Dyno

[rblong]

Well I dyno tested my car today in preperation for a change in pipes. Came to 279 RWHP with 378 RW torque. I did not think that was too bad for a pretty stock 428CJ. Ought to get a little more out of it since dyno showed I need to jet up the carb. Think I will wait to change the pipes before making any changes. I can't even imagine how fast some of you guys cars are when you post alot more RWHP than mine. I have enough trouble getting my 315s to stay stuck!

[Tim Brewer]

I sure would have thought a 428 CJ would have put down more than that. I know if you still have the sidepipes from Lonestar,they're choking your engine to death. Those pipes are for a small block. You mentioned new sidepipes, make sure they are 2" befor the collectors. Also, I would remove your headers and match the exaust ports and port the other end at the flanges,(sometimes they have sloppy welds that restrict flow). I was also wondering if you have aluminum heads and intake, that would help alot.
My .02, Tim

[2KWIK4U]

Rb and Tim,
I was reading rb's thread on sidepipes and having just completed my LS build, am also considering sidepipe options. Running a KC 496 and seem to have plenty of power but I know they are very restrictive. Dynoed at 650 on Keith's dyno and am planning on bringing it to Plano for the chassis dyno soon. Tim, what options did you find other than the stock LS sidepipes. Rb great looking car. Thanks

Brad W.

[Tim Brewer]

Hey Brad,
First, if you haven't already, have someone that knows what they are doing,(i.e. race fab shop) build you some headers. The Lonestar ones will get you going, but are not what you want on your engine. The sidepipes I got from Finish Line,(but were built by Boffin Motorsports, you might be able to buy from them direct) they have 2" primarys, 3 1/2"x 4" auger mufflers with a 3 1/2" turn out. Wow, I just checked out your car and it looks like you have 2" headers, and like the rest of your car look great. You just need new sidepipes. Notice how your headers are 2" and the sidepipe is 1 3/4. That 496 will be choked down way too much at the flange. Also, the packing in those $5.00 mufflers will be gone in 500 miles and you'll need ear plugs to drive your car. Good luck,
Tim

[rblong]

My existing side pipes are not from Lonestar. They were custom made by someone prior to me buying car, have 2 inch primarys to 4 inch OD side pipes. They have no baffles or mufflers at all. The only restriction I can see is they have 3 inch turn downs approximately 6 inches long. I run stock cast heads, aluminum dominator intake and Demon 750 CFM carb, MSD ignition (limited to 5800), high capacity wires, one step up from factory cam etc. My test did indicate I need to jet the carb up a little since I ran a little lean in a couple of places. Looking at stock specs on engine the 428CJ were rated for 335 BHP/440 lbs torque at crank. Without doing a crank HP test the test shop was estimating my efficiency may be 25-35%. Using 30% that would give me 400 HP/540 lb torque at crank. I know this is a guess, but that is where I thought I was probably doing pretty well with my current set up. I have read original figures were under rated when published. I would love if someone out there had some good experience with 428CJ and could tell me what are some good set up. I enjoy the heck out of it as it is since it is still a lot of HP for the weight and will get loose on me in a instant through three gears. I want to keep it streetable, but enough horsepower is never enough!!! Thanks for everyone's input - as a Cobra/Ford newbie it is appreciated.

[SCOBRAC]

Interesting RB,

Indeed your 279 nets you 335 hp at the crank. The 428 had an advertised HP of... 335.

Which carb / intake are you using? which cam?

[392cobra]

RB,
I had a 428CJ in a '69 Torino. They had an adv. hp of 335, but that was underrated to get into a better NHRA class.NHRA caught on later. The accepted hp was 360. Certainly closer to the truth.

Most all Lone Stars I have followed from a known crank hp to the chassis dyno have shown a 23% loss with a GOOD exhaust system. The loss runs from 28-30 % with the stock sidepipes.The stock mufflers have a 1 3/4 - 2" core.

My 418w has 2" primaries into a 3 1/2" merger collector.The Howe mufflers have 3 1/2" core. You can put your arm through it !

Your 279 rwhp with a 23 % loss put you at 362 hp with some rejetting left to do. 490 Torque.

I think you are right on target.

Check out my gallery and you'll see something that looks familiar.

[rblong]

Fred - Yea, I think I am pretty close to guessing correct also. Look at my gallery and you will see my pipes have no mufflers - just straight though 4 inch tubes. They were not built by Lone Star. Your car is nice - hope to meet you sometime. I appreciate your responce.

Michael - Unfortunately I don't know the cam grind since I did not build the motor. It has an obviuos lope, but nothing radical. I am currently trying to put a build book together for everying on the car. The carb is a 750 Barry Grant Speed Demon with mechanical secondaries and no choke. Intake is a Edelbrock Performer 390. The ignition is MSD 6 Al with 5800 RPM chip limiter and MSD Blaster Coil.

I will probably drive it this summer as is and just enjoy it. I won't be racing it competively or anything. So far I haven't needed any more horse power than I have to stay ahead of anything around here - at least from light to light! I will be looking into what I can do to the 428 in the future to beaf it up, or I have even been reading about the Genesis 427s.

The exploration of options is as much fun as anything - these cars are a blast!

Bruce

[JAM1775]

I do not know what RPM your peaked HP . I imagine the basically stock 428 may not want much more than low/mid 5's. However, if it held strong to 53-5500 or if you got near the higher 5's before peaking you may benefit from a Perf RPM intake. The Perf drops off at rated 5500...I usually subtract a few from their advertized ratings. Overall...you're making some pretty good torque !
I bet you make really good tq at 2000-2300 rpm.....that is a big motor afterall.......perhaps it's a matter of adjusting one's perspective ? It won't take very much [pedal to get that big boy rolling hard !

[rblong]

We made three runs. HP was peaking about 5400 and that is about all she wanted. Torque peaked at 2500 - 3500, but pulls good through low 5's. I have hit the 5800 rev limiter a couple of times in "the heat of battle" with a couple local rods. Almost feels like a power band on a 2 stroke dirt bike. And no, it don't take much pedal to get her on the move.

[rblong]

Just wanted to clarify some numbers since I did not have my dyno sheet with me earlier - Hp peaked about 4000 and started down at 5200. Torque peaked at 2800 and stayed pretty level till 4200. I have read alot of the old posts and obviously a head change, carb rejetting and maybe a little different cam would take me up considerably. Thanks for you posts. I always appreciate your input and look forward to you helping me in the future. I know a lot of you think the 427 is the way to go, for my light to light run I thing the 428 does pretty well.

[392cobra]

RB,
With your engine flatlining at 4000 you are leaving alot of hp on the table somewhere.

If you hadn't already said that you have open sidepipes I would say you had the LSC stock sidepipes on.
This is what has shown up on the chassis dyno time and again with a heathly engine and restrictive exhaust.Right at 4000 rpm.

Before you go spending money on heads,cam,etc. I would figure out what is shutting you down.

[rblong]

Thanks, I did some measuring last night and the primaries to the first flange are 2 inch, but then drop to like 1 3/4 inch from side pipe flange to collector. The collector is also only three inch and then the down turn down is 3 inch. Even though the side pipes are 4 inch, I suspect the primaries, collectors and turn down are restrictive. I am building my new pipes with 2 inch primaries, 4 inch collector, 4 inch side pipe with a bolony cut on the end so I will eliminate the restrictive turn down. This should eliminate any exhaust restriction. Everyone's input is really appreciated - I am learning a lot.

Bruce

[Tim Brewer]

Bruce,
Turn downs arn't restrictive, they just need to be 3 1/2". You mentioned the pipes from the flange to the collector being 1 3/4". I think the previous owner cut the LS mufflers out and replaced them with something else. When you cut your existing mufflers apart, I think you'll find they have or have had something in them. A 4" hollow tube in a sidepipe would be unheard of and you can't tell by looking at them. All sidepipes are loud and will set off alarms, it's just a matter of what degree of loud. Just trying to help,
Tim

[rblong]

And I will take all the help I can get! Lone star was even freeked today when I took them by to get them sized for a new collector, cause we opened them up and they ain't nothin but a 4 inch piece of tube - always been that way! LS said they did not build these pipes. Empty as my tank aftar a hard run. I wasn't BSn when I said they was loud, even the Dyno guys were like "the neighbors ain't gonna like this one". I think if there was any restriction it was with the 1 3/4 inch primaries. New pipes have 2 inch prims. They are great loooking pipes - look at my gallery, but there wasn't nothin in them. I am going to keep them for when I want to be LOUD! Pulled the carb today and have 76s in primary and 83s in secondary. Monday I will pick up some new jets to solve my lean run at the top end.

I love the challenge of new toys!
Bruce

[Tim Brewer]

Wow, I can't believe anyone would put together hollow sidepipes. They really must have been LOUD! Good luck on your pipe build. If you like, let me know when they're done, i would like to check them out and meet you as well..
Tim

[rblong]

I figure it will take a month by the time I get them all fitted and coated. I will check with you then.

Bruce

[rblong]

Well it has been a while and I really can't find out why the motor is flattening out on HP so early. I have changed the side pipes to 2 inch collectors, 4 inch pipes with 4 inch turn downs. I have removable baffles and have run the car with and without the baffles (deafening without the baffles). Timing is 16 to 30, jetted up the carb. Pulls like a freight train through 4000, then just kind of levels off. No miss, no nothin. It will go on up to 5000 or so, but just isn't pulling hard from 4000 to 5000. I haven't had it dynoed again, but really don't think much has changed from before. I am not hitting the rev limiter. I have the stock rockers, could I be getting some floating - how could I tell? Car is still a blast to drive, but you know how it is - first few thousand miles you think this is as fast as I will ever need, then you get used to it and start to look for more HP. Could it be the cam, unfortunately I don't know what grind it is.

Thanks,
Bruce

[392cobra]

Bruce,
It is starting to sound to me that you are running out of cam.
Something like a "RV" type cam.Low RPM,high torque.

Have you run it without an air cleaner ? What size are you running ?

What fuel pump are you running ? Good filters ?

What ignition system are you running ? Is it getting the volts & amps it needs ?

A 428 CJ shouldn't be going flat at 4k rpm.

[Clois Harlan]

I agree with Fred, I think you are running out of cam. Your power curve may be something like 1500-4500. Cam change would be a nice winter project and not to expensive.

Clois