[351CJ HELLCAT]

I got my 67' dynoed and the results were surprisingly not what I expected. For my cougar I built a 351 CJ Cleveland .40 over with boss pistons and made a full hydraulic roller enfine with the cam, lifters, and roller rockers. Itd take 2 pages to type what all was done but the bottom line is that this was going to be a hot motor. It ran ok but kind of hot and i wanted to dyno tune the engine to make sure everything was running correctly to avoid hurting my investment. After 6 runs and making the carb richer, idling lower, and advancing the timing to 34 degrees I gained 30 ft lbs of torque and 50 horses at 6000rpms at 114 miles per hour (370 gears). I ended with 300.1 ft lbs of torque and 291 hrpwer. Ive got a c6 tranny and a long drive shaft lol. Just wanted thoughts if this is good rear wheel power for a well built cleveland. It does get up and go very respectfully as i found out after the dyno. Thanks again fellas!

 

[Bad69cat]

That sounds very respectable - a 50 horse gain with some basic tweaking tells me there still much left if you really want to go digging, but you have have to take many things into account. Hitting everything just right takes many hours of tweaks or going with an already known recipe. It never fails to amaze me how many guys come to the dragstrip thinking they are gonna throw up some fantasitc numbers because they did X/Y/Z ---they very quickly find out how tough it is to hit the numbers they thought they could hit!! Use your dyno time wisely and take very good notes on changes/results. Keep this info handy and see what area you can work on for next time. Come prepared to make any changes you think you may need quickly and accuratey to maximize your time on it;;;;

A 3.90 rear on a 3 speed trans is gonna to want to make most of the power in the lower range, so you can look at what you have for a stall and see if it really matches up with what your cam profile is delivering...see if that A/F ratio is hitting where you think it should be at that point in RPM - could clue you in on if there is something lacking on the carb or exhaust side. Also look at what your intake flow is rated for...

 

[1970fastcat]

That doesn't sound too bad, especially since the C-6 is a big power robber. What are the cam specs and details on the heads?

I need to get mine to the dyno, but am sorta scared. I am hoping for 450 to the wheels, but am afraid my heads may not allow that.

 

[J Cat]

I had my 347 dyno tuned the other day. They were only able to get me an extra 10 hp. 310hp and 335 lbs. of torque. C-4 with
355 gears.

 

[351CJ HELLCAT]

The dyno did a wonderful job and i think i was just bein a little unrealistic. The cleveland had been punched .40 over with eagle h beam rods, kb boss domed pistons and the whole assembly balanced. The heads were flow tested and i gave the numbers to Lunati and they made a hydraulic roller cam to match. 610 lift on both exhaust and intake with a 230/240 duration at .50. I used hydraulic roller lifters and lunati voodoo roller rockers. Also a torker single plane intake and barry grant carb. My stall was only 2500 and should have been 3500. The dyno used road friction and air resistance in the testing. The cougar definately earned those numbers.

 

[Bad69cat]

Yeah, the stall really sounds like where she's falling flat....that's a huge area for improvement considering all the mods you have....610 lift is gonna suck air like - well - a porn star! LOL The single plane intake is gonna keep it a midrange monster with the duration you have and clevo heads can flow that no doubt...... Plenty of room to roam with a clevo of that stature for sure. try out one of those benchtop dyno's with diferent combo's and I bet you will find some good thoughts there....the big boys use em, and they are tried/tested/proven to reduce trial and error. That kitty has the heart of a Lion! You should bea able to bring that out in time.

 

[351CJ HELLCAT]

I believe is i did anything id change the gears and the stall. However ive spent 4 and half years building this car and want to enjoy it so ill probably just be happy with the current rear wheel power. If any one lives near Owensboro, KY and wants a professional dyno tune, Speedy Dyno and Discount Muffler is wonserful. The owner has 4 cougars od his own and is a knowledgable Ford guy as well as chevy and mopar. I cant say enough how happy i am with their service. Thanks again fellas! Look them up on google, " Speedy Dyno.".

 

[FasterCat]

compression ratio?

 

[351CJ HELLCAT]

About 11 to 1. Have the 4v open chamber heads. Also have headers, x pipe and 2.5 inch exhaust all the way to the back.

 

[C Gauch]

Be proud! 300/300 from a 351C to the rear wheels running through a C6 is damn respectable for a street car.

Most people have unrealistic expectations about what they will achieve on the dyno. It's easy to fall into that trap.

Now get thee to the drag strip... :burnout:

 

[RoadRacer68]

I agree with the over zealous expectation on dyno numbers...if you have all the numbers pm me and I can plug it into my desktop dyno..if you're curious. Need head flow numbers if you have them, I can get it close..

 

[dfwcatsclub]

Can you give a few more detailed specs about your engine? It should have made another 30+HP based on experience. I have engine dyno and then chassis dyno with C6. Only about 65HP peak hp loss seen.

I suspect you're either giving it way too much fuel or way too little. Need to know cam/intake/carb to help.

 

[Spartikus]

Im with DFW, something is missing. You said you have done a lot of work on the bottom end which is great for strength but obviously cant be expected to produce a big change. Post your Carb info. Here is what I see in your build so far:
Base 351 block .40 over
Headers
2.5" exhaust
full roller setup
custom cam with .610 lift 230/240 (aren't those duration numbers low?)

Based on the fact you have a cleveland base engine I am very surprised you aren't closer to the 1:1 hp per cubic inch benchmark. Sounds like stock heads but those cleveland heads are monsters and should flow enough to get a few more ponies than that. Kind of hard to get a true feel for a "Stock" 351C number at the rear wheels as there is so much crap out on the net but I am curious as to your intake's abilities to breath for that cam and your carb's ability to feed it. Knowing that clevelands are monsters once they hit the mid range your intake will have a lot of impact on your performance IMO. If that is an old school single plane Torquer I series I bet there are some ponies hiding there.

Hey nothing to be upset about 300/300 rocks but I am betting you have another 20-50 ponies hiding in that beast. A .40 over 351 C roller with a strong bottom end sounds awesome good lick with it.

 

[Cougrrcj]

230/240 duration is at .050 lift, which really tells more than the total (advertised) duration.

But I agree that something sounds a bit off. Heck, my relatively mild 393W (9.4:1 and .545/.545 lift 224/230 dur @ .050 retrofit hydraulic roller cam) is putting 380hp down to the rear wheels through an AOD - that figure is based on actual dragstrip results - and the car is not optimized for racing, either!

 

[Royce Peterson]

With that much compression I would expect to see 38 degrees of total timing or a bit more, provided you had good 110 octane fuel in the tank. 34 degrees might be all you can use with pump gas 92 octane?

About 11 to 1. Have the 4v open chamber heads. Also have headers, x pipe and 2.5 inch exhaust all the way to the back.

 

[351CJ HELLCAT]

The 351 is a cobrajet out of a 72 mach 1. The carb is a barry grant special(race demon). The dyno showed the air fuel mix at 12.5 to 12.0 from start rpms to 6000rpms. So i know that running lean or rich is not the problem. The advance gave the motor more torque and ponies until we reaxhed 36 degres, which at point it dropped off. So then we took it back to 34 degrees. The gas i used was half 90 octane ethanol free mixed with 110 racing fuel. The whole engine performed well but i think the low stall speed (2500) and gears (370) held back power. If this helps ill list all aspects of the engine. The block was turned .40 over. The crank was turnes .10 over. We used clevit race bearings. Eagle h-beam rods and keith black pistons (called "boss" domed pistons) with a 250 dome were used. The entire assembly was balanced. The block was squared off and the deck height was droppd .60. We used cometic head gaskets that were .60 thick for the heads. The heads are the 4v open chambered heads flow tested. I sent these numbers to lunati and they built the cam to specs: 230 240 duration at .50 tappet and the advertised was 284 and 296 with a lobe seperation of 109. The is a hydrualic roller as well as the lifters and i also have voodoo roller rockers. We used manely swedged push rods and the torker single plane intake. The oil pan is a 9 qt milodon with a high volime oil pump. The filter is the factory motorcraft FLA1. The heads were fitted tapped for 7/16s studs and guideplates for the rockers. They were also given new valve seata for unleaded fuel. The fuel pump is a holley high volume pump. The water pump is a weiland high volume. The ignition is the msd digital 6 plus with blaster 2 coil, msd distributor and 8mm wires. The plugs are motorcraft racing plugs gappd at .60. This is everything. The tranny was rebuilt with a b&m shift kit. I think i fouled up on the stall as i said before, but maybe you guys see somethinf i dont. Thanks again.

 

[Spartikus]

There are some great Cleveland experts on this forum... I am not one of them Couple of random thoughts though.. There was some serious cam/crank/timing detuning happening in 72-74 blocks. How sure are you it is a Q code block/crank?
Just as an example of how messed up things were getting the HP rating on a Q code 351C CJ in 72 was about 260 horse. The regular 351C engines were rated at 160ish. In 70 they were rated at closer to 300 ish.

If the timing was retarded internally (I think it was about 4 degrees) I believe you need to set up the timing chain with a 4degree advance to correct it. Please do some research on this before you do anything though. Like I said at the start Im no expert and still dont understand all the detuning details of the 72-74 years myself.

Best o luck.

 

[Royce Peterson]

Your cam is pettty mild and the short 230 degree intake is designed to give you more vacuum signal and smoother idle, but hurts performance compared to a "square" design 240 / 240 degrees. It is more streetable than a wilder cam would be.

You could probably pick up 10 - 15 horsepower by running 100% 110 octane and advancing the timing several degrees.

 

[1970fastcat]

I would try tightening the gap on the plugs to.045. Higher compression can blow the spark out on a wider gap. Just try it and see if it helps.

 

[dfwcatsclub]

Components all sound good for ~425 crank HP which would make me look for 340+ at the tires. Have to see the plugs and look at the exhaust ports (inside the header) to figure out what's going on.

Was the cam degreed in? Where?

Would I tighten the gap? Absolutely! I run .035" max even with a hot ignition.

And you did check to make sure the gas pedal was fully opening the carb? This has slipped by more than one of us!