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valve opinions

So just wanted to see what everyone thinks or feels about larger valves. Numbers are just a reference, I have a spare head and will be chopping it up soon to get exact numbers..

So this is more towards the ohv and being FI.keep in mind the ohv has very small valves and I will be stroking it and running 4" pistons.now lets say you have .200 of clearance for the valves to go larger.what would be best for FI and the fack my motor will be larger and stock is super small.

So would you
A-increase the intake valve .200 and leave the exhaust the same?
B-increase the exhaust .200 leaving the intake the same?
C-increase both .100?
D-increase the intake larger say .150 and smaller exhaust increase .050(or any other equal number)
E-increase the exhaust larger say .150 and smaller intake increase .050 (or any other equal number)

What whould you do and why??;)
 


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jd4242

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Sounds very promising power wise. So let me get this straight, there are NO off the shelf valves that can be modified to fit? Custom made vavles are what's keeping me away. Well that and having custom made forged pistons and rods. I've done some looking but your route (all custom built) seems to be the only way to make this motor strong enough for mean boost or a big shot. Keep the great info a coming!!

All custom.last I checked they ran $38 a valve. ...
 


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QueenCitySleeper

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Damnit. Valves plus 3 angle are gonna be upwards of 450 at least depending on machinist. I couldn't justify that. Glad to see someone's got the balls too though.
 




jd4242

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Damnit. Valves plus 3 angle are gonna be upwards of 450 at least depending on machinist. I couldn't justify that. Glad to see someone's got the balls too though.

3angle hell my last set has a 15 job on them.yea its running me $250 to have them fit and ported around them to flow right.heads already have a slight port and polish to them..valves alone was like $456ish.

Way I look at it but don't kno if my math was off, they other guys flowed 15% better.throw in I'm boosting and that 15% becomes HUGE!!!
 




QueenCitySleeper

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I wouldn't consider much math. You are so far past the engineered limits that any "math" is as good as educated guess work. Best thing to do is look at aftermarket engineered head designs with similar flow characterics. Without rigourous testing calculations are useless. I think the boosted t-bird 3.8, GM 3.8 and lightning 5.4 would be a good start if you haven't looked there already. Look for 2 valve factory engineered configs for maximum reliability and efficiency. Just my 2 cents.
 




jd4242

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Just stand there, turn your wallet upside down, and shake.

On one hand I read a n/a cam with not too much overlap is the best for boost, then on the other hand I read a custom cam can do wonders for a boosted motor. I really have no clue what to say. I would think that the most lift possible and the least overlap would be best for boost. Read square cam lobes in top this. That is kind of what the 422 cam tries to accomplish.

No clue. Im learning from you.
Wow, this is really tough.

Have you thought about talking to a custom cam grinder?
A custom cam would change things dramatically also. You would be able to alter valve heights, durations, and the timing of the events.

This would mean that they could recommend what valve sizes to use, and make a cam to better enhance the characteristics of the valves for boost.

Just a little more info on this.sense I used my 422 cam in my NA explorer motor I contacted comp cams about making me a custom grind.I gave them all my new stroker motor specs and he came back with about what I knew already. He said that the lift really couldnt be changed and he wouldnt suggest changing the duration either.but he did suggest changing the LSA to 114.stock is 112, the 422 gives you an overlap of -4 degrees which is super low.rule of thumb on a FI is not to have more than 30* but the lower the better.going to 114 would alow the sc to build more boost.he then states that it wouldnt even be worth the cost of a custom grind when compared to the 422, he said the specs on the 422 mimic the ""blower"" cam specs of their other cams..

I then talked with Tom and he said he can do custom cam grinds but would be a solid roller cam.soild lifters and adjustable rockers would need to be used and he could make one up to .700 lift.well thats outa the question because im not running a solid cam or lifters on a street motor. He then let the cat outa the bag about his new 1.8 roller rockers, now on his web page.this would increase lift 80thousands and not change my duration or LSA numbers meaning no added overlap.he did say the pricing may change but for now he has them list at $800 us!!!!:(so if the pricing does change ill end up running them but he needs to do more testing and see how the market is for them..

http://www.moranav6racing.com/category.html?CategoryID=32
 




Dono

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Tom did say he was working on these. I think you mentioned it in the past also.
$800.00 though. Ouch.

So 35 horse on a N/A motor. I wonder what that means stroked and boosted. 50 horse?
If that's the case, its $16.00/hp. Not bad. We can justify anything if we put our minds to it. :)

oops...I miss read. Its 25hp on a stock motor. So, say you see 40hp on your motor. that's $20.00/hp
 




Dono

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Tom has some cool stuff coming. I love the M112 stuff.
Can you say 'mad scientist'? I love this guy.
 




jd4242

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Tom did say he was working on these. I think you mentioned it in the past also.
$800.00 though. Ouch.

So 35 horse on a N/A motor. I wonder what that means stroked and boosted. 50 horse?
If that's the case, its $16.00/hp. Not bad. We can justify anything if we put our minds to it. :)

Lol yea we can!!!:D I have a feeling they will come down to the $400 range which I would be all in if he does, thats about what his other rocker go for.he also is coming out with a m112 mount but hasnt released the price, someone said he said it would be in the $700 range but i didnt talk to him about it.may even try and talk him into selling me at a reduced price for testing. ..only could hope he go for it!! Lol
 




jd4242

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Tom has some cool stuff coming. I love the M112 stuff.
Can you say 'mad scientist'? I love this guy.

Yea just posted about that..I put a test price sell on my m90 kit out but ive got so much money in it noone would come with a real offer.also been looking at twin turbo kits;) if the internals can handle 700 why not test it and m90 wont produce enough boost for that.but a larger shot of NOS will:shifty_ey:shifty_ey o also they make a kit for the gm m90 where it uses m112 blades and snout in the m90 case, been looking at that also
 




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