308 V12 conversion begins

Yes, exactly. It would be a pretty easy mill job that way.

The right angle head would just let me cut from the side instead of the top, so it wouldn't really add anything I don't think....I'll probably use it to put the center drill in the end and drill the hole pattern for the sprocket though.

 

no, no, no I'm not milling cams, that would be crazy

I wanted new cams to make hp but didn't want to spend the money until I realized that I need new cams because the firing order on the TR cams doesn’t match the 400 crank unless I somehow reverse the rotation direction of the cam.

The cam company wasn’t interesting in making the entire lobe out of weld (they’re much smarter than me), so I need to make billet blanks for them. The blank just has a diameter where the lobes go and is +.020 oversize in all the journals. The cam company will harden it, grind the journals, and grind whatever lobe I ask for.

One of the heads in particular has some scoring in the in the first journal (the drive end) so I will probably clean it up oversize and make the cam to match. I’m also thinking about changing the spacing between the intake valves a little to flow better with bigger valves that will now fit in my bigger bore….it’s a viscous cycle.

 

You can't swap side to side becasue ever cam in the engine looks the same, but starts in a different timing position, they have to be becasue there is only one crank.

If I could flip them end to end it would solve the problem, but I can't because the bearing journals are not symetric about the cam lobes.

If I had to save the cams I could put the lower chain sprocket directly on the crank instead of thru the gear drive cauing the cams to turn the opposite direction and solving the time problem.....but that's a lot of bother to keep cams I never really liked anyway.

New cams are the answer. It's not going to be a ton of money and will pay big returns in hp.

 

Exactly. I'll start making the blanks in a couple weeks it looks like.

 

Tonight I got the bushing holes in the block re-cut. I had to go .020" oversize to get it to work out right. The next time I get into the shop I'll re-cut the caps the same way and make the new bushings then this problem is fixed and on to the next.

 

I just had another (crazy) thought. If I took the 24 37mm 400 bucket out of the 400 heads and put them in the 24 intake side 33mm hole in the TR head I could move the valves up to 4mm farther apart. That is coincidentally the same 4mm I lose if I replace the 29mm valves it has with the 33mm valves I think I want.......hmmmmmmm

 

Now I haven't decided anything about it just yet, it's still a hypothetical with plusses and minuses to think about.

In the Plus column I think we have:
A bigger diameter will tolerate a higher lift cam
Moving the valves should improve the flow with big valves
I have them so they’re free


In the minus column:
They add weight to the valve train
3-4mm is a LOT of over sizing the bucket, the valve guide, valve seat, and port holes in the head…. I’d be a little worried about wall thickness remaining.
It’s time consuming. Not just the actually moving everything but also all the port design work to go with it.

I’ll need to decide exactly what I’m doing with the head before I can even start the cams blanks

 

The more I think about it, then more I like the idea of separating the intake valves and running bigger buckets. I've now convinced myself that +2mm would still work with the 37mm buckets while not causing as much wall thickness concern, although there it's still a concern.

I would love to have a TR head I could saw opened and see how much metal there is where.......I want them to flow good but I don't want to find the water jackets in the process.

I sent the cam guy an email explaining what I've got and asking for recommendations for what we can do that will live on the street. My computer thinks around 235*-240* at .050” lift is about ideal but that I also want .420”-.450” lift for the intake lift and I’m not sure those 2 numbers work together, at least not for very long. The bigger buckets will help some……I’ll see what he comes back with but I’m guessing I’ll need to take more duration on the intake side at least. I'm not too worried about the exhaust side as I think the stock TR intake grind of .348" lift with 222* at .050" lift which clearly works since it's stock is about the right lift and adding duration doesn't make it any harder on the valve train.

It’s really a little early to be picking cams but I need to make cams to finish the timing chain fitting so I don’t have a choice. I’ll most likely err toward the aggressive side because it’s way easier and cheaper to have metal ground off then it is to have to weld it back on.

I also asked the cam guy about the shim under vs shim over. I have the shim over buckets and would like not to have to replace them if I don’t have to for both cost and ease of maintenance reasons….but now would be the time if I need to.

 

I'm talking to American custom cam
http://www.americancustomcam.com/

They were recomended by the shop I bought the head and engine from as doing good work and the prices seem really good. They quoted about $1500 to finish to the blanks (heat treat, journals, lobes) which is about 1/3 what webcam would charge. They said they had about 3000 masters to choose from

 

It's hard to add duration without adding overlap though.

The intake and exhaust are separate cams and can be timed any way I please so I don't need to decide that up front, but it just always seems to turn out that the balance is a good thing. By balance I mean the same or nearly the same lobe centers on the intake and exhaust. Something around 108 will probably make the best hp but around 110 for best overall and 112 or so for the best low end. Then the overlap is what it is based on the duration of the cams.

This will be an EFI engine so it is much less sensitive to then it would be with webers which are kind of primitive carbs really. I think I could go to 260* or even 270* duration at .050” lift and still have it be perfectly drivable since the engine is plenty big now….but it just won’t be quite as nice. The longer the duration the high the torque peak moves but the hp peak will be flow limited by the heads so it will hit an rpm wall and the power band will just get narrower and narrower as duration goes up.

I’ve got a bike with similar bore/stroke (2v though) and 270 at .050” duration on both intake and exhaust and it pulls hard from about 1200 rpm and idles at around 800, torque peak around 6500 and the hp peak at 8500 limited by the slightly too small carbs. That is pretty much the engine I’d like this to be I think so taking the 2v vs 4v thing into account and the relative valve area I’d guess I’m talking about 255-260* at .050” to be a comparable cam for this engine.

We’ll see what the cam guys feel good about making and go from there….it’ll all work out in the end I’m sure.

 

Is that 270* total? That would be around 230-240 maybe at .050" lift. The 270* at .050 cams I have in the bike are about 310 total degrees.

The word I'm get from he who knows (Dave Helms) is that I really need to move to shim under buckets if I want anything like reliability at 8500 rpm so I guess that will be on the list too.

 

The first cap fits again and looks pretty good if I do say so myself

6 more to go.

I've been talking to Dave Helms about the buckets. He's been working very hard to find an affordable solution to the shim under conversion and I'm confident something will turn up. If I'm only moving the intakes 2mm I could go to a 35mm bucket instead of 37 and I think I've found one but I need to get pricing to see if it's a viable option.
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There are lots of option and really no "right" answer but a lot of wrong ones. The cam place I'm going to go with is american custom cam, I should be doing that in a month or 2 so I can let you know how it went. Over the phone they sounded quite knowledgeable.

Going straight to the cam grinder may not be the best plan. You might give Dave Helms a call or PM, I've been very impressed with his knowledge and connections and I guess he’s worked on plenty of SOHC engines over the years. Carobu is another place to try. Either place should be able to get you a cam source based on their experience that will meet your needs. In my case I feel pretty good about picking a cam I’ll like, but the I’m leaning on Dave quite a bit to help me sort out the buckets which I know nothing about.