Tech: 45 tuning for speed - The Jockey Journal Board

Go Back   The Jockey Journal Board > The Archives > Tech Archives

Reply
 
Thread Tools Search this Thread Display Modes
Old 08-31-2007, 04:38 AM   #1
sLowrider
Senior Member
 
sLowrider's Avatar
 
Join Date: Jun 2006
Location: North of England
Posts: 1,041
Default Tech: 45 tuning for speed

Harleys baby twin, the 45, is a rugged workhorse in standard trim. Built to War Department specs it's in a very low state of tune and has a rugged bottom end, therefore it can be pursuaded to perform a lot better at little expense and with no loss of reliability.

Here's a brief run-down of what I did to the engine in the Jive Bomber. If you can use machine tools the work is very simple. If not, a good machine shop should be able to do this work for a reasonable cost. The main areas to cocentrate on are:

Setting the squish and compression.

Porting and relieving the cylinders.

Valve train.

Fuel/exhaust system.

First, obviously, make sure you are starting with a healthy motor. The first simple tuning step is to set the squish - the distance between the piston crown at TDC and the cylinder head surface. This distance is critical for getting flathead motors to perform well. Opinions vary but I feel that a good squish for a street motor is .035". I measured my stock squish by bolting the cylinders to the cases (don't forget the base gasket) and using a dial gauge to measure the distance between the piston crown and the cylinder deck, then added the thickness of the copper head gasket (usually around .018" to .022"). In stock trim mine measured .085" front and .075" rear!!! Clearly some room for improvement.

To set the squish I mounted the cylinders in a Bridgeport mill and milled off the required amount from the gasket face - don't forget to subtract the measured thickness of your head gaskets from your calculations.

Next the heads. With #5 heads there are some complicated calculations you can use, after relieving the cylinders, to arrive at the optimum amount to shave off the heads, but a good rule of thumb is to remove .120" to make them #6 spec - as fitted to the WLDR Sport Solo. Don't be tempted to remove more, street flatheads don't like high compression as it interupts flow. You can use the mill again to shave the heads but I used a 4 jaw chuck in a suitable lathe.

Last edited by sLowrider; 08-31-2007 at 06:17 AM.
sLowrider is offline   Reply With Quote
Sponsored Links
Advertisement
 
Old 08-31-2007, 05:08 AM   #2
sLowrider
Senior Member
 
sLowrider's Avatar
 
Join Date: Jun 2006
Location: North of England
Posts: 1,041
Default Re: Tech: 45 tuning for speed

The next step is to port and relieve the cylinders. This is where you really improve flow and get that thing spinning. You will need a die grinder (air or electric), a set of porting tools (stones and emery's) and a carbide grinding bit (I found that a 1/4" dia bit with a rounded end worked best). For a street motor you don't want to remove too much metal from the ports, just smooth out the rough cast finish with the stones and emery's and smooth out the short side radius (the 'roof' of the inlet port where it turns sharply up to the valve seat).

Now for the BIG one - relieving. This is the oldest trick in the book for tuning flatty's. What you are aiming for is to relieve the area around the valve seats to get the gas flowing into and out of the cylinders quicker. Trace round the inside of a head gasket on to the gasket face of your cylinder. This is the absolute limit of your reliefs! However, you will notice the V shaped 'fence' between your valves? (see pics). You must not remove this as it is critical for maintaining 'swirl' and cylinder scavenging. You are aiming to grind off material between the valve seat and the cylinder bore, on the same plane as the valve seat (remember the valves are not set in the cylinder at the same angle as the bores - 12 degrees out I think). The reliefs, when viewed from the cylinder bore, should be deeper on one side than the other but should be a constant depth all the way from the valve seat to the cylinder bore (see pics) Aim to get a 'mirror effect' by working on both cylinders at the same time. The limit of the depth of the reliefs is the top edge of the valve seat but any metal removed will dramatically improve flow. Use the carbide bit to rough out your reliefs then smooth them with the stones and emery's. You may not get a perfectly polished finish but try to do your final polishing in the direction of flow.

Go easy with the die grinder - those carbide bits will cut through cast iron like cheese and please wear eye protection!

To check your 'mirror effect', clean and remount your cylinders on the cases. With one piston at TDC and the valves fitted, fill the relief/area above the piston with Spackle Clay/Plasticine and level it off with a straight edge, a steel rule etc. Remove the clay, roll it into a ball and drop in to an accurate measuring cylinder with a measured amount of water in it. Measure the displacement and repeat for the other cylinder. You are aiming for no more than 5% difference between each cylinder.
Attached Thumbnails
Click image for larger version

Name:	Afbeelding015 (Small).jpg
Views:	949
Size:	51.3 KB
ID:	20176   Click image for larger version

Name:	relieving-07.jpg
Views:	828
Size:	31.1 KB
ID:	20177  

Last edited by sLowrider; 08-31-2007 at 06:19 AM.
sLowrider is offline   Reply With Quote
Old 08-31-2007, 05:35 AM   #3
sLowrider
Senior Member
 
sLowrider's Avatar
 
Join Date: Jun 2006
Location: North of England
Posts: 1,041
Default Re: Tech: 45 tuning for speed

Next we'll look at the valve train. First the valves themselves. There are a number of options for bigger inlet valves - KNS, Chevy etc, but as we're trying to keep costs down the stock valves can be improved quite a bit. Also, the big valves only work properly with a bigger inlet manifold (Model U) which involves some complicated machining.

Anyone who has stripped a 45 motor will have noticed that the valves are BIG, like big enough to use as door stops! If they're big, they're heavy - if they're heavy they take more force to open and are more likely to bounce at high revs. By machining the back of the valve heads a considerable amount of weight can be removed and flow can be improved. Mount the valves in a lathe, centre drill the heads and use a fixed centre to support them. Then with a tungsten carbide tool take a back cut off the heads. From the lowest edge of the valve face make a 7 degree cut (inlet) or 11 degree cut (exhaust) until it nearly reaches the valve stem (about 1mm off is fine). Use a fairly slow cutting speed as valve steel work hardens as it's machined - and use plenty of coolant (it might still squeal a bit). Radius the join between the stem and the cut using a coarse round file and finally polish with emery. You want a smooth finish with no grooves - 'stress risers' - that can cause failure. (see pics).

It is possible to reduce the width of the valve face and do the same to the valve seats in the cylinders but this may advesely affect the life of the seats.

Some more weight can be removed from the valve train by grinding out the centre boss from the cam followers (you can see Mert Lawell doing this in 'On Any Sunday') and drilling the valve spring keepers.

Finally the cams. Unless you change your carburettor these are the only components where you need to dig your hands in your pockets. If you can obtain a NOS set of WLDR cams cheap - go for it (unlikely). Otherwise get a set of repops from 45 Parts Depot etc. There are wilder cam profiles available but they involve sending your cams off to Leinweber or someone similar and the consequent waiting period. I found the WLDR cams worked well for me. Time them as standard.
Attached Thumbnails
Click image for larger version

Name:	Afbeelding021 (Small).jpg
Views:	575
Size:	41.0 KB
ID:	20178   Click image for larger version

Name:	Afbeelding024 (Small).jpg
Views:	614
Size:	40.2 KB
ID:	20179   Click image for larger version

Name:	Afbeelding026 (Small).jpg
Views:	687
Size:	46.4 KB
ID:	20180  


Last edited by sLowrider; 08-31-2007 at 06:21 AM.
sLowrider is offline   Reply With Quote
Old 08-31-2007, 05:52 AM   #4
sumo
Senior Member
 
sumo's Avatar
 
Join Date: Jul 2006
Location: dunstable ENGLAND
Posts: 1,077
Default Re: Tech: 45 tuning for speed

fuck - a propper in depth tech with some real tech details

thanks johnny you rule [printed for when i get round to it some time when my 45 manages to make first project status again...]
__________________
Biltwell Parts, Helmets & Four Aces Triumph Rebuild DVD
now available in England!


Check out VintageChop.com
sumo is offline   Reply With Quote
Old 08-31-2007, 06:00 AM   #5
sLowrider
Senior Member
 
sLowrider's Avatar
 
Join Date: Jun 2006
Location: North of England
Posts: 1,041
Default Re: Tech: 45 tuning for speed

The last step is the fuel and exhaust systems. I'll include the inlet manifold here too. The inlet manifold should be polished internally and you should try to radius the area where the manifold splits to each cylinder. The smallest restriction in the inlet is the inlet nipple. Open this up by boring it to around 32mm.

Linkert carburettors can be made to perform well, they are very simple devices that perform some very complex functions but they do seem to pour fuel into your cylinders. I used a 32mm Amal MK1 Concentric and I get around 65 MPG from the hot motor while my mate gets around 35 -40 MPG from his stock Linkert equipped 45. Useful if you're running a peanut Wassel, Sporty tank or similar. I had to make a simple adaptor to fit the Amal 2 bolt flange to the Linkert 3 bolt manifold.

Jetting for my Amal is 160 needle jet - needle clip in the bottom groove/#3 slide/240 main.

Finally the exhaust. The ideal exhaust system should be 1.2M from the valve face to the end of the tailpipe. This means loooong shotguns. I went for form over function and used high/low cocktail shakers. I could only get 1 5/8" inlet shakers at the time so I had to make larger diameter headers (standard is 1 1/2") and sleeve them down to fit the 45s ports. They look good, sound like I've got a much bigger motor and seem to work well. My rear cylinder, with the short pipe, runs slightly leaner but it's still perfecly acceptable.

Right then, put it all back together as per 'the book'. Break it in if you need to and enjoy. I found that, with this work, power was similar up to about 1/2 revs then it comes on the cam, takes off like no stock 45 could ever hope to and smooths right out. It loves to rev now and, with the Trump tranny I've used, gives a cruising speed of around 70mph and a top whack of about 85-90.

If you're considering doing this you should really get hold of the Victory Library booklet and I'd be happy to answer any genuine enquiries I haven't room to cover here via PM.

Flatheads Forever

Cheers Johnny
Attached Thumbnails
Click image for larger version

Name:	DSC_0101 (Small).JPG
Views:	539
Size:	39.9 KB
ID:	20181  

Last edited by sLowrider; 08-31-2007 at 06:23 AM.
sLowrider is offline   Reply With Quote
Old 08-31-2007, 06:31 AM   #6
wgemeinhardt
Senior Member
 
wgemeinhardt's Avatar
 
Join Date: Jun 2006
Location: New Jersey
Posts: 334
Default Re: Tech: 45 tuning for speed

Great article! Thanks!
wgemeinhardt is offline   Reply With Quote
Old 08-31-2007, 06:48 AM   #7
chopperking
Senior Member
 
chopperking's Avatar
 
Join Date: Aug 2007
Location: zurich, switzerland
Posts: 346
Default Re: Tech: 45 tuning for speed

Quote:
Originally Posted by wgemeinhardt View Post
Great article! Thanks!
couldn't agree more. thanks a lot.
see ya
chopperking is offline   Reply With Quote
Old 08-31-2007, 07:20 AM   #8
45Brit
Banned
 
Join Date: Jun 2007
Location: UK
Posts: 377
Default Re: Tech: 45 tuning for speed

Fran-6 from Milwaukee Belle told me that the #6 heads plus KNS inlet cams and valves were the best value tuning you could do, in terms if what you got for the outlay and work required.

I have also seen it written in several sources that most tuned 45s are over-carbed, and Amals down to 26mm will work equally well and give better flexibility - anyone know anything about this? I would suspect this is probably true for motors in street trim, I have seen a couple of fast Norton 16H's running around the vintage bike scene ( one was at Red Marley last year ) and they have 1 1/8" Amals. My 350cc JAP grasstrack bike only has a 28mm ( 1 1/8" ) carb and the 500cc speedway engines used 32mm ( 1 1/4" ) so I would guess that that same would apply to 45s.

long exhausts is right. Extractor effect is very valuable. My 45 project has an exhaust based on a suggestion in one of the Victory books, viz a Paughco drag front pipe, stock rear, panhead y-piece ( to give the same area as the combined front pipes ) and panhead silencer. The whole thing is as long as the bike will stand, which in fact makes it about 50" for the front cylinder, a bit less for the back. Don't know how it performs yet

Most people seem to agree that Amals give better fuel consumption than Linkerts. That wouldn't really be hard!

I would guess that smaller diameter pipes would give you more flexibility for no power loss, but whether you would really notice on the road, is hard to say.
45Brit is offline   Reply With Quote
Old 09-02-2007, 10:27 AM   #9
sLowrider
Senior Member
 
sLowrider's Avatar
 
Join Date: Jun 2006
Location: North of England
Posts: 1,041
Default Re: Tech: 45 tuning for speed

Only downside with the Amal, as I was reminded this morning, is that they do like to suck in water -"cough, splutter, fart"! At least they're easy to drain and a bit of WD40 gets you going again.
sLowrider is offline   Reply With Quote
Old 09-02-2007, 12:19 PM   #10
Bonzer
Member
 
Join Date: Nov 2005
Location: Engerland!
Posts: 75
Default Re: Tech: 45 tuning for speed

This is gold dust! I'm still trying to work out the best way to do something similar to my Big4. I've read tuning for speed and seen the victory stuff. Very useful. Though actually having first hand advice is good. With the exhaust lengths, is that a value specific for the 45? Same with the squish, as my piston has a slight dome (I assume the 45's are flat?) Other plans i was considering were; 26mm Mikuni (bigger?), compression up to about 6:1, opened up the ports and polished. Cams are normal.
Bonzer is offline   Reply With Quote
Old 09-02-2007, 01:12 PM   #11
45Brit
Banned
 
Join Date: Jun 2007
Location: UK
Posts: 377
Default Re: Tech: 45 tuning for speed

there are a couple of very quick Norton 16H on the vintage scene. One of them comes to Red Marley sometimes.

the exhaust length you can calculate from "Tuning for Speed" if you can find a copy, but as a general comment 40" will do you quite well for a whole range of 350cc - 600cc cylinder sizes up to about 6000 rpm.

again as a general comment, by the time you get past 6:1 you will be running into problems with masking of the inlet, and valve to head clearance issues

look at the KNS site and you will find lift and dwell values for UL big twins, which are a similar cylinder size. More "cam" on the inlet is usually the way forward with sidevalves, the inlet depression is lower than on ohv motors. Most 1930s designs are too big on the exhaust anyway, ohv or sv.

squish is a general comment on sidevalve engines. Most of these engines are made to fairly wide tolerances and will benefit from being "tightened up"

slowriders' valve pocket relief pics are worth having, what he has done seems to work. Nortons will be easier to understand because the valves are both parallel to the cylinder bore, which on a 45 isn't so and it's important that this is allowed for.

most fast sidevalves have big carbs, but once the carb is bigger than the inlet port you aren't going anywhere useful.
45Brit is offline   Reply With Quote
Old 09-02-2007, 03:24 PM   #12
Richard D
Senior Member
 
Richard D's Avatar
 
Join Date: Mar 2007
Location: Texas City, TX
Posts: 1,311
Send a message via Yahoo to Richard D
Default Re: Tech: 45 tuning for speed


Quote:
Originally Posted by sLowrider View Post
with the Trump tranny I've used, gives a cruising speed of around 70mph and a top whack of about 85-90.
How about a tech article on the trans swap?
Richard D is offline   Reply With Quote
Old 09-02-2007, 08:53 PM   #13
hectorville
Member
 
hectorville's Avatar
 
Join Date: Jul 2007
Location: Tulsi-town
Posts: 33
Default Re: Tech: 45 tuning for speed

+1
hectorville is offline   Reply With Quote
Old 09-03-2007, 11:04 AM   #14
sLowrider
Senior Member
 
sLowrider's Avatar
 
Join Date: Jun 2006
Location: North of England
Posts: 1,041
Default Re: Tech: 45 tuning for speed

Tech on the gearbox might not be much use to you fellas thinking about putting one in your 45s. Reason being my frame uses the lower rails from a Triumph Pre unit rigid - the rest's home made. This made alignment of the engine/gearbox simple. All I had to do then was ensure the engine was roughly aligned and all true, then machine a harley taper sprocket hub and bore/weld a Triumph engine sprocket to it. For details on fitting a Brit gearbox in a 45 frame I'd check out 'British Transmission Ideas' from Victory Library. Here's some pics anyway. Bike's filthy from a big ride out at the weekend.
Attached Thumbnails
Click image for larger version

Name:	DSCN0288 (Small).JPG
Views:	336
Size:	53.4 KB
ID:	20293   Click image for larger version

Name:	DSCN0289 (Small).JPG
Views:	316
Size:	58.1 KB
ID:	20294   Click image for larger version

Name:	DSCN0290 (Small).JPG
Views:	302
Size:	50.6 KB
ID:	20295  

Click image for larger version

Name:	DSCN0291 (Small).JPG
Views:	313
Size:	57.8 KB
ID:	20296   Click image for larger version

Name:	DSCN0293 (Small).JPG
Views:	317
Size:	57.6 KB
ID:	20297   Click image for larger version

Name:	DSCN0292 (Small).JPG
Views:	351
Size:	56.6 KB
ID:	20298  

sLowrider is offline   Reply With Quote
Old 09-03-2007, 09:21 PM   #15
hectorville
Member
 
hectorville's Avatar
 
Join Date: Jul 2007
Location: Tulsi-town
Posts: 33
Default Re: Tech: 45 tuning for speed

Thanks ,I'm leaning toward using a big twin frame. since I have an old 70's Paughco in decent shape. I've got a late model norton left hand shift tranny...One piece at a time...
hectorville is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


All times are GMT -5. The time now is 05:05 PM.