454Corvair
01-27-2007, 07:06 AM
Last summer I dug out my TPIS MiniRam and installed it on my newest 408ci SBC. Last December I tried to install a set of 1.6 ratio Crane rocker arms but the push rods were touching the head. I removed the Miniram and to my surprise I found that the port impressions in the manifold gaskets from the Miniram were 0.100 inch lower than the cylinder head ports. I wondered how this could be, as the ports in the GM heads are huge (Felpro 1206), 2.150" tall, and intake manifolds are always smaller to avoid a ledge that would cause significant turbulence and hinder air flow. The MiniRam Ports are Felpro 1204, which are 1.99" tall. I checked the thickness of the gasket seal surface below the port on 6 sets of standard port 23 degree SBC heads, and all had from 0.250 on stock mid 1980 GM heads down to 0.175 on all out Bowtie heads. The average of these heads was about 0.230".
Thirty years experience in the Automotive world as a mechanic, Journeyman Toolmaker and Mechanical/Electrical Engineer in areas such as cast product and manufacturing engineer, powertrain design engineering and powertrain research tells me that 0.230" is a good seal surface and that I needed to take a close look at the MiniRam. What I found was that the port floors on the Miniram from bank to bank appeared to be too low and/or too close together. If the ports are located properly on the face of the Miniram, as Tuned Port Induction Specalties insists, then the only other possibility is that the port faces are machined too close together, allowing the manifold to drop too far into the valley.
I managed to get two measurements from TPIS from one of their manifolds. The measurement they offered was of the vertical location of the port floor, the other measurement (one I requested) was the distance between the port floors from bank to bank (manifold upsid down). The measurement they supplied was useless and made no sense unless their memory or math was seriously off. I compared the measurement I requested to my manifold (which was much narrower) and calculated the thickness of intake gaskets I would need to raise the manifold high enough to get the port floors of the Miniram and head to line up. The result was that I needed between 0.175 and 0.198" thick manifold gaskets to align the port floors on three of my long blocks, all of which have much larger ports than the Miniram. Even the Miniram TPIS measured needed 0.126" gaskets to work on any of my engines. I compared the TPIS bank to bank port face floor spacing to several other manifolds, and my Miniram was much narrower, another strong indicator that it was not machined correctly. TPIS tried to accuse me of modifying the ports, but they are the exact dimension of the smallest port openings TPIS made and I know the complete history of my manifold.
I made many other measurements not discussed above to make sure I didn't have a bunch of oddball blocks, heads and manifolds. I also used some old GM performance manuals with block, head and manifold drawings.
Sometimes you just have to suck it up and move on, but this Miniram manifold was expensive! I've run into other bad companies, like Scat- rods with forging cold shuts and poorly aligned big and small ends, machine shops that bench grind splayed main cap registers before line boring, bending connecting rods to align big and small ends because of poorly installed bushings, aligned boring mains 0.002" too large, crankshaft main journals ground with different centerlines, Eagle crank journals ground to small, cam dowels mis-located, partially machined piston rings, piston sets with 20g variations......
In summary STAY AWAY from TPIS Mini Ram manifolds.
Thirty years experience in the Automotive world as a mechanic, Journeyman Toolmaker and Mechanical/Electrical Engineer in areas such as cast product and manufacturing engineer, powertrain design engineering and powertrain research tells me that 0.230" is a good seal surface and that I needed to take a close look at the MiniRam. What I found was that the port floors on the Miniram from bank to bank appeared to be too low and/or too close together. If the ports are located properly on the face of the Miniram, as Tuned Port Induction Specalties insists, then the only other possibility is that the port faces are machined too close together, allowing the manifold to drop too far into the valley.
I managed to get two measurements from TPIS from one of their manifolds. The measurement they offered was of the vertical location of the port floor, the other measurement (one I requested) was the distance between the port floors from bank to bank (manifold upsid down). The measurement they supplied was useless and made no sense unless their memory or math was seriously off. I compared the measurement I requested to my manifold (which was much narrower) and calculated the thickness of intake gaskets I would need to raise the manifold high enough to get the port floors of the Miniram and head to line up. The result was that I needed between 0.175 and 0.198" thick manifold gaskets to align the port floors on three of my long blocks, all of which have much larger ports than the Miniram. Even the Miniram TPIS measured needed 0.126" gaskets to work on any of my engines. I compared the TPIS bank to bank port face floor spacing to several other manifolds, and my Miniram was much narrower, another strong indicator that it was not machined correctly. TPIS tried to accuse me of modifying the ports, but they are the exact dimension of the smallest port openings TPIS made and I know the complete history of my manifold.
I made many other measurements not discussed above to make sure I didn't have a bunch of oddball blocks, heads and manifolds. I also used some old GM performance manuals with block, head and manifold drawings.
Sometimes you just have to suck it up and move on, but this Miniram manifold was expensive! I've run into other bad companies, like Scat- rods with forging cold shuts and poorly aligned big and small ends, machine shops that bench grind splayed main cap registers before line boring, bending connecting rods to align big and small ends because of poorly installed bushings, aligned boring mains 0.002" too large, crankshaft main journals ground with different centerlines, Eagle crank journals ground to small, cam dowels mis-located, partially machined piston rings, piston sets with 20g variations......
In summary STAY AWAY from TPIS Mini Ram manifolds.