Deciding on replacement intake (318, details in post)

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J1MMY said:
Current engine/drivetrain in my valiant is as follows:

318
167 KB pistons
360 heads ported
Lopey Isky cam (exact spec unknown but it seems there’s only 2)
Solid lifters
273 rockers
HEI distributor
Tunnel ram w/dual 450 carbs
Long tube headers
4 speed
3.91 explorer rear w/locker

There may be other mods as well but these are not known to me, no idea on output but it runs healthily and pushes the car along very nicely.


It may seem mad to some but my intention is to remove the tunnel ram & 450s and replace with something I can either get under the hood or a low hood scoop.

Reading on intake choice has pickled my newbie brain - air gap, RPM, or an altogether different choice? Car is not a daily driver, weekend/sunny day fun and the odd trip down the strip.

Advice is always appreciated.
Click to expand...
My opinion with that combo, a tunnel ram isn't needed. Mess with it if you want to. A 318 with those parts will only put out so many horsepower and a dual quad tunnel ram won't make the numbers go up much more than single 4 barrel and a good manifold. (Air gap or the like and a 650 as an example)
 
toolmanmike said:
At least he's got the KB167's. Starting out at zero deck (or .001 below) is a good start. All the charts say 65-73cc for the 360 heads. How much compression with a .027 or a .040 head gasket? And yes, the op should do a compression test to make sure. There are a lot of unknown's here.
Click to expand...
I did the math.
On a 9.600 LA-deck, the 167s math to .0095 below deck. that is ~1.87cc
The pistons, as far as I can tell, have 5cc eyebrows.
the .028 gaskets are ~6.8cc
The 360 heads, by all accounts are usually ~72cc. I have none smaller.
Throw in 1cc for the crevice volume
That totals 86.7cc

at 3.91bore, the swept is 652.27
That makes an Scr of 8.52

The .028 gaskets need a rough deck, else the fire-rings like to migrate, and it doesn't take long.
With the .039 FelPros, the numbers work out to
(652.27 + 88.5)/88.5 = 8.37

Plugging that into the Wallace with a modest cam (Ica of 66*) at 500ft elevation (guessing OPs elevation); I get
Static compression ratio of 8.37:1.
Effective stroke is 2.52 inches.
Your dynamic compression ratio is 6.60:1 .
Your dynamic cranking pressure is 124.24 PSI.
Your effective boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of PSI is 6.50 :1.
V/P (Volume to Pressure Index) is 90

V/P of 90 is just about 3% stronger than a factory 225 slanty.
The Effective DCR of 6.5, is about 1.5 points low and;
and Cylinder pressure of 124psi, is a good 30 psi low for open-chamber heads, and the Q is so huge as to be ineffective.
If OP had a stock convertor and hiway gears, this would be guaranteed to be sluggish to around 3000 to 3500 rpm.
Thankfully he has a manual-trans and 3.91s..

Op said
J1MMY said:
Advice is always appreciated.
Click to expand...
My advice still stands. but now with a low cylinder pressure design), I would add; Notta chance would I run this engine, in it's current iteration, with any other cam but the factory-sized one. With an Ica of 48*, the numbers improve to
Static compression ratio of 8.37:1.
Effective stroke is 2.89 inches.
Your dynamic compression ratio is 7.43:1 .
Your dynamic cranking pressure is 145.79 PSI.
Your effective boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of PSI is 7.33 :1.
V/P (Volume to Pressure Index) is 121
VP of 121 is similar to a stock 5.2 Magnum. I could live with that..... if I had to.

But If it was mine;
I'd still run a compression test to see how bad it is. Then if it sux as bad as I suspect, then
I'd Zero deck it rough, to hold those .028s, then install 60cc closed-chamber iron, small-port heads. With an Scr now of 9.85, a Q of .028, and modest cam with an Ica of say 60* , the picture changes to

Static compression ratio of 9.85:1.
Effective stroke is 2.66 inches.
Your dynamic compression ratio is 8.10:1 .
Your dynamic cranking pressure is 163.55 PSI.
Your effective boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of PSI is 8.00 :1.
V/P (Volume to Pressure Index) is 125

Now you got an engine!
Couple this with the 4-gear and 3.91s, and you are guaranteed to have fun in any A-body, and especially so in a light-weight Valiant.
To save a lil cash, I'd try it with the current decks and .028s, for a Q of .038ish; but the heads gotta be closed-chamber. and the intake I would use, would have ports matched to the head, and a Thermoquad.
But,
I have this Dual-Port, I got from a member here a few years ago, that I've always wanted to use on something.
Ima thinking Magnum heads and a port-match, to go with that lopey cam. Or, I'd really like to try the stock 360 sized cam, with this intake;
Static compression ratio of 9.6:1.
Effective stroke is 2.78 inches.
Your dynamic compression ratio is 8.21:1 .
Your dynamic cranking pressure is 166.49 PSI.
Your effective boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of PSI is 8.11 :1.
V/P (Volume to Pressure Index) is 133

Oh yeah, this is starting to look like fun.........

Since the current cam already has a lopey idle, I'd screw the Magnums on, or any aftermarket closed chamber LA-heads and redo the compression test. If it ain't too bad, then, with the OPs 4-speed, and 3.91s, I'd try it.
So, at this point, my only cost is the closed-chamber heads and gaskets, cuz I already have a spreadbore intake, and matching 4-bbl.
If the heads I get have small-ports, I have this small-plenum Excelerator looking for a home.................

Like @toolmanmike said;
toolmanmike said:
There are a lot of unknown's here.
Click to expand...
I just narrowed it down some .....................
 
AJ/FormS said:
I did the math.
On a 9.600 LA-deck, the 167s math to .0095 below deck. that is ~1.87cc
The pistons, as far as I can tell, have 5cc eyebrows.
the .028 gaskets are ~6.8cc
The 360 heads, by all accounts are usually ~72cc. I have none smaller.
Throw in 1cc for the crevice volume
That totals 86.7cc

at 3.91bore, the swept is 652.27
That makes an Scr of 8.52

The .028 gaskets need a rough deck, else the fire-rings like to migrate, and it doesn't take long.
With the .039 FelPros, the numbers work out to
(652.27 + 88.5)/88.5 = 8.37

Plugging that into the Wallace with a modest cam (Ica of 66*) at 500ft elevation (guessing OPs elevation); I get
Static compression ratio of 8.37:1.
Effective stroke is 2.52 inches.
Your dynamic compression ratio is 6.60:1 .
Your dynamic cranking pressure is 124.24 PSI.
Your effective boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of PSI is 6.50 :1.
V/P (Volume to Pressure Index) is 90

V/P of 90 is just about 3% stronger than a factory 225 slanty.
The Effective DCR of 6.5, is about 1.5 points low and;
and Cylinder pressure of 124psi, is a good 30 psi low for open-chamber heads, and the Q is so huge as to be ineffective.
If OP had a stock convertor and hiway gears, this would be guaranteed to be sluggish to around 3000 to 3500 rpm.
Thankfully he has a manual-trans and 3.91s..

Op said

My advice still stands. but now with a low cylinder pressure design), I would add; Notta chance would I run this engine, in it's current iteration, with any other cam but the factory-sized one. With an Ica of 48*, the numbers improve to
Static compression ratio of 8.37:1.
Effective stroke is 2.89 inches.
Your dynamic compression ratio is 7.43:1 .
Your dynamic cranking pressure is 145.79 PSI.
Your effective boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of PSI is 7.33 :1.
V/P (Volume to Pressure Index) is 121
VP of 121 is similar to a stock 5.2 Magnum. I could live with that..... if I had to.

But If it was mine;
I'd still run a compression test to see how bad it is. Then if it sux as bad as I suspect, then
I'd Zero deck it rough, to hold those .028s, then install 60cc closed-chamber iron, small-port heads. With an Scr now of 9.85, a Q of .028, and modest cam with an Ica of say 60* , the picture changes to

Static compression ratio of 9.85:1.
Effective stroke is 2.66 inches.
Your dynamic compression ratio is 8.10:1 .
Your dynamic cranking pressure is 163.55 PSI.
Your effective boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of PSI is 8.00 :1.
V/P (Volume to Pressure Index) is 125

Now you got an engine!
Couple this with the 4-gear and 3.91s, and you are guaranteed to have fun in any A-body, and especially so in a light-weight Valiant.
To save a lil cash, I'd try it with the current decks and .028s, for a Q of .038ish; but the heads gotta be closed-chamber. and the intake I would use, would have ports matched to the head, and a Thermoquad.
But,
I have this Dual-Port, I got from a member here a few years ago, that I've always wanted to use on something.
Ima thinking Magnum heads and a port-match, to go with that lopey cam. Or, I'd really like to try the stock 360 sized cam, with this intake;
Static compression ratio of 9.6:1.
Effective stroke is 2.78 inches.
Your dynamic compression ratio is 8.21:1 .
Your dynamic cranking pressure is 166.49 PSI.
Your effective boost compression ratio, reflecting static c.r., cam timing, altitude, and boost of PSI is 8.11 :1.
V/P (Volume to Pressure Index) is 133

Oh yeah, this is starting to look like fun.........

Since the current cam already has a lopey idle, I'd screw the Magnums on, or any aftermarket closed chamber LA-heads and redo the compression test. If it ain't too bad, then, with the OPs 4-speed, and 3.91s, I'd try it.
So, at this point, my only cost is the closed-chamber heads and gaskets, cuz I already have a spreadbore intake, and matching 4-bbl.
If the heads I get have small-ports, I have this small-plenum Excelerator looking for a home.................

Like @toolmanmike said;

I just narrowed it down some .....................
Click to expand...
all that figuring is just mused ramblings till you know witch of the 6 sbm solid tappet cams isky makes that he's running, and its IVC point!! with isky solid tappet grinds with lifts from .425 to .580 and duration's from 216 to 312 there's no guessing where that IVC point is and isky ant sharing that info ether....id really like to know my self....i just hate guessing!
 
Well that escalated :lol:

Compression test results to follow some point over the festive period

measured up and its possible to keep the tunnel ram, do away with the velocity stacks and fit a hood scoop - bit that comes with its’ own ups and downs.

Merry Christmas/happy holidays
 
Well it look longer to get round to than hoped but I managed to get the compression figures. All 160 or close enough, the gauge is in 5psi increments and the needle was either tipped just under or over the mark. Warm engine (idling 15 mins)

Now who would like to do the math :D
 
J1MMY said:
Well it look longer to get round to than hoped but I managed to get the compression figures. All 160 or close enough, the gauge is in 5psi increments and the needle was either tipped just under or over the mark. Warm engine (idling 15 mins)

Now who would like to do the math :D
Click to expand...
Have you been driving the car ?
Does it work fine ?
If so does it really matter if the cr is a bit low ?

Your not gonna know unless you take it apart and measure, AJ's math is based of a bunch of assumptions like the builder didn't do any milling to get a decent cr and picked cam with a poor ICA, for the build based on nothing.

And in the end of the day AJ think 318's are worthless performers even if build to his liking.
 
If you did get to drive it with the tunnel ram how did she run?
 
Yeah, the car pulls well for what I want - that’s not been an issue. Im curious more than anything to know what it’s making so some dyno time is in order. Would also benefit from some carb tuning no doubt - that’s beyond me, I need to learn about it
 
Well time flies, I picked up and parted out an Aussie Valiant, worked on the bikes and got back into this. It’s been interesting and have filled in some of the blanks. I am wondering if I should rename this thread ‘engine rebuild strategy’!

The cam is not an Isky, it’s a Crane 691191. Quite a frisky grind for a 318 from what I’ve read…!

Heads are 360J heads, 915 casting (one B and one H). 66cc chambers from my ‘fill it and empty with a syringe’ measurement technique

273 rockers and adjuster pushrods. Solid lifters.

Pistons are plus .040. They’re pretty sooty so I’ll clean the tops to make sure they’re all the same. They’re flat tops with eyebrows, but have a slightly milled centre (I assumed it was for spark plug clearance and haven’t found another pic of any like it)

At this stage it’s only the bottom end to come out and it’s stripped.
 
junkyardhero said:
that's a whole big ol' honkin' bag of camshaft for a 318.

hope it's got a bucket full of compression and some gear out back.
Click to expand...
That’s an awesome way to put it :D

It doesn’t…but I’m open to ideas for that to happen if it’s viable.

4 spd and 3.91 currently
 
Well you said it worked decently but always can make it better.

Is it zero decked ?
Did you end up swapping intakes ?
 
273 said:
Well you said it worked decently but always can make it better.

Is it zero decked ?
Did you end up swapping intakes ?
Click to expand...

I haven’t gotten round to working that out yet but in terms of deck clearance it’s ‘not much’ in the hole.

tunnel ram has been rehomed (sold) so will be getting a new intake.

Am absolutely into making it better ideally by considering optimising what I have rather than chucking a 360 bottom end and a pair of alloy heads on (if possible)
 
J1MMY said:
That’s an awesome way to put it :D

It doesn’t…but I’m open to ideas for that to happen if it’s viable.

4 spd and 3.91 currently
Click to expand...
the 4 gear cog box and 3.91's are about what i would consider the limit for a regularly street driven car so you're doing good there.

you just need to understand that it's going to have a narrow peaky power band is all.

you can get some compression by swapping heads and running a thinner headgasket, but those are kind of band-aids. the best solution is pistons and machine work. which means really, you should probably just get a 360.
 
junkyardhero said:
the 4 gear cog box and 3.91's are about what i would consider the limit for a regularly street driven car so you're doing good there.

you just need to understand that it's going to have a narrow peaky power band is all.

you can get some compression by swapping heads and running a thinner headgasket, but those are kind of band-aids. the best solution is pistons and machine work. which means really, you should probably just get a 360.
Click to expand...
360? Stop that :poke::D id really like to wring as much as I can from the stoutest 318 I can build - peaky is fine. It’s a fun car, I have sensible daily drivers.

Pistons, machine work, rebuilding heads…I’m good with that
 
J1MMY said:
360? Stop that :poke::D id really like to wring as much as I can from the stoutest 318 I can build - peaky is fine. It’s a fun car, I have sensible daily drivers.

Pistons, machine work, rebuilding heads…I’m good with that
Click to expand...
stroker kit is the best VFM, but some magnum heads are probably the eaiser route to take....

some ported magnum heads with roller rockers on that bottom end with that cam and an appropriate intake and carb would make about 375. but it would be all uptown, that kind of set up doesn't start to wake up till about 3K and gets choochin' about 4500

conversely, the stroker would make about the same power overall, but more power by a wide margin and at 1000+ rpm less
 
junkyardhero said:
stroker kit is the best VFM, but some magnum heads are probably the eaiser route to take....

some ported magnum heads with roller rockers on that bottom end with that cam and an appropriate intake and carb would make about 375. but it would be all uptown, that kind of set up doesn't start to wake up till about 3K and gets choochin' about 4500

conversely, the stroker would make about the same power overall, but more power by a wide margin and at 1000+ rpm less
Click to expand...
Dammit, for the cost of getting a stroker kit landed here I could as well find a 360 and Magnum heads are no easy find either. Looks like I may have to rethink the stubborn desire to keep it 318.

Randomly stumbled across this whilst looking up the cam grind for the crane. Pokey!

Old School 340 Build
 
J1MMY said:
Dammit, for the cost of getting a stroker kit landed here I could as well find a 360 and Magnum heads are no easy find either. Looks like I may have to rethink the stubborn desire to keep it 318.

Randomly stumbled across this whilst looking up the cam grind for the crane. Pokey!

Old School 340 Build
Click to expand...
1st what are you trying to get out of the 318, power and rpm wise ?
A 318 just gonna need more rpm and gearing than a similarly built 360
Eg. 400 hp is around 5400 rpms for a 360 and 6000 rpms for a 318.
 
273 said:
1st what are you trying to get out of the 318, power and rpm wise ?
A 318 just gonna need more rpm and gearing than a similarly built 360
Eg. 400 hp is around 5400 rpms for a 360 and 6000 rpms for a 318.
Click to expand...
400 hp at 6000 for a 318 would make me very happy.
 
Heads are gonna make or break your combo with weaker heads (.300"-.500" lift flow numbers) you'll need more cam and cr with better flowing heads can get away with less cam and cr.
The so called magazine 400hp combo there like 4 of them, basically are an 750 with airgap, headers, 230 cam, 10:1 cr and magnum heads or a 230 cfm LA basically mild ported with 2.02 valves. If you want less cam need the heads to do more work by having better .300"-.500" flow numbers.
 
273 said:
Heads are gonna make or break your combo with weaker heads (.300"-.500" lift flow numbers) you'll need more cam and cr with better flowing heads can get away with less cam and cr.
The so called magazine 400hp combo there like 4 of them, basically are an 750 with airgap, headers, 230 cam, 10:1 cr and magnum heads or a 230 cfm LA basically mild ported with 2.02 valves. If you want less cam need the heads to do more work by having better .300"-.500" flow numbers.
Click to expand...
When you said ‘magazine’ I thought I’d put the wrong link!

Headers - tick.
Air gap - no problem, will order.
750 - no problem, will order.
Cam - happy to make what I have work
 
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