What are some of the engine mods that are proven for an '88 ElectraGlide Sport with an 80". I bought it with aftermarket pipes, S&S carb and the Mikuni Pass-A-Truck cam, other than that it's pretty well stock. I was hoping that some of you would have some ideas that worked for you. Thanks.

 

You,re probably pushing 73 hp rght now...head work should get ya up to 80-85 ...then, reliability becomes an issue. imo

 

Checking and adjusting Deck Height, milling the heads and setting the quench are easy and cost effective performance mods for an EVO engine. Add to that ported heads and a good cam and you might be a little surprised how well an 80" EVO can perform. If you don't go radical with the cam (ie bolt in), it will be a very reliable build.

Here is thread that talks about most of the above .... https://www.hdforums.com/m_245806/tm.htm

 

You've already got the best mods for your bike. I'm sure that Mikuni cam is an EV 13 which keeps your power down in the rpm range where it's needed, especially in a heavy bike. Actually didn't that pass a truck kit come with a Mikuni carb? Anyway, you can stroke that engine out to 88" with no significant change in realiability. Along with headwork and maybe better pipes (without knowing what you've got) that's all you should need to have a sweet running bagger.

 

Does stroking an 80" to 88 involve just boring of the cylinders and a piston change and no change to the case? I've been told by someone else to skip head work and get hi compression pistons, but have also been told that with the weak starters that this creates an issue. I'm dreaming about a combo of all those possibilities, i.e., boring to 88", installing hi compression pistons and a polish and port and then a hi torque starter, what say you?

 

Stick with the stock pistons and shave the heads, and use a .030 head gasket. You'd be well advised to keep the compression ratio below 10:1 or you will have problems. You won't need to use compression releases and you can keep the stock starter. You will also get a lot of detonation if the CR is too high, even with 93 octane gas. Domed pistons are not as efficient as flat tops when using stock-style heads. You want to shoot for a "squish zone" of about .030 inch. That's the area next to the combustion chamber between the head and the top of the piston. This is important for proper combustion. Head work will make a HUGE difference in performance! If you can afford it, do it! There's a shop near here that does it for $300 a set.

Here's what I've done to my most recent ride, an 80 inch 1995 Dyna. It's putting out 92 ft.lbs and 89 HP

S&S Super carb w/ Yost Power Tube (eliminated the off-idle hesitation)
Dyna 2000i ignition with custom advance curve
Vance & Hines Pro-Pipe HS w/ tuned baffle (3 different 2-2 systems I tried caused me to lose a lot of low end torque)
Heads ported and flowed
Comp Cam valve springs w/ titanium collars
S&S adjustable pushrods (not the EZ install)
Stock lifters
Black Diamond valves (stock diameter) with 5-angle cut
Heads set up for .600 lift cam
Currently using EV27 cam, but will be switching to Woods W6H soon. This should push me over the 100 ft lbs mark
Heads shaved .070
.030 Cometic head gasket
Stock pistons
This results in a compression ratio of 9.98:1, static pressure is 195 psi
Energy One racing clutch (extra-plate) with heavy duty spring ($90.00 from energyoneclutches.com)
-These are the same clutch plates used in Rivera's racing clutch kits. It costs a lot less to buy them straight from the manufacturer

And of course, a good dyno-tune by an experienced tuner is mandatory if you want to get the most out of the engine

The engine pulls strong from idle on up to about 5200 rpm, then the torque gradually drops off until 6000, then levels out until 6500
Torque starts at 75.5 ft lbs at 1500 rpm, then goes up from there. NO DIPS, thanks to the Pro-Pipe exhaust!
0-60 times average 5.2 seconds at 190 feet elevation and 72 deg. F.

The head work will not cause reliability problems, but increasing bore and stroke might, in the long run

The Woods cam will make a huge difference in torque due to it's .590 lift and 240 duration. Roller rockers are recommended, but not necessary. It's about the best hi-torque cam on the market, but is a bit on the noisy side.... not that it matters to me. I like to hear the engine working . Even the EV27 ticks like crazy, but it runs great!

I was tempted to go with a big bore kit, but decided against it since there are other (and cheaper) ways to get torque numbers over 100 on an 80 incher. It just takes the right combination of parts and careful tuning

I'm happy with it, especially since I have no trouble pulling ahead of any stage 2 Twinkie. All that torque is really helpful up here in the mountains I almost never need to downshift when climbing a hill or passing someone.

 

Stroking means extending the amount of travel of the pistons and requires replacing the flywheels and has nothing to do with boring the cylinders.

The stock EVO cylinders can't be bored out to obtain 88". You would need Big Bore cylinders and that requires boring the cases to make them fit. The stock cases aren't really thick enough to hold up in the long run IMO. This is especially true from 92-93 and up model years. Your '88 cases could handle it but I don't recommend it.

The thread I mentioned above explains how to obtain the correct squish and resolve base gasket leaks. Then milling your heads to obtain a desired compression ratio.

Although I am Biased, I believe the Heads are always the first step in a performance upgrade.

Feel free to ask any questions and I would be happy to clarify any of the above points.

 

springer, you're probably going to get sick of me asking questions, more than likely ones you've answered a million times, and I'll totally understand, but I'm going to keep asking. I get the whole working heads in order to increase flow and change compression ratio and I followed the thread that you referred to, but I'm a little lost on how it is determined what the proper squish measurement is. The thread explained how to mill the cylinder to recreate the previous squish measurement, but how do you know that's where it should have been in the first place. Is this the "zone" that Spectrexx is talking about and is .030 just the magic number that creates the best combustion. If that's the case, than doesn't milling of either the heads or the cylinders change this and if so, which is the better route to go. I'm almost positive that I've seen machine shops on the net that will do head work requiring just the head to be shipped to them. Now with that possibility, wouldn't they need to know my piston to top of cylinder measurement at TDC in order to do the best job. I really appreciate everyone's input. I don't want to go overboard, but it's fun to know where you stand in the order of what next to do.

 

Keep firing away with the questions and I will answer any that I can.

The consensus is that .030"-.035" is the ideal squish.

There are several things that need to be considered when setting the squish area. The first is deck height, we'll assume your piston sits .015" Below the top of the cylinder. Using a stock head gasket at .045" on top of the cylinder and then bolting the head on, places your piston .060" away from the bottom (squish area) of the head.

Now if you mill the head, the bottom is still going to be .060" away from the top of the piston (.015" + .045"). So milling the head doesn't effect squish at all. Thats the first thing to understand.

Next, the stock head gasket is .045" thick. If you want a squish of say .030" then the piston has to actually go .015" into the head gasket. In this example the piston sit .015" Below the top of the cylinder at TDC. And we want it to sit .015" ABOVE the top of the cylinder at TDC. This would place the top of the piston .030" away from the squish area on the head. To achieve this the cylinder needs to be shortened .030".

As mentioned above, you could use a .030" head gasket. If that was the case you would NOT want the piston to sit above the cylinder or it would be too close to the head. You would want the piston to have a 0 deck height (flush with top of cylinder). Zero deck height plus .030" head gasket yields a .030" squish.

When we build engines we try to do it for the most convenience of the customer. What I mean by that is to build an engine that anyone can work on and anyone can get parts for. This is especially handy if you should be on a road trip and have some sort of break down. Example, using the stock head gasket instead of a .030" special order head gasket. If you are 500 miles from home and you blow a head gasket for whatever reason, you are probably near a Harley Dealer. The Harley dealer will most likely have the stock head gasket on the shelf or some local indy shop will. The chances of finding the stock gasket are MUCH better than finding a .030".

As stated above, milling the heads does not effect squish area. Milling the heads only adjusts the size of the combustion chamber. Once the deck height and head gasket thickness is known, you can adjust your combustion chamber size to obtain a desired compression ratio. You don't have to do all of this. You can just mill the heads and increase you compression and run a thinner head gasket and not have the "ideal" squish. But turning the base of the cylinders is a good idea to help prevent base gasket leaks. If you are going to turn them anyways, why not correct the deck height as well and get everything to its best possible spec? IMO, this is simply paying attention to detail. This can maximize your build potential, be cost effective, reliable and easily worked on by anyone using stock HD parts that are readily available.

 

Sweet, believe it or not, I'm actually understanding this. I've rebuilt a couple of engines in pickups, but most of that was follow the book kind of stuff along with replacement of some bolt on performance parts, so not alot of spec build experience. I can understand why you have your opinion on cylinder base milling. What is a typical off the assembly line squish measurement on an Evo and how do you determine how much to mill off of a head to acquire a desired compression ratio? Thanks again for your patience.

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