I hope this question isn't a repeat. Does anyone have experience using the FIRST TPI intake? From what I have read, the FIRST TPI intake is said to have a torque curve like the Accel Superram, possibly with a little more lower end torque being the difference but less lower end torque when compared to the stock TPI intake with long runners. I am trying to figure out if you take a loss in lower end torque for the gain in flow to higher RPM. Does anyone use this intake for a daily driver and not suffered from any loss of torque down low?

 

I was hoping someone else would respond because I hate seeming like the FIRST poster boy. However, not many folks have run one and I have run a ported stock base TPI/SLP runner combo, the FIRST, and a Holley StealthRam on the same 355.

The short answer to your question is yes, you will lose a fractional amount of power at the lower end of the spectrum going from a stock TPI to a FIRST. This is a function of the physics involving the difference in runner length and diameter. However, depending on your combination that may actually be a good thing.

If you say what you plan on running it on, I could probably give you a pretty good idea of what to expect.

 

Well, if anyone knows my profile name then they will know that I plan to have my second-gen LT1 fitted with a TPI intake. I have been reading as much as I can from Chevy performance magazines to various forum posts by those who were looking to do what I wanted for their daily driver. I was given a solid performance suggestion on another forum using a mild comp cam with 1.6 RRs designed for the TPI 350 and to use the FIRST TPI intake. However, right now I am growing impatient and eager to get the intake on my car and have it properly tuned to work on my LT1. After enough reading, I have concluded that the stock TPI with it's stock runners should work fine enough on my f-body LT1 with it's factory camshaft and factory gearing. It seems like many have modified their L98s to the same specifications, using stock LT1 cams and similar gearing to mine. Then, modifications to switch over to use fourth gen exhaust.

I just purchased on ebay a decent used TPI intake from a 1991 Z28 Camaro, which ironically had it's engine swapped to an LT1. So, I figure the stock TPI should be safe to use on my LT1 given my current stock set-up and for my own evaluation to determine if I want more higher end torque from the suggested comp cam upgrade and FIRST TPI or if I am happy enough with this set-up as it is! I probably won't get it done this year but hopefully before spring of next year so that I can beat the rush of race cars to the engine shop I plan to have install and dyno tune my car.

 

Ok, now I remember - I replied to a post you made awhile back about converting an LT1 over to TPI. I think you've moved in the right direction in trying out the stock TPI to see if that meets your objective(s). Research and planning is a good thing, but many times it takes busting the knuckles and first hand experience to make sure you really get what you're looking for.

 

With regards to the thread topic, thank you for backing up my findings and other comments which support the shifting of the power band when moving to larger size runners and even stepping up to a FIRST TPI intake. Since my car is not getting cammed and since I am not having my heads ported, I really have no need for the FIRST TPI intake and it's flow ability. Furthermore, if some guys are selling 55 chevys and 67 chevelle malibus with TPI engines to get those all metal heavy body cars rolling and with some decent power, I have to figure that this intake on my LT1 should give me something of what I am looking for given my requirements for stockish performance including EPA rated fuel economy. I am going to have to have a machine shop clean out the plenum, runners, and base since they have a solid coating of carbon deposit and to modify the base to bolt on to my LT1 heads.

So, I am finally confident that keeping the TPI stock and using it on my stock LT1 is the right move to make at this time and for me to see how the engine behaves with the TPI intake on it.