Disappointing dyno results
No it's a flat tappet. Do I need a smaller carb?
Here's my recap.:
Everyone who has said carb size (flow rating) is not related is correct.
I've illustrated the difference in running with secondaries and running the same carb on primaries. It doesn't change the curve really, just less and less HP gains from about 3000 rpm to the top. Vacuum starts to rise a bit as well.
While bigger can help to a point, too big is not a problem in this case.
if there was a MAP on the dyno log, we could say more about this aspect.
Your carb running rich won't cut horsepower that low. You need to go back to the basics and look at each component. The wrong pistons can lower compression. Your small cam isn't helping at all. Was the dyno run with headers?
Mostly agree. Running that rich is a part of the problem, or could be. It may be a combination of things that add up to the total disappointment. I've illustrated how much difference jetting can make on a chassis dyno
here: About 10 hp for the entire power band.
Doesn't explain the curve unless the engine is so loaded up it can't accelerate...
You've been given the correct answer by now. Chrysler spec'd their cams differently so the shop manual number cant be used to comapre. Your cam is similar enough your engine should be in the same ballpark.
And wasted $800.00 on dyno.
Add my 2 cents that not entirely wasted. You got break in and some information.
On the other hand, I myself have had first hand experience with dyno operators who really didn't know what they were doing.
Got less HP, the distributor curve restarded from where it was when I brought in (in his atttempt to get it to run bettter?) and no data because he didn't know how to copy files. I don't know if its how he loaded the dyno or something else. I wasn't familiar with that particular above ground set up even though it was a Dynojet. (I've made over 30 runs with that car/engine combo on dynojets.)
For tuning, I find its often up to the customer to lay out the test plan, as well as goals.
The things you can look at from engine dynos are fuel consumptions vs rpm which can indicate somehting different than what the WBO2 is showing.
Do you know what effect leaning A/F ratio will have on numbers.
View attachment 1716141700
My link above shows on a chassis dyno. On an engine it would be slightly more.
Does your guy really know how to run a dyno? What standards did he correct to? There are SO many variables here it's pathetic. I can run a dyno and make a stock 318 show 500HP. So there's THAT. lol
Unfortunately that's the truth.
it would be good to know the rate of acceleration allowed. IIRC 300 and 600 rpm/sec are two common standards.
Hi Rob. He can run a dyno. Was trying to correct for A/F ratio. He only had a bigger carb than mine. Test results were not much different.
Hi ch1ll. Regarding Carter AVS. Dyno operator only had a lager Holley which yielded similar results. He will receive 600cfm Holley for pull tomorrow if weather permits. Humidity is currently high. Operator does not have any replacement jets or metering rods. The Carter I had rebuilt was stock unit for 68 or 70 340 4 speed application. Can't remember which. Would only think jetting would be correct.
Cam is from Camcraft. I know, you never heard of them. Wish I hadn't. Only looking to make stock horsepower. That's all I can expect using stock engine components.
I think the cam is close to what you want, and running a known carb certainly wouldn't hurt to verify that it isn't (or is) carb related.
Definately throw some fresh spark plugs in and verify timing at a couple of rpms. I would check 600 rpm (or whatever the slow idle is) and 3000 rpm since 3000-6000 is what you will be really testing on the dyno. Also look at the plugs removed and verify they look rich. WBO2 can only interpret AFR accurately within a certain range of burn.
No … not really . Dyno time is so you can break in the engine , check for leaks and find performance issues before you spend days installing , tuning , diagnosing and then having to pull the engine againe and start all over .
although $800 seams spendy for a dyno shop that wont even rejet your carb muchless redegree your cam or set lash etc….
Agree!
Please someone with real world experience jump in here but if I move the timing +/- 6 degrees it will NOT devastate the curve like that in the simulation model. Your curve is totally crazy. All it really does is shift the peak around, it does not make it collapse like yours does.
it could make it a little lazy but basically agree.
I posted some timing curve vs power simulations along with some real life experiences.