TOPIC: 1973 Mercury 850 Reed Block rebuilding

I was wondering if anyone has any specific info on the rebuilding of worn out reed blocks . My 1973 850 is apart and I would like to redo the blocks but can’t find any concrete information on preferred tolerances to achieve a consistent idle . My crank shows rub marks from the aluminum reed block and those marks are only .0005 deep …. On the other hand the inside diameter of my reed blocks are (1st ) 1.252 (2nd ) is 1.248 ….the crankshaft mic’s 1.238 . I’m very interested in reviving these and have full access to a machine shop . I’ve read here the Doc has had this done before and was looking for more detailed info of the process and tolerances. Thanks in advance for any help .

By chance has anyone had the opportunity and measured a new 1973 850 Reed Block ?

tapered cyl's will affect the idle.

True enough Dave ..thanks for the response … my pistons are in rough shape …#1 and #3 have stuck rings and some scoring … the block is being prepared for boring +.015 and honing… no bleed restrictors present so 8-32 set screw with .035 hole will be installed .
Just didn’t want to leave the reed blocks out of the equation …. If they need attention ….now’s the time ….my manual absolutely has no wear tolerances to use for a guide line to state either good or not for these reed blocks

Does anyone have contact with Doc Frankinmerc ? Would like his take on this …. or anyone else that can help .
Thanks

I sent an email to the Doc, hopefully he'll weight-in on the topic............ed

I have (2) complete NOS sets I will sell.
I don't reuse any that the labyrinths measure over 1.247" at any point.
Dave Bernard:
If this fellow calls you for my contact info, please share it, but please don't post it.
My health is on the rocks, and I can't keep up any more.
doc

Thank you Doc for the response… That helps . I’m so sorry to hear your health is failing . My hopes are for you to recover from what ails you . If and when that happens I’d love to talk about the rebuilding of these blocks . Because you’ve already done it ,I was considering having a go at it . I read somewhere you had a Canadian do some machining on them . I was curious about the process . Thank you again . R

It definitely was not "cost effective" to hire those fabrications, but I will try and find my old documentation on the process.
doc

IMHO I would just replace them with new ones. You're not gonna get any better than a factory original.

I am attaching pictures of the modifications I had completed to restore the labyrinths.
One set of pictures is related to inserts made specifically for reed blocks.
The other set of pictures were for the creation of labyrinths in old main bearing housings to act as isolation barriers between cylinders to run a (6) carburetor (Twister II-x) intake and pyramid reeds.
Two different ways used to secure the inserts.
doc

Thank you ! Great info … I’m trying to imagine the sequential process ..I’ll try … please correct me …
1) Strip reed blocks , lightly stone and reassemble .
2) Bore soft jaws on lathe to correspond to reed block OD .
3) Dial down chuck pressure as not to crush reed blocks
4) Bore out assembly to 1. 450 ish
5) Set this aside
6) using 6000 series aluminum turn 4 pieces , ODs are to match 1.450 ish dimension less .0003 or so .
rough out the ID ….say to 1.125 , and width to match reed blocks too
7) Machine the 4 pcs individually in a precision vice …say .020 above centreline … this will give 4 inserts with precise OD and flats proud of the centreline .
8) insert the inserts into reed block halves and pin as an assembly ( split pin ? )
9 ) using the precision vice , indicate 0 , across flats of reed block ,then mill proud areas of inserts down to match the reed blocks .
10) bolt reed blocks together
11) back to lathe with soft jaws , bore to 1.245 , groove to the original depth , width ,and spacing

It looks as though your inserts are held with a single pin and once assembled , everything is locked in …. Yes ?
Thanks for input R

Doc …you said you have NOS blocks for a 73 850 … I’m interested …If I can get your contact info some how ….that’d be great . Thanks

I get overwhelmed when I post my contact info,...
I'll see if I can get another member that has my info to figure out a way to share my info without posting it.
Sorry,
doc

Call me for information. 1 914 310 7086 Dave.

Dave can share my contact info with you if you call him.
doc

Old Merc’s, I hope this thread is still active?
Have myself knee deep in 74-76 850’s. 1 I have is giving me trouble if I start it with starting fluid she starts idles and runs great. Shut it off and I have to use starting fluid again. Choke works, good compression, cards have been gone through a couple times. I’m thinking reed block sealing but not sure. Any suggestions.

I hate to bother ya Doc but what are you askin for the reed blocks?