The engine rebuild

brad black

the throttle body bore of 50mm has a throtle blade in it, maybe 2mm thick and a shaft 7mm thick at a guess. the actual flow area, assuming nothing about disturbance, is equivalent to a 45.3mm hole.

748 outlet is 44mm, 916 and 996 46.5mm.

got2dv8

thanks Brad.. that means I could (have) pick up a pair of tb's from a 916/996 to use on my 851 project and not have to bore out the 748 tb's... Of course i read this after an auction ended for some S4 tb's.. bummer

Robert

griff851

Valve /port completed

I got the heads back today and here are some pics of the finished job. The seat to the port is pretty much like a 748rs, a continuous wall. The valve dia to port ration is 88.2 .Well with in that Mondello bloke's reckoning of how things work. The Inlet valves now sit all most totally flush with the deck of the head, the exh just slightly below. The valve shroud was also dealt with a tad more than i had done, where the first angle continues on to the seat itself. I hope this all works the way its supposed too now.

Griff

RED

Nice heads Griff. I think you will be quicker with your project.

A pic of my heads

griff851

Red, it all just slowly comes together.
The other day I started re-assembly of the heads. Due to a lack of new half rings I decided a practice run on one head was in order. First fitted new valve guide seals, then I bearing blued the valve seats and check to ensure the newly cut seats were Ok. 1.05mm on the exh and 1.35mm on the inlets with full contact.
Then I fitted the lower arms springs and basically followed the normal procedure. On the Drop Cam head the spring arm on the Inlets is a bit of a trick, cutting a "V" into the screw driver made it easier. As I was using second hand half rings due to the new ones not turning up yet, it turned out to be a check assembly to see that all the shims were with in range. All bar one were right in the middle of the shim range, the other slightly larger by 0.2mm. So taking the time when to measure the valve gaps and get the seats cut to the right depth worked out well. I set them all with out to much drama to 0.050 closers and 0.15 opener. Still after talking to Bob and Bevan the other day I might set the closers 0.080.
Still not sure on the web between the valves, but after seeing Steve's in the other thread in Classified, I tending to want leave it as it is.

griff

Mr.R

Griff,
Waiting for new 1/2 rings??
Why the Fcuk aren't you using MBP Colletts?
I know that cash is a hard to find thing these days but...
Sell a child or a vital organ and buy some of these they're the way to go on a hot Desmoquatro motor IMO.
Extending the period between shimming by as much as 3X's and being able to rev the snot out of the motor without the worry of valves dropping in to say hello to the pistons has got to be worth the outlay IMO!
I've a set inside my 851/916 motor and have some put aside for my little 250 Desmo.
Everyone who I've spoken to (Who know what they're taliking about, Championship winning bike builders!) say that they're a bloody good idea and well worth the expense of fitting them.
However they are a bit 'fiddley' to fit despite what the makers claim, I've found this out for myself!

Steve R

marvin

+1 ! I put them in everything.

griff851

Hi guys, Yep MPL colletts are the go, I agree 100%, As always things are a tad more complicated than they first look. I tried to convince Bob to get a set at the shop (remembering all the shims in the kit have to modified). As far as the shop side goes, it's not going to happen. But I have planted the seeds of doom 2 weeks ago. His own bike is another story. My next attempt will be in a week or so and I will be using the "going halvies in a shims set" method. For now the shop had no half rings in stock so I ordered a full set, that should keep the boys happy for a year. Once I've finished my clearance and compression checks dialing in in cams etc and Bob has come to the party I can swap them over, before I fit the engine.
Meanwhile the bit I need for the lathe is not orderable so I have pull the screw thread out and send it away with the brass nut to get a new nut made up. I might get this project finished by 2020.😄

Griff

marvin

Griff,
Unfortunately you can't just put the MBP collets in and go. You will have to set all of the valves again as the collets will give you different clearances. If I remember correctly (as I seldom do!) all of your closing clearances will be .004-.005"(inches) tighter.
I bought one of the carbide endmills very early on for boring the OEM openers, which unfortunately Guy no longer sells. One could be made up out of a stock size end mill if you know someone who has a tool/cutter grinder.
I don't know why he quit selling that endmill. My guess is that he got tired of all the calls from frustrated customers who tried to use it in a drill press and burned everything up!

P.S. Or set all of your openers first, then set your closers with the collets, send me your openers and I will counterbore them for you. However making your own "special" carbide endmill will probably be less expensive than postage. (I can give you the specs. on grinding the endmill) "Special" tool is nothing more than a carbide endmill with a step ground on the end which acts as a pilot (6mm) and a stop which bottoms out in the opener.

griff851

Hi Marvin, postage on 8 openers is going to be cheap compared to the f-around factor. Once I get one back I can get a carbide end mill made up if need later on. There's even a stepped end mill in the collection, but from memory its bigger, I'll have a look tomorrow and let you know. I could use the Bridge port, mmmm. Thanks. Much appreciated.

Griff

Just got an email back from Guy. http://www.emsduc.com/ has the closers for $8.50 each.

marvin

griff851 wroteHi Marvin, postage on 8 openers is going to be cheap compared to the f-around factor. Once I get one back I can get a carbide end mill made up if need later on. There's even a stepped end mill in the collection, but from memory its bigger, I'll have a look tomorrow and let you know. I could use the Bridge port, mmmm. Thanks. Much appreciated. Griff Just got an email back from Guy. http://www.emsduc.com/ has the closers for $8.50 each.

Griff,
OK, set your openers, put each in a marked packet so you know which valve they are for and send them on.
I use my lathe with a 5C collet and put the endmill in the tailstock, slow speed. You could do it that way with a standard endmill if careful about depth of cut. Bridgeport could be made to work as well! Will email my address to you.

Mr.R

marvin wroteGriff, Unfortunately you can't just put the MBP collets in and go. You will have to set all of the valves again as the collets will give you different clearances. If I remember correctly (as I seldom do!) all of your closing clearances will be .004-.005"(inches) tighter. I bought one of the carbide endmills very early on for boring the OEM openers, which unfortunately Guy no longer sells. One could be made up out of a stock size end mill if you know someone who has a tool/cutter grinder. I don't know why he quit selling that endmill. My guess is that he got tired of all the calls from frustrated customers who tried to use it in a drill press and burned everything up! P.S. Or set all of your openers first, then set your closers with the collets, send me your openers and I will counterbore them for you. However making your own "special" carbide endmill will probably be less expensive than postage. (I can give you the specs. on grinding the endmill) "Special" tool is nothing more than a carbide endmill with a step ground on the end which acts as a pilot (6mm) and a stop which bottoms out in the opener.

Guy quit selling the end mills because the guy who used to turn them down for him (Cheaply) died!
MBP supplied me with the spec and the speeds to use, I had a tool made up which I used to their instructions.
It chipped very early on whilst I modified my quite large shim collection.
The 1st tool I used was a 4 flute Carbide end mill, I then tried 2 X's 2 flute end mills and have only recently recieved my 'Latest' 4 flute end mill!
All of the end mills I've used have been made by Dormer which's top quality kit and have been Ti' coated.
After the 1st 3 died/chipped I asked the suppliers who are highly respected, very experienced tool suppliers/modifiers/engineers "Why is this happening?"
They thought that the lathe that I was using wasn't 'Man Enough' for the job and lacked the torque/flywheel effect needed.
The lathe that I've been using has a 4ft bed, so it's not a 'Hobby' lathe, I've got use of an 8ft bed lathe at my place of work so I'll try this one next.
With all of this 'Faffing' about it would have been cheaper to have bought a set (Or Two) of already modified EMS shims.
You live and learn...

Steve R

marvin

cutter/shim/pic

For reference here is a pic of the MBP supplied cutter, one stock opener, one modified,

Steve,
I would be interested in getting the specs. on the modification if possible. I will at some point have to make another as i can see that the points on the tool are getting a bit blurry. I use a 8ft. x 16" swing lathe, perhaps that's why mine has lasted as long as it has, plus I only modify tho openers as I need them. (I don't have a whole set!)

P.S. The tool started life as a 3/8" 4 flute carbide end mill.

2nd P.S. Oops, typo, lathe is 5ft between centers, not 8ft. Steve, I hold the opener in a 5C collet with a collet stop which might make for more rigidity plus my lathe is really tight.

griff851

marvin wroteGriff, OK, set your openers, put each in a marked packet so you know which valve they are for and send them on. I use my lathe with a 5C collet and put the endmill in the tailstock, slow speed. You could do it that way with a standard endmill if careful about depth of cut. Bridgeport could be made to work as well! Will email my address to you.

Thanks Marvin, once again much appreciated.

Griff

griff851

I've just been getting serious about choosing con rod bolts. The Corrillo's are out due to ridiculous price. US$43 each. ARP do a set of 8 bolts for AUS$100, corrillos worked out at AUS$380 for 4. The ARP bolt is a 5/16 thread 3/8 drive head with a 1.500" length. The material has a quoted tensile strength 220,000 psi, thats more than 12000 lbs clamping force. The part number is AP200-6210.
Of coarse you can go silly and get a tensile strength of 260,000 psi set for AUS$415 for 8 bolts AP300-6607, and I'm getting a price on the new improved super bolts on Thursday. AP300-6708.
http://www.arp-bolts.com/catalog/Catalog.PP/2005Catalog035.html
Prices in AUS have importers and freight charges included. That makes them about 37 cents each in the US 😁

Griff

griff851

The super bestest set of 8 bolts, 300-6708's are AUS$515 plus $100 freight. Odd as the blurb on the website says they are cheaper.
I'll be using the 200-6210's as I am not building an aerospace vehicle this week.

Griff

got2dv8

griff851 wroteI'll be using the 200-6210's as I am not building an aerospace vehicle this week. Griff

Thanks a lot Griff!😡 I guess now we have to cancel that trip to Mars...😯

Robert

griff851

got2dv8 wroteThanks a lot Griff!😡 I guess now we have to cancel that trip to Mars...😯 Robert

My dirt tires are on back order, so no point until they come in. 😁

Griff

griff851

So after a quick sabbatical, today I got a bit more done. Stick con rods to crank in a permanent fashion.
The bearing shell have been coated with a ceramic compound that will take something in the order of 360,000 kp or psi I can't remember. A lot anyway. Knowing how normal bearings scuff I was hoping to get it right first time. As usual that never happens. I'd asked for a minimum coat as I only wanted a poofteenth added. I put on rod 2 with plasti gauge, all seemed fine. Then rod one, which immediately went tight. Dam. Wrong bearing set in rod. I pulled them apart expecting scuffing. Nothing. Woohoo. I did it again torqued up and measured...... I was a bit worried I'd come really close to 0.025 min, if not just under it(not good). I pulled it apart and low and behold about 0.03 to 0.033 on both. Bang on where I wanted it. I cleaned off the plasti gauge lubed it up with moly and oil, and slapped it together. A good day. Now I have very slippery light con rods with pressure fed little end bearings.

Griff

griff851

Woohoo! Today the lathe became operational. A slight issue with the new drive nut, which was rectified with good old filing and shimming. My first test to see if the chattering stopped was the 748 throttle bodies. Bored out to 46.35 outlet from 44mm, 1° taper from 47.8mm just after the transition taper. Standard 50mm TB inlet. I left 0.15 for port matching. A few minutes with 120 grit. Ta da matched TB's and manifolds. Ooooo..... clean flow all the way to the valve.
Hardest part was convincing the injectors that they need to get out more often. I had to resort to chemical weapons. Silkolean "Maintain" in this case, as it was the nearest pressure pack stuff to hand. Then poke them with a stick to coax them out. Twisting their necks as they emerged to make sure they were dead. 851 injectors are much easier to get out. They will be sent to the injector reviver guy to be checked and cleaned. A quick bath and back as new.

Griff

« Previous Page Next Page »