Intake Manifold

[SouthportFLRT]

I probably should have "searched" to discover if this topic has already been covered in the Forums but alas...I have not. Watching on YouTube (the world's source for answers to problems that may or may not exist) Gixxerfoo and HarleyGeezer1954 have both discussed the issue/problem with the stock H-D intake manifold being manufactured with composite plastics.

Per their perspective and more importantly the possible historical perspective that due to the heat generated by the M8 motor and the constant cycles of heat/cool the plastic has an eventual problem with cracking thereby creating a major issue with throttle response and riding in general. The Screamin Eagle aluminum intake manifold can be bought in both 55mm and 64mm sizes. The original plastic manifold is 55mm. H-D parts website states both will fit those of us with the M8 motors.

S&S also manufatures aluminum intake manifolds for a few dollars less...thru Parts Giant.com. I do not have any issues yet but thought I would inquire if others have possibly experienced this problem. Aluminum intake manifolds (55mm) are approximately $200.00 plus the cost of installation....but it seems like a rather straightforward swap to my non-technical, non-mechanical mind. I could very well be wrong.

I am a retired Pharmacist not an automotive mechanic. H-D also claims a retune will be neccessary which I truly doubt if one simply swaps a plastic 55mm for an aluminum 55mm. I am certain asnwers to this inquiry will be forthcoming and I look forward to discovering what others have done. Again...my 2019 M8 114 is not in dire need but I would rather prevent a problem than fix one. The very reason I had a Fueling Shorty Sump Plug installed during an oil change. Tech did not charge any labor for that because he said it took longer to read the simple instructions than doing the actual installation.

 

[HDUSA1]

I went through the same thing a couple years ago on my 2020 Ultra Limited with 20k miles. I was installing a cam, mufflers, catless headpipe, tuner, etc. from Fuelmoto and had read stories about them warping and leaking.

I wasn’t going with a high horsepower motor with a big bore kit and all the reviews I read said the 55mm was more than adequate. So, it came down to selecting a Screaming Eagle $201.95, S&S $195.99 (or the rebranded Fuelmoto $187.99), or the Amazon $114.99 unit.

I can’t find the review right now, but I had found where they dynoed them back to back. I was expecting the S&S to be better, but the Screaming Eagle outperformed them all. That’s what I went with and it was ported, smooth flowing, and finished very nicely inside. The Amazon unit performed good, but they commented you might want to spend some time deburring, grinding out some of the bosses inside, and smoothing.

When I took my plastic intake out, I didn’t find any cracks or warpage. However, one of the bolts holding it to the head was missing! I bought new H-D bolts and rubber gaskets to put it back together with.

Couple of tips I read about that made removing and installing the intake bolts much easier. I ordered a set of extra long ball end hex (Allen) bit socket set from Amazon.

https://a.co/d/he6gaN8

I also purchased the Yost Harley intake manifold wrench which was critical for one of the lower bolts.

Harley Intake Manifold Wrench Big Twin Sportster #WRNB Yost Performance USA MADE | eBay

Part Number - WRNB. The Yost Intake Manifold Wrench works on all Evolution motors on sportsters (1986 & Later), and Big Twins (1984 & Later). Also works great for installing all Yost Power Tube kits.

www.ebay.com

 

[HDUSA1]

Sorry for the long read. Couldn’t find the link, but this was from Alpha Performance Engines. Pay particular attention to the last paragraph. That’s why I went with the Screaming Eagle manifold and just bolted it on as is:

M8 Inlet Manifold Testing


Massive thank you to Neil from Warflow for spending the last few days on the flow bench


All testing was done with the manifold bolted to a +2mm Warflow Ported M8 Cylinder Head ( Heads off our 9 second Bagger ). Each manifold was individually tested with a radiused adaptor in place of the throttle body. Position of adaptor played a critical role in obtaining a true and fair comparison between the manifolds. Neil also mentioned that the position of the adapter and the cylinder head which the manifold is bolted to may cause a difference in peak flow numbers in similar testing ( ie if another shop was to do a similar test ).

Peak flow numbers aside, we tested these manifolds back to back under the same conditions


Tested at 28” depression. Both the SE and S&S 55mm manifolds are designed to replace the plastic unit and bolt directly to the stock 55mm throttle body .

• Stock Plastic Manifold - 297cfm Front, 304.8cfm Rear

.• SE 55mm out of the box - 325.6cfm Front, 330cfm Rear

• S&S 55mm out of the box - 308.6cfm front, 321.7cfm Rear

Neil then went on to port the SE & S&S units -

• SE 55mm Ported - 332cfm Front , 336cfm Rear..Only a small increase, but a gains a gain


• S&S 55mm Ported - 329cfm Front, 331cfm Rear.. Massive gains to be had by porting this unit!

Once again , thank you to Neil for collating this data and we hope you all find it interesting


One other thing to mention guys, peak flow numbers on the bench doesn’t always lead to the best performance once fitted to the engine - A manifold that flows a few CFM more in stock form with a relatively smooth finish may not perform as well throughout the whole rev range as a slightly lesser flowing unit with proven surface finish

 

[HDUSA1]

At the risk of beating a dead horse, will caution you on the fuel rail that bolts on to the manifold over the fuel injectors.

The Harley fuel rail is plastic. If you try to disconnect the fuel line from it, it comes off VERY hard and will most likely break the nipple off the fuel rail. The 2020 & prior fuel line is a poor design and was updated in late 2020.

Instead, disconnect the fuel line from the fuel tank and leave it connected to the fuel rail when you are unbolting it from the manifold.

OR, replace the fuel rail with an aluminum unit like found here:

NICECNC Fuel Injector Rail Fuel Rail Kit Compatible with Harley Road Glide Road King,Street Glide FLHX/Special FLHXS 2017-21, Electra Glide,CVO Ultra Limited FLHTKSE 2017-21,See Fitment(Black) https://a.co/d/fEfX9dE

It won’t work with the old style fuel line however and will leak. You’ll need to order the new fuel line part number 61200022A. This is what I’m putting on my bike.

 

[SouthportFLRT]

At the risk of beating a dead horse, will caution you on the fuel rail that bolts on to the manifold over the fuel injectors.

The Harley fuel rail is plastic. If you try to disconnect the fuel line from it, it comes off VERY hard and will most likely break the nipple off the fuel rail. The 2020 & prior fuel line is a poor design and was updated in late 2020.

Instead, disconnect the fuel line from the fuel tank and leave it connected to the fuel rail when you are unbolting it from the manifold.

OR, replace the fuel rail with an aluminum unit like found here:

NICECNC Fuel Injector Rail Fuel Rail Kit Compatible with Harley Road Glide Road King,Street Glide FLHX/Special FLHXS 2017-21, Electra Glide,CVO Ultra Limited FLHTKSE 2017-21,See Fitment(Black) https://a.co/d/fEfX9dE

It won’t work with the old style fuel line however and will leak. You’ll need to order the new fuel line part number 61200022A. This is what I’m putting on my bike.

Thank you HDUSA1 for your information and sharing of such. Very important information especially concerning the fuel lines! The news today is the the Motor Company is in possible dire financial condition. Our bikes were built years prior to today's financial environment yet back then, as today, saving a few dollars to the Corporate bottom line causes we the buyers to spend out of our own pockets to correct the $$$ savings that apparently was squandered in other endeavors..i.e. Livewire. Billions spent for ????....sales of Livewires yet to reach into the thousands! Acura built the latest version of the famous NSX at a net loss of over $100,000 per unit. Honda can afford such a costly plaything. H-D cannot. Below information copied and pasted for possible review.

In 2024, LiveWire Group, Inc. sold 612 electric motorcycles, which is a decrease from the 660 sold in 2023, while also experiencing a decrease in overall revenue. However, they are forecasting increased unit sales between 1,000 and 1,500 in 2025.

Here's a more detailed breakdown of LiveWire's sales and financial performance:
2024 Sales & Revenue:

• EV Motorcycle Sales:
  LiveWire sold 612 EV motorcycles in 2024, a decrease from 660 in 2023.
  
  
• Consolidated Revenue:
  LiveWire's consolidated revenue decreased to $10.8 million in 2024, compared to $38.0 million in 2023.
  
  
• • Operating Loss:
    LiveWire's operating loss was $110 million in 2024, which was $7 million less than the prior year and in line with expectations.
  • Q1 2024 Sales:
    LiveWire reported an 86% sales increase in Q1 2024, with 117 electric bikes sold compared to 63 in Q1 2023.

 

[Old Road Dog]

I installed the S&S manifold a couple years ago. Wow! 50% more torque and 100% more horsepower! I fly over potholes. I can wheelie my trike across parking lots and power slide up to the coffee hooch. OK I lie. Can't tell any difference but you know that plastic really dosnt belong on an HD motor..deep down you know. Just like those stupid anti rotation lifter cuffs are replaced with S&S billet cuffs. On the shelf sits a S&S billet fuel rail 160-0280 ( Fuel Moto $116.95)and a HD 61200022A fuel line. I'll get around to installing them as soon as I'm done installing more barrels of foogas on my hilltop fire and interdiction support base. I'll fix those dang chicken thieves.