Fuel distribution in Ford Medium Riser intake manifold?

[427LX]

Hi..new guy here and have a question on how the fuel distribution is on the factory MR intake manifold design?
Do the middle cylinders tend to run lean or rich compared to the end cylinders?
Thanks for any info.

[RJP]

Which manifold? 1 x 4...2 x 4...single plane, dual plane? It would help to know what we're working with here.

[Autoholic]

I'm not saying that no one on here will know the answer to this, maybe Jay or Berry will, but this is a rather difficult question. To know for certain, would require individual monitoring of the cylinders with O2 sensors on each primary and at least a MAF sensor. Just looking in the intake after running the engine for awhile might not be good enough, so visual inspection would require a wet flow bench with a dye in it. Something else to consider is how the carb and the porting job will effect the outcome. Heck, some cams might work better with slightly shorter or slightly longer intake runners. There are a lot of factors that impact flow, including your primary lengths and how good is the merge collector. Just one wrong part theoretically could screw everything up and result in fuel pooling, so anomalies can happen.

I mention all this just to cover the scope of the question. Jay or Berry might know, as these two guys have a lot of experience with FE's.

I think the better question would be how tricky is _______ specific intake manifold to tune with? Is it stingy or really flexible? How difficult a particular intake is to tune a carb on can be an indicator of problematic flow. Also, an intake might have a sweet spot a 1000 RPMs wide where it just sings with the engine, and then suddenly goes very rich or lean so RPMs comes into play too.

[427LX]

Yes I forgot to mention it would be the dual quad intake.

[jayb]

I don't have A/F data, which would be the most reliable, but I do have exhaust temp data from the dyno testing done for my book.  You didn't say whether this was a low riser or medium riser 2X4 intake, so I have provided both below; medium riser is the first graph, low riser is the second:





Generally (and I mean VERY generally), hotter exhaust temps mean the cylinder is running leaner.  There are exceptions to this rule.  Both graphs show that cylinder #8 runs the hottest, and on the low riser manifold both 1 and 8 are significantly hotter than the rest.  This data was taken when running the manifolds on my 390 stroker dyno mule.  The MR intake peaked at 517 HP, and the LR intake pealed at 493 HP.

[Barry_R]

Similar deal here - I have EGT but only O2 in each collector.  The EGT numbers are largely disregarded these days as true indicators of mixture being "rich or lean", but they are certainly valuable as indicators of something being "different".  I often use them just to see if we have a bad plug, wire, or injector.

I can say for certain that I see a noticeable and repeatable trend for the O2 values in the two banks to be different.  Not looking at data right now, but I recall it being about one half to three quarters of a ratio.  A one inch spacer does smooth that out a bit and will sometimes pick up a bit of power - possibly by fattening up the lean cylinders and leaning out the fat ones.

[Stangman]

What's up guys I have noticed that 1 and 8 are leaner do I jet to get those cylinders to look right plug wise. Because I think it's a smidge rich already

[427LX]

Very nice data on the EGT..Thanks Jay! 
Now regarding carb spacers on the factory intakes that have the 4 hole plenums...that would be 4 hole spacers or open?
The manifold I'm working with is a slightly scaled down version of the FE Medium Riser manifold in that it fits the 351 Windsor type block.
I'm setting this up on my 427 Dart based Windsor build which has head flow in the 330 cfm at .600 lift.
Since the runner layout is similar I was trying to gather a bit of info on what you guys see with the MR manifolds and 600 cfm Holley carbs.
There's not much dyno or tuning info with my particular setup and I will learning this as I tune using A/F monitoring and looking at the plugs.

[Autoholic]

If you go with an open spacer, the fuel will mix and cross in a 1" space and then go to the individual runners / dual plane. I imagine the 4 hole spacers were designed specifically for your type of intake, for a reason.

[427LX]

I would think the a/f mix might separate a bit when hitting the entrance of the four holes with an open spacer?
Just wanted to know what you guys with 4 hole type FE manifolds run spacer wise.
The manifold pics are of the flat cut manifold and mine is a bit taller with the 4 degree angle cut on the carb pads.
Will be using a 1 1/2 inch tall spacer combo.

My setup

[Joe-JDC]

What heads and what intake are you working with on the 427W?  I can give you flow figures on most every intake available for the 351W or FE.  You can't even compare the 8V MR intake to a 351W for fuel distribution.  They are not even close in similarity.   Joe-JDC

[jayb]

I don't think I've ever seen a case where with the four hole flange on the factory intakes, an open spacer made a significant power improvement on the dyno.  Those manifolds always seemed to prefer a four hole spacer. 

[427LX]

I don't think I've ever seen a case where with the four hole flange on the factory intakes, an open spacer made a significant power improvement on the dyno.  Those manifolds always seemed to prefer a four hole spacer.

Thanks Jay! That's the kind of info I'm looking for. My spacers are the four hole type.

[427LX]

What heads and what intake are you working with on the 427W?  I can give you flow figures on most every intake available for the 351W or FE.  You can't even compare the 8V MR intake to a 351W for fuel distribution.  They are not even close in similarity.   Joe-JDC

My heads are TFS High Port 225 intake runner cc. They came in a ported intake manifold and head package from Total Engine Airflow. They flow in the 330 cfm range at .600 lift and exhaust in 250 range. Intake manifold was the Edelbrock Super Vic with my custom Holley 4bbl flowing 950 CFM. This setup has worked extremely well for the last 5 yrs. but wanted to move on to an FE like dual Holley setup for my nostalgia reasons.
New manifold is from Price Motorsport Eng. and he is the only guy to make a dual Holley manifold for the 351W block!
I'm moving along on the project and into building the 600 cfm 1850 carbs.
I only know of one shop that ran this setup on a 393W build with more cam than I run and claimed to have made 600 HP with this intake. He is well known in the Michigan area and has been an Engine Masters competitor.

[Joe-JDC]

The PMS 8V for the 351W is probably the only intake I have not flowed on my SF-600.  I can't help you there.  Sorry.  It will be hard to outperform the SV.  Joe-JDC