Here's the dilemma. Im wanting to install my new 113s on my Trans Am, but im not sure whether or not I want to just port the stock TPI a little more or install the new Miniram I have. But there is an issue, Read on!

I have a 1991 Trans Am GTA with 166k on the factory 350 that as far as I can tell has never been rebuilt. And the engine is about as stock as it can be. Behind the engine is a nice fresh rebuilt 700R4 at 2000rpm stall that should be good for 400tq, for what that's worth . That all runs back to a stock 10 Bolt with factory Posi and 3.23 gears.

Now in the garage I have a nice set of 113s off of a ZZ4 that were run about 500 miles and they have not been touched yet as far as porting. Intake ports measure 1.96 x 1.15. I also have that nice TPIS Miniram, but its ports are 2.33 x 1.285! They are HUGE! Now im pretty sure I could physically get them to seal up, but we are talking about a huge lip from the heads to the intake. So if I want to use the Miniram I would need to port match the heads at least!

So, the decision I would like you all to help me make is. Do I install the heads on the old engine and just put on the factory TPI? Thus keeping the RPM band down and the engine "Safe". This option would be the easiest, fastest and safest. But we all know it wont make the best power. So knowing that, do I just take my time and port match the heads and then put on the miniram, and hope that the new found RPM doesn't spell the end of my hard working 350?

You tell me.

 

The 113 heads have a different intake bolt pattern than your stock cast iron 87-up heads. They also have no EGR ports so your EGR system will become non-functional and likely throw a code, particualrly when highway cruising. Frankly, I don't think the 113 heads are worth much power over the stock cast iron units. They build a little more compression and weigh less, but flow-wise they are nothing to write home about.

About the MiniRam on a stock motor.... My brother had a high mileage 350 TPI in his T/A years back and swapped the MiniRam onto it with no other changes (other than headers and exhaust)- it traded off low end torque for higher end power as you would expect vs. the TPI. That also meant he spun it higher than with the TPI to get that power. Overall it was not much of a performance gain- rather disappointing. And it didn't take long for the old motor to spin several bearings from revving it higher than it was used to. Out it came, in went a 400 with good heads and a sizable performance cam- a combo that suited the MiniRam beautifully and then the car really rocked.

I wouldn't touch the stock motor. Build another one (or rebuild your existing motor fresh) with heads, cam and the MiniRam so that the components are all designed to work together. I'll add that the 113 heads probably aren't a good match for the MiniRam regardless. Aftermarket heads with some more serious flow potential would be a better choice to work with the MiniRam.