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 Post subject: Re: 351c alm blocks?
PostPosted: Fri Mar 30, 2018 11:33 am 
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Ray, the Dart is the right way to go.

Steve, you may not believe it, but that doesn’t mean that it’s not true. Again, call Lance..... ;). It’s not a story, it’s not something that happened 10 years ago, it’s dyno results from this year and last and it’s a very common rule of thumb.

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 Post subject: Re: 351c alm blocks?
PostPosted: Fri Mar 30, 2018 11:45 am 
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blykins wrote:
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.


Some of those sprint guys can get really crazy when it comes to saving weight. Four bolts in the back of the crank instead of six because its lighter... I know of a very well regarded sprint car racer that won the Knoxville Nationals one year using a flat tappet cam instead of a roller because it was..... lighter. That had to sacrifice some torque and HP in a 410 inch engine.

Kaase and those guys who build really big inch drag engines also run aluminum blocks because an iron block with a 13 inch deck height would be impractical.


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 Post subject: Re: 351c alm blocks?
PostPosted: Fri Mar 30, 2018 11:53 am 
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Brent I beleive there is a small difference but not enough to offset the weight. Every drag racer I know would switch to alloy if the cost was down. Thats the only thing other than class specific rules. If Trackboss, Dart etc sold alloy at same price as cast it would be for the most part game over for cast. Thats not a story either.


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 Post subject: Re: 351c alm blocks?
PostPosted: Fri Mar 30, 2018 1:16 pm 
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DaveMcLain wrote:
blykins wrote:
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.


Some of those sprint guys can get really crazy when it comes to saving weight. Four bolts in the back of the crank instead of six because its lighter... I know of a very well regarded sprint car racer that won the Knoxville Nationals one year using a flat tappet cam instead of a roller because it was..... lighter. That had to sacrifice some torque and HP in a 410 inch engine.

Kaase and those guys who build really big inch drag engines also run aluminum blocks because an iron block with a 13 inch deck height would be impractical.


Right, most of those guys run alcohol or other combinations where coolant is not needed, so water jackets are not needed. A solid cast iron block would weigh a ton.

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 Post subject: Re: 351c alm blocks?
PostPosted: Fri Mar 30, 2018 1:39 pm 
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Steve.k wrote:
Every drag racer I know would switch to alloy if the cost was down.


Every one? I think that may be a little bit of a stretch...... ;)

I've got quite a few customers who bracket race. One guy runs a 7.50 1/8th mile. We have to run the smallest restrictor plate that we can find to make it easy for him to hit his dial-in. All-out, his car runs 6.80's. I freshened his engine last year. He had been running it for 8 years. Why would he want to switch to an aluminum block?

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 Post subject: Re: 351c alm blocks?
PostPosted: Fri Mar 30, 2018 2:09 pm 
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From Speedtalk a few years ago....from user maxracesoftware, Larry Meaux:

"a back-to-back Dyno test on SBC
cast-iron Bowtie Block -vs- alum Block
everything exactly the same, just blocks were swapped
there was 30 HP difference at 600 rpm/sec

another back-to-back Big Block Chevy test = approx 40 HP

another back-to-back SS Hemi test on Cylinder Heads only
with cast-iron -vs- aluminum = 12 HP more w/cast-iron
same flow numbers + port vol CC's

the above were actual Dyno tests,
for theoretical HP/TQ differences between alum -vs- iron Blocks
by using FlowBench CFM Numbers -vs- what HP the different
block materials made on the Dyno =>

the results were=> for the same Flow CFM numbers,
i have yet to see an aluminum block engine make
the same HP/TQ that the cast-iron Block engine makes.

so far in all my Data,
the cast-iron Block always 100.0 % PerCent of time
makes more HP/TQ than an aluminum block

the last Dyno test was a recently as 2 months ago
with Brodix SBC and SB2.2 Heads
again the aluminum Block did not make as much HP
as the Flow Numbers suggested, about exactly the 30 HP
i found in those back-to-back Dyno test i did about 10 years ago
with another manufacturer's alum block -vs- Bowtie cast-iron.

to date, i have never seen an aluminum block make
1-the same exact power/torque as cast-iron
2-make more HP/TQ than cast-iron

it has always been LESS so far ."

There's another guy saying that the dyno showed a 40 hp bump on some engines with cast iron blocks. That's a big bump.

Darin Morgan (who works for Reher-Morrison) replied to Larry's post with:

"We see the EXACT same thing. The Billet blocks are the only aluminum block I have seen that makes the same power as a cast iron block. Aluminum blocks take longer "season" and stop moving around as well. The second or third rebuild always nets anouther twenty HP. Also, as the aluminum block engines get hotter on the dyno the crank case pressure rises dramatically and the power goes south in a hurry! They just expand and move around so much its impossible to maintain any semblance of stability."

Larry Meaux followed that up with:

"just example from ProStocker

BaseLine= 6.670 ET

6.616 ET = 100 Lbs less weight
6.709 ET = same previous weight, but 30 HP less
6.665 ET = 100 lbs Less + 30 HP Less
6.666 ET = 100 lbs. less + 40 HP less

if your alum block weight -VS- your cast iron block weight = 100 Lbs
then alum block is the way to go even though it looses 30 HP

almost dead even with 100 Lbs less + 40 less HP
at that point..no gain for aluminum block

so it would appear at that performance level,
an aluminum block has no advantage"

So, from guys who are a lot sharper than me, with some actual & factual numbers, if the hp difference is in the 30-40 hp range, you will not see any ET difference with the lighter aluminum block.

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 Post subject: Re: 351c alm blocks?
PostPosted: Fri Mar 30, 2018 2:52 pm 
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Yes i text 10 guys this morning and 9 replied. 8 alloy 1cast. The reason for most less nose weight. Cast guy was worried about threads and the above mentioned hp losses.I still believe the weight especially offsets the hp. Especially when using a stock block that actually has to be filled to hold up to big power. The ford a460 has even more weight added in to keep it tough. Which it is. In big block form 100lbs is easy to lose. You can build your engine to compensate these losses also which one guy mentioned in survey this morning to offset inherent losses.


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 Post subject: Re: 351c alm blocks?
PostPosted: Fri Mar 30, 2018 3:39 pm 
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Joined: Tue Jun 02, 2015 2:28 pm
Posts: 216
I am not a master motor builder but I do understand how most thinks work.
How would you compensate for the HP loss when using an alm. block beyond filling with stuff?????

I see the HP loss of alm. more of a heat adsorbing thing over an iron block that holds heat better..
Like it or not HP has a lot to do with heat and its buy produces.

Solid blocks with no coolant will help with this..........Not real good on the street..

Not trying to be right just a different look.

Something's just need to be warmed up if you want them to move.


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 Post subject: Re: 351c alm blocks?
PostPosted: Fri Mar 30, 2018 4:14 pm 
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Joined: Wed Oct 31, 2012 4:57 am
Posts: 161
Gday,
Not wanting to get into the block debate.
What i just see here is one of the main reasons i believe alcohol and cast iron heads work so welĺ together.
Heat is power in the combustion chamber, cast keeps it in and alloy dissipates it quickly , its why if chambers everything else is identical then the alloy head will want more timing.
Cheers
If i was going alloy it would be an old school fontana block☺


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 Post subject: Re: 351c alm blocks?
PostPosted: Fri Mar 30, 2018 5:04 pm 
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Joined: Tue Jun 02, 2015 2:28 pm
Posts: 216
Any body remember the cast iron domes in alm. heads?

That must have been a casting mightmare.

In the 70s


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