1.88" Exhaust Valve

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mhuppertz

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A machinist told me today that 1.88" exhaust valves are too large for a 440 and will scrub the cylinder wall. I'm pretty sure the MAX Wedge head had 1.88" valves on a smaller bore than the 440 (413 and 426) so I am guessing the machinist might not be right.
Thoughts?
 
I think the 426 max had a notch in the top of bore for valve clearance.
I don't know if clearance is an issue with 440
 
RustyRatRod said:
He's fullashit.
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Dead on. My ex-boss,dropped in 1.88 exhaust's,in '87 (Early maxie castings). The heads,really wake up. The basic valve drop in ,fails here. You really need to work the exhaust bowl & port,to make it work. When the exhaust port & valve job is right,it just rattles & cackles like hell.
 
There are a few ebay sellers that would be pretty disappointed to find out the stainless 1.88's they are selling won't fit.
 
http://racehemi.maxwedge.com/topics/heads.php


Conventional wisdom today is that the 1.88 exhaust valve was to big and restricted the intake valve size from going bigger for improved flow. Today the hot set up for racers is the original max wedge port size with a 2.14 or 2.18 intake valve and 1.81 exhaust valves. This also a more favorable valve combination if you are building a large cubic inch stroker.
 
70aarcuda said:
http://racehemi.maxwedge.com/topics/heads.php


Conventional wisdom today is that the 1.88 exhaust valve was to big and restricted the intake valve size from going bigger for improved flow. Today the hot set up for racers is the original max wedge port size with a 2.14 or 2.18 intake valve and 1.81 exhaust valves. This also a more favorable valve combination if you are building a large cubic inch stroker.
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Interesting... Are these based,on original M/W castings ,Tony?...
 
needed the notch on 413/426. 440 is probably ok, you may need to notch the cyl and the head to increase flow for it to be worth it. Also want to check valve to piston relief clearance
 
Abodybomber said:
Interesting... Are these based,on original M/W castings ,Tony?...
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I have no idea...was looking to confirm the notch needed....read the article and saw the comment towards the bottom about using the smaller exhaust valve with larger intake for better performance.
 
70aarcuda said:
I have no idea...was looking to confirm the notch needed....read the article and saw the comment towards the bottom about using the smaller exhaust valve with larger intake for better performance.
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No problem ,Tony ... A question to ask....
 
The 413 and 426 M/W engines needed a notch to clear the 1.88 exhaust valve. I've got nothing to tell me how to prep a 413/426 block for the 1.88E, so I don't have a feel for how much less might be needed for the 440 (if any). I also don't know how close to your intake valve a 1.88 inch exhaust will get. There appears to be a trade-off between the intake and exhaust size.

FWIW, the intake on the M/W III head used a 2.08 intake & 1.88 exhaust. The Stage VI heads use a 2.14 intake, 1.81 exhaust. P4876386 uses a 2.25 intake, 1.81 exhaust.

Here's a comparison of the area of the two valves 2.573²" w/1.81, 2.776²" w/1.88. The smaller valve has a roughly 8% smaller "window" for fuel vapor to pass through if you want to compare it that way.
 
While I am in 100% agreement about the theory that the 1.88 exhaust valve is too big in terms of flow, I was under the impression that the OP was asking if the valves would physically fit. Which they will.
 
RustyRatRod said:
While I am in 100% agreement about the theory that the 1.88 exhaust valve is too big in terms of flow, I was under the impression that the OP was asking if the valves would physically fit. Which they will.
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hemi`s came out stock w/ 1.94 exhaust valves. rats had bigger than that w/ less cubes. I`ve got 1.91`s in my r/b, so the flow isn`t too much, it may not be needed w/ you head flow tho------bob
 
I have 2.14" Intakes to go along with the 1.88" exhaust valves. Did a fair amount of blending in the bowls and it looks good there, but need to unshroud the exhaust valve in the combustion chamber still.
I feel better now, thanks guys.
 
With all the pressure still within the cylinder when that valve opens there's really no reason for a large exhaust valve. It's even less important for a street type build with a full exhaust system.
 
moper said:
With all the pressure still within the cylinder when that valve opens there's really no reason for a large exhaust valve. It's even less important for a street type build with a full exhaust system.
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I know what you mean, but my heads are already cut for them and I already have the valves ($30 a pop) so I am going to make the best of it by making the port flow as well as possible. If I end up stroking it then the extra flow will help.
 
famous bob said:
hemi`s came out stock w/ 1.94 exhaust valves. rats had bigger than that w/ less cubes. I`ve got 1.91`s in my r/b, so the flow isn`t too much, it may not be needed w/ you head flow tho------bob
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That's what I was tryin to say. The head will only flow what the engine demands.
 
mhuppertz said:
I know what you mean, but my heads are already cut for them and I already have the valves ($30 a pop) so I am going to make the best of it by making the port flow as well as possible. If I end up stroking it then the extra flow will help.
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I wouldn't suggest you do anything other than what you're doing and try not to keep making the port bigger behind it. The port flow will be whatever it will be and how well it works will be much less a function of a large port but a function of the cam working with the exhaust manifolding and system downstream. Exhaust is pretty easy - open the valve enough at the right time with the right system after the port and it takes care of itself.
 
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