When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Hello all, I am new to the TPI world. I have owned 4 3rd gen trans am's and i am now on my first TPI. I have a 92 T/A convertible with the 305 TPI. I am looking into doing a heads, cam, and intake swap on it along with full exhaust. I have been reading many threads and trying to research things on my own and I am just getting confused and frustrated. This car is not going to be a race car, I am wanting something I can go cruise around town with all my buddies. I am wanting it to sound well and have a somewhat lopey idle but not sacrifice drive ability (I.E large stall). I have been leaning towards the trick flow super 23 heads but I'm not sure that will work with the Chevrolet ram jet intake i am looking at as well. I also have no clue what cam specs to go with either. I would love to get some input on what H/C/I combinations everyone else is running or for someone to point me in the right direction. I am a LS guy and have thought about swapping it but there is just something pulling me away from doing that. Thank you for the help in advance. 1992 Trans Am WS6. 305 TPI Convertible
I'm not sure I'd ditch the TPI on a 305. probably will make it a lot more sluggish on the street unless you plan to run upwards of a 3.73 axle ratio. it doesn't have the cubes or the long stroke of the 350, so short runners may be a detriment if you're mainly building an around-town street driver.
It's hard to really say where a cruiser stops and a race car starts. One mans race car is another man's cruiser. But that being said, you can do a LOT for your driving experience with a rear gear and proper stall converter. -all without going "big", and staying WELL within reason for a cruiser. Exhaust is a given, but after that I believe I'd look at stall and rear gear. ....or why not just go with a manual for fun factor?
I don't understand why you are being pulled away from an LS Swap. Once you do a H/C/I swap you will lose the look of the TPI, probably have as much coin into it as a used LS, and potentially still make less power. Especially if you throw a cam in the LS1 to get the sound you want, the LS is going to make more power.
The only reason I am hesitant on a LS or LT swap is that there is something in the back of my head that tells me to keep it a 305 TPI car. If i was going to swap it i plan on a L86 with the 10 speed.I will have someone do the LS swap since I do not have the tools or the time. I have had several quotes ranging from 10k to 14k. But I am thinking i am more along the lines of a set of the Trick Flow Super 23 175cc heads with the 56cc combustion chamber to raise the compression. Now the cam i am not too sure about. Do yall think the compcams 280h is a little bit too much for this motor? Also it is a Hydraulic Flat Tappet cam, should I find something more along the Hydraulic Roller line? I am looking for a decent cam with around a 110-112 lobe separation. Also I will keep my TPI and just do the port matching and see if I can get my hand on some SLP runners. I will be adding a small stall and I will definitely beef up the rear end. Do yall think the stock Auto will be okay with these mods?
The only reason I am hesitant on a LS or LT swap is that there is something in the back of my head that tells me to keep it a 305 TPI car. If i was going to swap it i plan on a L86 with the 10 speed.I will have someone do the LS swap since I do not have the tools or the time. I have had several quotes ranging from 10k to 14k. But I am thinking i am more along the lines of a set of the Trick Flow Super 23 175cc heads with the 56cc combustion chamber to raise the compression. Now the cam i am not too sure about. Do yall think the compcams 280h is a little bit too much for this motor? Also it is a Hydraulic Flat Tappet cam, should I find something more along the Hydraulic Roller line? I am looking for a decent cam with around a 110-112 lobe separation. Also I will keep my TPI and just do the port matching and see if I can get my hand on some SLP runners. I will be adding a small stall and I will definitely beef up the rear end. Do yall think the stock Auto will be okay with these mods?
I know you are knew to TPI's so I am going to beat a dead horse There are not a lot of "built" 305's for a reason. I am not saying they can't be fun and respond to some bolt on's, but a 350 bottom end that is rebuilt won't be much of an additional expense. The 305 Bore shrouds the valve and reduces the 305's ability to pull air in versus a 350. A 3.736" Versus the 4.0" bore of the 350, both using the same 3.48" stroke. The older 327 being known to be a good performer also had a 4.0" Bore, so did the late 60's 302. The infamous 307's also ran less that a 4.0" bore at 3.875". Anything you do to a 305, is going to make much more power on a 350 due to size and air flow. Good news being, most of the bolt ons will be interchangeable if you want to bolt things on until you are ready to pull the motor. However, there is information out there on building 305's and even stroking them.
More specifically to your question about the cam, I too like the LT4 Cam, but you will need to change the runners for it to work well. My brother had this in his built TBI car with a manifold swap and pulled really strong to north of 5800RPMs and caused no vacuum or idle issues. It will not work efficiently with a stock TPI Base/Runner.
Here is a good ARTICLE on a 305 build. This is with a Carb and they mention in here that the TPI's would start to be a restriction. A lot of their gain came in upper RPM's and by allowing the engine to breathe at the upper RPMs. The power output they achieved is roughly a mild LS territory. Which is very good. So, if you want to put the money into a 305 and stay naturally aspirated, this is about the best you will do. A TPI will require a new intake system to get to these RPM levels. Also, I think you will find you will need to step up injector size and will certainly need a custom tune to run it.
10-09-2018, 11:14 AM
