Ok, like the title says I'm looking for the diameter of the valve faces on the 4.6 liter Northstar heads. Also does anyone know the specs or where I can find the specs on the N* cams (lift and duration)? If some one has a pair of heads laying around could you get a measurement of the widest point on the valves as installed (outside of one intake to outside of one exhaust at a diagonal). Trying to see if I can install N* heads on the smaller bore Aurora 4.0.

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'88 Coupe (extensive mods underway)
http://www.fiero.nl/forum/Forum2/HTML/086359.html

[This message has been edited by HTXtremes (edited 10-28-2007).]

I think there was someone who tried installing northstar heads on the 4.0 to get lower compression for a turbo.

Not sure if they were successful or not. Or maybe it was vice versa to get higher compression.

N* cams vary... there's the 275hp and 300hp version. Difference is in the intake lobes.

The 300hp have 266 duration and .370 lift intake, 244 duration .339 lift exhaust

It's challenging to get an accurate measurment on the diagonal across the valves due to the shrouding, but it's pretty close to 3.36 . if this puts you in the ballpark, get back to me and I'll try for a more accurate measurment when the sun is up .

Russ544

That does help Russ, The bore of the Aurora is 3.425", I was looking at going .060" over for more clearance, that would leave me with 1/16" of an inch on each side. If the valve are angled in much it would provide even more clearance when the valves opened.

Were you able to get the diameters of the valves, Russ?

Thank you both for your time and measurements, this helps out alot!

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'88 Coupe (extensive mods underway)
http://www.fiero.nl/forum/Forum2/HTML/086359.html

I doNOT think you can bore a sleve that far

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Question wonder and be wierd
are you kind?

I'll measure the valve dia when I get home this eve. it was cold and dark out where the heads are stored last night.

Russ544

You live in Oregon, it's always cold and dark out.

The valves are 1.30" and 1.14" INT/EXH according to my engine program. And I think I pulled those numbers from the factory service manual.

quote Originally posted by ryan.hess: You live in Oregon, it's always cold and dark out. The valves are 1.30" and 1.14" INT/EXH according to my engine program. And I think I pulled those numbers from the factory service manual.

Only at night. in the day time it's cold and light out.

I'll double check the size later today anyway

Russ544

OK. I did some more measuring and came up with
intake valve = 1.310
Ex vlv = 1.144

diagonal across closed valves. will be less when near deck height (open) = 3.357

diagonal across valve pocket opening at widest point = 3.665


BTW, I just looked at your F-40 build thread. pretty cool. keep posting. what do you plan to use for an induction sys? what about the ECM?

Cheers,
Russ544

[This message has been edited by Russ544 (edited 10-29-2007).]

I'm going to use twin T3 turbos for now, upgrade to ball bearing turbos later. The ECM will be the 7730.

Thank you for the compliments, and for your help!

I'm thinking of having the 4.0 machined for the 4.6 valves the porting and polishing! Desktop Dyno 2000 is saying around 553 peak HP at 8k rpm and 427 ftlbs torque at 5500.

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'88 Coupe (extensive mods underway)
http://www.fiero.nl/forum/Forum2/HTML/086359.html

sending pm shortly

Russ544