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Re: MEL Engine Series Combustion Chamber & Piston Design

Posted: Mon 2. Aug 2010, 10:55
by Theo
Here's a link to an interesting post that Rick "Shelby#18" has posted just recently. It's interesting informationon on how much factory stated HP rating can differ from real world dyno results.

Re: MEL Engine Series Combustion Chamber & Piston Design

Posted: Mon 7. Feb 2011, 16:57
by 430 6V
The step pistons are indeed the best. No matter what the compression ratio I recommend the quench pad or "step" be at zero deck with a .040" head gasket. .020" in the hole if you use a .020" steel shim gasket.

In theory it not only helps with squish and turbulance but allows you to run higher compression with out detonation due to improved piston cooling.

Re: MEL Engine Series Combustion Chamber & Piston Design

Posted: Wed 4. May 2011, 22:38
by mugundhan
I'm new here.
I'm looking forward for the wonderful topic and new learnings. :roll:

Re: MEL Engine Series Combustion Chamber & Piston Design

Posted: Thu 8. Mar 2012, 18:07
by Chris Craft crazy
I have been doing some research on Chevrolet 409 engines lately, and came across the following quote from wiki, which I post here. As some of you may know, the 409 also had a triangular combustion chamber, and it was in the cylinder, like the MEL series of engines. In 1963, you could order a Impala SS with a dual quad 409 which produced 425 horsepower. The 409 had a brief but storied life, but it was this information that interested me.

Unlike many of its contemporaries, the "W" combustion chamber was in the upper part of the cylinder, not the head, the latter having only tiny recesses for the valves. This arrangement was achieved by combining the use of a cylinder head deck that was not perpendicular to the bore with a crowned piston, a novel concept in American production engines of the day. As the piston approached top dead center, the angle of the crown combined with that of the head deck to form a wedge shaped combustion chamber with a pronounced quench area. The spark plug protruded vertically into this chamber, which tended to cause a rapidly moving flame front during combustion.

The theory behind this sort of arrangement is that maximum brake mean effective pressure is developed at relatively low engine speeds, resulting in an engine with a broad torque curve. With its relatively flat torque characteristics,

Re: MEL Engine Series Combustion Chamber & Piston Design

Posted: Fri 9. Mar 2012, 01:38
by Theo
Here's an other important note 'bout the 409 ;)

Re: MEL Engine Series Combustion Chamber & Piston Design

Posted: Fri 9. Mar 2012, 15:39
by Chris Craft crazy
I love Junior Brown... a wicked guitar player.

Re: MEL Engine Series Combustion Chamber & Piston Design

Posted: Thu 15. Mar 2012, 19:54
by 430 6V
I've thought it curious that the 409 and MEL chambers have been described as having a fast flame front or fast burn.

It makes cense yet on the dyno mine made it's 420hp peak with 43 degrees total.

Due to the lack of shrouding that would indicate a slow burn. And I would think that same slow burn contributed to the 430's smooth power.

Re: MEL Engine Series Combustion Chamber & Piston Design

Posted: Thu 2. Apr 2015, 23:25
by mrbthebarber
An interesting and frustrating topic - I bought a rebuild kit for my 58 back in 03 and in total naivety fitted the flat top pistons and whilst the engine runs well I could never understand the lack of power. The car used to lay down rubber in a straight line, no chance now. What to do? Are the stepped pistons available anywhere now?

Re: MEL Engine Series Combustion Chamber & Piston Design

Posted: Tue 14. Apr 2015, 03:26
by Shelby#18
mrbthebarber wrote:Are the stepped pistons available anywhere now?
Please see the second page of this thread, third post down. That is the order form for the step down pistons.

Re: MEL Engine Series Combustion Chamber & Piston Design

Posted: Wed 8. Nov 2017, 11:01
by WerbyFord
Shelby#18 wrote:
Thu 22. Jul 2010, 10:35
The dyno video.....Turn up the volume!
Rick / Shelby#18:

Hi there, I found my own post way back asking for specs on your build. Time flies!
I see the specs and dyno result are now here.
Searching the forum I found tons of good new info on the MEL, particularly head and cam specs in that History thread.

Well here are what would have been the Gonkulator predictions of your engine:
SAE Gross, 60f 29.92 dry air, no belts except water pump, open exhaust no restriction
Torq 450 at 2700
Powr 333 at 4400

And here is what I get from the Gonkulator, assuming that 2" (??) pipe adds some exhaust restriction, plus the belt and small pulleys- in other words yours was close to a "gross" dyno test but a little bit of "net" losses in there too:
Torq 437 at 2800 (10% high vs dyno)
Powr 299 at 4400 (5% high vs dyno)
I am ASSUMING they corrected the air to 60F 29.92 dry air like it says on the dyno sheet.

That is still quite a bit higher than you got on the dyno.
Of course, there could be several causes, and although I have well over 1000 dyno tests to back up the Gonkulator, only a few are on the MEL, and yours is the 1st stock MEL. However, I also Gonkulate all the period road tests, and if the Gonk was way off I could not match up with those. As far as the dyno result, the engine might have wanted different timing, jets, or even a more friendly carb (like the original "List 1850-0" Holley, those always run good). Beyond the timing being way off (which I assume you checked), there is one thing about the build that could cause what you saw: retarded CAM timing.

I retarded the cam 11 degrees in the Gonkulator (so it went from 4 advanced to 7 retarded) and got
Torq 397 at 2900 (right on vs dyno)
Powr 287 at 4600 (+1% vs dyno)
This lines up quite well vs the dyno.

WITH ALL THAT SAID I had a few questions:
1. I cant see the dyno video, is it just me?
2. Were those exhaust pipes on the dyno 2" OD?
3. The cam specs of 196-196 duration, 115 Lobe Sep, where did you get those? They sound a little like the later 462 cam. No big deal, just wondered on the specs.
4. UPDATE - is it running in the car? Have you weighed the big wagon? I guessed 4800 lb, full tank but no driver. I also guessed a 2.91 rear, shifting about 4200 rpm, and 2" pipes/mufflers.
5. You can check if the cam is retarded or not in the car pretty easy, just pull the valve cover for #1, and lay a straightedge across the valve retainers. Check first at TDC compression - they should both be closed and level. If not, shim the level so it reads level at this condition. Then, go around to TDC overlap. The valves should both be open the same amount since intake & exhaust duration are the same. If the cam is installed right, the level will be level at 4 BTC (cam advance). If it's retarded as I guessed, they wont be level until say 7 ABC (cam retard). Also fairly easy to fix, no need to pull the motor for that.
6. How does it run? Any performance testing?

Based on all that, here is how I would Gonkulate your car should you choose to check it with a stopwatch, GTECH, or timeslip (THAT would be a fun evening!)
As it "should" run: 183rwhp
9.1 0-60mph
2.46 60ft
10.71 at 65.9mph 1/8 mile
16.67 at 81.6mph 1/4 mile

As it ran on the dyno: 164rwhp
10.5 0-60mph
2.69 60ft
11.41 at 63.1mph 1/8 mile
17.60 at 78.9mph 1/4 mile

That is a BIG difference - my rule is, a second in the 1/4 mile feels like "a totally different car". It is also about 8-10 car lengths. Even with a stopwatch and an accurate speedometer you could probably get a handle on 0-60mph. In other words, maybe the dyno was just stingy!!! The proof is in how the car runs, not what the dyno said.

Rear wheel dyno's are even worse - I got 183rwhp or 164rwhp, but it depends a whole lot on the chassis dyno conditions. Mostly they are a tuning tool for timing and carb, jets, etc. Sometimes there will be a chassis dyno trailer right at the dragstrip!

Well I am very curious now to see how this near-stock example does -
Thanks for any of the info above if you are able to reply!!