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 Post subject: Re: 351c alm blocks?
PostPosted: Fri Mar 30, 2018 7:25 am 
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Brent, I agree. We all have out opinions. I state how I feel, and if people do not like it, that is their opinion. I don't waste my time trying to prove a point, I do what I knows works for me. You build a lot of engines, so have that vast experience. I know the CGI are not going to be ready in the next few months, seems like the foundry business is overloaded in the US. I really don't get that, but what would I know I work in an ER, no experience with manufacturing. I would be so tempted to just change parts to aluminum trackboss, and have a 408. But with what I want to do, it would be lot of effort to see the difference between iron and aluminum power levels. I am going big bore 4.155 or 4.185 ish.

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 Post subject: Re: 351c alm blocks?
PostPosted: Fri Mar 30, 2018 8:19 am 
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I think the cast iron and CGI Track Boss blocks will be awesome, especially with the cast iron block being close to the cost of a Dart SHP Windsor block.

If I were doing a strictly Cleveland blocked drag race engine with an aftermarket block, I would hold out for the cast iron.

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 Post subject: Re: 351c alm blocks?
PostPosted: Fri Mar 30, 2018 8:32 am 
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Location: Stranded in Iowa - Better get the Breakdown squad out
Not taking a side either way here but just a few more considerations.

I'd like to know a little more about the side by side engine comparisons. I don't doubt the test outcomes but the differences may caused by a variety of different factors.

I'd expect two identically configured (except for block material) pushrod engines to perform differently especially if they were solid cam engines.

The hot/cold lash difference is much greater in an alloy engine, in fact as much as .003-.005". So let's say they're both set hot....well if you think about it, that requires some courage (or maybe discretion) to set an engine up at zero lash cold. Romping a cold engine = bent push rod.

There is a similar discussion on piston fit. If you set the two engines up the same cold, you could expect the growth to be as much per side (~.0007" .001") as cited on the main bearings EXCEPT, there is that inconvenient fact that the sleeve isn't aluminum so by itself it won't grow as much as the block which negates this issue a little bit but you do tend to loose an amount of squeeze on the liner press fit which isn't helpful.

The tensile strength of aluminum is actually greater than grey iron.....nearly double for 6061-T6 but probably comparable for A356-T6. However, the elastic modulus of aluminum is less than iron so the translation is it may move more but will not break until being more highly stressed. The latter can be a factor for harmonics as well. If you've ever built a machining fixture or used a machine tool made out of aluminum and compared it to iron, you see poorer results from the aluminum fixture/machine for the same tool loading. To an extent you can compensate for differences by where you choose to put metal in the block but you can't change the amount of material between cylinders.

On the subject of repairs, sure aluminum blocks are readily welded and that may be OK for small boo-boos, but if you think they are ever the same after a major repair, you'd be mistaken because the filler material does not have the same strength as the tempered base material, the base material temper no longer exists in the area of the repair, and the block will in most cases no longer be dimensionally sound. Minor repairs maybe but if you are fixing a stress induced crack with a weld, that area will not be as strong after the weld and you can expect it to break again when it sees that loading, assuming the area was ever properly tempered in the first instance.

Heat treating is another non-trivial area to deal with out of the box in alloy blocks because uniformly achieving high temper/strength on a structure like an engine block is not easily achieved and controlled because the material has little strength at the process temperatures and keeping them dimensionally stable throughout the process is not child's play.

Even if the gains in weight loss were equally offset by power loss, that might equal no benefit to drag racing but you cant say that about road racing where weight (and how it affects CG) and cornering speed are directly related.....but you have to be competing at a very high level for it to matter.

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Kelly


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 Post subject: Re: 351c alm blocks?
PostPosted: Fri Mar 30, 2018 8:58 am 
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I know on my all aluminum engines that I set cold lash .014” tighter. On the camshafts that I use I still have lash when it’s cold. Either way no matter the block material we still end up at the same hot lash under operating temperature on the dyno.

Good thoughts, Kelly, regarding the material properties.

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 Post subject: Re: 351c alm blocks?
PostPosted: Fri Mar 30, 2018 9:10 am 
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Posts: 177
Kelly thanks for the reply. And like most things there is trade offs, i really beleive the alloy blocks have narrowed the gap. Like you say the weight maybe a bigger gain than the hp loss. On my own cougar for example where the excess weight on front end and long nose the nearly 100lbs off nose is a huge blessing. I would like very much to see dyno sheets on this subject. Like the rod discussion I never had access to the dyno reports, maybe those builders still have their literature for us. My guess is that if topfuel good squeeze another 3-5% out of cast block they would switch.That class is real competitive and every thing counts there.It will be interesting to see how this new alloy Trackboss has stands up to the others!!


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 Post subject: Re: 351c alm blocks?
PostPosted: Fri Mar 30, 2018 9:39 am 
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No one has said it was a percentage.

It depends on ring seal losses. Comparing a top fuel engine to our 700 hp Clevelands is not exactly apples to apples either. As mentioned several times so far, repairability is the clincher there.

Let me ask you this: when was the last time you saw an aluminum Cup block? In the 900 to 1000 hp range all of those blocks have always either been cast iron or compacted graphite. Those guys are always looking for one or two horse power increments.

Call Lance, he’s got dyno sheets.

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 Post subject: Re: 351c alm blocks?
PostPosted: Fri Mar 30, 2018 9:47 am 
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blykins wrote:
No one has said it was a percentage.

It depends on ring seal losses. Comparing a top fuel engine to our 700 hp Clevelands is not exactly apples to apples either. As mentioned several times so far, repairability is the clincher there.

Let me ask you this: when was the last time you saw an aluminum Cup block? In the 900 to 1000 hp range all of those blocks have always either been cast iron or compacted graphite. Those guys are always looking for one or two horse power increments.

Call Lance, he’s got dyno sheets.


i'd say that the reason you don't see an aluminum "cup" block is simply because of the rules. This is also why you don't see any blocks from Dart, World Products etc at those races either, rules. How many dirt late models or sprint cars do you see with iron blocks when the rules allow aluminum blocks to be used? In some types of racing weight percentages on the chassis are very important and saving weight on the engine is worth doing even if it costs some power which it does undoubtedly. In other situations I agree 100% that a cast iron block is tough to beat.


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 Post subject: Re: 351c alm blocks?
PostPosted: Fri Mar 30, 2018 9:53 am 
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The dirt track and sprint car applications are unique. Those cars depend more on handling and weight bias than all out horsepower. They can’t even hook up the horse power that they have. Those venues of racing also see more pronounced engine failures… When you are constantly turning 8000 or 9000 RPM component failure and windowed blocks are more common. That gets us back to that repair ability thing.

For our intents and purposes here, most of these guys are drag racers.

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 Post subject: Re: 351c alm blocks?
PostPosted: Fri Mar 30, 2018 11:02 am 
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Posts: 216
After a short talk with the money guy and explaining your going to have 600lb of mud
after the first run what little lb you save is meaningless.
Just to say we have a alm.block in the pits at night is not worth it..
spend the 2000.00$ on weed and beer...

He agreed.
Unless there is a better iron block? A Dart will be own its way...
Thank you for the input...

Update as things move forward in the reconstruction.....


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 Post subject: Re: 351c alm blocks?
PostPosted: Fri Mar 30, 2018 11:08 am 
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Joined: Mon Oct 23, 2017 9:53 am
Posts: 177
This is correct the iron block may make a smidge more hp.on the 750 hp engine you talked about losing 40hp that's roughly 5%. However I personally don't believe its that much and on bigger engines the weight saving is more of a benifit. I have a cousin running a 470 inch hemi dodge. After they windowed their cast block the bought a used alloy block.They swapped all their parts over ( that they could)and built the same engine in alloy. The only reason they went alloy was this used block was the cheapest way for them to go. They seen nearly identical times with car only a smidge quicker. He attributed the slight quicker et to better weight transfer with nose weight down. The other is a 605 hemi. But he upped cubes so doesn't have fair comparison. He does say he will never go back to cast after running this motor.All the upper end fast racers i know whether its mud,drags or you name it. All Run Alloy!


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