I've been watch this thread and would like to chip in on my learning experience with engine mods/dynos. I added AFR heads, Marine kinetics cam shafts and increased compression to my carb 500 hps. Luckily I had many discussions with Bob Madera before going to the dyno and knew what to expect and had a defined goal for the dyno time. I also got lucky and went to Larry Meaux of Meaux Racing Heads in Abbeville, LA for the dyno of my motor.

The first pull was 517 hp at 5600 rpm which was totally devastating. Bottom line is that with Bob Madera, Larry Meaux we fixed some issues with the valve train, carburetor issues and went back AGAIN and pulled 595 hp corrected and 605 hp uncorrected CF was .97 or so.

The lesson learned was that if I had not gone to the dyno and installed the motor in the boat after assembly; I would not have gone faster, in fact I might have slowed down. So, the knowledge that Bob is offering I believe is the key to a successful build.

Another point:

EDIT (I should have ) spent the money and dynoed the 500 hp BEFORE I tore it down. That would make the improvements easier to gauge before installation in the boat.


My dyno sessions were not performed with accessories or the marine exhausts due to limits of the dyno. I think that if I had dynoed the base engine I would've been more comfortable with no accesssories or marine exhausts.

Final judge was the boat dyno, gained 6-8 mph (nominally 80 mph to 86/87 mph) and great torque throughout the power band. (32' Active Thunder) My goal was 10 mph at the start of the project and the BAM web site calculated that an added 100 hp/motor would get me there. Looks like I came up 20-30 hp per motor short based on the BAM calculator. Now looking at drive/prop improvements to get the rest of the way.

Thanks to Bob Madera who kept me from myself on my project.

Bob is this SAE what most Dyno shops use?????????

SAE J1349
SAE J1349 standard of 77?F (25?C) / 0% humidity / barometric pressure of 29.234 in-Hg (99 KPa). [/QUOTE]
No.
The J1349 is the current SAE standard used by the OEM’s (GM/FORD/Mercury Marine/ etc) and R&D firms to conduct their testing. It is the most current standard used today. The older J607 (60 Deg F / 0% Humidity / 29.92 Baro ) is actually considered obsolete by the SAE. It is, however, far and away the most commonly used C/F in the high performance industry today. Why? It will correct approximately 5% higher than the J1349. That is the reason why the Merc 525 EFI rates @ close to 550, and the Z06 Corvette (SAE 505 HP) around 530 HP, with the J607 factors. Being that peak HP numbers largely drives the high performance industry, most engine builders and performance parts manufacturers, are forced to use the J607 factor to avoid the appearance of giving up 5% to the competition.

Bottom line, no matter what C/F you use; slight changes in the input of data can greatly alter the perceived performance potential of your investment. If an engine builder or dyno shop cannot or will not provide ALL pertinent data and VERIFY that is 100% accurate , your choice of engine builder/assembler is greatly simplified. I agree, the ultimate dyno is the water. Unfortunately most of the pre-purchase advertising claims happen on dry land.

Bob[/QUOTE]

Bob I also would like to ad if the Dyno operator doesent calibrate the break with the 3 foot arm thingy it will be off. Thats is the eazy way to fool a person or a dynoless engine builder that doesnt have the knowlage to know anybetter.There"s more ways to fool a dyno .Just dont be worried about the corection factors only.

Some mees with the strain gage and some play with corction factors.

Rob

Larry Meaux is prob the smartest guy I have ever met.In the middle of no were a barn in a corn field He is more famous on his head porting!! I used him on my old Chevelle motors.He could find hp in a motor while still on the dyno just by tuning.Most people say he has the most Conservative dyno in the country.I have heard he has gotten a little on the eccentric side.He picks what and who he wants to work with. You have to call his answering machine to set up a appointment just to talk to him I couldn't even get him to do a mild blower motor.Thunderstruck congrats on the speed, Like Larry says it doesn't matter what the dyno says it how fast it is,

Rob

Nordic,

If I may be so inclined to respond to this post without creating any bad feelings or trying to sound one sided:

Correct me if I’m wrong:

The dyno runs from Mike at Roccard were with the original cams (much “larger” cams then you currently are running) with dry exhaust. Right? Motors were installed in your boat with the old exhaust (Gils if I remember right). Didn’t you discuss the fact that you were going to upgrade your exhaust at a later date and understood the limitations of the Gils? Seems to me WE had that conversation.

I found almost 100hp difference between wet and dry exhaust with my combo and nearly 40hp difference between the Gils and the CMI E-tops. Plus, with the lower or “smaller” profile cams currently in your motors, the upgraded exhaust and other modifications you have done, these sound like reasonable gains to where you are today!

Don’t beat me up, but I don’t think you can still compare what you had before with what you have now horsepower wise. Those same modifications to your Roccard motors, I believe, would have produced the same results.

Just my .02

Dave

Dave,

What I was comparing were the dyno sheets first.Yes you are correct in one aspect,I was running Revolution Marine manifolds,but had no plans to upgrade and this set up is what I needed a motor built for and it was not.That was why we changed the cams out the first time.After the cam change it was much better but no where like it should have been.Now with the new combo I have a new custom ground cam and the updated CMI headers and I can understand the seat of the pants difference,but what I dont understand is:

Dyno by Roccard-634 HP dry 2" exhaust no accersories.

Dyno by JC Performance-565 HP 2" dry exhaust no accersories

These numbers are what I question and this is what this paticular thread is about.How could second build be much lower even after we did a bunch of more work to the combo that should have made more power then what Roccard had built?This is where the numbers don't work out.As you know engine building is more of a science then black magic.I learned a lot with my experience and the second time around the gurus showed me on paper with real numbers,"head flow numbers" how the first combo could have never even supported those numbers that came off of Roccards dyno. We flowed my heads before and after the head job and the numbers dont lie.I am not hear to bash,just trying to understand and help others understand about dyno numbers.

Nordic95

Nordic,

You've already read my thoughts on your first engine build, so we don't need to go there again, but I have a question on these numbers.

What were the specs on the cams that were in the Roccard motors when those dyno numbers were run, and what were the specs on the cam that you only gainned 1 mph on when run? Were the same cams in the engine when it was dynoed, as were in the engine when it was run in the boat?

and then what are the specs on the cam that JC put in your motor that of course, as we see, shows less dyno number, but gainned you a LOT of top end?

Mike11,
I'm sure this topic is worthy of discussion, however not at the expense of this thread. I would suggest that if yourself and Axapowell would like to discuss the relative merits of Roccard Engines track record, it would certainly be deserving of a stand alone thread. I'm sure now that there is before/after performance evaluations to compare and photo documentation of the rebuild process there would be more than enough information to promote a lively debate.

Thanks in advance for your consideration.

Regards,
Bob Madara

yall chill so this thread doesnt dissappear

Ok what would it correction be with the STD J607 ???

Thanks
Rob

Duke,
The cam that was chosen by my first builder was the crane 651,but it was a special cam,it had a variable lift and duration,as the lift got less so did the duration of the cam and motor.The more run time on the cam the smaller the lift would become to minimize wear and tear on the drive train. That is the cam that got me 1 MPH faster but I'm sure would lose more as time and wear went on .The second cam he installed was custom ground by RM builder and I do not know what it was,that cam in the same set up got me 80-81 MPH.Then with the oil passage way cleaning particles that were added to the engine on the first build I decided to have them rebuilt and cleaned out.This is when the second builder came into play,this is also when I decided to upgrade the build with some mods and cmi exhaust and also a new set of custom ground cams by RMbuilder.With this set up I am now running mid 80s and tons of mid range.

So lets not get off track and talk about what this thread was started for,THE TRUTH ABOUT YOUR DYNO NUMBERS.

Thanks to BOB-RMBUILDER for all this usefull info and the help he has givin me.

Nordic95