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

There is a Rollmaster on there.

 

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

Ok. Thanks Larry. That gives me a way forward. I am feeling better now about my build knowing that ultimately all that really gave me cause to worry was my unrealistic expectation concerning power output that I would obtain from the build as it is.

 

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

Hello Ed,

I just caught your post here....I can tell you from experience how disappointing numbers can be when they don't come in as expected.
My build yielded 426 hp and 498 ft/lb trq. Iron heads bowl work stage one valves and springs. roller rocker 1.6
I honestly think it's all in the heads. your short block is more then capable. I made the same mistake by using Iron heads.
I was looking for 500+. My guy should have said right there "NO WAY" your getting that without aluminum.
Run the engine for a while. get all the bugs worked out of the entire car and drop 5k on a stage 2 upgrade in the future.
that will change your whole world. don't frown on it.. we have all been there.
I wish I was more involved in your build. I would have told you where I went wrong on mine. maybe would have helped maybe not.
Keep making forward progress. hind site is 20/20

 

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

I would tend to agree with Mike T that what your probably seeing here is the result of installing big valves in the heads, without the required relief cut in the chamber. This can actually hurt airflow, and trim your ability to create high rpm HP.

Torque at 480 is right there where it should be for that build, so cam and ignition timing have to be close, as well as engine sealing and valve train function.

What your seeing is classic cylinder head limitation, and as Mike said, you might have made more power with small valve heads.

I would not worry about it a bit, although the next engine builder you chose, make sure he degrees in every camshaft, every time. That omission in the build is telling...

Toss it in, and bolt some alum heads on it down the road.

Have fun

JW

 

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

I went rounds with my rollmaster on my current 464 with 308s. Had to be at plus 6 to match the card, when I wanted to advance it 4. I had to actually go forward 1 tooth on the cam, then retard the crank to get to 104.

Seem like buick added 4 degrees in the stk set, all the cam blanks take the into the grinds, the rolaster pulled the 4 out on their setup. At least that's what I was told twice.

Without knowing where your intake valve truly closes your dynamic numbers are a guess, if the cam is in right then they should be what you figured, if it's not then it off.

I agree it won't make 50hp. For some reason your rings might not be fully seated as well. Our last motor picked up 2 tenths just running it over a couple month period. No timing or carb adjustment. I leak down test with air would answer that question. Ours had very little leakage till it got almost to tdc then 40%. After it sealed all up less than 3% across the board.

 

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

Thanks fellas,

Those are some nice encouraging words. I was getting a bit worried about actually being in a position to stop spending $$$ on this project in the not so distant future...........what a relief! p

There is another aspect that folks haven't mentioned here........maybe those with experience take it into consideration automatically, but I am wondering about the different readings that are given by different dynos. My engine was done on a Superflow. I have seen in my Google research that some dyno units are more "generous" with their readings than others.

It would seem that on other brand units, I may have not have been as disappointed by the results obtained. Whether or not they were more or less accurate is another story.

Regardless, I am ready to throw it in, have fun, and save my money. :TU:

 

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

Engine dynos are a bit closer to one another vs the chassis dynos. What correction factors did they use there? Or did they not use any and gave you results?

Some dubious dyno operators will use data WAY out of the norm to inflate numbers, like set the current atmospheric pressure close to what it would be in the eye of a typhoon around 26 bar when the norm is usually between the high 28s to the low 30s. Of coarse telling the dyno the pressure is 26 would in your case add around 150 HP!!

If the shop used the appropriate correction factors then that's what your numbers are, if they aren't corrected to sea level then the numbers will be a bit down.

But, eh, its exhausting thru un-ported manifolds and breathing thru an unported iron intake. On the bright side, I think you're going to like the torque if you can get it to hook on the street.


My 2001 F-350extended cab long bed 4x4 with a 7.3L diesel has 500 ft lbs of torque and only 250 HP but manages to smoke the 33" tall tires when I want to. I'm sure my truck probably weighs close to twice what your car does, and I know diesels run different than gas engines but torque is torque.




Derek

 

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

Ed, I had no idea you were that close to getting yours running. I know you and are running similar builds.
Mine is more stockish on the bottom end with oil mods. Basically a stock 70 SF bottom end.
We run the same cam. We just degreed mine in last week and it was dead on if that matters.
My rockers were worn so I had to order new ones from TA, those go on soon as I measure for pushrods.
Now to the heads...
I opted to keep small valves in mine. I ported mine and concentrated most of my work in the bowls and throats.
Seat height was checked and good to go. Using new TA stage 1 springs.
All in all similar builds. Mine should be together and running in a couple months. I'll post up results so we can
compare notes.
One other note, when I checked my dynamic CR it comes out to just over 8.1 and I probably have slightly less
static CR than you. My ABDC is at 45*. Did I miss-figure something?

 

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

X2 on what 99GTP said. Installing the Rollmaster without degreeing it in is a sure way not to have a correctly installed cam. You'd have a better chance of having it right with a stock timing set. If you are not degreeing it in stay away from the Rollmaster. At the very least I'd ask them what keyway they installed it at. If it is at the +4 spot at least it may be close to straight up depending on how the cam was ground. I believe you can at least have them check the cam timing and they wouldn't have to take the timing cover off. At least you'll know where it stands. If it is not right they can correct it now. Why be wondering down the road if you left anything on the table. As said you won't pick up 50 HP but if it off you can certainly pick something up.

For the exhaust manifolds I'd like to see a longer exhaust duration but if you're putting a set of headers on it later you may pick up more that you would normally expect. Did they at least put extensions of a foot or so on the manifolds. Plain open exhaust manifolds with no extension really don't work well.

They should be able to tell you what work they did to the heads to install the valves. If they weren't unshrouded I'd look into it plus what did they do under the valve after the seat was opened up? Did they mostly block off the exhaust crossover in the heads to keep that heat out of the intake? That is a scorcher. What about the distributer? Any carb tuning? What was the A/F ratio? What preload are the lifters at? Did they use adjustable pushrods or at least figure it out? Decking the block and cutting the heads doesn't work well for HP use with stock length pushrods unless you are really lucky.

Maybe I'm off but it seems to me that torque peak is a few hundred RPM too high or the peak HP is a few hundred too low. I don't think much about only an 1100 rpm span between peak torque and peak HP or maybe I'm off? It may be making more torque lower than 3900. Of course the exhaust manifolds or heads could be causing a problem but I'd think that cam should be peaking around 5300. I'd agree with others that said you've built a slightly better than stock Stage 1 so you're not down far but if the things mentioned weren't paid attention to you will be leaving something on the table.

That dyno looks like it is in NJ or am I reading it wrong? If it was me and they don't want to do any more work on it and you were really serious I'd ship it up to Rob Chilinski at Stage 1 Automotive and have him look into it.

 

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

Thanks for your thoughts Mike. Lots of interesting points there to think about. No extensions were attached to the exhaust manifolds. I am thinking along the same lines as you are concerning the impact that headers may have concerning power gain given that fact.

I do plan to enquire further into the de-shrouding or lack thereof concerning the valves and the cam timing.

After that, I will decide what I will do further.

 

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

If you want to do a quick check on the cam timing, remove the valve cover over #1 cylinder, Put a dial indicator over #1 intake pushrod when the valve is closed.
Turn crank clockwise till the indicator reads .050". At that point the crank timing mark should be at 5 degrees BTDC.
This will at least tell you if the cam timing is close or very far off.

 

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

Thanks for the cool tip!

 

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

I'm almost postive max torque is lower than 3900 and higher than thus pulls shows. If you look torque is on the way down from the beginning. Some dyno won't start a pyll down in the mid 2000 rpm range. Our motor from the factory made peak torque below 3000. Be nice to know what they are from a lower pull,

Maybe if cam timing is off, if your doing work to the heads, you can talk then into getting another pI'll again for a way reduced figure. See if they can start the pull 1000 or 1500 rpm lower.

 

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

FWIW, I used TA_288-92H for my cam, 9.5-1 compression. and had valve reliefs in the pistons

 

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

isnt the whole advantage of a big block over a small block to generate low rpm torque? and yet they dont test for it? makes no sense.

 

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

Hey I know those bad boy pistons.:bglasses:

Right on Mr.Sunset. You are going to need some sticky tires for your ride. :3gears:

 

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

The type of dyno we mostly see for hot rodding stuff can't hold the engine well down low.
To be able to test at a lower rpm the water dyno brake has to be a large enough diameter or a dual brake to hold the engine.
Diesel dynos are huge.
Olds 455 and Cadillac 500's focusing on low end torque are well on the downslope from peak torque before a stable measurement can be taken.