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Exhaust Valves


D83ZXT

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Ever try going to sleep with motor rebuild running through your mind? Grrr......

 

Exhaust valves...

 

I am getting confused as to whether or not this should be done.

P-90 Street/Race

 

Sunbelt "doesn't" recommend larger exhaust valves over stock. They say the durations of the exhaust valves stays open more then closed. That's from their head flow tests results.

Geromaly's doesn't seem to see this necessary either, as long as a street/race port & polished job was done correctly.

I do know a few who was has Robello work, and Dave does open them up.

Any body else have evidence that larger exhaust valves does make a difference or not?

 

So what give here???

 

Think that was fun, try going over cams with different people... lol

 

Donna

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Donna-

Can't sleep huh! With all the cam specs and confusing opinions going through your head....gee I wonder why!

 

As you know I run the larger exhaust valves. I don't know if they make a difference in my set up or not! I don't have a baseline for comparison. I would think with some of the Nissan builders and cam grinders such a Isky emphasizing the intake side on their cam specs for turbo z motors, maybe larger exhaust valves are not the way to go... only a guess.

 

I would spend the extra money on porting your head, focusing on smoothing out the runner walls and concentrating on blending and smoothing the pockets around the valves.

 

Or you could buy chocolate and send it to Sacramento!!

 

On the left

TimO

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ROFL.... Now, how I can pass you, if you're always on the left? Just you WAIT!!!

 

Thanks for the input, I do believe that's the plan for now. Keeping exhaust as stock size. James, thanks for the addition insight. I will discuss this further, while my head is being opened up even more then before. Tim, your right about the larger intake over exhaust cam findings. Boy, wasn't that fun... Talk about flipping durations around.. Hey, at least I know what center lobes to go with my Turbo unit (per Reed) LOL.... I am waiting for recommendations from Elgin's. (faxed motor info spec sheet today) So far, I am leaning towards the ISKY, over Sunbelts $600 cam/springs. That's quite a bit difference in price. eek2.gif Trial and error, but we'll see what works.

Tell you what... Why don't "You" buy it, then you can show how it runs on the dyno :D

 

SEE's....Yummie

Hey! Now that's a way to add more weight!!! Since you already know about the bag of cement that I was planning on slipping into your Z....

 

Me Evil? Nahhhh....

 

Donna

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When I had my performance turbo cam installed I had a minimal amount of head work done too. I had the opportunity to install a larger exhaust valve, but my builder commented on the fact that since I was running the stock bore, a larger exhaust valve would be significantly shrouded by the cylinder wall. He had a flow bench set up with a junk P90 and said he got better results flow-wise by simply unshrouding the stock valve instead of installing a bigger one.

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LOL... Joel

How's your beast doing?

 

I am keeping the exhaust valves stock size.

Maybe someday TimO and I could swap heads around to see if there's really a difference. I believe he's going to get the same cam as I am. It would be interesting though to see smile.gif

 

Donna

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