Last ditch effort for used 318

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mycuda

mycuda

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NO LOW END POWER.
Got 318 1984 Police edition motor used, stored heated garage. Put in 69 Dart project. 727 trans rebuilt bought from member. Didnt touch lower end or heads. 120lbs psi all cylinders, added 468/ 268 approx. purple shaft cam. hooker 1 7/8 headers. Proform 4bbl/action + Weiand intake. Proform electronic ign. Stock TC, but had 2500 stall before i changed, same problem.
This engine runs great, shifts great. Can drive all day. But no real power until after 2200RPM.
I was told the cam could be retarded due to chain (new) stretch? Off a tooth?
Did all tests to prove wrong,Maybe. Deadstop TDC test was Accurate. Putting #6 cylinder TDC compression stroke and Measuring #1 cylinder spring tension difference of intake/exhaust
of .030 int.-.060 ex. was good. Ive put bigger cams in stock engines with no issue.

Tried points dist./different good carbs im lost for answers

Help before I put bigblock in...................

PS. 3.23 suregrip 8 3/4 rear


Thanks D
 
Dude, all we have a bunch of run-on gibberish that leaves out the most important information: What is the cam specs, and what is your timing and timing curve? How light are the springs in the distributor?

Do you have a wide-band o2 sensor so your can see your a/f ratio? If not get one. It will change your life.
 
Give it as much initial timing as it will take and still start warm. Then shorten the advance curve to 36 degrees or so without vacuum. Details man.... Looks like more cam that it wants or needs for the compression available.
 
Ive given anywhere from 15-40 initial timing. My 67 cuda big block dont even run vacuum advance. But thats more compression built engine.

D.
 
Do you have a timing gear set that will let you advance the cam? Either that or throw in a 340 grind.
 
Dano, No did not degree cam nor the previous many mostly with gear drives.
The question of springs was next on my mind
 
If you get a chance to see the head casting #s that could tell us more. Maybe a set of 302 swirls or some 273 closed chambers would wake it up.....
 
Guner, your thoughts are mine respectively.
Before I open up front of engine, i wanted to here options.
 
If those numbers are 240+ @ .050 I might lol.

Duration_v_RPM-Range_wIntakeManifold01.jpg
 
The cam could be timed "by the marks" but that does not mean that's where it needs to be to run good, especially in a "torque" street engine. One of the members on here and I had to advance the CRAP out of a purple shaft.

You need to find out WHAT exactly cam that is. Then ask here where (several good people on here) think it should be timed. At least some of these purple cams don't run well 'straight up' in a street engine.

Read this for some insight.

http://www.forabodiesonly.com/mopar/showthread.php?t=244033
 
mycuda said:
120lbs psi all cylinders,
Click to expand...
Golly, my stockish 1962 slant 6 has 130 psi cylinder pressures and that is with a mild cam. You engine does not appear to have much compression ratio at all; a good guess is that this has the pistons that are .080" in the hole and maybe even open chamber heads.

mycuda said:
I was told the cam could be retarded due to chain (new) stretch? Off a tooth?
Click to expand...
It does not even have to be off a whole tooth to be doggy; just 4 degrees retarded will show up. Unless you time the cam, you'll never know where it is


mycuda said:
Putting #6 cylinder TDC compression stroke and Measuring #1 cylinder spring tension difference of intake/exhaust of .030 int.-.060 ex. was good.
Click to expand...
Do you mean the LIFT was .030" int.-.060" ex. with #1 TDC at overlap? Seems to be pretty retarded cam timing. The exhaust will be a BIT more open, but .030" sounds way too much, indicating retarded timing. But a true cam timing exercise is the only way to know.

I would be doing a proper cam timing exercise and looking at the thickness of head gaskets used. Not much you can do about the stock pistons being so far in the hole at this point.
 
The first things I see are a low compression engine with the heads being a cork and probably a cam that needs to be toyed with (advanced) to enhance what can be gotten out of the engine. 3.23's are not helping much with the converter, or the hungry 727, no matter the tire size.
I'd like to know the exact cam being used.
How heavy is the car?
 
I have the .450 lift 250° purple shaft in my 81 318 with totally stock short block. I ported they hell out of the heads and port matched the intake and run a stock electronic distributor and orange box. Intake is an edelbrock performer 318/360 and 850cfm TQ carb. Motor pulls real hard but I run manual trans and no tach. I am happy with the motor, maybe you need a hair less cam.
 
^...SO this is what I'm thinking is going on, I could be wrong, I hope I am.:

He put in a cam too big, as mentioned he put the STOCK stall converter back in, which is maybe 1800 stall on a good day, more like 1200, with highway gears, then wonders why he has to rev it up to 2,200+ rpm (which happens to be around when total timing comes into play) to get any power... Add a poorly tuned carb, and lazy , heavy springed timing curve your asking for trouble.

The right way to go about this is to select the right cam, with the right timing curve, with the right QUALITY stall, with the right gear. It's a system that has to work together... I see all the time; people spend 20k on a engine and then spend $300 on the converter. Not doing yourself any favors there either.... The converter is arguably the most important part of any combination. Hard personal lesson shared right there.

This is also a good read:

http://www.hardtail.com/techtips/selectingconverter.html
 
I here ya woods, just got a cheap engine to get the car drivable.
The car is setup for big block but cant sell the car if its a 4 cylinder off the line.

Figured while changing timing chain might as well put a street cam in.
Obviously compression cant handle duration I get it.
 
IMHO your on the right path putting a street cam in there, I hear good things about the Summit K6900 1200-5000. Inexpensive, and so I've heard works well with the low compression. And still pull real well once you get into it. With a mildly tired 318 and 3.23's your going to need all the help you can get with 'off the line' performance. This means getting that vacuum advance working like a clock as well.

Some rough numbers for that @ 2500rpm might be:

10-16 initial
32-38 total (plugged vacuum advance)
44-52 w/ vacuum advance hooked up (back off a couple degrees when it starts surging while crusing)
 
One real question.
is advancing this cam physically gonna make much difference?

268/272 duration 450/455 lift

Thanks
 
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