360 build info

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360moparjunkie

360moparjunkie

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Re-freshening my 72 360 w/ J heads. Installed 9.8 flat tops. How do I calc. actual compression? Quench Ht.? / cc head chambers? (first timer)
Any cam advice? Currently have .410-.440 re-ground crower baha from years ago.
Would love to stuff comp cams smallest thumper line cam @ .497-.483 w/287/304 duration in this motor. I realize proper valve springs would be in order.
I do have a new set of Rhoads lifters for this motor if I choose to use them.
Edelbrock LD340 Alum. intake (lg. dual plane)

Any advise on direction?
 
For head cc chamber, you'll need a small square of plexi glass sealed to the chamber with grease. Then a burret of liquid to poor in and measure the amount of cc's missing from the burret.
Head gasket thickness and bore size are added into any of the various calc's on line with the head cc chamber amount and how far down in the hole the piston is. Don't foregt to add in the cc amount of the vave reliefs.

What direction do you want to go in? What do you want the car to do or how well it'll perform at the track?
 
When the total cc count is known how do I convert this to actual compression? Is this called static compression?
We are working on this motor to spin in the 6000 rpm range with as much usable power a possible. We do not have to smog this one.
A stall convertor is an option I am willing to go with if need be.
What are thoughts on the cam choices without machine work (only new springs)
 
Once you have all the above numbers to plug into a calculater, the calc will give you back the ratio. And yes, static compresion.

Again you ask for advice on direction and cam without giving me a clue to what it is you want to do.

"As much useable power to 6000 rpm's" is still unclear. Part of the reason, beside opinions being so varried, is what you want to do with the car. AKA;

Daily driver
Street strip
Strip only

Tell me about the car. Trans type and rear end gears, weight and any reduction in it if done.

My thoughts on cam's and how to choose them are simple. First, they should work as part of the combo of the car, AKA, gear ratio, stall converter if need be, cars weight and RPM band you'll be driving in.

Secondly, the cam should be matched with a intake capable of the task at hand and the heads should be preped accordingly.

3rd. Now that the above is in your head, or should be, a plan, choose a cam with the duration matching the driving RPM range. Then, with knowledge of how the heads are in terms of flow, get the cam with as much lift as the heads flow or as close as possible without exceeding the heads abilty to flow that amount of lift.

In otherwords, if the flow of the heads stall (Decrease) at .550 lift, for most applications, there is really no point in getting a cam that lifts the valve to .570.

A 110 centerline is the basic set up cam manufactures set a cam up with and it works well on 340 - 360 engines. A 108 is also OK to use.
 
Hope everyones holidays are going well.
Thank you for the help thus far.

As far as direction the build objective is a high 12 sec build. (street/strip)

Build is a 52 1/2 ton pu w/ 68 pass. car running gear.

Weight, gears, tire dia. currently unknown as we just got started.

360 on my stand has a freshend up bottom end. We would like to target the 350-380 hp on a modest budget. Will this hp obtain our objective?

I understand the objective of fabo. We are hoping the tech. hand of members are willing to overlap into our type of mopar build.
Any tech help would be greatly appreciated.
 
My truck is a '67 on a '84 chassis,,,,360 .030 over,roughly 10.2 CR.,,balanced blueprinted,,eddy heads,,,comp.EX268-H cam,,,air gap intake,,eddy 750 carb.
727 trans with shift kit,,,,8 3/4 rear with 3.91 sure grip,,,,
I have not had it on a dyno, but i am thinking it has roughly 400 ponies,,,
at 4200 feet elevation I ran a best of 15.04 et. at 93 mph.
that was with a stock stall converter,,,,,I have since put in a 3000 stall,,,but i am still buttoning things up,,,,
I had the truck weighed with me in it and a half tank of gas,3940 lbs.,,it is a 32 gallon tank.
it is a short bed,,,,,,27 inch tall tires.
Good luck on your build.
 
A high 12 sec. goal is sounding a little lofty.
Maybe a 14 second bracket will be more realistic.

What type of power can one expect to pull out of a 360 w/ flat tops, factory J heads w/ no machining for fancy valve parts? (springs, port, etc)

Back to static compression.
I have top of piston average of 4 different holes.
32.25cc (with head gasket thickness)
Once I have cc'd the head chamber (w/ spark plug in hole using plexi-glass cover w/ 2 holes drilled) How do I then figure my compression?

What is the correct equation to use?
 
Thank you for the static comp. calc. web site.

Appears as though my static compression with my flat tops is 8.715 (this is providing my head chamber proves to be 63cc......Have not pu the plexi glass yet.

If I were to shave the block:
.050=9.647
.060=.9861
.070=10.085 to 1
This would leave an av. .0392" to top of deck.

Does this sound like a cost effective direction for more power since I already have the new pistons?

What type of problematic issues could result from this. ie. intake now may fit incorrectly.


What is dynamic effective compression ratio? First time I've heard of this..seen it on the calc. site.
 
360moparjunkie said:
Thank you for the static comp. calc. web site.

Appears as though my static compression with my flat tops is 8.715 (this is providing my head chamber proves to be 63cc......Have not pu the plexi glass yet.

If I were to shave the block:
.050=9.647
.060=.9861
.070=10.085 to 1
This would leave an av. .0392" to top of deck.

Does this sound like a cost effective direction for more power since I already have the new pistons?

What type of problematic issues could result from this. ie. intake now may fit incorrectly.
Click to expand...

The stock heads will most likely be in the 70 cc range. If you deck the block and mill the heads you will have to mill the intake side of the heads and probably the end rail area where the intake seals the block.

How far in the hole are your pistons at tdc?
 
Pistons are .1092 @ tdc from top of bare deck.

I thought by buying the higher comp. flat tops would rase my comp.
Maybe static was just that much less before.

FYI This motor made incredible torque before w/ all stock components and a 2bbl.....was probably the .410/.412 cam 252/256

Currently .1092 to top of deck.
 
That is far down in the hole, more than my stock 360 pistons in the '79 engine @ IIRC, .090.
 
Okay, keeping my chin up....I'm getting closer to the actual quantitative figures that I seek.

Working my best to understand.

How does static compression compare to the advertised piston that I purchased.

Looks like static compression is the real compression of my engine and just forget what the box says, right?

What device is best used for measuring the volume of liquid that I will pour into the holes I have ready in the plexi-glass? (one that's easily obtainable)

Can I use wd-40 in place of some formal cc fluid. (my book say I can use parts cleaner.)

Thanks in advance for all the help
 
There is advertised compression ratio, and then reality. For a psiton manufacturer, published numbers depend on the block an parts being used being exactly the same specs as theirs. Reality rarely matches those sepcs...lol. You have to remember that calculating static ratio is the right and only way to know what the true compression is... and that most shops rebuilding engines don't do this unless you pay them to blueprint the assembly. That's because the dimensions of the block's deck height, stroke, rod length, main bearing bores, valve seat depth, valve design, head gasket type, and cast chamber volmues are all variables until you verify and se tthem where you want them.

What you will calculate will be your actual static compression ratio. The box and published figures are at best a general guide and worst not even close.

I have a nice lab type burrette. But the same results can be gotten with a garden variety large animal syringe from a farm store. You need it to be metric to standardize the results with the rest of the world. This number does get converted to english measure for the calculations. As far as fluid, any non-oil is fine. I would not use WD40, I use isopropyl alcohol with some coloring added to it. Blue windshield washer fluid would be fine too.
 
360moparjunkie said:
Pistons are .1092 @ tdc from top of bare deck.

I thought by buying the higher comp. flat tops would rase my comp.
Maybe static was just that much less before.

FYI This motor made incredible torque before w/ all stock components and a 2bbl.....was probably the .410/.412 cam 252/256

Currently .1092 to top of deck.
Click to expand...

What pistons are you going to buy? The speed pro H116cp are the higher compression, set is 265.00 from Summit with rings, or KB makes some too.

This may help you too.
http://www.rbracing-rsr.com/compstaticcalc.html
 
66,
Pistons were already purchased a while ago. Already installed onto rods.
Advertised comp. was 9.8...what a joke when compared to actual static.
These flat tops do not have valve reliefs.
Please check out my new thread on the engine tech forum.

Thank you all
 
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