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  #16 (permalink)  
Old 10-12-2013, 10:34 AM
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Personally, I put quite a lot of credence in DCR. It gives you an indication of what the cylinder pressure will be for a given camshaft intake valve closing point and my opinion is that those of you who poo-poo DCR just have not taken the time to get your mind wrapped around the concept.

Gearhead346 has figured it out. The rest of you should be able to figure it out too.

As far as elevation, air density decreases to the tune of about 3% for each 1,000 ft. elevation, so at 5,000 ft., the motor can be down on cylinder pressure by 15%. If you aren't taking this into consideration on your build, then you are not using all the tools available to you and the motor could turn out to be a pooch.

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Old 10-12-2013, 11:02 AM
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Quote:
Originally Posted by Gearhead346 View Post
I think the part number was 00212s or 00211s through crower cams. I was figuring a .050" quench for the 11.2:1. I can only find the eagle kits with -6cc, -7cc, and -30cc pistons. The -30cc pistons would put me way down to around 8.8:1. I some what believe in DCR... my other engine runs 10.8:1 scr with 8.5:1 dcr and runs 91 octane no problems, but that may also be because of my aluminum heads.
I don't know what calculator you use, but I have become accustomed to the one on Keith Black Pistons site. I've used it long enough to be able to figure out whether a combination will work or not.

What I'm seeing with the SCR at 11.50:1 and using the Crower 00212 cam timing, the DCR figures to 9.33:1. This motor will not run on pump gas. You need to be nearly a full point lower on DCR.

With an SCR of 10.50:1 and using the Crower 00212s, the DCR on the KB calculator is 8.54:1, a number that is perfectly acceptable for pump gas in my experience, particularly with using aluminum heads.
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Old 10-12-2013, 11:06 AM
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I can only find the eagle kits with -6cc, -7cc, and -30cc pistons.

You did not look in the Eagle on line virtual catalog.
The right kits are there.
-16cc and -21cc D dish
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Old 10-12-2013, 11:16 AM
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So I found a different rotating assembly from scat. Here it is

http://www.summitracing.com/parts/sc...50bi/overview/

This will give me -18cc pistons and put me at 10.16:1 SCR with 64 cc heads and .040" quench. DCR at 7.27:1. Will this be more reasonable and still make decent power? Also if I check the clearances and buy Comp cams 787-16 retainers will the LS3 springs handle that .492/.510 cam?
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Old 10-12-2013, 11:21 AM
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Eagle kit w -21cc pistons and 5.7 rods
ESP-13012030

You need to measure the seat and open pressure and shim the springs to ge the right sepcs.

You will spend more fooling around than just doing it right. Just because you got something there does not mean it is the right stuff you need.
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  #21 (permalink)  
Old 10-12-2013, 11:30 AM
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A bore of 4.155 (+0.030") and a stroke of 3.750" will yield a 408 cubic inch motor. Using a 64cc chamber and 16cc piston will produce an SCR of 10.3:1. Using the Crower 00212s (intake closes at 48 degrees after bottom dead center @0.050" tappet lift) and installing it straight up will produce a DCR of 8.38:1 on the KB calculator.

Same motor, using the Crower 00211s, (intake closes at 44 degrees ABDC) will produce a DCR of 8.62:1, a perfectly acceptable figure for pump gas. This cam has nice, easy ramps and will make power from 2500 to 6400 in a 408 cubic inch motor.

Gearhead, you can specify the piston crown displacement when ordering the kit. They'll include any piston that you tell them to. Use the 16cc piston.

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Old 10-12-2013, 11:52 AM
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Quote:
Originally Posted by techinspector1 View Post
A bore of 4.155 (+0.030") and a stroke of 3.750" will yield a 408 cubic inch motor. Using a 64cc chamber and 16cc piston will produce an SCR of 10.3:1. Using the Crower 00212s (intake closes at 48 degrees after bottom dead center @0.050" tappet lift) and installing it straight up will produce a DCR of 8.38:1 on the KB calculator.

Same motor, using the Crower 00211s, (intake closes at 44 degrees ABDC) will produce a DCR of 8.62:1, a perfectly acceptable figure for pump gas. This cam has nice, easy ramps and will make power from 2500 to 6400 in a 408 cubic inch motor.

Gearhead, you can specify the piston crown displacement when ordering the kit. They'll include any piston that you tell them to. Use the 16cc piston.
Does the Crower 00212s also have easy ramp rates? Sounds like above the 240/246 at .050 duration 108 LSA .492/.510 is the better choice for me.
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  #23 (permalink)  
Old 10-12-2013, 12:06 PM
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Quote:
Originally Posted by Gearhead346 View Post
Does the Crower 00212s also have easy ramp rates? Sounds like above the 240/246 at .050 duration 108 LSA .492/.510 is the better choice for me.
Yes, both cams have easy ramps. Personally, I'd use the smaller cam, but I'm conservative that way. I'd rather have more power on the bottom and mid-range, where the motor operates 99% of the time.
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Old 10-12-2013, 12:18 PM
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You cannot determine the hyd ramp rates by looking at the advertized numbers.
The checking height of the Crower camshaft is not specified. It could be anything.
Advertized numbers are often fudged. Thats why they are called advertized duration.

Without knowing the actual checking height spec, you cannot make any kind of a
value judgement as to how intense the cam profile is.
These are agressive high performacne hyd cams.
The hyd ramp rate will be very similar to other brands.
Don't get all fooled by the advertized numbers.

If you want to know the real seat to seat duration at the SAE spec (.004" lifter rise) call Crower and ask specificly for this. spec. If you want to compare to a Comp cams ask for the duration at .006" lifter rise spec.
Specificily

They know the real seat to seat specs @.004" and @.006" but you have to ask the right questions.

Or get one and measure it yourself.

The typical dynamic compression calcs are all BS as they do not specificy the checking height, and still won't actually predict the in cylinder actual trapped amount of air in the RUNNING engine. Or predict the fuel octane requirement.

If all it took was delayed intake valve closure point to allow 11:1+cr on pump gas in a high perf engines there would be no purpose for high octane gasoline.

High compression ratio engines 11:1+ require high octane gas.

Keep the compression ratio under 10.50:1 for pump gas.
YA IT matters.

Garbage in garbage out.

Last edited by F-BIRD'88; 10-12-2013 at 12:24 PM.
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Old 10-12-2013, 12:53 PM
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Thanks guys for the input, I just realized that rotating assembly is with 6" rods vs. 5.7" rods. This was the whole reason I was buying a small base circle cam because of the 5.7" rods. Won't 6" rods cause rod to block clearance issues and cam to rod clearance issues? So with the small base circle cam I would be good with 6" rods, but not on the block side. If it does have clearances issues can I grind the block slightly to make it clear? I almost wish I could buy an assembly with 5.565" rods but they don't even make them anymore
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Old 10-12-2013, 12:54 PM
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Quote:
Originally Posted by techinspector1 View Post
Personally, I put quite a lot of credence in DCR. It gives you an indication of what the cylinder pressure will be for a given camshaft intake valve closing point and my opinion is that those of you who poo-poo DCR just have not taken the time to get your mind wrapped around the concept.

Gearhead346 has figured it out. The rest of you should be able to figure it out too.

As far as elevation, air density decreases to the tune of about 3% for each 1,000 ft. elevation, so at 5,000 ft., the motor can be down on cylinder pressure by 15%. If you aren't taking this into consideration on your build, then you are not using all the tools available to you and the motor could turn out to be a pooch.
Didn't mean to imply that DCR calcs are not valuable & critical tool when building an engine.It is when used in conjunction with everything else.More so for the novice or less experienced.It is a valuable tool.I just meant that it shouldn't be solely used.It is an important piece of the puzzle.As far as elevation goes,my thinking is,if I live in a higher altitude & build my engine on the edge of what may work there,then,have to go out of this setting,or,maybe sell the vehicle/engine to someone @ a somewhat lower elevation,you could have issues.I see ppl saying my DCR is XX:1,so,I can run xx octane & it ain't quite that simple.Dcr has to be used along with everything else.
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  #27 (permalink)  
Old 10-12-2013, 01:02 PM
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Quote:
Originally Posted by Gearhead346 View Post
Thanks guys for the input, I just realized that rotating assembly is with 6" rods vs. 5.7" rods. This was the whole reason I was buying a small base circle cam because of the 5.7" rods. Won't 6" rods cause rod to block clearance issues and cam to rod clearance issues? So with the small base circle cam I would be good with 6" rods, but not on the block side. If it does have clearances issues can I grind the block slightly to make it clear? I almost wish I could buy an assembly with 5.565" rods but they don't even make them anymore
Use longer pushrods to take up the slack left by the smaller diameter base circle cam and clearance the oil pan rail for the big end of the rods. Make certain that there is sufficient clearance between the pin end of the rod and the underside of the piston crown. Clearance flat tappet bores at 0.0015" (one and one half thousandths).

Read and heed......
http://www.crankshaftcoalition.com/w...ips_and_tricks
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Old 10-12-2013, 01:06 PM
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Quote:
Originally Posted by jokerZ71 View Post
Didn't mean to imply that DCR calcs are not valuable & critical tool when building an engine.It is when used in conjunction with everything else.More so for the novice or less experienced.It is a valuable tool.I just meant that it shouldn't be solely used.It is an important piece of the puzzle.As far as elevation goes,my thinking is,if I live in a higher altitude & build my engine on the edge of what may work there,then,have to go out of this setting,or,maybe sell the vehicle/engine to someone @ a somewhat lower elevation,you could have issues.I see ppl saying my DCR is XX:1,so,I can run xx octane & it ain't quite that simple.Dcr has to be used along with everything else.
I contend that it really is that simple, but I'm tired of arguing about it. Use it or don't use it. No hard feelings.
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  #29 (permalink)  
Old 10-12-2013, 04:17 PM
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Quote:
Originally Posted by Gearhead346 View Post
Thanks guys for the input, I just realized that rotating assembly is with 6" rods vs. 5.7" rods. This was the whole reason I was buying a small base circle cam because of the 5.7" rods. Won't 6" rods cause rod to block clearance issues and cam to rod clearance issues? So with the small base circle cam I would be good with 6" rods, but not on the block side. If it does have clearances issues can I grind the block slightly to make it clear? I almost wish I could buy an assembly with 5.565" rods but they don't even make them anymore
6" rods will have the same cam and block clearance as 5.7" rods, if they are the same brand/type. 6" rods are just longer in the beam area, they are the same as 5.7" rods at the big end and the pin end.

Many aftermarket SBC rods now come "pre-cam clearanced" but you will still need to check cam-to-rod and rod-to-block clearance at trial assembly to verify that you have enough room. Small base circle cam and cam clearanced rods will almost 100% clear each other at the cam size you are looking at...but you, THE BUILDER, still have to check it.

Block should clear the big end of the rod, as it was cast to clear the long 3.75" stroke from the factory, but you still have to check it/mock up, and grind block if neccessary. Block clearance is usually only a problem when putting a 3.75" or longer stroke in a 350 block, or when using aluminum rods with the stock 3.75" stroke in a 400 block.
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Old 10-13-2013, 12:04 PM
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Quote:
Originally Posted by F-BIRD'88 View Post
You cannot determine the hyd ramp rates by looking at the advertized numbers.
Ummm, yeah you can. You're wrong.
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