Improving my 360 combo. Need advice/input

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daves66valiant

daves66valiant

68 Dart 340/727:66 Signet Vert 340/5spd: 68 D100
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Okay guys here is the setup from the previous owner. Bless him for not knowing mopars very well and I'm not much better. Here are the specs on the car as best to my knowledge.

360 unsure if bored over

KB pistons 10.5:1

Heads: Not sure on the heads but assuming/imagine they are J-heads with smaller 1.88 valves. Would be a bonus is the 2.02 valves. They have only been cleaned up...no major porting done. Proform roller rockers 1.5 ratio, comp cam springs and retainers, crane pushrods.

273 exhaust manifols. Needs headers I know already. 2.5 exhaust straight pipes no H or X.

Intake is a Edelbrock Performer with Spread bore pattern (boo-boo by PO) because the carb is a 750 Speed Demon and the ports are smaller than the J-head ports as far as I know. Have not pulled the intake to see yet.

Camshaft is were things are a real problem too with the previously mentioned parts: Erson .510 lift, 242 duration intake, 246 duration exh, 3500-6500 rpm range.

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I am thinking of getting a new cam either a solid or hydraulic XE268 or XE274

I have a M1 and a Holley #3310 ready as well.

What are your suggestions to get this beast to open up a little more,
 
Dave -
That poor motor needs to BREATHE. I believe the poor thing is being strangled by the intake and 273 exhaust manifolds. There's been quite a few posts on here regarding valve sizing and the consensus (as far as I interpreted it anyway) has been the 1.88 valves are good in order to keep up flow velocity and aid cylinder filling.
The 750 Speed Demon should be good since Demon carb flow is measured wet vs. the dry flow measurement method used by Holley. Where you want the improvement will determine what type of manifold you should replace the existing one with. The M1 is a good manifold but is built for higher rpm flow. Street performance cruising will be best served by a good dual-plane manifold.
Cam numbers sound like the PO wanted this thing to really run on the big end but he did almost everything he could to restrict it's ability to breathe when it really needed to.
By all means you need headers. The PO was trying to get that 360 to exhale through stock manifolds that were originally meant for an engine 75% the displacement of the 360. It couldn't exhale and that also restricted the ability to inhale since you probably couldn't get enough of the burned gases out of the cylinders.
That poor engine was simply confused due to the parts mismatch.
 
Not a terrible combination but could be improved. Performer RPM Air gap if the M1 is the single plane version. This is probably the best overall dual purpose manifold. The Crosswind is a chaper alternative, a Chinese copy of the air gap Summit sells.
TTI stepped headers 1 5/8 to 1 3/4. Expensive but so much better than cheap headers, which will find every pot hole!
If the heads are J catings, the J will be visible in the area around the spark plugs. If they are later heads, there will be sort of a square flat spot cast in.
Casting numbers are on the intake branches, pull a valve cover to find out. Even if later, no big deal.
A light car can get away with a single plane easier, what vehicle is it in?
Keep us informed, we'll try to help you out!
Alan
 
the PO knew he needed headers but got the wrong headers and had trouble spending $$$ on tti and did lots of bodywork to repair the fenderwell holes when he got the car. he just ran out of time/money to research and fix it right.

since the current cam is rated for higher RPM 3500-6500 the M1 will be god for top end. A mighty demon would have been a better choice with this radical solid cam. I think I can get it to work.

The Holley I have was originally tuned for my 410 hp 340 with the M1 intake. Im thinking I can just drop it in and go with it until I get some headers and go through the speed demon and get it cleaned up and tuned for a more radical cam.

I want this car to be more street but it will be setup like a strip/street if I use the what I have.

oh the dilemma

thanks OC
 
Man I didn't realize the RPM range of that cam until your second post. Wow I think that is a bit much for a street car isn't it?
 
I know. crazy huh. a total slug down low.

this is why I was looking for cam swap sugestions. I did the comp cam program yesterday and the 268 and 274 grinds seemed to be the suggested grinds. been hearing that the valvetrain can be noisy. Id like to hear about other cam options with a M1 single plane and 750 carb with future headers.

my 340 combo for my other valiant is kickass.

the 360 could lean towards a track car too
 
I would swap the intake for a performer rpm and add a set of headers.

What does it have for gears and converter ? I would want to see at least 391s and a 10 or 9.5 converter in the 3200 rpm range.
 
It is a 4-speed with 8 3/4 sure-grip with 3.23 gears.

The RPM Performer is what I have on my 340. I really like it so far. I would hate to see my M1 go to waste since it is brand new basically.
 
He has a Performer on it all ready.

If you have the M1 I would try it out before buying another intake. You need gears bad though. 323s with that cam must suck.
 
What adam said. 3:91's or 4:10's would rock. Must be nice not having to worry about a stall! ViVa La Cam!!!
 
Check out Lunati cams if your interested in a good high velocity cam that's quiet. I had a Comp XE274 in my 360 first. Had problems with their junk lifters going bad twice in less than 750 miles so I put a Lunati 60404 in it which is slightly bigger than the XE274. Runs fantastic and has had no valve train noise or problems in over 1500 miles. The Lunati's are ground so they let the valve down gentler than the Comp so even though it's just as aggressive opening it's quieter. The 60404 even has more low end torque than the XE274 had which surprised me since it's 4 degrees bigger and has .025 more lift. Unless you go with a much smaller cam and keep a dual plane intake you need lower gears as suggested above. Like the guys also said above the stock exhaust manifolds need to go for any type of performance engine. If it can't exhale it can't inhale.
 
I have a dumb question....

What are your goals for the engine?

If you want an upper end engine, then a Performer RPM, LD340 or air gap would be a good choice. Needs some gear and headers. That thing is really bogged down with the current intake and exhaust.

Looks like the cam is similar to a MP509 grind.
 
AdamR said:
He has a Performer on it all ready.

If you have the M1 I would try it out before buying another intake. You need gears bad though. 323s with that cam must suck.
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I'm not able to tell if they suck or not yet because the thing runs like crap. It is one big constipated :bootysha: pig right now. It needs to take a big sh it through some headers and a better intake. LOL.
 
The gear thing has got me thinking now. I almost forgot I have a rebuilt 8 3/4 rear with a 489 case in my 68 Dart that has 3.91s and a Sure-grip. I could easily swap pumpkins. I guess my only problem is that the current rear-end in the 66 hardtop is a 742 case. Wonder if I would have to get a new drive shaft?

Crackedback you always have dumb questions......LOL.............Boomer

I tell you what. The more I think about things the more options I get tangled up in.

The highway cruising with 3.23s is really nice, 3.91s would sure put you in your seat though. Tough one.

I may take a look at the Voodoo/Lunati cams.

I guess I want something that will kick you back in your seat, roast the tires and have good street manners. I guess I could clone my convertible build. LOL

Would be nice to open this engine up with as little as possible since I have many of the parts needed.

Guess the only thing I really need to buy is headers right now. A new camshaft and intake would be next if things still suck.

Thanks
 
Seriously, if you want something you could drive around town and hit the highway with too, then how about a 3.55 or even a 3.73 rear with a good dual plane intake. Keep the spread bore carb and put a nice set of headers on it with a multi-spark ignition. Maybe a little smaller cam to make use of that 10.5:1 compression. You can blend streetability and performance if you want or go fully one way or the other. That`s a choice you`ll have to make before you do too much one way or the other. I like a car I can drive.
 
i agree with checking out lunati or crane. i have 2 comp cams and one went bad that was not its fault but they both are noisy. i just picked up one of the voodoo cams for the 318. as far as gearing i personally would go with 3.23's and pick a good cam that still has low rpm torque. nothing like being able to fry the tires and still haul *** on the freeway. oh yeah and get decent mpg doing it.
 
Longgone said:
Seriously, if you want something you could drive around town and hit the highway with too, then how about a 3.55 or even a 3.73 rear with a good dual plane intake. Keep the spread bore carb and put a nice set of headers on it with a multi-spark ignition. Maybe a little smaller cam to make use of that 10.5:1 compression. You can blend streetability and performance if you want or go fully one way or the other. That`s a choice you`ll have to make before you do too much one way or the other. I like a car I can drive.
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HAHA pull the vert drivetrain..........:thebirdm:

For about $750 I can have some early-a-body tti headers. This might not be the cheapest, but would be the easiest and quickest way to get things hauling azz. The Spitfire headers from Harold would probably take months to get.

We'll see.
 
daves66valiant said:
HAHA pull the vert drivetrain..........:thebirdm:

I thought you`d like that.:-D


For about $750 I can have some early-a-body tti headers. This might not be the cheapest, but would be the easiest and quickest way to get things hauling azz. The Spitfire headers from Harold would probably take months to get.

We'll see.
Click to expand...

Yeah, second that. Headers have got to be on top of the list.
 
daves66valiant said:
The gear thing has got me thinking now. I almost forgot I have a rebuilt 8 3/4 rear with a 489 case in my 68 Dart that has 3.91s and a Sure-grip. I could easily swap pumpkins. I guess my only problem is that the current rear-end in the 66 hardtop is a 742 case. Wonder if I would have to get a new drive shaft?
Click to expand...


If I understand you correctly that both are 8-3/4 rears and you just want to swap the 3rd members out the driveshaft won't be a problem as long as both have the same size yoke. Even if one is the small yoke and the other is the big yoke you can cheat by changing the rear u-joint to the one that is small on one side and big on the other.

The highway cruising with 3.23s is really nice, 3.91s would sure put you in your seat though. Tough one.
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The 3.91's are getting pretty deep for a street car. Like Longgone said maybe consider a 3.55 or 3.73. I have 3.73's in my Cuda and can tell you that with 27" tires it's as deep as I would care to go on the street but that's just my opinion.

I may take a look at the Voodoo/Lunati cams.
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I only recommend them because I like mine so much and have talked to several guys that run them and they like them also. I even talked a buddy of mine into putting one in his 406 Corvette and he loves it. As Camd64 said Crane is another good cam. They are high on my list also.

I guess I want something that will kick you back in your seat, roast the tires and have good street manners. I guess I could clone my convertible build. LOL
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You probably wouldn't want to go with a cam as big as the 60404 I have then. It sounds neat but is pretty lumpy. If you want to keep the 3:23 gears you have and want great low end grunt go with a 60402. It'll have a noticeable idle but not ragged and will have tons of low end grunt.


Would be nice to open this engine up with as little as possible since I have many of the parts needed.

Guess the only thing I really need to buy is headers right
now. A new camshaft and intake would be next if things still suck.
Click to expand...

I know where your coming from about hoping not to open things up all the way and headers will definitely help but with the cam and tall gears your running I wouldn't bank on them solving all your problems. I think you'll find you really need to change all 3 components to work together and then you'll see the huge improvement your wanting.
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If the vert is set up as a nice cruiser I would build the new car as a more serious street/strip car. The 742 case should swap right in. You can use the same drive shaft. At most you may need to change the rear u-joint.

I would leave the cam for now and see how it is when the exhaust and gears is done.
 
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