makes really low compression. If your 403 is in good shape and your 350 is a mid-late 70s block (everything Redog said made perfect sense to me), I'd do the 403. If the 350 is an older one, that's the one I'd pick. Whatever you do, I'd keep the other one handy, just in case. 
- GoldOlds
- GoldOlds
May 31st, 2007, 04:28 AM
#5
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Join Date: Oct 2004
Location: Southern CA
Posts: 2,212
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