Building a Vortec Head SBC 350

[K5ride]

I'm building a 350 for my 75 Stepside. I've read and heard so many good things on the Vortec head and L31 that I started with that. I picked up an 880 engine core but when I took the 062 heads into the machine shop they were both cracked. I picked up a pair of Summit Racing Vortec heads for just a little more than rebuilding stock ones (due to core charges) and they already have all the mods done. I also picked up the Edelbrock Performer 2716 manifold that has the coolant bypass provision in the front. After extensive research on the coolant bypass issue, I'm not sure which way to go to achieve the bypass. I've read about the issues with drilling the thermostat and don't want to go that route. Some use the heater core as the bypass but my return line goes to the radiator and I've read it should only go back to the water pump and bypass the radiator.

While my heads were in the shop, I started tearing down the 880 block and found the #1 rod had a spun bearing. I was already on the fence about this block due to not having a mechanical fuel pump provision but I still wanted a roller cam setup. I went on Craigslist and found a 92 638 TBI engine that still ran for $100. I tore it down and everything looks good. It has a mechanical fuel pump provision and all the roller setup is already tapped, so I'm using the 638 block with the new heads. The 638 block has the coolant bypass. It seems that I should just be able to drill holes in my new heads and call the bypass issue done. Has anyone done this or heard of anyone doing it. I searched online and I can't find anyone mentioning it. It seems like the simplist solution to the bypass issue. Am I missing something?

 

[DoubleDingo]

I used the heater core as the bypass and haven't had any issues.

 

[Bextreme04]

I'm building a 350 for my 75 Stepside. I've read and heard so many good things on the Vortec head and L31 that I started with that. I picked up an 880 engine core but when I took the 062 heads into the machine shop they were both cracked. I picked up a pair of Summit Racing Vortec heads for just a little more than rebuilding stock ones (due to core charges) and they already have all the mods done. I also picked up the Edelbrock Performer 2716 manifold that has the coolant bypass provision in the front. After extensive research on the coolant bypass issue, I'm not sure which way to go to achieve the bypass. I've read about the issues with drilling the thermostat and don't want to go that route. Some use the heater core as the bypass but my return line goes to the radiator and I've read it should only go back to the water pump and bypass the radiator.

While my heads were in the shop, I started tearing down the 880 block and found the #1 rod had a spun bearing. I was already on the fence about this block due to not having a mechanical fuel pump provision but I still wanted a roller cam setup. I went on Craigslist and found a 92 638 TBI engine that still ran for $100. I tore it down and everything looks good. It has a mechanical fuel pump provision and all the roller setup is already tapped, so I'm using the 638 block with the new heads. The 638 block has the coolant bypass. It seems that I should just be able to drill holes in my new heads and call the bypass issue done. Has anyone done this or heard of anyone doing it. I searched online and I can't find anyone mentioning it. It seems like the simplist solution to the bypass issue. Am I missing something?

Maybe I'm wrong here, but I don't think its a concern on a squarebody, because you have a natural bypass through the heater core. You come out of the intake manifold to the heater core and from the heater core to one of the plugs on top of the water pump. In most old trucks it will go to the radiator(this should also work) but will have less suction and circulation than going straight to the suction side off the pump body.

 

[K5ride]

Maybe I'm wrong here, but I don't think its a concern on a squarebody, because you have a natural bypass through the heater core. You come out of the intake manifold to the heater core and from the heater core to one of the plugs on top of the water pump. In most old trucks it will go to the radiator(this should also work) but will have less suction and circulation than going straight to the suction side off the pump body.

The articles I've read said to route the heater hose to the water pump instead of the radiator. I'm not sure why. Seems like it would not make any difference. I have the hose going from the heater core to my radiator. Maybe I'm just over thinking the whole thing.....LOL. I've also seen where they "T" into the heater hose from the water pump. This seems to be a confusing topic on the internet with much conflicting information.

 

[77 K20]

Oh boy- this question. I bought a GM crate engine: the HT383. From GM itself it says you have to use a bypass. I did a TON of searching. Some guys said they had to, others said they didn't as they just used their heater core.

I tried just the heater core bypass. (*The stock GM performance manifold had no easy way of doing a bypass). I have an aftermarket VDO coolant gauge and noticed at least twice a minute my temps would creep up, then rapidly cool down when on the highway. One of the engine builders I knew said that was because I'm not running a bypass. I switched to an Edelbrock manifold- and I put in the bypass and now the temp is steady and doesn't do this.

So your results and it seems like the results of a few thousand might be different.

GM said to do it, and I had some weird fluctuations. So I did the bypass. It works for me.