Problem with putting in larger valves?

tucknroll

Active member
I'm planning my build of a D5 head and I'm going over the final details before I start ordering parts and sending stuff to the machinist. I was planning to go with the larger 1.50/1.75 valves but I was wondering what issues would arise if I went with the slightly larger ones offered at ClassicInlines?

NOTE: Optional valves sizes (over 1.50/1.75) require custom machine work to maintain proper clearances. Verify prior to ordering.

The way I see it, the machinist is already going to need to enlarge the holes, the only difference is what size "drill bit" he's going to use. So where am I going wrong in my thinking? Are the results worth it?
 
Jackfish
No offense but where the hell are you posting your pics? When I clicked on the link I got some kind of BS about someone in my area looking for a "friend".
Life's too short.
 
Wow! Thx for the pics! What sizes are you using? That almost looks excessive. Now I'm wondering how much unshrouding is necessary and how easy would it be to screw it up? Porting was definately in the plans, but not like that. Would the potential gains be worth it? I can deal with losing a few hp by not doing it versus losing a few hp by not doing it correctly.

Edit: yeah, apparently Ryan is sending a wink to me? :lol: Oh well, can't control what imageshack or Ryan does! :lol:
 
Sorry I didn't know Imageshack was weird.
Perhaps because Firefox has a pop-up blocker I don't get that crap.

Those are the Classic Inlines 1.75 and 1.5 valves.
 
I was told by CI and several others that going larger than 1.5/1.75 isn't a goog idea. I too had planned to go with the super big size, but they require too much machining (according to Mike) and little power gained above 1.75.

Stick with 1.5/1.75 and you will have better luck.

Harry
 
I think the problem is if the holes get too big they start to interfere with each other; that why the "special" machining note. What dictates valve diameter is the centerline of the valve stems.

If you want more flow go with a bigger cam first, then the oversize valves. I would think a bigger cam would be easier (and cheaper) for extra air flow versus paying a machinist. The flow restriction in 200's head is more than just valve size.
 
I think I've decided on the 1.75/1.50 combination. I understand your point on the centerlines though. The pic above was probably the first I've seen on an unported head with the valves. I think they'll be plenty big enough. As far as flow is concerned, I've got 3 weber 34 ICH's that I hope will help a little with that (can't wait for the tuning process :roll: ). Already have a barely used Clifford 26? cam (been sitting a while, forgot the exact number) installed. Right now I want to make sure I know what I want to rebuild the head. Measure twice and cut once, eh? :D
 
You might consider springing a little extra for the CI valves that have the tapered stems, also. Might be worth a little more flow. As for the cam comments, I second those. I have a heavily modified log head and ratio rockers, and while it does make a bunch more power than stock, it's still a pretty flat performer with the stock cam.
 
Why do all that head work and not cam it up? You need the trifecta here, cam, larger valves, carbs. Rockers help too.

Harry
 
8) the reason you want to go no bigger than a 1.75in/1.50ex valve combo in a stock head is that if you go larger than that you will actually lose airflow due to shrouding. the classic inlines aluminum head was designed to use the larger valve combination from the start, and thus doesnt have the shrouding problem.
 
tucknroll":17zmrk9d said:
Already have a barely used Clifford 26? cam (been sitting a while, forgot the exact number) installed.

http://www.classicinlines.com/select_cam.asp":17zmrk9d said:
264: 264/264 - 208/208 - .444/,444 - 110* (verbal) - 2000-4500

I know it's a fairly mild cam, but I believe its better than stock. Here's the deal...the head came on the car when I got it. A month or so after I got the car I ran across an engine with the offy, webers, dual headers, port divider, aftermarket distributor (forgot what kind, but still had points), stock adjustable rockers, and a fresh rebuild on the bottom end. The problem was the head was the early log (C9 I believe). So I've swapped the bottom end into the car and I'm going to install the later head onto it (after building it).

As far as the pics (especially the bottom one with the overhead view) it looks to me like the valves are awful close to the sides of the combustion chamber. With them closed it looks like about a quarter of the valve wouldn't be able to flow freely when it opened because of the tight space. Perhaps the sidewalls of the head are tapered and I'm not taking that into consideration. Maybe it's no big deal at all. I dunno.
 
tucknroll":cvzjohws said:
As far as the pics (especially the bottom one with the overhead view) it looks to me like the valves are awful close to the sides of the combustion chamber.
The angle of the photo was not vertical on that, and may exaggerate the effect you're seeing.
 
Something to consider:

Depending on labor rates in your area, the cost of rebuilding a stock head + tri-power will come very close to a brand new CI head + intake from Mike.

And we all know which will perform better...
 
Yeah, I thought of that. I'm looking around locally for a good machine shop now. I'll have a better idea of total costs with this setup vs going with the aluminum head. The main selling point for sticking with what I have is just that...I already have it. Don't get me wrong, it's VERY tempting but life needs some of my money too.
 
Bort62":2ttx0plc said:
Something to consider:

Depending on labor rates in your area, the cost of rebuilding a stock head + tri-power will come very close to a brand new CI head + intake from Mike.

And we all know which will perform better...

i have ~$400 in my head, including all 3 carbs (not includong springs, seals, ect. because youll have to buy that stuff with the aluminum head anyways). i didnt have larger valves put in, and my valve guides were fine, so his will probably cost more. i think it will still be cheaper, the aluminum head will perform better though.
 
Patrick,

Mike's head may perform better but I still admire the old school, hot rod approach you're taking with your car.

Modifing what you have, as cheaply as possible is old school hot rodding and unfortunately a lost art in today's bolt-on society.

You have taken an innovative approach to your tri-power. I'm very impressed with your results so far. This is one of the reasons that I kept the six--you needed to use innovative approaches to improve since we didn't have all the bolt on parts.

I appreciate that Mike is providing more products for those who choose that route but there is nothing wrong with your approach to getting the job done.
 
My point is not that you can't do it cheaper... Certainly there are many of us who can/will.

But, if you aren't the type to do most of the work yourself, you can pretty easily end up spending 1000-1500 building a tri-power.

Already having it is a valid point, but if it's a question of dropping 1500 on a head you "already have" or dropping 1500 to get a brand new head + intake from Mike, I think that's a no brainier. (I think that is how much it costs).

It is the small costs that will kill you with building a tri-power head, and unless you do the matching/fabrication etc yourself, the labor costs will eat you alive.


So beware of false economy, and try to get an accurate cost estimate on your project, start to finish, before you decide. You may be surprised at how little extra the AL head would cost you.
 
Bort62":1du97bxo said:
...try to get an accurate cost estimate on your project, start to finish, before you decide...
And that's exactly what I'm trying to do! The post started out asking about the oversized valves. I 've been looking at all the options for each individual part as well as the project on as a whole. I'm doing as much homework and research as possible before I do make any final decisions or spend a dime.

You did forget one thing though....it's advertised as $1500 for just the head...
http://classicinlines.com/proddetail.asp?prod=ACH%2D250%2DASH":1du97bxo said:
Note: Intake Manifolds sold seperately.
Note: Gaskets and Stud Kits sold seperately.
Then add a carb on top of that. Now we're looking close to $2000. Or I could have someone fab 3 small intakes for the webers, but I dunno if I want to mess with synchronis carbs yet. I've yet to even tackle the progressive. Of course the resale value of some of the unused parts (mainly webers, maybe offy manifold) could offset the price a little, but I'm not going to factor that in because it's an unreliable prediction.

I see the biggest unknown is the cost of machining. It's not one of those nickel and dime thing that you say to yourself "oops, forgot about that". It's a major part of the project. Again, that's why the question about the valves. I want to be able to state exactly what I want as precisely as possible so there aren't any (big) surprises and I can make a solid decision as to which direction I will take.
 
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