Carb and Cam suggestion for stock '78 360

[68 Sport Satellite]

I'm looking for suggestions on carb and cam.

I'm working on a lot of different things for my '68 Plymouth Satellite. For the last 6 months off and on I've been doing some research on carb and cam selection for my fairly stock 360 motor. Please bear with me as I'm a newbie on engine internal specifics and all of the spec #'s quoted like lift and duration. This car is currently a weekend driver and it runs fine, but I would like to up the torque. When I bought the car, the previous owner had swapped out the stock 318 for a 360 from a '78 Dodge Truck, which means that it's the smog engine setup (which I've learned, is not all that bad where the heads are concerned.)

I've narrowed the carb down to either keeping my Edelbrock 1405 600cfm or swapping it out for a Quick Fuel street series vacuum secondary 680cfm. If the Quick Fuel will help me I'm all for it, but if it will hurt performance on my motor then......I don't want to overcarb. Is the QF 680 OK for my current stock mild cam? Will it also be OK if I go to the next level of mild cam (thinking either Isky Mega Cam or Lunati Voodoo - was looking at the 60401)

I'm not sure on the cam, but from what I've read, I need to keep it somewhat mild due to my low compression ratio. For now, I'm not completely concerned about a specific cam, but I would like to choose a cam manufacturer. I'm leaning towards either the Isky Mega Cam series or a Lunati Voodoo cam.

Here's the info for my car:
• 1978 360 small block from a dodge truck
• Stock 360 smog heads
• Currently has the stock cam
• Edelbrock Performer intake manifold
• Long tube no-name non-ceramic coated headers
• Dual exhaust with flowmaster mufflers
• Edelbrock 600cfm model 1405 carb with 1” phenolic spacer
• Mopar Chrome box electronic ignition
• 3.55:1 Suregrip 8-3/4 with 742 case
• TF 904 Auto trans with shift kit
• 99% street driven - 80% city / 20% highway - pump gas - usually 91 octane
• Theoretical compression stated for this engine is 8.5:1. Have not
measured cylinder pressure. Motor & trans have approx. 40K on them since being rebuilt by previous owner.
• The car lives in Northern California and doesn’t see many summer
temps higher than 90F.

Other things I've learned that I'm considering which I welcome comments on: If the cam is mild, The smog heads with the 1.88 valve back cut will help. Instead of porting the heads, it's been recommended to me to just have brass guides installed instead for almost the same performance and for less money since the porting slows the velocity of the intake charge at lower RPM's which costs you on the street.
Supposedly there are some brass guides out there that have an inside diameter that works well with the factory bowls.

Thanks for your input!

 

[Coronet 500]

That cam looks good, a back cut with a 3 angle grind would help. I like vacum secondaries on street automatic cars and your CFM is bang on. Have you seen Comp Cams Camquest6 program, look it up and plug in your numbers to see what they suggest.

 

[Meep-Meep]

8.5:1 will limit your cam selection as you seem to know and I would focus on a cam specifically designed for that low CR. Edelbrock makes some nice packages for low CR engines. I used the mild one on an FE Ford build and it ran great. It had 160 PSI and ran great on 87 gas.

Running 91 gas with 8.0-8.5:1 CR is not doing you any good. You want to be on the verge of detonation for maximum efficiency so in your case you should be running a lower octane (faster burning) fuel. There are many factors involved in matching compression ratio, cylinder pressure to an octane requirement, and I'm certainly no expert, but I can tell you an iron head 10.1:1 440 with 190 PSI is a bit too much for pump 91.

I like the AFB carb for the street and 600 CFM is plenty. If you have the stock TQ carb and intake that will work well too. The factory intake is a pretty decent piece and is not your limiting factor. I'd run it if I had it lying around and use the money that I would have spent on an aftermarket intake for a new carb or something.

A full on port job is not required but blending the pocket area will help low lift flow. I recommend you do this but don't go any further. A three angle valve job with back cut valves also recommended.

 

[68 Sport Satellite]

Thanks for the advice guys. Seems you both concur on the 3 angle backcut valve job. Meep-meep, thanks for chiming in on my octane requirement. I mistakenly thought that higher would be better. So would you run 87 or 89? Will it be a noticeable improvement in performance or how the motor sounds or something else? I'm in California so I'm not sure if the fuel blends are different and require additional considerations.

When I bought the car it already had the performer intake and Eddy 600 with headers and chrome box. I changed the gears to 3.55's. I just keep hearing that I will notice a power improvement if I go to a Holley Carb and due to some quality control issues with holleys lately I looked into the Quick Fuels as that outfit is run by two ex-holley guys. I have heard great things about their carbs and am wondering if I would notice an improvement just by switching to their 680 cfm with vacuum secondaries carb?

The cam is the stock cam that came with that motor. So I know the 60401 Voodoo cam is probably a good choice, but will it be a noticeable difference from the stock cam? If so, does that difference affect my carb selection here?

 

[Meep-Meep]

As long as you have the intake and carb then run it. That set up is not holding you back so spend the money somewhere else where it will do more good. Running a Holley is not a guarantee you will have some big boost in power but if the AFB is seriously messed up beyond a $50.00 kit then it probably should be replaced.

Focus on bang for the buck improvements like going to the 3.55's. Next will be making sure you don't over cam and kill your cylinder pressure. There is a balancing act between compression ratio, cylinder pressure and cam selection. I suspect with about 8.2:1 CR and 160 PSI you can make it work on 87 gas. I know the CA gas all too well. I'm about 35 miles north of you.

 

[Coronet 500]

I found a stock 360 2bbl = .410/.410" 252/252 the 4bbl = .430/.444" 268/276 so your numbers should do well. .454/.475" 256/262 if I got that right. You could try a little more duration but you might sacrifice cylinder pressure, low end pull and fuel mileage.

 

[68 Sport Satellite]

thanks for the advice guys. Just to clarify - all of the specs i've listed for my car is as it sits bolted together right now. I don't have spare parts waiting around to be installed - this is a driving vehicle.

So no guarantee on performance increase in swapping from the eddy 600 to the holley style 680.

Nobody mentioned much about the cam comparison. So with my current setup locked in except for the cam, are we saying here that I won't be able to improve torque and hp performance at all with a cam swap? I should just leave my stock cam in? That's a bit depressing. My car moves OK, but I really was hoping I could make some improvements with some minor tweaks or swaps to my current setup. If I'm not going to swap the cam at all, i wonder if it's really worth it to remove the heads and get the 3 angle backcut valve job with brass guides or just leave the heads as-is?

 

[Coronet 500]

I agree with your cam choice and with the head work and that 680cfm carb you will definitely get a great performance gain. My comments on duration were to mean a little more would be better but a lot more would be restricted by the cylinder heads. Too many over cam a good combination and kill it. Looking at your driving habits I think you are spot on for an engine with these heads and compression. Honestly you have built an almost perfect package, the camshaft upgrade being the missing piece. I say go for it.

 

[Meep-Meep]

There's no reason to increase CFM if your engine won't use it so stick with the 600 Eddy since you have it. A cam change as outlined above would be a good move if you can also increase compression. Using a steel shim gasket over a composition type and have the heads cut to some safe limit to reduce the chamber volume would be relatively cheap and easy. All this might get you nearly a point increase but you should CC before and after to verify. This cam would probably be a good choice with 8.5:1 - 9:1 CR but check with the manufacturer http://www.summitracing.com/parts/EDL-2177/ Don't look so much at the valve lift and duration but at the lobe separation. This cam is on a 110 LSA and the factory 360 cam might be at 115 deg. The lower LSA cams like the 108 deg will build more peak torque but for that one you will need an increase in the CR to deal with the overlap and the late closing intake valve, not to mention deeper gears.

Another cam that might be a good choice
http://www.summitracing.com/parts/CRN-693902/

 

[68 Sport Satellite]

Meep-Meep and Coronet 500 - thanks for the great advice. The details on the lift, duration, and lobe separation are VERY much appreciated since I am new to talking cam specs. I will look more into which cam is best for me from what you've stated and do that work along with the head work all at once and then I will run that setup with the 600cfm carb I've got now & maybe compare the 680 performance later.