tbi to l31 vortec swap. have questions about timing cover and coolant bypass????

[fish4hc]

Ok, I decided on doing the l31 vortec swap in my 1995 chevy keeping the tbi on top. Just got my brand new motor and still not sure on a few thing. Ive went through to many threads to count and never really got a clear answer so if anyone can please help that would be great.

What timing cover do I need to swap mine with. I know one without the sensor hole but is there a part number or can I reuse mine from my lo5?

Do I need to run a coolant bypass hose or can I just drill holes in the t-stat? If I run a bypass hose is there a hole plumbed in the gmpp tbi/vortec manifold and do I buy a vortec waterpump as the tbi waterpump doesnt have a extra hole for a bypass hose.

Thanks!!!

[fish4hc]

Also, is it better to swap in a timing cover or can I plug the hole with a crank sensor? I just dont want any issues down the road.

[Busted Knuckles]

Use the TBI timing cover. We built one for my son's truck, used a TBI block and Vortec timing cover. The Vortec cover barely fit, we had to move it around to get a good seal. There's a bit of difference in the area on the block where the cover fits and it's enough to make a big difference if everything doesn't line up - like a quart of oil leaking out during break-in!!
Oh, and those Vortec timing covers are supposed to be a one use piece, toss it and get another after you remove it.
Been too long, can't help you with the bypass question.

[randeez]

vortec block, use the lo5 cover ... no double roller chain/gears- lt4 has a hd replacement single roller iirc. and if you use the tbi water pump you should probably drill out the bypass for it (extra hole on the left). It is (most likely) not drilled out on the 880block unless you get a crate vortec. the hole is cast there but doesnt go all the way through. dont know about the gmpp parts

[GreaseDog]

no double roller chain/gears-

wrong, get one for a small block chevy with a roller cam. (92 Camaro 350 is what i looked mine up under.

and if you use the tbi water pump you should probably drill out the bypass for it (extra hole on the left). It is (most likely) not drilled out on the 880block unless you get a crate vortec. the hole is cast there but doesnt go all the way through. dont know about the gmpp parts

i have a Vortec crate in my truck... L05 water pump, 4 1/8" holes drilled in the stat... no cooling issues whatsoever. in fact, i think it runs a little too cool with a stock stat in it.

[fish4hc]

So no l05/tbi timing cover then huh?

I will look for one for a roller motor then.

[randeez]

timing cover from the lo5 is good to go, i think he was correcting me about double roller chains- i have been wrong before

[GreaseDog]

http://www.summitracing.com/parts/PRO-141-753/ this is the cover i am running.

[GreaseDog]

sorry, its not Cloyes who sells the double roller i am using, its a Summit set... though when i opened my box, it was clearly Cloyes parts in a Summit wrapper.
chain and gears... http://www.summitracing.com/parts/SUM-G6601/
cover... http://www.summitracing.com/parts/PRO-141-753/
pointer... http://www.summitracing.com/parts/SUM-163800/

[skylark]

http://www.summitracing.com/parts/PRO-141-753/ this is the cover i am running.

I could be wrong here...
Are you using the tbi or the vortec balancer? I thought the vortec one was shorter due to the crank reluctor. Are you running the reluctor behind that cover for the spacing?

[GreaseDog]

nope. the Vortec balancer is the same as the L05. the crank gear is thinner to allow for the reluctor ring, and makes up the difference in thickness between the Vortec crank gear and the traditional crank gear... the thinner Vortec crank gear is the reason you "can't" use a double roller timing chain. eliminate it, and there is no issue.

:edit: the truck is a 94, and still wears its original TB, so i removed the reluctor, and installed the above mentioned timing chain cover.

[skylark]

So if I'm reading this right... My application doesn't need the crank sensor so I should be able to yank my plastic cover (ugly) off of a vortec longblock and swap the early style cover on (a pretty aluminum one) and be good to go without having to remover the reluctor, change the gears or balancer. Correct?

[GreaseDog]

uh... i don't know about that. i removed the factory chain and gears, reluctor, and cover... and replaced them all with the above mentioned parts. not sure if the reluctor will fit the old style cover.

[skylark]

So tbi chain and gears, trash the reluctor and replace with an old school cover. Sweet! I was going to order my ugly cover and timing set on friday. Now I can order pretty! I want to have the engine assembled by thanksgiving...

[fish4hc]

timing cover from the lo5 is good to go, i think he was correcting me about double roller chains- i have been wrong before

Ok, good. Ill run the l05 cover off my old motor then. The thought of buying much more parts just hurts the wallet.

Heres a few pics of the truck and the new vortec crate motor.
[IMG][/IMG]

[helo]

my (89) tbi water pump had a plugged 1/2" (NPT??) hole for coolant bypass or heater return. Just needed a water pump nipple from NAPA to make use of it. I think it was a 3/8 square drive plug. My radiator had a heater core return, which is why the water pump return hole wasn't used from the factory.

The vortec and tbi water pump pulleys and pulley flanges are different, FYI. I run l31 accessories, so no comment on needing the bypass hooked up. I'd say you might be prone to get hot spots on the intake with the bypass hole plugged. The bypass line allows the coolant to circulate continuously and stay at a more uniform temperature throughout the engine.

[fish4hc]

my (89) tbi water pump had a plugged 1/2" (NPT??) hole for coolant bypass or heater return. Just needed a water pump nipple from NAPA to make use of it. I think it was a 3/8 square drive plug. My radiator had a heater core return, which is why the water pump return hole wasn't used from the factory.

The vortec and tbi water pump pulleys and pulley flanges are different, FYI. I run l31 accessories, so no comment on needing the bypass hooked up. I'd say you might be prone to get hot spots on the intake with the bypass hole plugged. The bypass line allows the coolant to circulate continuously and stay at a more uniform temperature throughout the engine.

My tbi waterpump has that unplugged and used as the heater core return line. Thats why I wanted the waterpump for a l31 as it has two lines. I didnt know the pumps were different though as far as pullies. Guess I will have to use the tbi waterpump and plug the bypass hole on the intake and drill holes in the t-stat im guessing unless someone has a better idea?

[fish4hc]

One last question for now. I got my bored 47mm tbi from rv machine. Im probably going to take my intake and tb spacer in the morning to have it bored to match. Is is really worth it and will it make enough of a difference to pay the money to have the intake and spacer bored to 47mm?

[GreaseDog]

my (89) tbi water pump had a plugged 1/2" (NPT??) hole for coolant bypass or heater return. Just needed a water pump nipple from NAPA to make use of it. I think it was a 3/8 square drive plug. My radiator had a heater core return, which is why the water pump return hole wasn't used from the factory.

The vortec and tbi water pump pulleys and pulley flanges are different, FYI. I run l31 accessories, so no comment on needing the bypass hooked up. I'd say you might be prone to get hot spots on the intake with the bypass hole plugged. The bypass line allows the coolant to circulate continuously and stay at a more uniform temperature throughout the engine.

my 94 uses a stock TBI pump on a completely unmodified block. the 4 1/8" holes in the thermostat eliminate the need for the bypass. actually thinking about swapping out the stat for one that only has 2 holes. it runs a little cool IMO.

My tbi waterpump has that unplugged and used as the heater core return line. Thats why I wanted the waterpump for a l31 as it has two lines. I didnt know the pumps were different though as far as pullies. Guess I will have to use the tbi waterpump and plug the bypass hole on the intake and drill holes in the t-stat im guessing unless someone has a better idea?

factory TBI runs the 3/4" heater hose to the intake. plug the one in the pump, and hook it to the intake.

One last question for now. I got my bored 47mm tbi from rv machine. Im probably going to take my intake and tb spacer in the morning to have it bored to match. Is is really worth it and will it make enough of a difference to pay the money to have the intake and spacer bored to 47mm?

what intake are you running? looks like the GMPP intake. what size are the bores now?

[fish4hc]

Yes, the gmpp tbi/vortec intake.

Mt throttle body is bored to 47mm or 1.85" and the intake and spacer are stock size at about 44mm or 1.75"