DragBoss wrote:
That Mr. Coffield, was a dissertation on metallurgy, that I have never heard in detail. A lot was over my head, that was for sure. I know though that this aluminum alloy does not expand as others. The first trackboss was just dynoed, and for example, lash was set to .012 cold, when warm they increased to .015, one was .018, the main bearing clearance was no different than with iron block. Brent said he saw 40 hp, who knows anything is possible. Bottom line from Darin Morgan, is that you may loose 20hp between aluminum v iron, that is about it. Hell with the weight off the front end, be like gaining double that, when you figure in scaling and weight transfer. In truth, what does it matter, zip. Not sure where this debate of aluminum blocks being so terrible came from. I know Brent does not like them, that is for sure. If they were so weak, and power robbers why do all the big dogs with high Hp run them? I have a goal of 850hp, Morgan is helping me with this, and said, no problem, I can make that easy, he said. "withhim porting BT 3.6, designing a cam, from his 2000 lobe profile library, and Scott Cook making one of his race intakes, I got to trust him. He said I have to bore lifter bushings to .904, and 55 mm bearings, don't need roller ones. He said be really hard to try and make 850hp, without 55mm/.904 or .937 keyway. The stock lifters would be too weak, said they would turn to dust, lol. I have the 55 all ready, so it is going to machine shop after I get it deburred to my liking.
The big dogs with high hp use them because they are easy to repair. Aluminum is a lot easier to weld than cast iron, plus sleeves are able to be removed and replaced when necessary. BTW, I've never said aluminum blocks are weak. They are just structurally less rigid.
Lash grows extensively with heat with an all-aluminum engine. The amount of growth will depend on how hot the engine gets. If the water and oil temps don't get high then it's not going to grow as much as a heat-soaked engine that's been driven on the street, road race course, etc. If you're dyno'ing at 130-140° water temp and the oil temp isn't getting that hot, you're not going to see a lot of growth. Doesn't mean it won't happen. Same with main bearing clearances.
To me, aluminum blocks have their place. I just don't believe that most bracket classes are that place. That's my opinion. Even if you lose 100 lbs of weight, you will still lose 30-40 hp and then the delta isn't that great (I'd rather have the horsepower), especially when you're looking at a $2500 block versus a $6000 block. I would never ask one of my guys to spend that much money for one, just because the pros don't outweigh the cons. Good news is that it's a free country and guys are free to do whatever they want.
However, I know quite a few engine builders, who when given the choice, would not choose an aluminum block over cast iron. I have seen 40 hp differences at the 700 hp level. A few other engine builder buddies (Rabotnick, Lance Smith, Blair Patrick, etc.) have also seen as much difference.
I'm not sure where all the debate has come from either. We've had this discussion on various forums and the majority of engine builders are aware of the inherent natures of aluminum blocks, but the end users are generally the ones who take offense to the discussions. My guess is that the average DIY'er who wants an aluminum block and spends $6000-7000 on one doesn't really want to hear that they are inferior in some ways to cast iron. I can understand the novelty to the average guy though. Aluminum blocks just aren't as plentiful and when we're dealing with Windsors, Clevelands, and FE's, you just don't see a lot of aluminum blocks. At the end of the day, you want what you want, and if you want to buy an aluminum block, you buy an aluminum block. I'm not trying to poo-poo on anyone's decisions, but I just feel like most guys aren't informed. I had a gentleman call to order a 496ci FE the other day and started the conversation by saying he wanted a Pond aluminum block. I explained to him that I generally see about 40 hp difference between cast iron and aluminum and the blocks were $2000-3000 more. He quickly changed his mind.
Bottom line, Tim, is that if you are happy, THAT'S ALL THAT MATTERS!!! And I'm happy that you got what you wanted.
I agree on the lifter bore diameter. I usually use .904" diameter lifters at least. Guys are kinda getting away from roller cam bearings. The larger diameter Babbitt bearings seem to work very well. My 9000 rpm 1200 hp pulling truck engines with 1300 lbs of open spring pressure use Babbitt. The key is to check the bearing clearance like you would a main/rod bearing. A 55mm cam journal needs about .0025-.003" oil clearance. I use a mic and a bore mic and check the clearances and then polish the cam journals to get clearance if necessary. High spring pressures put a lot of loading on the cam bearings. FWIW, I always green Loctite the cam bearings in, or pin them on aluminum blocks.
Brent, I understand what your saying to a point, in regards to expansion rates, and strength. You have that engineering degree, and engine building experience. This clearly gives you the insight and understanding of aspects of engine building and performance. I appreciate those facts. I also like that you agree that if the person is happy, then so be it. And that is the bottom line. I am not going to totally do this whole build myself, I have a machinist, that will help me, We have not discussed the parameters of the build, about who will put it together. He may want to do the whole build himself, or may allow me to help him. I am just going to play that by ear. It really comes down to his thoughts on if something happens, and liability. Whose fault type stuff. I am not a vindictive person, and understand that aspect. I figured the repair, and renew aspect, is why the big dogs like aluminum blocks.
I did not ask Darin whose library it is, may be comps, I will text him later and ask. He does not work for Reher-Morrison any longer. His brother who assembles lot of the engines there, still does. He works for Mast Motorsports, and Endyne, Larry Widmer's company. Those 2 business merged, and are together. This TrackBoss build will be a great learning experience for not just me, but for anyone interested in Clevelands. Smith Bros, is one of my sponsors, They are sending me 3 sets of different length push rods to work with. I am making a video on mid lift theory. I must have at least 15, big name companies. Not that you need anything, but others here, if they need anything, they can contact any of my sponsors, and they will hook you up, just tell them DragBoss sent you. Hopefully dyno this 409, in the next few weeks. This covid, has affected everything, as you know. I appreciate your honesty, and advice, thank you so much Brent.
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