Need help! No torque 360.

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BarryC

BarryC

'74 Duster 360
Joined
Jun 30, 2008
Messages
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Location
Leitchfield, KY
I could use some help. My 360 is a dog. It has been since it was put back together about 14 years ago. I had to piece it back together after blowing the bottom end apart and not having the money to build it to go really fast. It is together with stock replacement internals except for the cam and carb. When it was completely original and never been apart, it had all kinds of torque. It had a stock converter and 3.55 gears.
I've had a couple of different cams in it. One was a purple shaft .450/.455 lift. I had it in for years. No torque. I changed the converter to a Fairbanks 3000 stall. It will go 2600 against the brakes. Didn't help torque at all. Then I installed 3.91 gears. Still it didn't help the power. Now I have a Comp Cams Extreme Energy 268 in it with a Holley 750 vacuum. This works a little better than the old cam with the Thermoquad, but still not like it was from the factory. I'm still running the stock intake and manifolds with flowmaster mufflers and stock size pipe and tailpipes. It has stock replacement speed pro pistons that are dished with Felpro Blue gaskets. Standard bore with bone stock heads.
Originally the 60ft time was about a 2.06, but the last time I ran it a couple of years ago all I could get was a 2.25. I only drive it on the street now to cruises, but get embarrased when it cant even do a burnout. It won't even squeak the tires taking off unless I use the line lock to help it out.

Please help me. What do I need to do.
Thanks, BarryC.
 
302 heads would also make it a torquie motor with 6k max rpm
 
do a compression test so we can tell what your compression is maybe thinner head gaskets to bump it up dish pistons suck. maybe the cam needs to be c/lined. cam timing can adversely affect performance. what is total timing? maybe mech advance is not coming in.
 
Where is your timing set???? Are you sure the secondaries are opening fully?? Do you have full throttle??? Check fuel pressure...Did you install the cam straight up??? Are the pistons dished or do they have valve reliefs and how many??

Sorry for all the ?'s. This might help rule some things out...

Bob
 
timing is at 32 on full mechanical and vacuum advance brings it to 50. I'm lacking just a little on full throttle, because of passing gear linkage. It isn't enough to hurt anything. Not sure what my compression is, but the best I remember about the pistons, I'm pretty sure they are a full dish with no valve reliefs. I degreed the cam to the cam card and it ended up being straight up. The cam is suppose to have 4 degrees advance ground into it. I'll try and check my compression this weekend. I messed with secondaries when I installed carb, pretty sure they are fully opening. I does pull a little better than the t-quad did and I know it was opening. One friend said headers will make an enormous difference, but I can't see it making that much for the troubles they bring.

Thanks for the replys. I appreciate the help. I just wish it would run at least what it used to. Origianally ran 9.30 in 1/8. Lucky to get 9.80 now. Would love to get 8.50 in 1/8.

Thanks again for the help. I'll try anything.
 
Total timing doesn't mean anything. What's the split, initial and the 32* total.

Compression test would be a good start for diagnosing the issue.
 
Initial timing is 10 deg.
mechanical takes it to 32 deg.
mechanical and vacuum takes it to a total of 50 deg.

Also, my vacuum at idle at the base of carb is only 12". Does that seem about right??

Thanks,
BarryC.
 
With the vacuum gauge hooked up, keep advancing the timing until it stops picking up vacuum and keep your idle setting at the same RPM. As you advance it, the engine will usually pick up RPM. Once you reach the top point, pull 1" back out and lock down the distributor. Hit it with a timing light to see where it sits.

I'd say you are little light on the vacuum. I think my friends same set up pulls about 14-15".
 
it seems though if i advance my timing anymore,, it feels like it surges going down the road. Does my timing settings sound about right (initial, Mech adv. , and total with mech and vac. advances)? I checking these at about 2500-3000 rpms and initial at about 800-900 rpms.


Thanks
Barry
 
The timing curve you described sounds very sluggish for low compression engine with a moderately sized cam and is probably the main culprit behind your sluggish 360 because with low compression and a cam the size you have you need to build cylinder pressure faster. Since you say your slugs are stock dished units your compression is probably only about 7.5 ~ 8 to 1 That's really low for a 268xe cam. Do what crackedback said and advance it at idle to the point where it don't gain any more vacuum or it is hard starting. Of course if it kicks back on the starter you need to back it off until it quits then that's where you need to set the initial timing. You mentioned when you advanced the timing it surges down the road. Maybe that's because your still running the vacuum advance and that causes too much timing. Most performance engines eliminate the vacuum advance and just run centrifugal advance with light springs to come all in by 2000-2400 rpm. Of course when you find your optimum initial timing your total timing will probably be way over 35 degrees so you need to weld up the advance slots to limit the travel. Shorten them up to .375 will give you 18 degrees of advance for example. I have a chart I can dig out if you get to this point.

Another thing to look at is the plugs. Have you done a plug read? If so what did they look like?
 
If not eliminating the vacuum advance at least shorten it a LOT! Set your initial to as much as it will take without the hard yank on the starter when hot then adjust your mechanincal advance from there. Low compression usually will like 36 to 38 mechanical and sometimes even more depending on heads etc... Your optional vacuum advance should bring it to about 45 at part throttle cruise.
 
Maybe you just need more converter. My fresh 360 felt sluggish to me until I swapped out the factory "hi stall" converter for a TCI Streetfighter 3500 unit. My car feels like a pro-stocker now, lots of grunt down low with excellent mid range and higher rpm pull... and that's with a 3.23 gear! When I tried my buddies 4.56 pig, I thought the car was going to rip in half it pulled so hard!
 
A a few things;

1. Stock replacement pistons are typically a little lower compression than the factory pistons.

2. The Fel Pro blue replacement head gasket is thicker than the factory gasket

3. The XE268H cam like about 15 degrees of intial timing.

4. Open chamber 340/360 heads typically like about 34-36 degrees of total timing. Your vacuum advance has no impact on perfromance and is only there to impreove economy.

5. A 750 carb on that engine is way big. A 600 holley would be a much better choice. The smaller carb will give you much better low end reponse and will give up nothing on top with the rest of the set up.

1 and 2 have lowered your compression to less than 8:1. And, number 3 needs 9:1 minimum to run well.
 
I suspect cam sizing and positioning, The cam seems too big for the lower compression engine, and the lack of headers is only adding to the problem. If you want to keep the cam, and no headers as currently equipped, investigate as to which will provide better low end, advancing or retarding the cam. A call to the cam help line at Comp or Crane, will give you the direction you need.
 
dgc is dead on. The XE262 would have been a better choice. Get that cranking compression number. It will be telling. Like was said, initial can be as high as you can... I'd be looking at 18-20° initial. Limit total to 38, and the vacuum advance is fine. Also, learn to tune the carb. Cars dont run by bolting on parts, but by getting all the parts to work together. I dont believe the manifolds are really hurting you if the 360 engine always had them. It's just down on power.
 
Ok, thanks for all the input. I chose the xe268h because it wasn't too far off from the original cam. It came factory with the same cam the 340 was delivered with; 268/272 dur. .429/.444 lift. The comp cam does have considerable more lift.
I'll check into these different things this weekend if I get a chance.


Thanks,
Barry
 
I know you probably don't want to hear this, but I think the only way you're ever going to get truly satisfying performance out of your 360 is with a compression boost to at least 9:1. Along with that I'd say go to a smaller cam, such as the XE262. Those two things will definitely bring back low-end torque, and then the addition of a smaller (~600 cfm) carb and possibly headers will make it a quick street engine with torque all over the place.
 
Do what fishy says with the timing.
Also I would put 2*-4* more cam timing into it those two things alone will increase torque and vacuum.
On the vac adv [designed only for gas mileage] once your timing is set
Then try limiting the vac adv canister, try 10* of vac adv and go up from there till it pings then back it off , then again you don't have to run it.
 
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