View Full Version : Javelin 360 Horsepower rating

01-30-2005, 10:54 AM
:eek: Here it goes. I recently took my rebuilt 360 in the car for a dyno test and to say in the least I was somewhat disappointed in the results. Horsepower at the rear wheels was 153.6 and the torque was at 250 lbs. From talking to a expert in the engine rebuilding, this engine should have done much better on the test. The 360 is overbored by 30 using standard compression pistons, an Isky cam (not sure of the model number right now), and sidepipes simialiar to the trendsetters (the generic type). According to the expert, it is most likely the Isky cam that was installed. The Isky cam was designed along the lines of GM specs and there is good chance that the engine is not accepting this setup. Not accepting this setup, the net gain is dramatic horsepower lost.
Any comments are welcomed and I should have known that I should have installed a Erson cam in the first place. (have a Erson cam in the 390 AMX and have yeilded outstanding results from it).

01-31-2005, 03:51 PM
What year model 360 is it?

Low compression ~8.2-8.4 to 1 360?

I could see this being caused by a whole bunch of tuning issues...not just it's an Isky cam. Are you sure the cam is installed straight up and not 4 degrees retarded? Carb. jetting or carb. condition....etc. etc.

Did you degree cam when you installed? It could be a bad cam...they do exist...could be a whole lot of other tuning issues. I would start eliminating those first.

Current issue of Hemmings Muscle Machines has an article on a guy with a rebuilt '67 GTX 440 which was a beautifully restored car but ran like poo poo. By just fixing the carb. problems he had with stock AFB (he had previously 'rebuilt' it) he gained 40 HP (dyno verified) by bascially just getting the carb. back to proper specs....40 HP and his BSFC improved hugely on the dyno also so he was using way less fuel while making 40 HP more at same time!

All the restoration in the world without tuning is to a great extent wasted I have decided is a very true statement.

02-01-2005, 06:06 PM
Yes to a whole lotta of questions.
The cam went in straight up and down. I did not retard it and I did not advance it. The Distributor is a MSD electronic ignition type (magnetic pickup). The carb is an Edelbrock 4 BBL 625 CFM and jetted for attitude. We are at or slightly above a mile high (5400 ft high). The engine is a 1973 block with a 71 crank. This was done so I could still use the BW automatic (yea I know, should have converted to the torque-flite, much better tranny).
The car is timed at about 10 BTDC and I have been running mid grade gas with lead additive (real lead by the way). I am thinking of advancing the timing to about 12-15 degrees BTDC to see if that will improve the pony. I am also going to run premium gas in it with the additive. Back to the dyno test itself, the Air to Fuel mixture was right up where it belong. However when the actual test began, it seemed like that engine acceleration was slow to react, the next test I tried it without the air cleaner on and it only picked up less than a horsepower.
I am trying to eliminate everything first, mainly because I do not want to tear this thing open.
I have heard of Isky's giving some AMC owners fits before and I figured it just was what I call personal perfernance in that they liked whatever they used.
Note: The replacement pistons were standard compression for 1971 (8.5-1) and didn't really notice anything out of the ordinary with them. I will run a compression test on these just to eliminate that possibility. It could be the rings that was used. (hopefully not the problem, that would be worse than it was the cam!!)

02-02-2005, 12:05 PM
Carb is your problem... Big cam will suck gas plus it is too small for the 360.

In 84 I bolted on dual exhaust on my bone stock 76K 73 304, pulled the 2bbl intake and added a new Holley 650 dbl pumper on an Offy spreadbore 360 degree intake (sales person thought I was nuts). I also added a 1 inch spacer... this did fit under an AMX hood. Not much I did after that.

Well beat a lot of 350's and one 360 Matador wagon (frinds moms car) dono what year it was available at the time... did change the rear in 92 to a 69 dodge with 2.73 gears so I could get 23 MPG and cruise on the Freeway in 1st gear. Blew a few minds too! After many attempts to blow up my 304... I never did, it was fun trying!

02-02-2005, 05:37 PM
Yea I know the feeling on trying to blow up a 304. The first engine inthis car was a 304. Kind of had the same problem with it as far as performance is concerned. But what did that engine in was all of the sitting it did. Didn't real drive it enough. Oil seals leak (front and rear) and the valve seals were bad, just drank oil like it was soda pop or something.
As far as the carb is concerned, I rejetted and installed new needles in it and this really helped the performance of it. I have found that anything larger than a 600 CFM carb on AMC engines can bog down the motor. However I am willing to try anything just to avoid the hassle of tearing it apart. Question arises if I can get away with using a standard Holley with vacum secondaries? Open to suggestions...

02-03-2005, 08:08 AM
I don't know why a 360 with a cam cannot take a 750cfm carb???

In a past experiance with timing gears... some gears may have stamps on both sides. This raised confusion on installing them properly. I cannot remember the manufacturer at the time... NAPA may have been the issue. Mostlikely you did change the gears and chain... Just my two cents worth.

Why I said this... it happed to a Jeepstr friend of mine. It idled and ran fine until 2500 RPM (lost power). If it were not for the fact that he was using a factory cam and carb setup... he too would have been scratching his head. He had no choice but to check twice and sure enough there was another mark on the oposite side of the gear. I guess it is easy to confuse a tech manual with what you are to see as comparison.

02-03-2005, 04:26 PM
That is what I'm afraid of. When installing it, if someone didn't get the marks confused. Question-- Can I try to advance the dist enough to compensate for a possibilty of mis identifying the wrong timing mark??? I had have the dist advanced itself and never (at least don't remember) did really act funny or anything. Seem to run fine, and when I restarted it, it didn't bog down with or like an engine that was advanced too much. Betcha ya right on this issue.

02-03-2005, 05:58 PM
Well, the only thing you can do is redo the gear installation... the reason I said this is because this is a static timing issue (Dynamic is the distributer). By advancing the distributer or retarding it will cause back fire and make things worse (possibly putting a hole in a piston or two).

02-05-2005, 08:52 AM
I have read all the posts in regards to you issue. It is tough to say where the lack of power is originating. Cam specs would be helpful. Always have the best luck with a high duration cam at least 280 on up to 310 duration is where I feel you want to be. Also give it all the timing it will take, ping it and work back from there. I use a mallory in my 390 with a base time of 24 degrees no vac advance mechanical. Also open the plug gap up I use to use 35 but have since opened up to 40. Dump that vac advance 600carb shoot for mechanical 600 or better yet 625 or 650. Without knowing what else you have done I would not see a reason to go pass 650. What intake are you using? I assume a dual plane of some sort

02-05-2005, 02:09 PM
Thanks to everyone's post on this issue, but the 360 has lost it's bottom end. Drove it this past Thrusday and the bottom end was rattling like a baby's door knocker. Went back and looked at the specs that the guy who did them and it ended up that he was following GM Specs. Needless to say, when the engine was rapped up to about 4500 RPM, it let loose inside somewhere. I failed to look at the spec sheet that close, only wish I would have paid a little closer attention, but it was somewhat buried in the paperwork. Oh well, ON TO THE 401 and torque-flite tranny. Should have done this to begin with.