RD350 V's RD400 Cylinder Heads

General forum on engines, transmissions, gearing and modifications to each

Moderator: rztom

Post Reply
Message
Author
lemonhead
Posts: 9
Joined: Tue Dec 19, 2017 10:58 pm
Location: New Zealand

RD350 V's RD400 Cylinder Heads

#1 Post by lemonhead » Wed Dec 20, 2017 2:16 am

Hi,
So i purchased a dismantled 1975 RD350 and have nearly finished the restoration. I went to buy some spark plugs and the standard plugs are B-8HS. short reach or 14x13mm (1/2"). However the cylinder heads are long reach or 14x19mm (3/4"). This is odd I thought. So I found the RD400's have long reach spark plugs B-8ES.
I'm guessing at some stage I think the cylinder heads on my RD350 have been swapped for RD400 heads.
Is there any way to tell the difference between 400 and 350 heads.
Will it have any affect on the compression ratio or performance of my RD350?
and if this is a stuff up, do you think my RD350 will miss out on that stunning acceleration with RD400 heads on, Would RD250 heads be a better option or are Rd250 heads the same as RD350 heads?
Hope someone can help
Best regards
Mark O

User avatar
Questo vecchio rz
Posts: 1116
Joined: Sun Aug 16, 2015 5:55 pm
Location: Reconquista of California

Re: RD350 V's RD400 Cylinder Heads

#2 Post by Questo vecchio rz » Wed Dec 20, 2017 6:58 am

You cannot do much better than asking (Ed Earlenbach), you can P.M. him here he is member listed as EE. Give him details, and you will have most all your answers.
You can also contact in no particular order (Harry Klemm) @ Klemm Vintage, or (Scott Clough) @ SCR racing. And finally Gary Shumanke @ Spec 2.
These men are likley the leading guys in America for RDs, and likley once there gone..there knowledge will be lost as well. These guys are...the some of the best of the best.
Banshee (Baja) race bike,+ 2 A Arms,L.E.Ds, Toomey, +4 stroker IMS tank, run flats.
96 GSXR SRAD, Future Yoshimura rep.
85 custom Tri-Z
RZ/YZR bike(project)
86 VFR750 RC24 Merkel replica (project)
Royal Enfield Bullet 500

MK
Posts: 814
Joined: Sat Nov 26, 2005 11:44 am
Location: Wolfenbüttel, Germany
Contact:

Re: RD350 V's RD400 Cylinder Heads

#3 Post by MK » Wed Dec 20, 2017 1:36 pm

Ed's HP:
http://erlenbachracing.co" onclick="window.open(this.href);return false;
Bye
Martin

lemonhead
Posts: 9
Joined: Tue Dec 19, 2017 10:58 pm
Location: New Zealand

Re: RD350 V's RD400 Cylinder Heads

#4 Post by lemonhead » Wed Dec 20, 2017 4:08 pm

Hi Martin,
Many thanks for your help on the best contacts on this head issue. I'll send them a message. It's a pure annoyance (I'm being polite) that I have got so far with this restoration and was close to getting it running before Christmas only to find someone prior to my ownership has mismatch things.
Thanks
Mark O

bitzz
Posts: 121
Joined: Fri Feb 17, 2012 10:54 pm
Location: Omemee, Canada

Re: RD350 V's RD400 Cylinder Heads

#5 Post by bitzz » Wed Dec 20, 2017 10:57 pm

The 400 head has a larger compression dome visible on the outside.

Swapping 400 heads is a popular upgrade to use the 400 copper head gasket.

Do a google search for rd350 head and look at the images. The heads are quite different.

lemonhead
Posts: 9
Joined: Tue Dec 19, 2017 10:58 pm
Location: New Zealand

Re: RD350 V's RD400 Cylinder Heads

#6 Post by lemonhead » Wed Dec 20, 2017 11:20 pm

Hi Bitzz,
Yes Im just working through that as I'm told the fin arrangement is quite different and 400 have a lower compression dome. Sucks that i have someone elses mods. I'm not confident it will ever perform like the ballistic 350's with the lower compression head. However my heads do not protrude from the barrels by a half inch like the 400 as supposed to. So its still an odd thing.
Thanks for your help. Can I attach a photo on here without it being on a web site?

mboddy
Posts: 31
Joined: Sat Jan 20, 2007 6:20 am
Location: Canberra, Australia
Contact:

Re: RD350 V's RD400 Cylinder Heads

#7 Post by mboddy » Sat Dec 23, 2017 6:19 pm

Fit the heads. Check the squish clearance with some solder wire through the spark plug holes. Front back and both sides.
If the minimum is between 1.0mm and 1.4mm then ride it.
We race RDs, RDLCs, RZs, TZRs, TDRs and TZs at PCRA

lemonhead
Posts: 9
Joined: Tue Dec 19, 2017 10:58 pm
Location: New Zealand

Re: RD350 V's RD400 Cylinder Heads

#8 Post by lemonhead » Mon Jan 01, 2018 4:54 pm

some photos that might help. But I have been advised these might be peculiar to New Zealand / Australia and be 350 heads with a long reach plug

lemonhead
Posts: 9
Joined: Tue Dec 19, 2017 10:58 pm
Location: New Zealand

Re: RD350 V's RD400 Cylinder Heads

#9 Post by lemonhead » Mon Jan 01, 2018 4:55 pm

dam looks like the photos didnt attach sorry, I'll keep trying

lemonhead
Posts: 9
Joined: Tue Dec 19, 2017 10:58 pm
Location: New Zealand

Re: RD350 V's RD400 Cylinder Heads

#10 Post by lemonhead » Mon Jan 01, 2018 5:15 pm

RD400 heads are supposed to over hang 350 barrels, These do not
Attachments
350 heads overhang none.jpg
350 heads overhang none.jpg (244.19 KiB) Viewed 4021 times

lemonhead
Posts: 9
Joined: Tue Dec 19, 2017 10:58 pm
Location: New Zealand

Re: RD350 V's RD400 Cylinder Heads

#11 Post by lemonhead » Mon Jan 01, 2018 5:20 pm

Casting number 52100, I'm told are not RD400 casting numbers. And the other pictures show short reach and long reach plugs fitted.
Hope this helps
Attachments
350 head long reach plug fitted.jpg
350 head long reach plug fitted.jpg (67.9 KiB) Viewed 4020 times
350 head short reach plug fitted.jpg
350 head short reach plug fitted.jpg (204.13 KiB) Viewed 4020 times
350 head casting number.jpg
350 head casting number.jpg (219.68 KiB) Viewed 4020 times

evansje1
Posts: 267
Joined: Wed Jun 02, 2010 11:25 am
Location: Heber Springs, Arkansas, USA

Re: RD350 V's RD400 Cylinder Heads

#12 Post by evansje1 » Mon Jan 01, 2018 6:47 pm

400 heads should have A1A cast into the bottom side of the head. Look close at the raised area in this picture.
Attachments
image003-611x458.jpg
image003-611x458.jpg (103.59 KiB) Viewed 4010 times
1973 RD350
2014 Suzuki DT1000
1979 RD400F Daytona Special
1984 RZ350

evan_calgary
Posts: 1368
Joined: Tue Nov 12, 2013 2:34 am

Re: RD350 V's RD400 Cylinder Heads

#13 Post by evan_calgary » Tue Jan 02, 2018 12:18 am

The guys at the 2 stroke forum should make quick work of your conundrum. It is mostly RD 350 peeps.

Check them here:
http://www.2strokeworld.com/forum/index.php" onclick="window.open(this.href);return false;

lemonhead
Posts: 9
Joined: Tue Dec 19, 2017 10:58 pm
Location: New Zealand

Re: RD350 V's RD400 Cylinder Heads

#14 Post by lemonhead » Tue Jan 02, 2018 5:04 pm

HI thanks Evensje and even_calgary.
The RD400 heads have 3 long fins on the outside edge. Mine only have two long fins. So its all indicating they are 350 heads as the casting numbers arn't A1A, but they just have long reach spark plugs. I'll ask on the 2 stroke forum.
cheers

Post Reply