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16 Valve V.S. 8 Valve Heads on 740's?

B

beatyourvolvo518

New member
Joined
Jan 11, 2020
Hey I was just wondering if anyone out there knew the power numbers for the 16 valve heads vs the 8 valve and any weak points that come along with them.
 
I'm going with 8V heads if that helps.

mblISHMl.jpg
 
Just google up the original HP numbers. And assume the car will make something close to that at the crank with a good stage 0.

And 16V Whiteblock swaps are all sorts of fun.
 
beatyourvolvo518 said:
Well if the car was naturally aspirated with all oem parts with 130 ish thousand miles. a ballpark number even if its ridiculous. its a 1990 740 sedan if that helps.
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The 16v head is of course going to make more power. The engines are the 'same', but the 16v head flows MUCH better. 16v engines made roughly the same HP as a stock turbo engine.
 
for NA
16v is another type of animal compare to 8v.
a lot more easy to drive daily,
16v better from the bottom end to the top end and better fuel consumption.

for turbo,
8 or 16 depends on your propose of use.
in 150-250 HP they quite the same.

a lot of works to be done on 16V head swap.
8v is your onhand engine.
 
beatyourvolvo518 said:
Hey I was just wondering if anyone out there knew the power numbers for the 16 valve heads vs the 8 valve and any weak points that come along with them.
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using the same turbo and exhaust manifold, I went from a ported 530 with stock intake manifold and IPD T cam to a 16v with a sheetmetal intake manifold and also big cams. Went from 230ish whp (based on 1/4 mile times) at 18-19 PSI (peaking at around 5500 or so) to 280 whp at 10 psi (baseline gate pressure with no delaying boost signal for extra midrange) at 6700 with fuel pump problems. Now it makes obviously more as it easily spins to 7500. I lost the meat of the torque curve by 1000 RPM but more than made up for it on top.

Marvelous3 said:
16 valve heads are stupid
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What did your wagon end up doing again?
 
Harlard said:
What did your wagon end up doing again?
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Mine made 270 at the wheels on 10psi. With a shortened 16valve intake manifold and a heedspeed j pipe exhaust manifold.

The fitment bull**** on my car was all 240 related. In a 700/900 where the intake manifold was designed to fit you wouldn’t have these problems.

The understanding is that the first limit you really run into mechanically is the intake manifold before the cylinder head on an 8 valve head. Now stock for stock the 16 valve does flow more but for all the work required to fit a 16 valve head you could get a decent intake manifold that would probably negate any of the advantages swapping heads would accomplish.
 
Marvelous3 said:
Mine made 270 at the wheels on 10psi. With a shortened 16valve intake manifold and a heedspeed j pipe exhaust manifold.

The fitment bull**** on my car was all 240 related. In a 700/900 where the intake manifold was designed to fit you wouldn?t have these problems.

The understanding is that the first limit you really run into mechanically is the intake manifold before the cylinder head on an 8 valve head. Now stock for stock the 16 valve does flow more but for all the work required to fit a 16 valve head you could get a decent intake manifold that would probably negate any of the advantages swapping heads would accomplish.
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Mine has been pretty straightforward other than a minor issue related to the firewall AC pipes :e-shrug:

Stiggy Pop said:
0-350whp - built 8v
350whp+ - something that isn't a 4cyl
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Post up some dyno numbers, brah
 
Stiggy Pop said:
0-350whp - built 8v
350whp+ - something that isn't a 4cyl
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I'd tweak that slightly and say:

stock - 300 hp - 8V
300 - 400 hp - 16V
400+ hp - something that isn't a 4 cyl

Just in terms of cost-effectiveness. Sure, you could make a bunch of HP on either Volvo motor, but past certain vague and hazy limits, you're spending more money and getting less for it, other than the satisfaction of having a valve cover that still says 'Volvo' on it.

I think at roughly 300-ish HP (and YMMV, obviously) the 16 V starts to make things easier - the innate flow advantage finally outstripping the added cost/complexity of putting a turbo on a 16V, and then putting it in the car. Granted, that's a slight bit more work on a 240 than it would be on a 740.

And above 400-ish HP (again, very vaguely)? You're putting more and more stress on a 4 cylinder. Sure, Swedes get 1200 hp out of a redblock, but then again they tear them down and rebuild them with regularity, and run them on exotic fuels. In a street driven car - you should start to think a bit about reliability and durability if you want to use that 4-5-600 hp frequently.

And beyond the quantity of HP, start to think about the quality of the HP. A 2.3-2.5L 4 cylinder needs a lot of boost to make a lot of HP, and the small-motor/big-turbo recipe, even with gee-whiz turbos and careful tuning and building, is still more and more of an on-off switch. Not a whole heck of a lot of power off boost, all the power when on boost, and relatively less useable power in between the two. Vs a bigger engine with less boost.
 
Harlard said:
Post up some dyno numbers, brah
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I know what I have :cameron: (sunk costs)

JohnMc said:
I'd tweak that slightly and say:

stock - 300 hp - 8V
300 - 400 hp - 16V
400+ hp - something that isn't a 4 cyl

[snip]
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I could probably get down with that. I don't think 350whp is that far of a reach for an 8v at this point, given the more modern turbos and computers we all are generally using now compared to ten years ago. At any rate you start getting into custom manifolds and things start getting pretty expensive.

I do think people should get realistic about what their budget is and make smart decisions on where to spend that money; rather than always saying I NEED the car to make XXX horses of power.
 
Avery helpful part of that understanding comes from taking the time to read books. Books like Street turbocharging by warner and maximum boost by bell will help the person understand a lot more of what is going on for a good performance build. Then with help from experienced people like you guys they will know how they can accomplish their goal. :cool:
 
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