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SVOC
01-18-2016, 09:35 AM
Let's drag this discussion out.

Seems as though there is a lot of forward thinking on this, and even some testing that has happened some years ago, but never really any final thoughts or true results here in the question that I have been able to rely on.

So one of the main players here was BoPort back in 07' with some flow bench numbs that looked like this, for the 8 plug head:

Stock #'s

.050"-30.0
.100"-58.0
.150"-86.7
.200"-110.7
.250"-130.3
.300"-143.3
.350"-153.1
.400"-158.9
.450"-164.1
.500"-166.8
.550"-166.8
.600"-170.2

Here are Bo's numbers as he tried and tested, new things:

__Stock-DP___1.89___NOGUIDE__BIGPORT__STAGE 3 single plug
.050---27.3----31.4----32.2----32.8----30.9
.100---54.9----64.1----65.3----65.1----64.9
.150---78.3----99.0----101.0---100.0---98.0
.200---96.1----126.5---129.7---128.4---122.3
.250---109.4---147.9---152.4---151.5---143.3
.300---120.4---167.3---171.9---171.9---163.4
.350---128.4---182.9---189.4---190.7---181.6
.400---132.3---196.5---204.3---208.2---199.1
.450---134.9---206.9---215.3---223.1---218.6
.500---136.8---216.0---224.5---232.2---225.7
.550---138.8-----------232.2---239.3---224.4
.600---140.1-----------238.0---245.8---223.1
.650-------------------240.6---251.0--------

One huge key I did pickup from Bo's testing is that the ceiling on the exhaust port is very thin and easy to break out on.

He also mentions that the intake will take a flow number from 210 to 163, so there is a huge restriction in the manifold, but yet again, this is where it all stopped, and trying to find anything past this is null.

Funny this debate works it's way across the Mini Stock boards as well, saying that 8 Plug heads are a 50lbs penalty in their race cars, yet, on the flip side, they also mention that a "D" Port head will still kick their ass on the track.

We all know that the 8 Plug head was actually designed to promote a cleaner burn, and be more EPA emission compliant, with the "Swirl Port" design and waste spark ignition system.
The swirl port hurts in higher RPM application, such as anyone wanting to run a full on drag race engine or dirt track engine.

As many have proclaimed that the need a viable, and cost effective alternative for the ever lying issue of cracked "D" port heads, I have yet to find an answer as to why the development, and forward progress to make this an alternative had come to a stop.

Because I have quite a few of these pieces at my disposal, including both 1st and 2nd gen 8 Plug heads, and a few "D" post heads, and some where in the archives a round port head, it would kind of neat to know, what kind of easy mix and match might produce some easy and effective alternatives that could work with make some ponies and averting the lack of "D" port head stock.

AND some where I remember seeing, not to long ago, someone take an 8 Plug head, with an IHI, and shove it in to his wife's automatic convertible Mustang for a daily driver, who was that????

So, with all this blah, blah blah, let's get this topic off the ground, and wake some people up around here.

I've already done the TFI and DIS block Frankenstein builds, so let's see what kind of ideas and stuff you all can throw out there to make the gears in my head spin a little faster.


https://scontent-dfw1-1.xx.fbcdn.net/hphotos-xpt1/t31.0-8/12615725_10156485481025529_5813430455474931240_o.jpg

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MikeFleming
01-18-2016, 06:51 PM
Well, you're almost right on the twin-plug heads.

The original intention from Ford was to make an engine that was light-duty that could tolerate a fast-burn, high-EGR configuraiotn to lower NOx values for light truck use. The single-plug 2.3OHC was failing in theta category especially when the full "truck" loads were tested.

If oyu study the dual splug design, you will find that the exhaust plus fires slightly longer )longer firing time == more fcoil energy) whle both plugs start the fire at the same time. With the spark plugs on opposite sides of the chamber, time between start of spark and end of burn is cut in half (in milliseconds) so ther's less time to heat the unburnmed chanrge. And less advance is needed under all load conditions.

It is also worth noting that the exhaust side spark is cut off above specific vehicle speeds & RPM while under light loads (where a more normal spark timing curve can be seen.

If you want to understand more better how these dual-plug, high-swirl, high-EGR engines work, look for a SAE article from Nissan on the NAPZ engine design. published 1977, iirc. I have a copy in a box somewhere. Almost identical design except the NAP-Z was carb'd.