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Like the post on the HP says, the Chevette is "famously uncool," but in my opinion, that makes it even more of a sleeper. Seriously, who would be expecting 300+ hp from this baby?
Unsuspected turn of events today. I took my car over to the chassis shop to let them get an idea of what they'd be dealing with and ask about some extras. I explained how Ive been dealing with some intermittent idling stalling issues. So he gives me a number and a phone call later I was headed over for some idling tune work. Next thing you know the car is on the dyno.
Not 100% sure the numbers are final. We were seeing some serious trans slipping so he upped the line pressure. But he feels like it might still be slipping. The fluid is full and fresh. It was just rebuilt right before I ran at the track with the stock engine. So it easily has less than 5000 miles on it.
Anyways here's the end result graph. Mustang Dyno
SPECS:
346, PRC 2.5, FAST 102/102, BTR stage 3, 1.875" headers into dual 3" through dynatech split flow mufflers, 4L60E, Ford 9" -3.00 gear 24.5" tires.
No clue what pull this was. My phone died during tuning.
Just seems like a small increase in hp compared to what I was expecting/hoping for. I've heard of 391 with just a BTR stage 3 cam only car. I was just expecting a little more than 77 hp increase for HCI. Car in stock form ran 314 on a Dyno Dynamics dyno which I've read run comparable numbers to mustang dynos.
If the initial dyno pull was 5-10% optimistic and this one is 5-10% stingy, then that can certainty explain the difference. I never get hung up on dyno numbers. The real test of HP is MPH at the track.
My GTO made only 420rwhp at the wheels, but my best mph is 115. At 4000 pounds race weight, that's choochin...
Using my original dyno and an online 1/4 mile caculator my mph was exact. I was a .2 off on time but that could've been in my tires and launching the car correctly. I know the dyno is technically a tuning tool but I also see it as a tool to see if you've made improvements or not. I'll definitely get it to the track. But in my eyes if I'm making more hp on the dyno I'll be trapping more than if I was making less hp.
IF the trans is truly slipping, that would account for some less than stellar numbers. Can't expect tip top numbers if the setup isn't in tip top shape, IMO.
Also, really hard to compare apples to apples using two different dynos. Best of luck man! Love the sleeper
I'm not sure how much if any the trans was slipping on the run pictured in the graph. On one run it took about a 30hp dip in the middle of the run.
I placed an order on a new trans on Friday to change things up. I wasn't even expecting to dyno my car yesterday, it just happened. But I'm like every new to building a car person. You see and read all these "I made X number more HP" you just are a little sad when you don't make perfect numbers. I'll hope for more but it sounds like what I've got is fair, I'll live with my results.
For what it is worth, the only time I consider chassis dyno numbers is if they are on the same dyno. Here you have not only different dynos, but also different types of dynos.
06-28-2017, 06:56 PM
Sleeper Chevette on the dyno 
