Vortec street 355 max compression? Coolant bypass?

[ClassicRob]

Has anyone built or ran a Vortec headed SBC with 10.1 compression on a hot street car? Literally, I live in the south. I am betting the chamber design is good enough to where I shouldn't have any problems but then again I do live in Texas and it gets HOT. I have some new 062's which are getting some bowl and valve work done as we speak that are going on a 355 with a SCAT rotator and we are looking at about 10:1 compression. DCR I suspect will be near 8:1 but I am not sure yet as Mike is still doing the cam. Am I being paranoid?

Also what is the best way to address the coolant bypass issue? These heads are on a 77 010 2 pc block which has the second water pump (to cylinder head) coolant bypass hole but Vortecs dont have that hole. Do I just simply drill the hole using the head gasket as a template? Or do I need to use the manifold coolant port and tie into the heater hose? It would seem like a better idea to just drill the passenger head. Right?

I have heard many different ways of doing this, including drilling the thermostat. I live in Texas so the cooling system HAS to be top notch.

Thanks!

[F-BIRD'88]

If you have the extra water ports on the intake back at the diz hook up the drivers side rear water port to the wP on top of the water pump.

10:1 cr wants 92 octane gas. .max wot spark timing 32-36 deg.. (you have to determine that by testing.

no drilling

[ClassicRob]

No coolant ports or even anything to drill on the back of the intake.

[BillK]

I cant say that anyone I know worries about the bypass at all. The guys run those heads on the dirt track here locally and they are very popular on street engines. I dont even know how its addressed in the factory applications. Maybe they let some flow through the heater core ? Or the thermostat allows some flow ? I can look at my 99 Tahoe over the weekend, it has a 5.7 Vortec in it. I am not even sure if it is an issue.

[novadude]

I cant say that anyone I know worries about the bypass at all. The guys run those heads on the dirt track here locally and they are very popular on street engines. I dont even know how its addressed in the factory applications. Maybe they let some flow through the heater core ? Or the thermostat allows some flow ? I can look at my 99 Tahoe over the weekend, it has a 5.7 Vortec in it. I am not even sure if it is an issue.

I think you are right about the heater core. Pretty sure that's how the L31 truck engines accomplished "bypass", because the heater hose valve in those trucks allows full flow from WP to intake even when in the "off" position.

[prairiehotrodder]

i have a stock 350 vortec in an old deck truck that i use for hauling my race car. It has a chinese intake manifold and a 600 holley on it. I run a small coolant bypass hose from the front of the intake to the waterpump. Just like what is on a stock big block chevy. This motor and truck has worked hard for me for many years. Its not the engine in the picture, but the same idea.

Picture 161.jpg

[zums]

Drill the hole in the head, problem solved
Tom

[skinny z]

Vortec headed 355 at 10:1 with an advertised 276 intake lobe on a 106 ICL. DCR was in the low 8's. .040" quench. It took a full timing curve to 32 degrees with about 14 initial. Premium fuel was a must and with the vacuum advance adding timing at cruise it would rattle a little. Something I tuned around with a vacuum advance that was adjustable for both total amount and set point.
It doesn't get Texas hot where I used to live but it gets intense nonetheless.
As for the coolant lines, one from the water pump to the heater core and then back to the intake. No issues.

[Elroy]

Screenshot (5).png

[Bob Hollinshead]

If you have the extra water ports on the intake back at the diz hook up the drivers side rear water port to the wP on top of the water pump.

10:1 cr wants 92 octane gas. .max wot spark timing 32-36 deg.. (you have to determine that by testing.

no drilling

Why only the driver's side? wouldn't it be best to tap both sides-the rear cylinders run hotter for sure.

[F-BIRD'88]

If you have the extra water ports on the intake back at the diz hook up the drivers side rear water port to the wP on top of the water pump.

10:1 cr wants 92 octane gas. .max wot spark timing 32-36 deg.. (you have to determine that by testing.

no drilling

Why only the driver's side? wouldn't it be best to tap both sides-the rear cylinders run hotter for sure.

You could if you had 2 spots on the water pump to connect both sides to..
On my 400 sbc with vortecs I just ran it to the drivers rear side... No drilling, no special gasket holes.
No thermostat serging on warm up nore overheating.
It seems to cool much better.

[rfoll]

On my 400 with steam holes drilled, there were no problems with temperatures. I have a complete Vortec engine in my Impala, and the temperatures would swing wildly from 180 to 250 degrees at cruise speeds until I added a bypass from the intake to the radiator. More or less the same problem with the flat top 350 in my El Camino. Again, a bypass solved the problem. The 880 block in the Impala doesn't even have the bypass hole. The El Camino engine was already assembled or I would have drilled the hole in the heads. The bypass hole in the El Camino radiator is not much larger than 1/4" but it seems to do the job. The compression is 9.6 and it runs on regular. You might need to run premium at 10:1. The temperatures run right on the thermostat.

DSCN1423.JPG

The orange bypass hose goes to the radiator. The heater circuit goes through the intake for carb heat in the winter.

[In-Tech]

On my 400 with steam holes drilled, there were no problems with temperatures. I have a complete Vortec engine in my Impala, and the temperatures would swing wildly from 180 to 250 degrees at cruise speeds until I added a bypass from the intake to the radiator. More or less the same problem with the flat top 350 in my El Camino. Again, a bypass solved the problem. The 880 block in the Impala doesn't even have the bypass hole. The El Camino engine was already assembled or I would have drilled the hole in the heads. The bypass hole in the El Camino radiator is not much larger than 1/4" but it seems to do the job. The compression is 9.6 and it runs on regular. You might need to run premium at 10:1. The temperatures run right on the thermostat. DSCN1423.JPG The orange bypass hose goes to the radiator. The heater circuit goes through the intake for carb heat in the winter.

I've seen that swing at cruise. The "new" water pump had the wrong backing plate. A small bypass on both sides of the rear of the intake never hurts as it purges the air from the boil pocket. Unless you screw up the chambers, 28 degrees is about all a vortec head will like for timing, sometimes you can give it a couple more after peak torque.

[Bob Hollinshead]

If you have the extra water ports on the intake back at the diz hook up the drivers side rear water port to the wP on top of the water pump.

10:1 cr wants 92 octane gas. .max wot spark timing 32-36 deg.. (you have to determine that by testing.

no drilling

Why only the driver's side? wouldn't it be best to tap both sides-the rear cylinders run hotter for sure.

You could if you had 2 spots on the water pump to connect both sides to..
On my 400 sbc with vortecs I just ran it to the drivers rear side... No drilling, no special gasket holes.
No thermostat serging on warm up nore overheating.
It seems to cool much better.

You could T both sides together and still run one hose to the water pump?

[F-BIRD'88]

Why only the driver's side? wouldn't it be best to tap both sides-the rear cylinders run hotter for sure.

You could if you had 2 spots on the water pump to connect both sides to..
On my 400 sbc with vortecs I just ran it to the drivers rear side... No drilling, no special gasket holes.
No thermostat serging on warm up nore overheating.
It seems to cool much better.

You could T both sides together and still run one hose to the water pump?

yes