How to know what modifications have been done to 318?

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1975Scamp

1975Scamp

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I'm a new Mopar owner, I just bought 1975 Scamp with a 318 2 barrel carter with headers. It runs pretty strong just on a 2 barrel and no vacuum leaks, but has a good lobe to it at idle. How can I know what has been done to motor with no history from previous owner? My questions are:

1) I how it has been camed, but how to get specs? I know it is going to need to be torn down to measure. Do you measure the height of the lobes to get the specs? Standard specs?

2) How do I know if the cylinders has been bored out? Again, I assume a with a measurement across the cylinders. What is standard?

3) If any head work has been done?

Thanks for your input! I am just trying to put this puzzle together for a new intake and carb. Thinking about the Edelbrock Performer 2176 intake and the Edelbrock 1406 carb. I want to make sure this is my best option. I have also read 360 heads are better, but if the heads i have now have been done, is there any reason to go that route?

I'm just looking for a good streetible motor, that will accent the mods that have been done already! I'm not looking for a drag car nor a lot of HP!

Thanks again for any input!
 
im guessing with a 2 barrel still on it not much has been done to the heads but its really easy to tell if its been gasket matched and worked over. also measure the valves, stock is 1.78 and 1.5. cam is more complicated. you could just measure the lobe and multiply by 1.5 to get valve lift but for duration you need to get your hands on a degree wheel unless someone else has a cheater way to do it. stock bore is 3.91. as for the 360 heads, you would definately have to mill them down unless you already have hi-comp pistons. just measure how far you are in the hole. stock is around .100
 
Thanks for the responses! Any other advise, please post!

I will be tearing down motor shortly for Intake and Carb!
 
Unless someone put the 2bbl carb. and manifold back on it, i'm wondering why they put a cam in it with that setup. You say there is lope to the idle and i'm just wondering if it's the cam or just a tuning issue. A vacuum test before you tear it down may lead to what's really going on?
 
The intake and carb may have been changed back to original. Thanks for the info! I will put a gauge on it, but I have had friends tell me that 318's just don't sound like that! It burns no oil and plugs look great! I rebuilt the 2 barrel recently because of poor quick throttle response at initial WOT and rough Idle! Found several vacuum leaks that were repaired. I've had a few muscle car owner that I know look at it and tell me there is a definitely a performance cam in it but to what degree? That explains the rough idle!

Still has a weak throttle response at the initial quick take off. If I get into it real quick, it wants to sputter, then stand back into it it is fine! I'm thinking that carb just can not respond quick enough. Replaced fuel pump and filter as well (fuel pump was weak)(problems with fuel not staying primed). Any other word, please respond!
 
Your intake and carb choice is solid. I wouldn't worry about the heads right now if the engine is tight and not using oil. As far as the cam goes, i doubt it's anything huge. A vacuum reading of say 13in. or higher would be in line with the type of performance your after. You didn't say if you had headers and a good 2 1/4 or 2 1/2 exhaust, but that would go a long way towards what your after. Depending on your rear gear and torque converter you could have a fun package that has good street manners and will run pretty strong. Just remember when you get it together that timing and carb adjustments will pull the package together.
 
You could put it on a Dyno and then some of these pros could probably tell you real close to what the build was. Very nice looking car. Any other Mods under the hood? Ignition? Coil? etc...
My opinion is that the Flat spot when under "quick" acceleration is usually Carburetor related. As stated above tune it based on Vacuum. I definitely want to Dyno My 318 for the same reasons. I have no Idea what the build was. I just know that it gets up and goes and has a mean Idle.
My Fuel was not staying primed like yours and I changed out all the Fuel hoses with proper Clamps. Problem solved. I put a 600 CFM 1406 direct from Edelbrock and My "Flatspot" is completely gone.
Any More information you can give us will help us help you.
 
It has an Accel Super Coil and wires, stock ignition (orange box) and a stock distributor as far as I know. I would like to upgrade ignition to the silver box and coil, any ideas? I will recheck carb with vacuum gauge to see if that is the issue! Timing is advanced at -08 degree with no ping.
 
1975Scamp said:
It has an Accel Super Coil and wires, stock ignition (orange box) and a stock distributor as far as I know. I would like to upgrade ignition to the silver box and coil, any ideas? I will recheck carb with vacuum gauge to see if that is the issue! Timing is advanced at -08 degree with no ping.
Click to expand...
If you're not racing with an extremely built engine then your current Ignition system is more than adequate. As long as there's no "Weak Links" like voltage drop to the Coil or bad spark plug wires etc.. I used to advance the timing until point of Spark knock and then back it off just a bit. It always worked great for me with my Cuda 340. It seem that many people on this forum like using the Vacuum gauge better. I would Try that first. I'm not an expert but You should shoot for the Highest amount of vacuum at Idle in Drive.
Are you experiencing any Backfiring upon Deceleration?
I'll research the Accel Super coil for any know issues with stock ignition but I don't remember ever hearing of any issues with the later electronic ignition systems.
 
I would not call it backfiring, it does have a suddel rumble/pop, but no backfiring as to what comes to mind! No loud pops or bangs!
 
If you can take some video, that would give us a good idea. Also, about the only way to really nail down the cam is to send it to a cam grinder and have it mapped. You might can get close with a degree wheel.
 
Ok! Thanks! I will try to get a video on here soon! Do I post it on this thread or link it to YouTube?
 
Just post a direct link to it on this thread. It'll show up.
 
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