TPI intake base porting

[1991 RS 305]

I hope I'm asking this in the right section. I am in the process of porting an aftermarket TPIS base for my 85 IROC 305 TPI. I've done some mods (ported heads & plenum, 3 angle valve job, back-cut valves, headers & improved exhaust). The stock base is restrictive & leaves little room for porting. I have researched this and am approaching it with the intent of improving air flow as much as possible, not to 'hog-it-out'. Like the link below shows, I'm dishing the floor slightly on the runner entry side, and raising the roof slightly on the exit to head side to hopefully improve on the entry to head angle the TPI system has by design due to the low profile nature of the base. Here is a example sketch:

Third Generation F-Body Message Boards

In addition, I am smoothing the ports and straightening the dog leg just before the exit to the head as much as possible. I'm removing the pebble finish, hoping for a near 'extruded' finish, since the base flows air only. Comments?

[Robert_McDonald]

I am reading your question regarding the tpi manifold. I want you to know that I understand where your coming from. In my experience in porting on these, there is a lot of room for improvement. I have owned a flowbench for 15 years now and have ported mant of these in my day. Let me ask a question, What kind of engine is this going to be used for?

[Robert_McDonald]

Read reply to your tpi question

[1991 RS 305]

The base is for a 1985 Tuned Port 305, with the mods shown in original post along with 1.6 Comp Magnum roller rockers with stock 85 cam, giving .430/.443, gutted airbox with K&N's, air foil, ported & siamesed plenum & siamesed/fluted stock runners, 700R4 with S-10 converter, 3.42 posi.

[Robert_McDonald]

I know that you are working on a 305. The reason I ask is that so many people go with a 350 ci combo.Porting the intake base is fine, but I want you to dig a little deeper. No matter what you do that engine is not going to breath, unless you change the cylinder heads. If you want to know what I am talking about you need to remove the tpi base. Then I want you to take a flashlight and look down one of the intake ports. You will find that the intake port is narrowed down just at the valve. Its like the port has been cut in half. The port on a typical small block is around 160 to 170cc. These heads which are the same for a TBI combo are around 120cc. The reason for this is velocity. This was GM's way of being efficient. There is no way to port them because of there casting. This is why the valve lift numbers are so low. If you want to see the biggest bang for the buck, here is my suggestion. Put a set of edelbrock replacement heads on and change the cam.I have used a cam from comp cams that is a great replacement for the stock one.