Hey all. I had a few quick questions in regards to my 85 TPI 305 Bird.

Firstly, does anyone have experience running a rockauto camshaft in their Trans Am or Camaro? I found this one for a pretty decent price imo, but I am unsure if/what I would need to modify (on) my car to run it. I would like to avoid a retune on the ECU as I am not currently savvy with PROM flashing, nor do I have the burner or chips. t

Currently, I have a TRUCKLOAD of work to do to my car. 3rd and 4th are gone (def a 700r4 moment), so a trans rebuild is on the to do list, it has a solid timing chain slap coming from the timing cover, so I need to install a new timing set (already have one, a nice cast iron double roller set), it smokes on startup (valve stem seals and possibly guides), mystery coolant leak (so probably seeping from a hose or head gasket), and an oil leak from both the oil pan and valve covers (yippee). What I am getting at is that the car is one or two parts away from needing a full rebuild.

Because of this I have decided to go ***** to the wall and throw some power adders at it since hell, I'm already going to just about strip it down to the long block, might as well make it fun!

This very long winded prelude is just so I can ask this: How much power can I expect to gain with;

Either the cam I have listed or the longest duration, largest lift cam that will sync with my stock ecu and fuel injectors (I understand it will be mild),
A set of mid-length headers, (think somewhere in between Huggers and LTs)
A reroute of that god awful TB coolant system (I live in the south)
A diy port and polish of the Heads, LIM, and Intake Plenum, (Specifically the lip just behind the TB),
A chinesium "CAI" from ebay (Not my proudest moment but it does sound good)
A cat delete (I swear it was the crackheads officer),
Possibly a new DIY Y-pipe to improve the exhuast geometry (so turn in more into a 45/30 degree Y as opposed to the stock 90 degree)
And a Single in, Dual out MagnaFlow hooked up to the stock exhaust,

Other things that could be of note: My accessories are all stock with the exception of an R134 compressor and the total lack of an egr pump, I have the Borg Warner 9 bolt LSD, and I think the WS6 package (so aluminum driveshaft, better shocks, 4 wheel disk brakes, yadda yadda).

I'm sure a retune would give me more bang with some larger injectors, but I am on a budget for the project, and I plan on someday soon building a TPI 400 sbc with a little help from holley and possibly either 1st TPI or Edelbrock

 

for the time and effort, pull the SBC and sell it to someone.
install a junk yard 5.3 with a cam.
easiest and cheapest way to make 400hp.
youll be much much much happier in the end.
and itll be cheaper than everything you listed up above

 

Hmmm, I'm not seeing how an LS + swap parts is cheaper than headers, a flat tappet cam/lifters, timing chain, and gaskets....but I admit I haven't done that route and compared.

That proposed cam and mods list should get you to about 260-275ish NET, crank hp.

 

Oh yeah, I know that a 5.3 would be cheaper, easier, and faster, but I'm weird and I love TPI.

 

So would the camshaft I found work with my stock ecu and injectors? That's my biggest concern with this project atm. I know that the 85 is more forgiving when it comes to cam swaps due to the lack of a speed density sensor, but I'm unsure what the limit is.

As for the LS swap part, he was referring to my idea of doing a 400 sbc tpi swap in the future, which, yes, would probably be cheaper, but I'm a weirdo and want to keep TPI in my car.

Also, 260-275 would be awesome for me, I was thinking it would only be in the realm of 240-250 so that's great to hear. Would Torque climb 1:1 with HP, so more in the ballpark of 330-350 at the crank, or would it outpace hp gains due the runner "tuning" effect?

 

That's a subjective "yes". What does "work" mean, to you? There are "Toon-o-philes" on here who'd tell you that the world will end if you run that cam w/o a tune. My experiences says that 224/224 is a lot of cam for a 305 on a stock tune, so while I wouldn't recommend it...I might try it for my own junk. I think if you were:
* Willing to dick around with injector sizing/fuel pressure and base timing
*O.K. with poor running, some stalling perhaps, and knowing that it's not optimized
.....you could run the wee out of it for a while and it could be O.K. enough. It's a personal judgement call.



There is no hard "limit"...where it works below a certain cam and not above it. The further you manipulate the shape and range of the tq curve from stock (and that's what more cam does)....the worse the engine will run on a stock tune. Again....224/224 is a stretch, IMO. It'll run and probably work...O.K. But you'll have to accept some drivability issues, I think.


IDk...someone else might, but I bet tq wouldn't change much unless you raise compression.

 

See, that's exactly what I was wondering. I have heard people mention 214/214 as being streetable without a retune, and I would greatly prefer to stay away from having to learn how to reprogram/flash an archaic operating language onto chip from the mid-80's.

If/when I build out a TPI 400 I'm planning on just swapping to a holley obd2 ecu with a built in tcm and uprading to a 4l80e, and some 28-32# injectors.

But for NOW I'd like to keep it as streetable as possible without having to throw several hundred extra $ at it and another 20-50 hours of my time. I'm a younger dad and time is already at a very steep premium with a 2 year old boy getting into trouble at every turn 😅

As for TQ. You think I'd need to increase compression? I thought HP was just a mathematical formula of TQ x RPM (more complex I know, I don't remember the formula off the top of my head).

If I decided to talk myself into running the cam I listed, what # injectors should I run, and what to I need to retune on top of that? Just tweak timing and let the ecu think it's the original injectors, or will that cause issues with the fuel tables that I will have to PROM flash to fix? I'm no slouch on a PC, but the earliest OS I'm familiar with is probably Windows 98/2000, and this car predates that by a good bit.

 

I'm really not going to delve into the benefits of tuning anymore, but in your situation you don't really need one. You see, it comes down to fueling. When the system deviates from the shortest O2 correction factor possible, it causes other areas of the tune to suffer. This is why you will hear people say that they installed a cam and now their off idle is horrible, they are surging, and even stalling. This happens because the tune is now playing catchup with the fueling that was predetermined from GM based on the original engine specs that it came with from the factory. You're not going to see astronomical numbers with that cam, but go for it if you want to, its your car, but because of the altered valve events due to any cam swap, the fueling will immediately be off. Think cam swap with a carb, and how you would need to re-jet the carb to compensate and dial it in. That being said, just get yourself an adjustable fuel pressure regulator and vacuum gauge, and if you have the money, a cheap wideband setup. Install your cam, start the engine, wait for it to warm up, deal with any slight surge if any, and then slowly shoot for the highest Hg reading possible in conjunction with the closest AFR stoich reading possible (14.7) by adjusting the regulator until you feel where you need to be. This is not ideal but it will work until you get a grip on tuning, or until you get a Dominator ECU. You can bump up the base timing a tad, which will increase your SA overall, maybe advance between 2 to 4 degrees (from factory 6^ BTDC to 8* or 10* BTDC) and stick to what feels best.

Best of luck!

- Rob

 

Okay, makes sense, so an increase in fuel pressure to the rail and advanced timing would do it, or do I need to grab some larger injectors (Like L98 injectors) as well?

 

More FP will "cover" the area of the tq curve where the engine needs more fuel, but may run too rich at idle. FP is a global change, so it needs to be done in a way that provides the best (to you) compromise. I don't think that you'll need more injector. I recently made 289 RWHP on an L98 with stock injectors. No tune, either, but that was w/the stock cam.

HP is a function of TQ and RPM. By adding "more cam", you're going to raise the RPM at which the TQ happens (there is your More HP), more than you're going to raise TQ, IMO, with that combo.

 

Wouldn't adding total cfm to the engine by porting/polishing, adding headers, improving exhaust geometry, etc, add some gains in the TQ department by allowing the engine to better utilize that extra fp at idle/low rpm pulls?

More power is more power, and I'm not one to look a gift horse in the mouth, but would I somehow be killing low end grunt by removing intake and exhaust restrictions while adding fuel, lift and duration, and timing?

I'm good at parts changing, but this is one of my first projects where I'll have to actually do more critical thinking aside from bolt this into that and plug this in, and I would like to squeeze as much performance out of my dollar as possible (I am a cheap bastard after all &#128514.

I do understand that in a N/A engine, there are tradeoffs that you have to balance. Like if I shortened the intake runner length, say to around 18" as opposed to the stock 22" (24"? I don't remember what it was), I would move my power band up,, at the cost of losing the runner "tuning" effect of increasing intake air velocity, and as such losing torque, but would the cam or port job lower velocity to the point that the extra fuel and air wouldn't keep or increase torque down low? Or am I way overthinking this? (common issue).

 

Do the free mods stuff, exhaust and throw a 2-mid-teens cam in it, get the most out of it that you can w/timing and FP and enjoy until you build a fully developed product.

 

Now there's a message my wrench monkey brain can comprehend 😀
I'll have to start a new thread when everything gets going to keep y'all updated, I have some shorter projects on other cars that I need to finish first.

 

Karl, the ECM doesn't really care which injectors you are running, it's only looking for the closest percentage to O2 correction possible, that being 0%. So whether we calculate larger injectors using the stock injector values and pressure when more air is being introduced (mods), or running the stock injectors with stock pressure but increasing the injector values in the VE table through a tune. In the end the ECM wants to see 0% correction either way. The stock threshold on these older systems is about 6% correction, so once you deviate beyond that, that's when it becomes an issue. The cam will probably give you anywhere between 15-25 more horsepower if that, and that really isn't much, and can be compensated for using higher fuel pressure in a pinch.

Example;

Lets say your stock engine made 200 horse from the factory, so with a safe 80% Duty Cycle to avoid a static injector (wide open constantly), the engine would call for 15.5-lb injectors. Your engine came with 19# injectors, and GM did this to allow for some elbow room with varying ambient temperatures. From there, based on how much air is being presented with and without a load at higher RPM's, GM tuned the VE for as close to 0% correction as possible. If you install a camshaft that adds about 25 horsepower over stock, the now needed injector flow will call for 17.5-lb injectors for that same 80% Duty Cycle over the original 15.5-lb injector due to the increased air from the cam, so you would up it from 19# injectors to 20.5# injectors. So no, L98 injectors will be slightly too much because they are 22-lb injectors and you would need to reduce fuel pressure, which can be an option if need be to tell you the truth. Once you add more fuel at idle raising the pressure you automatically added more fuel up top. It won't be "dialed in" but it will be there. Just like with the distributor, once you increase base timing, you increased the SA up top. It won't be "dialed in" but it will work fine for the time being. If you stick with the stock 19-lb injectors after the camshaft install at 37.5-psi (w/vac) fuel pressure, you will need to increase fuel pressure to 50-psi (w/vac) to even it out. That's all. Or, you can keep the fuel pressure as is at 37.5-psi (w/vac) and install 20.5-lb injectors over the stock 19-lb injectors. That's all. Bottom line the ECM needs to be able to bring the 02 correction to as close to 0% as possible. All you're doing it helping it achieve that goal, it is programmed to do that. it doesn't know what you're running mechanically for parts, it only meters the O2 (Closed Loop). If Closed Loop is close to 0%, then Open Loop will be fine because it was preconfigured to be already. So it becomes that game of increasing and decreasing fuel pressure based on injector flow and modifications to get to 0% O2 correction the way we used to do back in the 90's running the '7148 ECM...

- Rob

 

Okay, Im starting to make much more sense of this whole thing now. The only thing the ecm actually reads is o2 when it comes to fuel tables, and an increase in fp will be supported by the original injectors due to the ample wiggle room provided by GM. Makes sense, so the only "tuning" I need to figure out is calibrating my fuel pressure at idle with all vacuum systems functioning. And dialing it in with the vacuum gage is just taking the reading of vacuum at the intake and subtracting from my reading at the rails to approximate injector psi.

Do you have a recommendation for a decent adjustable fuel pressure regulator by chance? BBK is sold out at the moment and I don't know if I trust the no name one for 80 bucks on ebay.

Also, sorry if I have still anything wrong, I swear I'm not as obtuse as I seem from my posts, I just like to have a firm understanding of what I'm doing before I dive into a new project.