Dyno Numbers - I am pissed.

[bigmanjbmopar]

UPDATE:

First of all, thanks to all of you guys for your honest opinions and sage advice. For me, hearing these dyno results is like waking up on Christmas as a kid and finding dog shit under the tree. LOL. BUT. . . we're still fine tuning and I wanted to let you guys know what I've learned since yesterday.

Dyno shop called me this morning and said that the motor is running great, no ring problems, etc. He said he has this thing called a whistler I think he called it and he can check the CR. He will also look at the cam timing. He asked me to send him the head flow numbers and the Mopar Muscle article and dyno sheets from their 383 build.

I also spoke to the engine builder. He says the slugs are .010 in the hole. He thinks there is another 30 to 40 HP in the motor with some minor mods. He can mill the heads .030 and use a thinner head gasket and acheive 10.3:1 CR, but is concerned with the pump gas. Is that too much? I was under the impression that you can run a bit higher CR with aluminum heads because of the way the heat disapates as opposed to cast iron.

He also thinks the motor/heads will benefit greatly by using the bigger Comp Cams XE285HL, as opposed to the XE275HL I have in their now, and topping it off with an 850 Carb.

Questions:

1) Will I have an issue with 10:3 CR using pump gas if I decide to go that route?It all depends if you want to go to other states here in Cal all we can get is 91 I built my motor with dished pistons, dished 24 cc for a 9.6:1 CR so I could run the 91. Something to consider

2) I'm going to call Comp Cams today, but will changing to the bigger cam (remember I have 1.6 ratio rockers) create any other clearance problems? Is it just a switching of the cam or does any machining need to happen? I am assuming I can use my existing pushrods, lifters and springs. The lifters and springs (double) came in the kit from Comp Cams for the XE275.Call Comp and have them part match what you need, you should be ok but never hurts to double check- I have a xtreame energy hydraulic roller cam using solid roller lifters and the 1.5 ratio rockers from 440source and can pull hard in any gear

Finally, many of you have commented about the dyno being a "real" number. I have since learned that this guy is known for giving conservative numbers and not just trying to tell people what they want to hear. I am using a eddy 800 AVS thunder series carb just to be able to pass at least 2 gas stations before refilling lmao...I get real power and drive-ability out of it but honestly I need a 930 to a 1050 to make another 75 - 100 hp. I would not sweat the dyno numbers, and like mentioned you need to spend all day there with your builder checking plug color after each run swapping jets and checking and tweaking timing the whole time in order to get the best results. You can just hook it up run a couple of times and flip out at the results with out playing with it. just relax and start with what you have and tweek from there don't go out and spen another 2k just to be disappointed again tweek what you have jut my 2 cents.

Naturally, I will keep you all posted.

Thanks very much,

John

 

[JJRJR]

Spoke to a tech guy at Comp Cams. He thinks the dyno numbers are very low as well. He doesn't think it needs a bigger cam or certainly not a bigger carb. He recommended checking the heads for pressure, valve seats, etc. and be sure geometry is right on. He believes the combo of parts in the build is perfect for a 69 RR and the 3.91 gears. I forwarded the info to builder and dyno shop. Let's see what they come up with.

John

 

[JJRJR]

The Latest in the Saga: Dyno Shop uses something called a DTS System which apparently monitors the atmosphere and adjusts to level the playing field. It is the "latest and greatest" in the Dyno world according to him. He said he could dyno a motor in the winter and the hot summer and the adjusted numbers will be the same, while the "raw" numbers will be much different. The 392HP/407TQ numbers he gave me are the "corrected" numbers. Interesting. When MaMopar gives the 335 HP for stock motor, is it "corrected" or a "raw" number?? Someone here mentioned that comparing the OEM 335 to my 392 may be meaningless because of this adjustment. I guess that's good news.

He is still going to check cam timing and CR, he said we may also get a bit more from it by advancing the timing to 37, it's a 35 now. He also thinks the heads are fine, etc. but is going to do a leak down test anyway. NOW for the question: He did say that in the Mopar Muscle 383 build, they used a single-plane intake. Mine is a dual plane. He says that is making a BIG difference. He thought if I went with a single-plane, I would get a good bit more HP and a little more TQ. Just not sure what else making that change may do.

The drama continues, but I guess I was glad to hear that the "corrected" numbers are nothing like the "raw" numbers, just wish I knew how to figure out what the "raw" numbers would be...

Thanks to all,

John

 

[A31PKG]

Generally speaking, the dual plane intake (like the factory one) is good for all-around street driving where low-end torque is what is required. Single planes make thier power in the upper RPM range...great for the track, not so great for the street. As has been mentioned, the true test will be once the engine is installed in the car and you mash the go pedal....then the only "drama" will be wiping the grin off your face!

 

[JJRJR]

Generally speaking, the dual plane intake (like the factory one) is good for all-around street driving where low-end torque is what is required. Single planes make thier power in the upper RPM range...great for the track, not so great for the street. As has been mentioned, the true test will be once the engine is installed in the car and you mash the go pedal....then the only "drama" will be wiping the grin off your face!

LOL. Very true. This is actually a great learning experience. Can't wait for that grin....

John

 

[metalstorm]

you can figure the raw dyno #'s by finding the correction factor.1%,2% so on.

 

[JJRJR]

my thoughts, carb will help, although I'm not sure it's going to give you the numbers you're expecting. :cents:
Compression could be better. I would have shot for 10.5:1 myself.
Just curious, did you deck the block, how deep are the slugs in the hole at TDC?

Engine builder says he can mill .030 from the heads and go with thinner gasket and get to 10.3:1. if I'm at 9.8:1 now, will that make a difference big enough to notice?

 

[69hemibeep]

I think your getting all worked up over nothing. Put a bigger carb on it and have fun, with 3.91s your going to have a ball :drive: :drive:

 

[JJRJR]

I think your getting all worked up over nothing. Put a bigger carb on it and have fun, with 3.91s your going to have a ball :drive: :drive:

I hear ya man, I know. Sorry to be belly-aching. The dyno guy confused me a bit. I was all set to just put an 850 on it (as he recommended yesterday) and be done with it. Then this morning he called and said, "I think the carb is fine, it's not going below 2 pounds of vacuum so it's ok." Not sure if pounds is the right word, but he essentially did a 180 on his advice yesterday of getting a bigger carb.

Do you think that set up would work better with an 850? Some tell me yes, some tell me 750 is plenty. Confucious Say, I'm confused!!! LOL.

Thanks,

John

 

[metalstorm]

i think if you are getting 2 inches of vacuum you can gain some hp by going to an 850 carb.

 

[moparchris]

UPDATE:

First of all, thanks to all of you guys for your honest opinions and sage advice. For me, hearing these dyno results is like waking up on Christmas as a kid and finding dog shit under the tree. LOL. BUT. . . we're still fine tuning and I wanted to let you guys know what I've learned since yesterday.

Dyno shop called me this morning and said that the motor is running great, no ring problems, etc. He said he has this thing called a whistler I think he called it and he can check the CR. He will also look at the cam timing. He asked me to send him the head flow numbers and the Mopar Muscle article and dyno sheets from their 383 build. Ask the dyno guy what SAE correction factor he is using. Also what were the actual atmospheric conditions at the time of the test. The dyno print out will have this info on it.

I also spoke to the engine builder. He says the slugs are .010 in the hole. He thinks there is another 30 to 40 HP in the motor with some minor mods. He can mill the heads .030 and use a thinner head gasket and acheive 10.3:1 CR, but is concerned with the pump gas. Is that too much? I was under the impression that you can run a bit higher CR with aluminum heads because of the way the heat disapates as opposed to cast iron. You can cut the heads, which works very well, that what I would do.

He also thinks the motor/heads will benefit greatly by using the bigger Comp Cams XE285HL, as opposed to the XE275HL I have in their now, and topping it off with an 850 Carb. The bigger cam will make more power no doubt. The bigger carb is a wash and will make more power on the dyno but probably wont see a difference in actual acceleration of the car. Also a single plane will make more power, I am a big proponent of single planes. Again it will be stronger on a dyno but not necessarily in the car going down track. I would dyno it with a 2 inch spacer under the carb. If the power goes up over 10 hp then think single plane.

Questions:

1) Will I have an issue with 10:3 CR using pump gas if I decide to go that route?NO!! A stock 383 has 10 to 1 and a cast iron head with a crappy combustion chamber design and runs fine on pump gas. An aluminum head will allow you to raise the compression 1.5 points to experience the same heat soak as cast iron. Most people read this and read that but the truth is that aluminum sucks the heat out of the chamber and that is horsepower robbed. So if you dont increase the compression it will make less hp and torque than a similar flowing head in cast iron. A lot less. Someone responded with the test on the 440 that was in Egnine masters magazine with stacked head gaskets to change compression ratio and monitor the results. Well that is true to some effect but by stacking head gaskets you ruin the quench of the combustion chamber thus robbing power and making the results look less dramatic.

2) I'm going to call Comp Cams today, but will changing to the bigger cam (remember I have 1.6 ratio rockers) create any other clearance problems? Is it just a switching of the cam or does any machining need to happen? I am assuming I can use my existing pushrods, lifters and springs. The lifters and springs (double) came in the kit from Comp Cams for the XE275. Yes bigger cam. I would not take comps recommendation on cams, I would look to a mopar specialist that has a vast experience with what works. The cam timing is what makes the most out of your head, not lift. No machining is necessary but you will have to check your valve spring pressure, both open and closed and make sure it is correct. This is CRITICAL since it will rob big power if you get into valve float. Which by the way is way more prevalent than you think and has no noticable symptoms except that power takes a dramatic dive at the upper rpm, which is usually blamed on too small of a cam. You'll need new lifters, but you can reuse your pushrods, rockers and possibly springs.

Finally, many of you have commented about the dyno being a "real" number. I have since learned that this guy is known for giving conservative numbers and not just trying to tell people what they want to hear.

Naturally, I will keep you all posted.

Thanks very much,

John

 

[JJRJR]

Results of the CR test with a whistler, he's BARELY getting to 9:1. My builder obviously didn't do what I paid him to do, which was 10:1. He said he got 9.8:1, but they are barely getting 9:1. He's going to calculate it using the actual volumes and get back to me.

Leak down test on the Eddy heads: 15% leak in one of the exhaust ports and other leaks of less than 5%.

Finally, he said the adjusters on the rockers are not right, they are loose on the rocker arm. So, the moral of the story is I knew something wasn't right and a competent shop found it.

I'm cutting my existing builder out of the loop and the dyno shop, which is also a racing engine builder of great reputation is going to fix this and re-run the dyno. He told me that one point on the CR, and a leaking head will surely negatively effect the Dyno results.

More to come guys. I need a beer, maybe two. LOL.

 

[metalstorm]

ask him to take video of the dyno pulls if he is willing to.
what type of rockers do you have and are that ball or cup?

 

[JJRJR]

ask him to take video of the dyno pulls if he is willing to.
what type of rockers do you have and are that ball or cup?

We're using PRW Stainless 1.6 rockers; ball & socket type. I'm going to be there for the next dyno run so will surely video. Engine builder wants to make it right; so he's gonna pick up the motor at dyno shop; mill the heads to get 10.3:1; fix the leaking valves on the eddy heads and tighten up the rockers.

After that, it's back to the dyno for what I hope to be the final time.

I'll keep you all posted. Thanks again so much.

John

 

[metalstorm]

when thay have the heads off check the cam end play and intermediat shaft play to the distrebutor.[.010]that will make your timing rock steady.