24v headwork - power gains

Tim0172
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Re: 24v headwork - power gains

Post by Tim0172 »

Hi Jim thanks for replying, When you flowbenched the 24v head did you also check the velocity in the Ports?
The car where the engine wil go in to is a 156 It must stay driveable on the street so good low down torque is a must.
I have a set of intake cams from colombo&bariani AR24.SM2 Stradale medio but not shure If i Will use them in this engine.

Regards,
Tim

Jim K
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Re: 24v headwork - power gains

Post by Jim K »

No velocity checks. I only did a cleanup job of the rough spots, NO enlargement at all.
If the 156 has a 6-speed gearbox, performance will be very good low down!
Jim K.

Tim0172
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Re: 24v headwork - power gains

Post by Tim0172 »

It has the short 2, 5 L 6 speed box with Q2 sperre differential. :wink:

I will try to do some flow and velocity checks beginning and after headwork.

Regards

Tim

Jim K
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Re: 24v headwork - power gains

Post by Jim K »

Very interesting, let me know what you find! 8)
Jim K.

AlanV6
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Re: 24v headwork - power gains

Post by AlanV6 »

With the short ratio of 2.5 v6 there will be no problem in low rpm driveability.
I didnt notice much negative effects on a fwd gtv with much longer ratio and AHM cams.

@ Tim
will you raise the compression?

@ Jim
I didnt forget about the 2.5 heads, the whole engine is gone thats' why i didnt send them to you :(

Tim0172
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Re: 24v headwork - power gains

Post by Tim0172 »

Hi Alan,

Yes compression will be raised to 11:1 or a little over.

Tim

Jim K
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Re: 24v headwork - power gains

Post by Jim K »

No problem Alan...! You lose some, you win some! :wink:
Jim K.

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Re: 24v headwork - power gains

Post by Bareass »

what about add material, or better yet, having valves made with more material to close up that gap, instead of filling in the port?
wouldn't that in theory speed up the air flow? the valves would be heavier, but a stiffer spring should fix that.

as for me, i plan on going 3.5. the 3.2 crank is just too expensive to get in canada to justify. i have 3.2 gtv stage II cams, and GTA intake runners, with an oversized plenum that will be getting a corvette (or similar size) throttle body
'84 GTV6 w/3.0
3.0L 24V engine stand!

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75evo
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Re: 24v headwork - power gains

Post by 75evo »

The 3.5 route isn't much cheaper. The custom liners, custom pistons, boring labor, labor for welding the heads a little, will come out to be more than the 3.2. And the custom head gasket is another headache. If it doesn't seal properly.....the 24V belt job is easily 2-3 times harder than the 12V job.

That's why I went with a 3.2 instead. I can use all OEM parts and get a nice boost in torque due to the 6mm longer stroke.Jim K found me a good deal on a 3,2 crank and I jumped on it. Awesome guy to deal with.

Actually now that I think about it, the best way to go for an N/A feeling engine is with a stock 3.0 and a rotrex supercharger. Very linear pull all the way to the top. But it's too late, I already have a 3.2.

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75evo
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Re: 24v headwork - power gains

Post by 75evo »

Well I got my 24v heads back, the ports were just cleaned, not even smoothened. Valves refaced and reseated. Heads skimmed to get about 11:1 CR. Should I even bother with the heads? Not porting, but cleanup the casting? I know the stock ports are already HUGE and if it's not going to give me much gains, I'm just going to slap i on the block.

I think I will just send the piston and JK speciale cams for coating and be done with it. Then send the assembly for balancing. Target is 300+ bhp or one day when the Greekster wakes up, he is in the Mediterranean :mrgreen:

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Re: 24v headwork - power gains

Post by Jim K »

Why send the cams for coating (what kind of coating?). They were already Nitrided and straightened when you got them; all you had to do is buff them lightly with oiled Scotchbrite to get the excess gunk off and you're all set to use them!
DON'T FORGET to elongate the follower bore oil supply holes upward by 2-3mm OR, widen the mid-follower notch downward by ~2mm.
Jim K.

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scott.venables
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Re: 24v headwork - power gains

Post by scott.venables »

Bit of a thread dig but with all this talk of 2.5 heads on a 3.0 has anyone done it or calculated what the CR would be? And are there likely to be any compatibility problems with oil passages etc?

Cheers, Scott

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