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Honda Goldwing engine modifications to fit it into a 1965 Hillman Imp car.

46K views 355 replies 24 participants last post by  yoeddynz 
#1 · (Edited)
Hi all,

Down here in New Zealand I own this little 1965 Hillman Imp that I restored from Feb 2018. I am now looking into the possibilty of fitting a 1990 Honda Goldwing GL1500 engine to potentially build my very own baby 911 :)

This is my Imp...

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Here's the Datsun 1200 engine currently fitted...

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My plan is to remove all of the transmission and most of the drive gears from the casing. I have been looking over my Honda workshop manual and have pretty much nutted out the engineering that I'll need to do . However- before I commit I need to find out a couple of things. I thought I would ask on here and hopefully someone here will have a stripped down engine that they can get me some measurements from.

First thing I need to check is the thickness of the flange on the crank that the alternator drive gear bolts to. It takes 6 bolts. Also- what size are the bolts? They look like they could be 10mm? This is all important because I'll be machining a boss to bolt onto this flange and those six bolts will take the loading of a custom flywheel.

Here's a shot of the crank flange I need to know the thickness of...

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Another question. What is the measurement from the centre of the crank to the bottom of the engine. This is important to work out just how far the sump will hang from the back of my car once installed.

I'll be back soon with more questions I'm sure !

Cheers
alex
 
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#9 ·
Yeah this is one of the reasons I'm excited about the prospect of having a GL1500 up the backside of my car. Apart from the sound and smooth performance its also the reliability I like the idea of.

I do have the Honda service manual but it doesn't mention the thickness of that flange anywhere because its not an item that wears etc. So I have to rely on asking others.
I have asked a question on a Ebay listing for a crankshaft and await an answer from them....
 
#10 ·
Rear wheel drive? Where is the radiator going to reside? Someone with access to a machine shop should be able to handle the job.
Yeah rear engined. Radiator is up the front. Ive got the machinary (that's my trade) but need to suss these things out before I commit to an engine I've been offered.

I tried adding a link to my restoration and build thread into this thread but this forum platform wouldn't allow it?
 
#13 ·
Well yesterday I picked up this ....
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I was a very excited chap and quickly unwrapped it....

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It handily has come with this manual...

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Plus I picked up another Subaru box that might come in handy, this time from a 1600 Leone...

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So tomorrow I will start the strip down and assess what I will need to modify within the goldwing engine.

One thing I have already noted is how tiny the inlet tracts are and the exhaust headers! When it comes to re-fabricating that lot I'll certainly be making it all so the engine is allowed breathe a lot easier :) Throw six itbs and full bespoke engine management in for the party.

I'd love to know what other 1500 owners on these forums, well the ones who have played about with the performance side of their bikes, have done with there exhausts ?

Also- out of interest at this point in time (due to money ..lack of it) are there any after market camgrinds available for these engines- ie for the cafe racer modification type folk?

Cheers
alex
 
#15 ·
Mother Honda has designed the intake/exhaust system to work very well. Even altering the air filter box can lessen performance. Without hogging out the ports I expect a good cleaning,smoothing and polishing the ports could be helpful.
There have been some exhaust modifiers. Torque loops come to mind.
I don't have an awareness of camshaft grinds from aftermarket but that is possible. There was one fellow who was working on a fuel injection system . As I recall, after he began the tuning phase of that work he didn't keep updating his posting.
It is quite common on the four cylinder wings that 4 carbs were replaced with single one and two barrel carbs. In your application you may have space to experiment that way .
 
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#16 ·
Yeah compared to the goldWing location I have loads of space above the engine. I'll post a pic later.

I'm not fussed about chasing big power but if I can get extra easily in my process of converting to efi and itbs then it's a bonus :) the extra torque and hp this engine already had over the Datsun engine I currently have fitted is going to make for lots of giggles anyway :) more then anything it will be the flat six sound in looking forward to most!
 
#17 ·
I think what he's saying is that bigger bore intake and exhaust pipes will probably not add performance, and may very well reduce it. The exhaust system in particular is probably tuned for a particular velocity of airflow that you won't get with a bigger pipe.
 
#18 ·
Ahhh yes I see what you mean. Certainly not much of an advantage if I don't touch the ports /valves or cam profiles.

I've looked on the Internet and there seems to be next to no info on hotting up these engines - this I attribute to the goldwings being perfectly suited to their job already and most riders not for want of any extra power?
 
#19 ·
Russ Collins used to make hot rod parts for them, but that was long ago.
Yeah, most riders would only want to increase peak torque, and Honda pretty much got a bullseye on that.
However, speed is just a question of money, how fast can your wallet go? There have been supercharger installs, or you could do a turbo. For drag racing there is always the bottle.
For a reliable daily driver I would just go with EFI and pretty much leave the rest alone. The stock tuning will be close to ideal for a lightweight car. (1500 pounds or so would be great)
 
#20 ·
Remember that each cylinder is only 250ccm and dosnt need much air in or out . ( the redline on these engines is around 6.000 rpm. ).
I know that the Valkyrie has 6 carburators and i THINK the camshafts are a little "sharper" .
The EFI project could lighten your wallet WERY much ! , - i vould go for the OEM GL1500 carburators .
 
#22 ·
The EFI project could lighten your wallet WERY much ! , - i vould go for the OEM GL1500 carburators .
Efi is soooooo much cheaper today. My last full standalone efi conversion job in my Vauxhall Viva cost me around say $750 NZD. That was using a $500NZD Megasquirt 2 ecu I built. This time round I'll be using a Speeduino ecu. I've started building it and if one is good at looking for deals on components you can build a working ecu for between $100-150NZD.
The most expensive one off purchase is a wideband controller for tuning, which are now available much cheaper from companies the likes of 14 point 7.
Most other parts used are just secondhand bits from various cars and bikes. I'll be on the look out for some small efi itbs to suit the tiny goldwing inlet ports. Otherwise I'll make or adapt something. Remember that this is a project I'm doing for fun with no urgency. We are now in a 4 week lockdown here in NZ so I have plenty of time in my workshop to use :)


AFIK, there has only been one successful EFI conversion to a gl1500, it was posted on this forum.

Thanks for the link- I'll check it out. Hopefully you'll see another succesful conversion soon :)

Update time- the engine is now being stripped down. Already its looking neater. I'll give the outside a good clean before I strip it further. A good sign is very little buildup and muck behind the valves suggesting a healthy low mileage engine. But time will tell. (I think the previous owner had bought a crash damaged bike and that was about 20 years ago!) I had seen videos of it running just before being pulled out and it sounded great.

There is so much that wil be removed/cutoff over the coming week once stripped. I shall weigh it today and then again once its at the point I want it- just a short height crank case and heads. Lots of fabrication to do after that!
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#21 ·
AFIK, there has only been one successful EFI conversion to a gl1500, it was posted on this forum.

 
#26 ·
Well I'm doing my best to continue on with what steel/alloy and other bits I have in stock. Most places here are shut due to the lockdown so I'll just do the bits I can. Next step now that its in pieces is to machine up a hub and shrink fit it onto the crank flange, so helping the 8mm bolts there deal with torsional stress from a flywheel.

While I still had the Datsun engine removed from my imp due to it needing a new rear main seal and ring gear I took the chance to size the Goldwing engine place. It looks fantastic, sits really low and quite far forward while allowing for the subaru box...

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#28 ·
Been following the progress, that fits in there very nicely!

Just thought I'd chime in here since the thought occurred to me, as sometimes we "Overlook the Obvious". We've all done it at one time or another, myself included!

Does the Goldwing engine run in the same rotational direction (CW vs CCW) as the original engine? If not, you'll find yourself with a vehicle that has a single forward gear and four reverse speeds.... This, too, can be overcome but it would present additional project design challenges...
 
#29 ·
Hi there. Yeah good question and one I'll get a lot.
Goldwing engines, like most pre 2000 Honda car engines, rotate anti-clockwise(counter - cw for you stateside folk) . Originally when I looked at the idea of fitting one a couple of years ago this fact put me off. I was to use either the imp transmission or a stronger vw box.
However, by taking a longitudinal transaxle from a front wheel drive car, in this case a very common subaru box, and turning it around 180 degrees it counteracts the anticlockwise rotation of the goldwing engine :)

Don't worry.. I've bench tested it just to be sure.

Also and very luckily the action of the subaru gear selection rod matches the imps gearstick action perfectly due to the fact that the two cars have differently opposed pivot points on their gear sticks. It would have been an easy fix but luckily I don't have to :)
 
#31 ·
Hi there. Yeah good question and one I'll get a lot.
Goldwing engines, like most pre 2000 Honda car engines, rotate anti-clockwise(counter - cw for you stateside folk) . Originally when I looked at the idea of fitting one a couple of years ago this fact put me off. I was to use either the imp transmission or a stronger vw box.
However, by taking a longitudinal transaxle from a front wheel drive car, in this case a very common subaru box, and turning it around 180 degrees it counteracts the anticlockwise rotation of the goldwing engine :)
The rear engine VWs you could just change the differential from the left to the right. People did that to make mid engine buggys. They changed it so only one side came off sometime in the 70s.
 
#30 ·
Well, sounds like you've already addressed the rotation question, the only other thing I can think of is transaxle lube. These don't have a pump, so no issue there, but since you'll be running it "Backward" (opposite of design rotation) there is the potential of lube issues. These run on splash lube, but lube will be flung in opposite directions from design. You might consider slightly overfilling the transaxle lube to help compensate....

Good Job! :) :)
 
#32 ·
Are you talking about the Subaru transaxle? Yeah I think it should be ok because the shafts run in the oil and it'll be getting thrown up all over the place in there :) A neat feature of these transmissions is that they have a dip stick as well- makes for quick easy check that the axle is up to the correct level . I could also certainly overfill it through the dip stick if I felt the need to .
 
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