Dyno tests, documenting the progress of my '73 T/A clone project

[DynoLee]

UPDATE:  11/19/2021   Took this car to the track for the FIRST time today.  I'll post details down below at "Reply #10".

I had some stuff posted awhile back, but it looks like it was all washed away when the board crashed.

A few years ago, I got a '73 Firebird Esprit, which the previous owner started cloning into a Trans Am - at least, cosmetically.  It still had a stock low compression 350 in it.  It had an HEI added, a Performer intake and a Q-jet.  The exhaust was a hodge-podge of stock manifolds with 2" head pipes, feeding into 2.5" intermediate pipes, going into 3" FlowMasters, and exiting through 2.25" tail pipes.

On the dyno graph below, the bottom curve shows the rear-wheel horsepower (RWHP) of the motor as it was when I got the car.

After making that pull, I played with various timing settings and adjust the Qjet to optimize the air/fuel ratio (AFR).  The line above that shows the power gain after the tuning.

[DynoLee]

The green line represents the next change to the motor.  I found a fellow with a relatively freshly built 455, but it had issues - mainly blowing LOTS of oil out of every orifice.  I bought the motor for CHEAP.

Turns out the rings were for a smaller motor, and gaps were up to 0.150" wide!  I replaced the rings. 

The heads were huge chambered "66" heads, pressed studs, and stock other than valve springs.  The cam had .454" lift, and the lobes & lifters looked great, so I knew the springs were sufficient for that lift or less, and they were left.  With the double-relief bevel-edged cast pistons, these heads gave a horrible 7.8:1 compression ratio!

I LOVE playing with cam designs, and designed a cam that is sort of a modernized version of a 744.  A bit more lift than a 744, but much milder than most other grinds with just about .440"/.435".  Duration at 0.050" is 222/242, on a 116lsa.  I had Bullet cams custom grind it for me.

This block was installed with the same exhaust, log manifolds, Performer intake, and Qjet as used on the 350.  So the green line shows          the power gain from using basically all the 350 bolt-ons, but with a 455 long block with a relatively mild cam.

[DynoLee]

The dark blue line represents something that is a bit troubling, as you can no longer easily duplicate this.  The SOLE change for this line, is the addition of a set of tri-Y headers, along with adjusting the metering rods to correct the AFR.  The only thing of note is that these headers eliminated all of the 2" pipe before the 2.5" intermediate pipes - but the rest of the exhaust remained the same as previous tests.

I was honestly stunned at the performance gain, as it was about double what I had predicted.  I suspect that a quality set of 4-into-1 headers will provide similar gains, but somebody else will have to test that.  Note that when I designed the cam, a free-flowing exhaust system WAS factored into the design.

[DynoLee]

The golden yellow line represents another change that I did not expect much/any gains from. 

I replaced the entire exhaust system behind the headers.  All 3".  An H-pipe was installed, along with 3" Borla ProXS mufflers, and 3" mandrel bent tail pipes.

Pretty much ALL the internet "experts" state that such an exhaust is total overkill for a motor this mild.  Some even think that the "too little backpressure" will cause a loss of torque.

Frankly, I have plans to keep upping the power of the motor, and this was supposed to be a modification that I could grow into, so to speak.

To my surprise, the FIRST dyno pull was noticeably higher than any previous run, but the AFR was shockingly lean.  After several changes to richer metering rods, I got the pull shown on the graph.

[DynoLee]

The next change served to help remind myself that I am NOT perfect.  I installed a FAST XFI Sportsman EFI system, along with the ignition control.  I failed to recognize that the throttle body had a bad injector, and kept trying different ideas to get it to run properly (I had successfully installed a few EFI systems at this point).

Long story short, I eventually flooded the motor, allowing gasoline to get into the oil without realizing it.  Not "flooded" as in got the plugs too wet to fire, rather "flooded" as in filled a couple of cylinders so that the motor would not turn over.  I know I should have changed the oil immediately afterward, but didn't.

I got the throttle body fixed, got the motor started, and soon had bearing damage.   

I pulled the motor, and the bores still looked fine, no wear at all and checked to be right at spec.  With more power planned, I went ahead and replaced the connecting rods with Scat H-beams and the pistons with KB mini-domes that have an effective valve relief of "zero".  The crank was turned, new rings installed on the new pistons, but all else remained the same.  The new compression ratio calculates to be ~8.3:1, still plenty low to run cheap 87 octane.

With those parts installed and broken in, and the EFI system working perfectly, I recently took the car back to the chassis dyno.  The brown line at the top represents my favorite pull of that test.  This was with an old Edelbrock P4B intake in place of the previously used Performer intake.

[DynoLee]

Here is the full graph of the dyno pull with the P4B intake, showing Torque as well as HP.  I used a lighter "smoothing factor" on this graph, so the numbers are slightly different than on the previous graph - but values are all within about 0.5%



I did test the Performer as well, and it was even with the P4B until the upper rpm, then just did not keep up. 

People have speculated whether throttle body EFI systems need a single-plane or a dual-plane intake.  Well, I test two dual planes and 3 single plane intakes (Street Dominator, Tomahawk, and Torker II).  The singles all were within 1hp of each other, and all made more power past 4300 or so, than the single planes.  The single planes ALL made more TQ, and the P4B was less than 3rwhp of the best of the single plane intakes.

Here is the P4B compared to the Torker II 

[5th T/A]

Lee,

Thanks for posting, you have some pretty impressive power gains. Nicely documented too. At what point did you switch from quadrajet to FAST XFI? Is the XFI still installed? Any plans to play with fuel mixture, timing and advance curves.

[DynoLee]

Lee,

Thanks for posting, you have some pretty impressive power gains. Nicely documented too. At what point did you switch from quadrajet to FAST XFI? Is the XFI still installed? Any plans to play with fuel mixture, timing and advance curves.

Thank you!

The XFI was installed AFTER the test with the 3" exhaust.  That is when I had a bad injector in the throttle body, which led to the engine damage (mentioned in the 5th post).  I now pressure test the fuel system (by activating the fuel pump) to make SURE there are no leaks in the injectors OR the fuel system, before starting the motor for the first time with a new efi system.

So, to be clear, between the gold/yellow line and the brown line on the graph, I added the XFI Sportsman system (fuel & spark), along with Scat rods, KB pistons, turned the crank (new bearings) and new rings.  The compression ratio raised from 7.8:1 to 8.3:1.  All other parts remained the same.

Something that may be of interest to some, is that my rather low-lift cam has a base-circle close to that of a stock cam.  This allowed me to keep the non-adjustable valvetrain.  I still have pressed-in rocker studs, stock rockers, stock adjusting nuts (torqued to 20)  and stock pushrods.  This is a simple, low-budget motor - I spent more money on the FAST system than I did on the motor.

I have played with ALL the EFI tables!  A good friend of mine, Eber Saenz of SXT Performance (San Leon, TX) sat in with me on the recent intake manifold testing.  Eber has been tuning EFI systems for about 15 years now, and "sees" things in tables that I just do not have the experience to recognize.  We made 5 tuning pulls with the old Performer intake, adjusting VE tables, timing tables, and AFR, before I started testing the other intakes.

Every dyno pull was data logged (a NICE function provided by the XFI system!)  which allowed us to analyze the timing and AFR during each dyno pull, and give us the feedback needed for tweaking the settings.

To keep the intake comparison as fair as possible, we left the tune alone during the testing, using the tune that gave the best results with the Performer.  I've since looked at the data logs more closely, and identified areas of the tune that could be a bit better.  Those changes would be seen more at the lower end of the curves, however, and would have no effect on the peak HP numbers recorded.

For giggles, I may test one or two other intakes in the near future.  But the P4B fits SO nicely with my shaker scoop, and by far provided the best average power.  I really believe for unported heads with EFI, that it is THE best intake to use.

[BBATCAR]

Great numbers and love the progression tests.

Sorry to hear about your EFI issues. I just recently ripped my EFI stuff off of my car and went back to a Holley carb. I know EFI gets better gas mileage but I'm not sold on reliability yet. Mine was nothing but problems, went through 3 tuners and money to try to get it working. Replacing so many parts and money then gave up.

I'm back to a Holley carb on my mild 462 stroker build and it just plan hauls butt...No Fuel issues, 1/2 push on the accelerator and it cold starts perfectly.
408 RWHP on mine. Keep us posted on your dynos.

[DynoLee]

Great numbers and love the progression tests.

Thank you!  Thankfully, my efi is now pretty well sorted out and working fine.  I've also installed several systems on other cars, and took a seminar at FAST headquarters a few years back, as well. 

I'm actually a bit surprised at the recent numbers.  I was HOPING it would break "300", but really thought 302 or 303 was all I was going to see.  I hit 307 with the Performer intake, and really didn't expect the old P4B to even match it - my mouth dropped when I saw the gain! 

I've been moving some of the intake test graphs over to a photo hosting site.  I'll try to make a post about the intake testing soon.

[DynoLee]

Took the car to the track today.  Traction was not as great as I had hoped, and the Mickey Thompson 255/60-15 drag radials spun more than expected.  The car was also a bit heavier than I thought, with me in it, it was right at 4,100#

I was finally able to do a softer launch, and get some 1.89 60' times, which were about 2-tenths slower than I had hoped.

The transmission was also not cooperating, shifting about 500rpm later than what I wanted it to (hit the rev limiter on nearly every 1-2 shift).

With a soft launch and still hitting the rev limiter, I was able to run a best of 13.20 @ 102.89mph, with the next best runs being 13.23 and .24, all around 103mph.

This was the first time I've had this car to the track.  It has EFI, but my lap top took a crap this morning, so I was not able to do ANY tuning.  All runs were made on 87 octane gasoline.  Give me some time, and I'll have it going quicker 



A link to a video of the best run.

https://i.imgur.com/lLJQP7I.mp4

[5th T/A]

I really enjoy reading your post.

I think 13.20’s are very respectable especially taking into account traction issues and bouncing off the rev limiter. If you can get past those two issues you could be running high 12’s.

If you don’t mind I have a few questions.
What is your axel ratio?
What RPM are you shifting?
Do you have subframe connectors, if not are you concerned about twisting the body while running slicks at the track?

Thanks!

[DynoLee]

Thank you for your compliments!

What is your axel ratio?  3.08


What RPM are you shifting?  I was WANTING to shift around 4700-4800rpm.  But the transmission was not shifting until around 5200 for the 1-2 and 5000 for the 2-3.   I believe I have over a full tenth to gain from shift points.


Do you have subframe connectors, if not are you concerned about twisting the body while running slicks at the track?   No subframe connectors.  I'm running MT drag radials, so not exactly "slicks".  The floor pan is SOLID though - no rust on the floors or trunk.  But if I race it much more, and go much quicker, then connectors WOULD be prudent!

[DynoLee]

Update for anyone interested.

I installed a shift kit, and the transmission shifts MUCH better.  I'm no longer hitting the rev limiter, and shifting is occurring around 4900-5000 (still a tad later than optimal, but much better).  My O2 sensor also failed, and that has been replaced.

I got the car back to the track recently.  Even though the air was much worse than when I ran 13.20 (about a 2,000' difference in density altitude), the car ran a new best of 13.12 @ 103.2mph.

My 60' times seem stuck in the 1.88-1.91 range.  I believe a better torque converter will be needed for me to break into the 12's.  Alternatively, with my efi system I can run E85, and that COULD possibly give enough power to bump the car into the 12's.  So the car is running quicker, but still hasn't broken into the 12's.

[70_71_78]

Edelbrock P4B. Been playing with one of those since my first pontiac in the early '80's. Bought it from the guy that had the shop space that I have now, along with a Holley 650 DP. that were from the late '60's. At the time, many said I would be better off with a stock manifold, but I had a square bore and I hate adapters. That intake with a proper carb and ignition tune always worked well. As I always have pontiac projects in the works and always watch local ads, I look at intakes. I saw some photos of intake manifolds and noticed the 'ole P4B raised lettering in the photo. I should have saved the photo, because I remember thinking that the runners on the top level did not look as large as my old one. I should have taken a look in person, but other things got in the way at the time. Leads me to wonder if there is more that one version of that model, possible changed to accommodate EGR? The one I have doesn't have EGR and I don't remember noticing if the photo did. I also wonder if that may have lead to the advice I ignored in the '80's. I gotta get myself in gear and get one of my projects back on the road! Getting tired of just reminiscing.
J

[DynoLee]

"Leads me to wonder if there is more that one version of that model,"

I have heard of 3 versions.  One for the early 60's motors, the newer version that I have, and another designed to fit spreadbore carbs.  I do not know of an EGR version, but there could be!