Disappointing Dyno Numbers -- I need advice please! I think something isn't right.

Re: Disappointing Dyno Numbers -- I need advice please! I think something isn't right

Hi Jim, I don't know how the distributor was set up....I sent them a new Mallory HEI that they did the break-in with. After the break-in, they couldn't get the engine started again with it to do the pulls, so they threw in a points distributor that they had lying around. I plan to troubleshoot the Mallory and put it back in.

 

Re: Disappointing Dyno Numbers -- I need advice please! I think something isn't right

I am definitely liking the sound of that! :3gears:

 

Re: Disappointing Dyno Numbers -- I need advice please! I think something isn't right

Glad to hear that your over it Ed.
Hp is that thing we are all chasing and always want just a little more.
That old saying, "How fast can you afford to go"?

I am very impressed to learn you did the seats yourself. I would be interested in learning more about this
and what level of difficulty you found it to be.

This is you in a few months :3gears:rowing gears. :TU:

 

Re: Disappointing Dyno Numbers -- I need advice please! I think something isn't right

Thanks Joe,

Regarding the engine, in reality on the street, torque is what I really want and need. Looks like I have plenty of that in the right place, down in the low-mid revs.

I am happy to help you along the way if you want to do your seats. I need to paint the metal seat parts and will then take some pics. (this weekend). I didn't find it particularly difficult. Let me know when and if you want to tackle the job. You could start by watching videos on YouTube. Legendary has some very good ones that show all the steps. PUI has some too just to get another perspective....I didn't find their videos to be as helpful though.

I had a lot of restoration to do re: the frames as well. Anyway, I will leave it at that for now. Drop me a line when I can help.:TU:

 

Re: Disappointing Dyno Numbers -- I need advice please! I think something isn't right

I would not bother degreeing the cam now at this point it must be pretty darn close to optimal. I would leave well enough alone and focus on optimizing the ignition curve and carb metering. Then when you add alum heads and a different cam later on just ensure you degree the cam on that build.

 

Re: Disappointing Dyno Numbers -- I need advice please! I think something isn't right

^^ Good catch.

 

Re: Disappointing Dyno Numbers -- I need advice please! I think something isn't right

And the Chassis dyno numbers will likely not give you much satisfaction I don't think. The engine dyno gives a much more accurate rating of the engine power vs the chassis dyno. There are just so many variables that effect the chassis dyno it is best used as a tuning tool. Converter slip, gearing, tire spin, so many ways to skew the dyno numbers not to mention the actual dyno itself and there is a lot related to how the operator does the testing.

Do a baseline run, change the timing, carb etc. one change at a time and find the trend of increase or decreases from your changes. There are 1000 HP cars that dyno well but cant get down the track and there are 500 HP cars that can run the number. Try not to get caught up in the HP race. This tuning takes time but if you are quick with your adjustments (or the shop is) then this can be a good gain for the $. Otherwise you can optimize the tune at the track or on the street but it will not be as easy to dial things in quickly. And of course once you have things dialed in on the dyno the car may need slight adjustments to run its best at the track.

 

Re: Disappointing Dyno Numbers -- I need advice please! I think something isn't right

I just completed an engine similar in that it had a stock intake, 850 Q-jet, Stage 1 converted heads, 9.95 compression I used a 284-88H .
I used the Pat Kelly DCR calculator. and with this cam I had to advance that cam to 106 to get the DCR that I wanted which I think is a nice safe place to not have detonation at about 7.8.
This engine made 514 lb ft at 3600 and 409 HP at 5100.
I have always used an old set of KB pulse headers for dyno use so I had a fair comparison between engines.
I have made tests in the past with different headers and manifolds. I can tell you that the stock manifolds on this type of engine will reduce torque and HP about 25 numbers.
That being said I say your torque is in line with this type of build but the HP is down a little and by the looks of the BSFC it may be a tad rich.
If the engine was timed with less than 36 degrees total that might cause the rich condition.
I have seen about 20 or more HP from 32 to 36 and sometimes 38 degrees.
Another thing you did not state is how many pulls were made. I have seen as much as 10-12 HP more from say the first full pull to the 5th or 6th when the rings come in (seat) and that is when I have done the cylinder honing (Sunnen CV-616) with a torque plate.
I have seen engines done at other shops where it took 10-12 pulls to get the rings to come in.
I'd say all in all you have a comparable engine to the dozens I have done similar to yours and I would be quite satisfied.

 

Re: Disappointing Dyno Numbers -- I need advice please! I think something isn't right

Hi Sean,

How can one tell that the cam "must be pretty darn close to optimal"?

 

Re: Disappointing Dyno Numbers -- I need advice please! I think something isn't right

Thanks Mike,

The dyno sheet says 35 degrees total. Do have a reference by chance where I can learn how to interpret BSFC?

Only a few pulls were done. The primary purpose was to break it in and check for leaks, etc before shipping. Maybe the rings aren't seated yet--I appreciate you sharing your experience.

Next time I talk to the shop, I will inquire about number of pulls.

 

Re: Disappointing Dyno Numbers -- I need advice please! I think something isn't right

If you cam was degreed way off then it would be down on power, but it sounds like your engine is making the expected power for the combo. Nothing wrong with degrreeing it now if it helps make you sleep at night, go for it.

 

Re: Disappointing Dyno Numbers -- I need advice please! I think something isn't right

Thanks for the heads up Larry. I will definitely take some time safely getting to know how the engine responds.

 

Re: Disappointing Dyno Numbers -- I need advice please! I think something isn't right

My 71 GS 455 with 343 observed/measured HP ran 11.90s @ 3500 pounds, with zero tuning, but the peak HP was not at 3000 RPM.

 

Being a “exmachinist”.

Please, someone ask of his actual experience in the field. Dates, his age at the time, how long he actually worked in a shop.