i've recently bored out the intake to 2" like in the tbi sticky on this forum. A friend told me it cant be done due to the water passages getting opened up during the bore process. I see two holes in the walls of the ports, are these the water passages or something else? Did i make a mistake in doing this? I thought per the sticky these were egr passages.

 

Tell your friend he's an idiot.those are egr passages in the intake.nothing to worry about.

 

thx.....i'll be sure to tell him that.

 

If the "holes" are wide-short slots, one in each bore, then those would be the EGR passages.

OTOH if the holes are rounded and in between the bores, in the bore divider region, THOSE would be openings into the water jacket that fills the interior of the intake.. and they would only be exposed after machining.

The water jacket helps vaporize puddled fuel AND it helps to stabilize the intake temperature during cruise when the EGR is running, preventing it from getting too hot.

 

kdrolt............I've read several of your posts in the past but I don't remember what if any mods you have to your engines. Question being do you run the heated intakes on your TBI set-ups?

Thanks............DM

 

Yes -- the TBI intakes manifolds I have still have engine coolant running thru them. The intake would be expected to get to the engine coolant temperature anyway, no matter if you allowed or blocked the flow of engine coolant, because the iron heads are going to be thermally limited to the coolant temp, so eventually the heated heads would cause the aluminum intake to get to the same temp.

OTOH the engine coolant also prevents the intake manifold from getting too hot (from EGR), so in some sense the engine coolant is more useful in keeping the intake manifold temp controlled (or "cooled") from steady cruise EGR than it is in heating the intake (because the heads would eventually get the intake to the same temp).

Most people think the engine coolant passage is used to heat the intake to promote fuel vaporization... and to a degree it is on a carb or TBI engine. But it's also there to stabilize the intake manifold temp as a result of EGR. That's why, IMO, the water jacket surrounding the TBI bores is so large. HTH.

 

Thanks kdrolt.............I ASSumed that the water would help heat the intake up faster. Never thought about it keeping the temp down or stable.

Have you or anyone else ever ported or done any work to the stock tbi intake for increased performance or is it a lost cause?

DM

 

For idle-5,000 rpm the stock intake is better than most others. I have put down 279 RWHP with the stock intake and stock bore TBI unit.

 

I have a ported factory TBI intake that still needs to have the (exposed) coolant holes welded shut. My MIG unit isn't the right tool for that so I need to get someone with a TIG welder to finish the job before I install it. It will be installed into my 93 Caprice LO3.

The porting was inspired by a neighbor of mine who did it to the intake on his 91 Caprice LTZ (305). He siamesed the bore divider down to the knife edge window that the factory cast in-place. He added stamped 1.6 rockers, kept the peanut cam, added a full N10 dual exhaust (manifolds/cats/intermediate/muffler/resonators) from a 96 Impala SS, a DIY cold air intake from a fwd v8 Cadillac + cone filter, and added copcar injectors along with changing the BPWC. IIRC he went from a bone stock 0-60 time of around 9 seconds to mid 7s. I drove it and it felt just as quick as a copcar LO5 Caprice. IMO the best mod was the exhaust, and the other mods helped on the intake side.

I additionally did some very mild porting on the runners, especially the lower plane runners, because Vizard's carb+intake book shows that stock dual plane intakes tend to flow less on the lower plane.

So I don't think it's a lost cause at all.

 

Kool....thanks for the info guys. I have several intakes and 081/416 heads sitting around for the next non Vortec build. Several ways to go as I also have a new in the box Wieand 7525 . My engine has never run better but it is getting the miles on it.