Went yesterday to the Dyno Shop, where I worked when I put the stroker in my '76.

When the motor was fresh, I was a bit disappointed that I never made my 300HP to the wheels goal with the stroker. See my signature for engine details ... but the bottom line is that my choice to use cast iron heads was the problem. I spent a fortune upgrading the heads, but if I had purchased aluminum ones with the same cash, I would have more power than I do now.

But anyway ... Last year I got rid of the problem child quadrajet that even Lars was unable to get dialed in just right on my car. I also removed the OEM HEI dist that the car had originally been dyno tuned with. I used a Mallory Billet HEI dist, and an Edelbrock 650 AVS carb. When the engine was built, the Performer intake was port-matched to the heads so I have never changed it.

My point though, is that the changes I had made to the car over the years since it was set up on the Dyno, cost me power even though I gained driveability.

When I got there yesterday the 'pre tune' run on the Dyno showed only 251HP at the wheels. After two hours and over a 1/4 tank of gas on the Dyno, I left with over 275HP at the wheels and 300 foot pounds of torque.

I may someday get around to putting aluminum heads on it to retry getting to my 300+ goal at the wheels. But for right now, I'm and happy as a pig in Schnitzel !

I took a couple of videos with my cell phone of the car on the dyno .. but the Moto RaZR phone only seems to take a few seconds of video at a time. So I left with four videos but totaling only maybe 15 seconds of dyno time.

But I left with 25+ more ponies than I had gone in there with! Proof positive that when you make changes, get it back on the dyno to get her set up properly.

 

Congrats That is what a dyno is for, tuning the motor after mods or just tuning it period. Alot of people think others put their cars on the dyno to brag about the HP.

If you think about it, after you make changes to your motor, it should be tuned, you would be stupid not to want to get maximum power after spending a few thousand in mods, and the chassis dyno is where you tune it.

 

Just curious..... What were the major changes that led to the HP boost?

 

Just the main things that get done on a dyno tune: A/F mixture and timing curve.

The Edlebrock AVS Thunder carb was just outta the box. And the Mallory ignition system more or less the same; I had verified when the curve came in and changed the springs in the top...but I sure as heck don't have a distributor machine like the shop does. He also changed the cannister on the dist; the Mallory one was adjustable -BUT- it didn't adjust as low as Mark wanted it to be. It still held full advance til 8 inches of vacuum; he wanted it to go to 4 I believe.

In addition, the bushings in the dist flyout weights were ALREADY worn through! This dist had maybe 5K miles on it - perhaps 7 but bottom line, the brass bushings in a factory dist last 100K miles. These lasted less than a tenth of that! Replacing these was certainly a must. I saw them when he put the dist on the machine. If I put another 5K miles on that dist, I would have had to buy a new shaft. In fact, that Mallory unit actually looked like a remanufactured shaft put into a new billet case. I was very disappointed in that. I know that these bushings had no effect on power (yet) but they were not optional.

 

I'd bet that you'd make over 300 RWHP if you'd go with a old Torker intake and a 4779 Holley 750 mech. secondaries carb...
You'd not lose drivability but your fuel efficiency would be worse with the mech. secondaries carb.. A mech. secondaries Holey is EASILY worth 10 RWHP over a vacuum secondaries carb alone..

 

What torque numbers on the dyno run? I think you still have some horses hiding somewhere. What cam specs?

 

I don't see how the timing curve would affect peak performance as there is no vacuum advance at WOT and mech. advance is at total timing... The only thing affecting the peak performance at WOT is the total timing.. Most 350's get most performance at 38 degrees timing and most 400 based engines perform best at 36 degrees..

 

The whole aluminum head vs iron head has been a topic of debate for some time. Here's some websites that go into it:

http://proformanceunlimited.com/heads.html

and another

http://www.chevyhiperformance.com/te..._engine_heads/

"There was a “what-if” question addressed a few months ago in our Performance Q&A column that piqued our interest. The question was simple: If you had a set of iron and aluminum cylinder heads that were as identical as iron and alloy can be, which would make more power? Even the most ardent aluminum head supporter will admit that iron heads have the power advantage because aluminum transfers too much heat out of the chamber during combustion."

Dep

 

I'd never use an open plenum on the street...just my pref. It's got a 25-2800 stall convertor in it ... but still. No open plenums for me.

 

The carb was jetted properly. It was going fat at WOT and costing some power loss.

 

She came just short of 300 foot pounds of torque. The cam is a Crane 272H flat tappet; heads have Crane 1.6 full roller rockers (plus screw in studs, guide plates, and some pocket porting).

It may have some HP hiding somewhere .... I'd absolutely LOVE to put better heads on it along with fuel injection. The bottom end is bullet proof being all forged. It's got 6" H-beam rods and 10:1 forged pistons, spinning around a forged Eagle crank.

 

Oh my gosh some real feed back lol. Pinch Me lol.

But he is right. All things being equal the Iron head will make more power.

 

Ahhh yes. But my point was that I spent lots of $$ on iron heads, and still have 1.94 valves instead of 2.02 -- and also I need to really watch that the gas tank has just the right stuff in it, so there is no ping.

With almost any aluminum head, I'd have bigger valves and no propensity for ping. Not to mention (I think, anyway) a combustion chamber configuration that's improved from stock. And I wouldn't have had to pay for the upgrades in the basic head design, such as getting screw-in studs and guideplates.

 

Ok, I am assuming you are running stock heads? If so, they are costing you at least 25 to 40 hp. Your combo is begging for some real heads, and a Performer RPM intake.

 

Yep. That's the plan ... exactly as a matter of fact! You are right on track with my mindset. What I want to do is pull the engine, freshen it up and repaint it as well as the engine bay.

I thought about it over this past six months but didn't want to spend the money (house needed a few things )

Now of course, it's summertime in San Diego. Trust me, the Vette ain't coming apart now for a long time!

 

I would tend to agree. But I'm not sure he needs aluminum heads unless he is gonna up his compression ratio or is running really HOT or is doing a lot of racing and needs to lose weight. Dart Iron Eagle heads are probably all that's needed for most guys on the street.

http://www.gochampion.com/Dart%20SBC...on%20Eagle.htm

Dep

 

Paul, Did you find the source of your RPM changing on you at set/steady throttle? The strange deal you showed me at open house. BB

 

Nobody "needs" aluminum heads. The advantages are: they weigh less, they allow you to run a bit more compression, and they are much easier to repair. But there are less expensive cast iron heads that make equivalent power.

 

It was lean at part throttle, and rich@WOT. Two pair of jets and metering rods fixed her right up.

Runs like a scalded dawg, I gotta tell you. I may whine about missing my HP goal, but I love this car. The stroker was the best thing I ever did for it.

On my last hot rod ('70 Nova single owner purchase), I got my hands on an early '80s 350 block and built it up good. I kept the 350 displacement because it didn't need to be bored. Never thought about 6" rods or a lot of the stuff that went into the stroker in the Vette.

I built a good 6500 RPM screamer out of it and loved the way that light car hauled my assets I put a Turbo 400 in it and a 12-bolt 4:11 Posi. There wasn't much on the street that could keep up with that Nova.

But I gotta tell ya - the torque that the stroker in my C3 puts out would have made that Nova very happy too. I may not come off the line at 6500 RPM any more, but I love what I've got!

 

Like I said before Paul, that is a sweet sounding critter. VERY responsive.