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Camshaft selection help 3.0L Stroker


VitaminZ

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Well I know this is a topic that has been discussed over and over again , I have read numerous threads on this but no engine is built the same so I thought I would start my own thread on this to get some assistance and advice on choosing a camshaft that would be suitable for my engine .

 

I have a 72 240z with  a N42 motor , bottom end has been built by Whitehead performance here in Toronto .  Bottom end is now 3.0L , compression 10:5:1 , valve reliefs on the pistons . I have triple 44 Mikunis with no vacuum advance , runs great no hesitation throughout , no upgraded ignition , still the 280 unit.

 I chose not to do any headwork at the same time as rebuilding the bottom end due to not having the money to do all together .  Engine has been running now for 3500k , very strong , now I would like to bring it to life with headwork .

 

 

I will have a machine shop do all the work , and I will just provide the parts .

My objective with my car is not a daily driver , I don't drive the car in winter for obvious reasons and in the summer I do drive on the street , and next year hoping to compete in time attack events and attend track days . I am not trying to have the fastest car on the track , I just want to enjoy driving my car and really bring out the potential of the motor as much as I can .

 

I really do not have a lot of knowledge about rebuilding a head and what springs , retainers , cam lift , valves I am going to need to be able to bring up the power . Basically can I get some advice on a  semi race / performance street camshaft that has been proven , valve sizes , spring setup , lash pads, I would really appreciate it...

Edited by VitaminZ
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My advice... Build the power band in the 4,000 to 6,500 range. You'll need a cam with a 290 duration and a lift around .530 to .550. You won't need bigger valves then what comes stock on an N42. Just a good full radius seat and port cleanup.

Thanks John appreciate the advice . But I'm guessing I should get SS valves? And I can get away with just a street port basically no heavy porting needed ? That rpm range sounds good to me.sorry for the dumb question but how do i choose lash pad thickness and what size valve spring shims to use ?

Edited by VitaminZ
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It's probably also worth mentioning I purchased a built N42 head from a member on here who claimed all the parts were kakimoto racing , and the purchased the head from Ron carter , I mean all of this could be true I really don't know anyways he wouldn't give me all the specifications on the cam or valve train , I guess that should have been enough red flags to not buy the head , anyways I did , when I passed it on to whitehead this is what they told me below about it .

Big valves have been installed. 38ex/46in . The seats and valve contact surface have been cut without a lot of margin so there's a sharp edge on the valve. This can create a hot spot that can promote detonation and it also reduces heat transfer from the valve to the seat, which can increase the chance of burning a valve. In normal use it should be okay.

 

There are erosion pockets in 2 of the chambers

 

The cam has .525" lift and likely close to 300 degrees duration. This is a full race cam and will not be street friendly.

 

The head has upgraded valve springs both outer and inner. We run just stiffer outer springs and stock inner springs as we find having both stiffer outer and inner tends to wipe out the cam lobes from too high seat pressure.

 

They have used stock lashpads and instead played with the valve installed heights to get the rocker arm geometry correct. This is not the best way to do this as changing out the cam may make selecting the correct lash pads difficult to set the new cam up with proper rocker arm geometry.

 

The combustion chambers spec out at 38.4cc's which is small. This will require a 2.5mm headgasket for 10.5:1 compression.

 

They tried fitting the head to the bottom end but got a lot of valve to piston interference so they told me its best not to use it which I didn't . So now the head is just sitting doing nothing so I'm thinking of just using the cam from it . Such a waste all the other parts .. Couple pics of the head below

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post-41738-0-87488400-1443482031_thumb.jpeg

Edited by VitaminZ
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Heavy porting and bigger valves are generally for higher rpm and more compression then what you are planning. I would try the 300 duration, .525 lift cam since you already have it and install the bigger valves. It should be good from 4,000 to 7,000. You'll need to change your rear gears (depending on tire size)

 

If you already have the parts, might as well use them. You might find you like more power up top.

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Heavy porting and bigger valves are generally for higher rpm and more compression then what you are planning. I would try the 300 duration, .525 lift cam since you already have it and install the bigger valves. It should be good from 4,000 to 7,000. You'll need to change your rear gears (depending on tire size)

 

If you already have the parts, might as well use them. You might find you like more power up top.

Thanks John , I have a 3.9 sti diff with a Cusco 2way LSD , I would really like to change the final drive to 4.1 or 4.4 though,

Would you also agree with the engine builder that the valves are too big ? They also told me they were the wrong length

Edited by VitaminZ
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I wouldn't trust that head either . Like John said, sell off what you don't want.

I had all kinds of issues with SS valves (SI), nothing wrong with stock Nissan valves for street. I'd try the cam, I think it would be plenty streetable.

I'd try a P79 or p90 with that cam, no oversized gasket needed.

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I wouldn't trust that head either . Like John said, sell off what you don't want.

I had all kinds of issues with SS valves (SI), nothing wrong with stock Nissan valves for street. I'd try the cam, I think it would be plenty streetable.

I'd try a P79 or p90 with that cam, no oversized gasket needed.

Yeh I'm over the head now it's a loss bad purchase on my path . I think I will stick with the n42 I have valve reliefs on the Pistons should be ok

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guys from your experience with valve springs and using a cam with .525 lift and 300deg duration , im wondering if I need stiffer outer and inner valve springs ? Advice from whitehead says that running both inner and outer stiffer springs tend to wipe out the cam lobes from too high seat pressure , so they just run stiffer outer springs and stock inner . whats your thoughts on this ?

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Depending on how that head achieved its 38.4cc combustion chamber size, and how your pistons are shaped and positioned,  you could still have piston-valve contact if you try the big cam in your engine.

 

Whitehead has been building and racing Z's for over 30 years. I thnk it's safe to say they know what they are doing.

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Depending on how that head achieved its 38.4cc combustion chamber size, and how your pistons are shaped and positioned, you could still have piston-valve contact if you try the big cam in your engine.

 

Whitehead has been building and racing Z's for over 30 years. I thnk it's safe to say they know what they are doing.

I agree with you I'm not debating whether they know what they're doing , they're experience speaks for itself , I am just asking for others previous experience

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  • 2 months later...

I'm considering buying those valves from VitaminZ for use in my Rebello 3.1 stroker turbo.  Dave has my head right now for porting, but it is waiting in line as it were.  The head is a P90, running the Isky turbo cam, the pistons are rebello P90 special forged 88mm JE with a static compression ratio of 8.5/1.  The springs and retainers are the upgraded ones sold by MSA.  Looking to get a good 400hp to the rear wheels.  In the opinion of those who have gone before, will these valves help my flow, or just complicate reaching my goal?  Thanks!

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  • 7 years later...

old topic.....but it would seem a thicker head gasket from Cometic would have eliminated the valve to piston interference.  I dont know how you had valve interference with 525 lift.  Guys run a lot more lift than that with much higher compression.

 

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