360 questions

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440BelII

440BelII

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I just picked up a basically fresh 360 shortblock,under 1000k miles runtime. The person I bought it from didn't know anything about it, other than it was in a truck before being pulled. It has the Sealed Power 405p .030 pistons and I can see through the fuel pump hole that it has a double roller chain. I don't know what size the cam is, I would have to think it has a "stump puller" cam in it. I'm going to put this in a'74 Duster, just wondering if I should bother changing the cam. This will be a street driver, not a race car.The other question I have is this; I was going to use of 360 heads with 1:88 intake valves on this , but, with this motor being low compression, I was wondering what would happen if I mounted a set of 318 heads on this. I have a pair 0f '675's in usuable shape, they are from a '68-'74 318 engine. I know the deal about mounting 360 heads on a 318, but what about 318, small port heads on a low compression 360. Thoughts and input welcome as this site is full of great info. It's helped me many times in the past.
 
IMO, besides just run it first, see how it is and then mess with it later, I'd just change the cam to suite your particular need. But then again, that cam in there may suite.

Head flow over compression. Don't bother swapping heads out for a higher ratio since the smaller port will lower the performance ceiling of what you all ready have. IF it was indded designed to do truck duty, and the cam is to suite a truck, it is small and a smaller head makes the package smaller.
 
As above and;
Before you install it, set it up to put one cylinder at TDC compression, and with the sparkplug hole as the high point, measure the chamber volume, to calculate exact compression ratio. I do this by filling a a 100cc syringe(vet shop) with 30 wt oil, and pouring some/most of that oil into the cylinder to the bottom of the hole. Be careful and slow down after 70cc. When you are finished, rock the crank back and forth a couple of degrees to prove the piston is at the top. Add oil as may be required, to the bottom of the hole.Work slowly and carefully,cuz if you spill, you will have to start over with a different hole.Finally read the syringe and calculate the true fill volume.If you used all the 100, your cr is less than 8.5. If you need to add more, add exactly 20cc to the syringe.Then continue filling, to the bottom of the hole.

The formula is (swept volume + fill volume)/fill volume = Scr
The swept volume for a 30 over 360 is (4.03/2)squared x pi(3.1416) x stroke(3.58) x 16.387(a constant). This equals 748.3 for you.
So a 100cc fill volume would be (748.3 + 100.0)/100.0 = 8.48Scr,
And a 106.9 cc volume would be(748.3 + 106.9)/106.9 = 8.0Scr

This true compression ratio number will be very useful later if you decide to make a cam change.Or a head change.
 
I agree, run it as is, you may be pleasantly surprised.
 
I will check the comp.ratio before install. I figured it to be around 8:1 ratio because , the pistons are .110 in the hole, they have a slight dish, and the heads are open chambered with little to no milling done. I read an article on another site that claimed this setup to be a 8:1 ratio.
 
I have a brand new, 0 mile 727 trans that I picked up to run behind the 360. It came out of a '72 van, complete with torque converter. I was thinking about just running it just the way it is, as suggested, and see how this "truck" drivetrain does in this car. I'm putting together a 8 1/4 Sure Grip rear with 3:73 gears.
 
a 4.03 hole and .110 down makes 23cc, the open chambers might be 70cc and the gasket might be 8.9cc. This totals 101.9. To make 8.0Scr with this, the dish would have to be very small indeed to make 5cc.
Of course there are other variables with other results. etc
For instance; thinner gaskets and shaved heads, smaller chamber heads....
Now, with the early closed chamber teener heads and a thin gasket, the total chamber size could be reduced to around 23+60+6.9+5=95cc. This would bring the compression up to about 8.9Scr.This is a very worthwhile gain in compression,allbeit with a horsepower penalty after the torque peak.Depending on your needs, this could be an alternative.

FWIW; I once put the entire teener top end,including the cam and 2bbl, onto a 340 bottom end. This essentially turned my junkyard340 into a big-bore, high-compression teener.I dropped it into a 65 Valiant wagon with fenderwell headers, and hiway gears.. It was a terror for what it was.
I remember it fondly.
 
Agreed with what was said above, install it AS IS, it will have plenty of bottom end! Change parts later after you see how it performs.
 
If you really want to check the cam out, can't ya just pull the rear plug and hope you can read a cam serial number? You do NOT want to have to change cams in car. It's no fun. No fun at all.
 
...............The 318 heads will really help out the low end and not take much away from the top end, I say go 4 it...........kim....... I have done this a few times.....
 
From what I see air flow adds more torque . Engines making 1.2 - 1.5 to 1 lbs-ft per cubic inch have serious carb head cam combo. Not saying you should throw on big port heads cause while it could make more torque per cubic and it will be at an rpm not so street friendly unless we're talking big cube engines. Smaller cam carb head combo will aid lower rpm torque but 318 over 360 heads would probably slightly advantageous to the very low end but at a cost to low mid to high rpm. I think everyone got everybody too afraid of air flow yes you don't want hogged out W2 on a mild 318 daily driver but I'd rather make power from heads than cam on a street engine like the new LS and Hemi engines.
 
273 said:
From what I see air flow adds more torque engines making 1.2 - 1.5 to 1 lbs-ft per cubic inch have serious carb head cam combo. Not saying you should throw on big port heads cause while it could make more torque per cubic it will be at an rpm not so street friendly unless we're talking big cube engines. Smaller cam carb head combo will aid lower rpm torque but 318 over 360 would probably slightly advantageous to the very low end but a cost to low mid to high. I think everyone got everybody too afraid of air flow yes you don't want hogged out W2 on a mild 318 daily driver but I'd rather make power from heads than cam on a street engine like the new LS and Hemi engines.
Click to expand...


Wow! Bro! Hold on a second here! Not trying to pick you a part here but IMO, your a bit all over the place. Let start with the numeric figures of torque you listed stating with 1.2 & then 1.5 and back down to 1.

At 1 ft. Lbs. per cubic inch is roughly a very mild came upgrade and or headers like in IQ52's low compression 360 thread. Very mild build with excellent results for the intended package.

This is a far cry away when you start doing the math.

360 @ 1 lbs/TQ per cube equals 360 of course.
[email protected] = 432
[email protected] = 540

I think that saying adding a large port head is vauge. What is a large port head and when did that come into the picture of possible with the OE poster wanting to possibly try and make use of sealing the STOCK HEAD out for a smaller 318 head?

He is talking about his 360.

Heck! He doesn't even know what the cam is and your advising what about it? Don't do large cams? What?!?!
 
rumblefish360 said:
Wow! Bro! Hold on a second here! Not trying to pick you a part here but IMO, your a bit all over the place. Let start with the numeric figures of torque you listed stating with 1.2 & then 1.5 and back down to 1.

At 1 ft. Lbs. per cubic inch is roughly a very mild came upgrade and or headers like in IQ52's low compression 360 thread. Very mild build with excellent results for the intended package.

This is a far cry away when you start doing the math.

360 @ 1 lbs/TQ per cube equals 360 of course.
[email protected] = 432
[email protected] = 540



I think that saying adding a large port head is vauge. What is a large port head and when did that come into the picture of possible with the OE poster wanting to possibly try and make use of sealing the STOCK HEAD out for a smaller 318 head?

He is talking about his 360.

Heck! He doesn't even know what the cam is and your advising what about it? Don't do large cams? What?!?!
Click to expand...

I'm not advising him anything just giving info so he can make up his own mind.

Why I was talking about lbs-ft per cubic inch and head flow and such was cause a lot of people have it in there heads that small ports and small cams and small carbs make torque and I believe that's not true. Stock engines make about 1:1 torque per cubic inch and torque per cubic inch goes up as you add more flow with matched cam carb heads etc... but of course depending on cubic inch it will be further up the rpm scale. I was just trying to show small ports don't necessarily build more torque especially when adding rpm.

Now for 318 heads which were really designed for the 273 size engine. While the ports aren't overly small and poor flowing and may pick up a couple of mpg's and pick up a few lbs-ft under 2000 or so rpm . The bump in CR will probably also help. If he's OK with shrinking the power band and losing some mid to high rpm power then go for it.

But really a small to mid size cam 4bbl exhaust and stock 360 heads will give up little down low while adding greatly to the engines power and even though he stated he's not building a race car but most of us like a reasonable amount of power ĺook at the power ratings of most new car.
Cause technically a car doesn't need more than 70 hp anything over that is a performance engine :)
 
Ok, I wanted to ask because I didn't want to "experiment" with these heads and have the car fall on it's face after 3500rpm or something dumb like that. Like I said, this one isn't going to be a racecar. just a driver but, I want it to run well also. I figure the rear gears that I picked will help. I picked that rear to run because, by the time I get done buying a used 8 3/4 A body axle, I might as well buy a new axle from a company with a warranty for the price I'm going to have invested into 40 year old parts.
 
440BelII said:
Ok, I wanted to ask because I didn't want to "experiment" with these heads and have the car fall on it's face after 3500rpm or something dumb like that. Like I said, this one isn't going to be a racecar. just a driver but, I want it to run well also.
Click to expand...

I get the sense that you really, really, want to know about those teener heads. And if you don't try it you will never know, and you will be forever wondering. So with that in mind I'll offer this; I have been able to use the Fell-Pro .039 headgaskets at least 3 times. They are on their 3rd life in my current engine for at least 12 years and pushing 100,000 miles and on 10.7 Scr.I have also, reused the FelPro intake gaskets. And I highly recommend a smallport single plain 4bbl intake,to go with the teener heads. This is not a deal breaker, but once you try it, you'll know why.
So I'd have to say, don't be afraid to satisfy your curiosity. It will cost you a few hours of your life, and a few dollars in sealers and glues. Then you will know.At the absolute worst you will have a story to tell.I love to tell my story.
Oh, and that teener top end still likes headers, and 3 inch duals! Let it breath,let it rev.Have fun.
 
When you say a"small port, single plane intake", I have a Holley Street Dominator for a small block in the garage. How would that be?
 
With a 360 under it, it won't much matter what smallport singleplain you use; but since you have it,
it is my opinion that
a small port Street Dominator, on teener heads, on an approximate 9/1 cr 360, with 3.73s, and a van convertor,will be seriously big fun, from idle to 4000ish, which will be 35mph in first. With the 727 ratios of 2.45-1.45-1.00, the rpm drops between gears are; to 59% and to 69%.So outshifting 1st at 4000, the engine will drop in at 2360. This will then require a 4000 - 2360 = 1640rpm powerband.So now you power up to 4000 in 2nd to 58mph(just about perfect! Outshifting 2nd at 4000, the engine drops in at 4000 x .69 =2760; a 1240 powerband requirement. Then powering through to 4000 in direct will get you 84 mph at 4000 again.Of course with the right valve springs, there is no reason to suppose your combo won't continue to rev well into the 5000s, which would get you about 105mph@5000.
Here's the kicker; your cam better not be designed for high rpm operation. But you will know that soon after the first start.
As to the valvesprings, I had good success with putting 360 springs on my teener valves with .060 shims at all locations.Bush league I know, but it revs to 5500 easy enough with the stock teener cam, headers, and a smallport TQ. I leave you to check your valve gear out, to make sure all the parts play nice together.
Just do it and tell us how awesome it is!
 
273, you don't know how many times I tell people that a car only needs about 50 HP or so to do the Hwy. speed. They all think I'm nuts for that and daily driving my mad *** old 70's snot rod around. Sorry, I just don't think 450HP is a lot.

Small ports on a big engine should draw a torquey responsive engine.
Staying with the stock head, small cam, etc... As you said should add torque but where it does add the extra torque is more of a function of the cams duration as well as other parts used to a lesser degree.

IMO, I think your overselling/overthinking/worrying about the issue. A little bit maybe due to the short stroke engines reaction (3.31) vs the longer 360 stroke. 3.58. Also to say that the torque will show up further on the (rpm) scale is also not exactly true ether as engine size, cam timing and size also effect this out come.

Just because you increase cam size doesn't automatically mean the curve or peak of torque moves up the rpm range. Sometimes, it just gets fatter.
 
440BelII said:
When you say a"small port, single plane intake", I have a Holley Street Dominator for a small block in the garage. How would that be?
Click to expand...
That would be a small port single plane for sure. What "other" intake is available to you?
 
I have a line on a Edelbrock Performer locally. Icould pick that up if it will work in my favor.I do have a Performer RPM but I'm using that on the 360 that's going in my Demon.
 
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