What's up guys. Long time no post.
I'm not sure how many people remember, but roughly 6 years back I made a build thread about building a 334 stroker and sort of lost track of keeping up with it over the years. Well, I'm here to tell you guys today that the engine is alive and well and I have the dyno charts to prove it.
Keep in mind, I'm really not posting this to brag (Maybe just a tad. I think the results are good for what the motor is), but moreso I believe the combo has even more left in it and I wanted some opinions and advice on where to go next.
For those of you who recall the original thread, I set a target goal of 350hp TO THE WHEEL. I was honestly being a bit optimistic with that number, however now I do not believe it is totally out of reach. I do believe, based on the numbers it put down, that I fudged the cam specs a bit (Will further elaborate later in post) and while 350rwhp MAY or MAY NOT be attainable, I certainly believe the combo has more left in it.
So without further adieu, allow me to lay my cards out on the table and let's get to rubbing those beards and brainstorming.
As far as components go, due to the small bore and limited valve choices, I wanted everything properly matched and VERY viable on the street which is why I chose 175cc heads and a TPI ontop. Engine specs are as follows:
- Virgin 40k mile 305 roller block out of a '92 TBI bird (Bored .030' over)
- Fully Blueprinted
- Eagle 3.75" stroker crank
- Eagle 5.7" 5140 forged I-Beam rods
- ICON 2618 forged pistons
- Ring gaps are set at .020" top ring and .022" second ring to safely allow nitrous/boost. Piston to wall clearances for use with 2618 forgings are set at .0055"
- Trickflow Super 23 175cc heads. 1.94/1.50 valves. No porting done. Bolted them on out of the box.
Here is the flow data:
- Comp Cams 918 beehive springs @ correct installed height.
- Calculated compression ratio is 10.5:1 static and 8.6:1 dynamic.
- Comp Cams custom grind roller cam. 222/230 @ .050. 110LSA. Lift is 569 Intake and 531 on the exhaust thanks to a 1.6/1.5 split ratio full roller rocker arm setup. Short travel roller lifters as well. The cam out of box spec'd in retarded 2.5* from ICL so I advanced it by 2*.
"Frankenstein" TPI. Flex Honed SuperRam base manifold. SLP runners lightly ported throughout and big siamese mod. I removed roughly half of the divider wall at the UPPER portion of the runners. Plenum matched, ported and smoothed throughout. 58MM Superram throttlebody. 22lb Bosch III Injectors running @ 60psi.
The whole thing is controlled by an EBL Flash that I have done all the tuning on since day 1.
Also one other thing of interest I'd like to mention is the fuel rails. These are stock MPFI rails other than the feed and return lines being plumbed to the rear with AN fittings. HOWEVER, I did ONE key modification to them which was to REMOVE the restrictor plug that is on the feed side of ALL F-Body MPFI rails. I eliminated the restrictor at the front crossover as well. After doing this, I noticed that my volumetric efficiency above 5000rpm went way up and the duty cycle went way down to the point that I had to SUBTRACT 15+% fueling to maintain the same AFR.
Toss in all the other "basic" build details such as a good balance, line hone on the mains, double roller, studded mains and windage tray/oil baffles.
As for the exhaust, we're looking at Hooker 2210 longtubes through 2x 2.5" true duals with an X-Pipe, Dynomax bullets and turndowns just before the rear axle.
Driveline weight reduction has been a focus as well. Chromoly SFI flexplate, smaller 9.5" torque converter, LS1 driveshaft and aluminum brake drums are a few highlights.
Now, some photos of the setup to illustrate detail:
Now, for the dyno video and, *DRUMROLL* results. The dyno used was a DynoCOM which is similar to a DynoJet. All results were obtained using heat range 7 plugs gapped @ .040", 36* of ignition timing all in by 2200rpm (With a dip to 33* @ peak torque) and 93 octane. AFR was a stable 12.5 throughout by the final pull. All results were through an UNLOCKED 9.5" Street EDGE converter. Coolant temp was consistently 170-180 throughout.:
The first pull, the car decided to flip me a big middle finger by putting down 298 to the wheel and we had a bad tach signal so no torque reading. After each pull, I would shut it down, review the datalogs and make corrections to the fueling. 4 more pulls each higher than the last. By the final pull, It was putting down 314hp/363lbs TO THE WHEEL. These are all motor numbers with no power adders. Also, for the final 2 pulls I disabled knock retard since I determined that the few counts I was getting were false knock from the converter flashing. So we can eliminate that variable.
I do believe I could have hit 320 however the operator was a nice guy and I was already overstaying my welcome. Certainly $75 for 5 pulls with AFR is not something to take advantage of.
Now, remember when I said I think the cam specs were mismatched? Here's why. Actually, a couple of reasons. Reason #1 is that even after the build was complete, I continued doing research to the point there are things I would do differently if I had another go around. I also talked to a very well known and competent cam grinder who informed me of the 75% exhaust relative to intake flow deal.
You want your exhaust flow to be in the neighborhood of 75-78% of your intake flow. Less, and you're choking the motor off. More, and you're blowing torque straight out of the tailpipe which will inherently cause HP to suffer. Given the duration on my cam grind and exhaust tube diameter/flow taken into account, I am around roughly 82%. I have more duration on the exhaust side than I do the intake which is totally backwards from what is optimal.
Also, something that piqued my curiosity was the power graph. While it does have a decent peak and a very "averagy" powerband flat enough to eat off of which is what you want for street use, I felt that it both peaked low and tapered off early. Taking volumetric efficiency and the small bore of motor into account, all the research I have done led me to expect a horsepower peak around 5500-5800 and to hold that peak to at least 6200. Take a look at the graphs and you will see that is not the case. It peaked at only 5200 and was really starting its downhill climb by 6000.
So guys, now that we have EVERYTHING laid out on the table (Please feel free to question any further details or point out anything I may have forgotten), my next question is, WHAT NEXT!?
I do believe this motor is pretty much maxed out in terms of NA performance HOWEVER I do believe it is being held back by the cam. I am setting a new goal of 350hp and 400 ft/lbs to the wheel. While I may fall a tad short of this OR I MAY actually hit my target is anyone's guess. But I'm damn sure gonna try.
One last thing I'd like to mention is that I know what the majority of the audience is thinking. It's the TPI. While I do KNOW that I could very possibly get NORTH of 350rwhp with a totally different intake, I've seen similarly modded TPIs hit that 350rwhp mark before. The runner siamesing was done a little differently and this was on a 355 we are talking about, however with more displacement and more cubes and a HIGHER RPM PEAK ON A LARGER BORE MOTOR. I think that illustrates the point I am getting at that the airflow and runner shape is not the restriction.
Who here remembers the trials and tribulations of dyndon and kevin with their 355TPI?
I guess we could also play with other ideas. Maybe keep the same cam I have now but try bolting a different, better flowing intake into place to bring the intake to exhaust ratio more into spec?
So guys, any ideas?