Archived Message
V8 cylinder head swop
Can anyone please advise if standard V8 cylinder heads are interchangable. I have a factory V8 and have been offered a set of 3.9 10 bolt heads which should improve performance. Does anyone know if the 3.9 heads can be simply bolted on to the early 3.5 block or is there a problem with the different bore size or a risk of the larger valves hitting the pistons.
Les Hughes
22/09/2012 @  20:16
Under topic: V8
Archived Reply(ies) received for this Message
V8 cylinder head swop
The heads are interchangeable. The valves won’t open more than the 3.5 heads (unless you change the cam) and there is no chance of them hitting the pistons. If you use tin head gaskets the CR will be increased but the composite gaskets are better.
Geoff King
22/09/2012 @  20:41
V8 cylinder head swop
As Geoff says.... I would only use comp gaskets with these, as the 10 bolt heads have combustion chambers of approx 28cc making them more suitable for comp gaskets.
Steve Illing
23/09/2012 @  15:58
V8 cylinder head swop
…unless you want to increase the compression ratio, but then you would need to check (and probably adjust) the cam follower pre-load as obviously the head would be lower on the block compared to the old Range Rover/GTV8 heads. And then there is the valley/inlet manifold gasket alignment to consider so unless you are prepared to do a little work I agree with Steve it’s easier to use composite head gaskets and just bolt it together.

There is no problem with the different bore size but use composite gaskets for a 3.5 such as these: it doesn’t matter that the gasket has the outer bolt holes.
Geoff King
23/09/2012 @  17:36
V8 cylinder head swop
thank you all for the great advice, its very reasuring and I can now look forward to changing the heads sometime during the winter.
Les Hughes
24/09/2012 @  20:10
V8 cylinder head swop
We don't have a registration of an MGBV8 from you so would you like to register your V8 using the convenient online form at:
V8 Webmaster
24/09/2012 @  20:45
Advanced Search
Search for all messages for
Last 2 days
Last 7 days
Last 14 days
All Messages
Search by key word
Search by topic
V8 RV8
Spares Events
General Online auction
Include archived messages in search
When making a posting
do note the system automatically signs off your posting with your name

You are welcome to post a message
or response
It could be a technical query or clarification, a maintenance or spares tip, a report of good service from a V8 specialist, or news of an event of interest to fellow V8 enthusiasts. As we welcome new members, this service is provided on a "free and open to all" basis and is not restricted by password access.

Spares adverts
Any spares or other items advertised for sale on the V8BB will be removed and posted on the V8 Spares webpage on the V8 website.

V8 Bulletin Board aims
to attract good quality postings in terms of content subject matter and accuracy. It is not a chat box so any "grumping or flaring" or other undesirable postings will be moderated at the sole discretion of the V8 Webmaster and V8 Chairman. Periodically the postings are archived to keep the list of postings to a manageable length. Please disclose your name and email address when preparing your posting.

V8 Register - MG Car Club
Neither the MG Car Club, the V8 Register or its officers and committee members can accept legal responsibility for any of the statements contained in any posting or postings made on this bulletin board. Any material considered to be undesirable in terms of its nature, content or implication will be moderated as promptly as is reasonably possible. Should any party feel the content or claims in any posting may cause them actual or potential damage, please contact the V8 Webmaster promptly so appropriate action may be taken.

V8 Webmaster