Technical 327 Strange Bypass

I've seen a lot of engines but can't say I've seen this strange bypass before.
It's a 66 or 68 327 220hp, 4 barrel, manual trans, according to the suffix code.
What's the deal with it, what application would've it been used in ?

 

it's a truck thing, YS is a truck engine

 

That's an odd duck alright. Strange looking "327" label on those smooth v/covers too.

You thinking light duty truck or something more like a 40, 50 or 60 series medium duty?

 

YS is listed for 20-30 series, but we don't know if someone did some swapping?

 

yeah that had to be out of a larger truck. You could look at the intake casting number to kind of figure out more I would think. Is that riser part of the intake or like a bolt on spacer then the thermostat housing bolts to it? Where the bypass would usually go is where the alternator bracket is bolted. Is that a special plug there or is it sealed off the water passage? It is an odd one for sure.

 

My 66 C10 had that,identical 4 barrel engine, except it had script valve covers, the "High Torque 327" sticker, and was Detroit diesel green from the factory.

 

I think that’s to balance the water flow when the thermostat is closed

 

Chevy put an external bypass hose on the six and small block V8s, when used in trucks, to help prevent hot spots in the engine. If you're using the engine in something besides a truck, then you can do away with it.

 

Chevy truck brochure says the bypass is to provide quick warmup for maximum efficiency….I was taught it’s to prevent hot spots during warm when drivers apply a heavy engine loading before it’s fully warmed up..

 

It sure is big as compared to the bypass on a big block.

 

You buy it?
Need another....

 

It should be a 67 327 Truck engine out of a 1-1/2 ton or larger.

 

I used to work with a guy that said his 327 block did not have the drilled bypass behind the pass side of the water pump. Would it be one of these? His must have been a large journal because he said the 327 crank was bad so he put a 350 crank in it, with 350 pistons.

Gary

 

Back in the day, replacement water pumps used to come with a small plug to block off the bypass between the block and the pump when using that bypass on large trucks. Don't remember too many of them being installed.

 

I have the 1969 Chevy truck parts book for light and medium duty trucks, YS is listed as a 327 in a C10-20-30 for several years. Not in the 1-1/2 ton or larger trucks at all, though.

 

1968 Z28 had a similar bypass , just smaller.

 

As did the L79's, kinda sorta.

 

I seem to remember a small bypass hose on a mid 60s fuelie 'Vette at a car show once.

Gary

 

No, remember I've got that bad ass 307 in the 57

 

Only 220 hp/w 4-barrel carb? If it's a low-compression torque engine, why does it have a 4-bbl?

 

I would run that bypass just to see the reactions of casual observers…..

 

so it'll make a lot of torque.

 

It won't do that with a 2-bbl? Really?

 

It won't make as much torque with a 2bbl, as it will with a 4bbl.

Study the drawing for a while...

 

Engines built for torque produce maximum torque at low rpm, where it's needed; for that reason, you don't see 4-barrel carburetors on high-torque, low-rpm engines. Vehicles equipped with such engines also are geared for hauling and use the low rpm torque to their advantage. A good example is the GMC V6 engine, which was not equipped with a 4-barrel carburetor.

 

My 2 pesos........
Truck cams engineered for a fat torque curve (aka: flat torque curve) are appreciated in boat engines, turbocharged engines, and by people who enjoy snappy, peppy, responsive rides on "cruise night". They have their niche in the hot rod community.

 

Funny... I seem to remember Holley 4bbl carb's on 366 & 427 truck engine's - factory equipped. Didn't rev real high and pretty torquey.

 

L79 327", Corvettes, Camaros and others with Winters HP high rise intake...

 

High Perf. Small block's with aluminum intake's had the bypass like that. Cast iron intake's didn't, they had the thermostat housing bypass... on some truck's, passenger car's didn't.

 

Ford used/uses a bypass in everything that I know of, water neck and heater lines.
I figure that large by pass was used when the radiator wasn't really needed like in a school bus that needed engine heat for the heaters in the passenger area, maybe even had a two stage thermostat.