Go Back   The Ford Barn > General Discussion > Model A (1928-31)

Sponsored Links (Register now to hide all advertisements)

Reply
 
Thread Tools Display Modes
Old 02-18-2020, 07:49 PM   #1
doug.nichols
Senior Member
 
doug.nichols's Avatar
 
Join Date: Apr 2015
Location: Olga, WA
Posts: 117
Question Manifold Decking

I have read numerous threads about the importance of having exhaust and intake manifolds decked as a unit to create a perfectly flat condition for mating to the engine block. I can't help but wonder if the original Model A manifolds were constructed to that high tolerance and, if not, how they worked for so many years? Any opinions? (Did I really say that?)
doug.nichols is offline   Reply With Quote
Old 02-18-2020, 07:57 PM   #2
Sunnybrook Farm
Senior Member
 
Sunnybrook Farm's Avatar
 
Join Date: Oct 2015
Location: Virginia
Posts: 406
Default Re: Manifold Decking

The big problem is when the thing heats up and the weight of the muffler causes the rear to sag. I have heard that the manifold can be fixed upside down and heated up very hot with a heavy weight on the rear to pull it back the other way.
Sunnybrook Farm is offline   Reply With Quote
Sponsored Links (Register now to hide all advertisements)
Old 02-18-2020, 09:13 PM   #3
redmodelt
Senior Member
 
redmodelt's Avatar
 
Join Date: May 2010
Location: Portland OR
Posts: 5,365
Default Re: Manifold Decking

More often when people say to get the two surfaced is because two different manifolds are joined back together or for example; a new exhaust manifold is installed creating two different levels between their ports. Case in point; we had a customers car in the shop doing some repairs. The previous owner bolted up a brand new exhaust manifold to the engine with out having it surfaced, something had to give so the new exhaust manifold cracked when they pulled it up tight.

As far as straightening one goes, it is not a heavy weight used to pull back in to alignment, in fact it does not take a whole lot of weight to do it at all, but it does burn a lot of gas and you have to used a rose bud. Using too heavy of weight or forcing it will more then likely break it. When Model T's manifolds are done, it is just the weight from a box end wrench turning a bolt in a jig to move back in alignment, nothing else.

Here is a sample of doing the T, the A should be about the same;
http://mtfctulsa.com/Tech/manifold.htm
__________________
I know the voices aren't real but damn they have some good ideas!
redmodelt is offline   Reply With Quote
Old 02-18-2020, 09:46 PM   #4
PalAl
Senior Member
 
PalAl's Avatar
 
Join Date: Jul 2016
Location: Orangeville Illinois
Posts: 376
Default Re: Manifold Decking

Here is a sample of doing the T, the A should be about the same;
http://mtfctulsa.com/Tech/manifold.htm

Redmodelt, thanks for the link.
I have heard about doing this but a picture is worth a 1000 words..........
PalAl is offline   Reply With Quote
Old 02-18-2020, 10:06 PM   #5
Kurt in NJ
Senior Member
 
Kurt in NJ's Avatar
 
Join Date: May 2010
Location: on the Littlefield
Posts: 5,340
Default Re: Manifold Decking

On mine I just flatten the exhaust, after installing I just finger tightened the 2 bolts enough to flatten the lock washer--- don't think that the heat helps the modern fuel, there's a little gap between the manifolds on my car now, have had several exhaust manifolds crack through the years--- used ones , same intake, never cut, though one manifold had to have 1/2 washer shims because it was cut so much crooked and it took a lot to correct
Kurt in NJ is offline   Reply With Quote
Old 02-19-2020, 10:14 AM   #6
Ray in La Mesa
Senior Member
 
Join Date: May 2010
Location: La Mesa Ca
Posts: 860
Default Re: Manifold Decking

Sponsored Links (Register now to hide all advertisements)
I did the upside down thing on an A manifold 30 years ago and worked fine but with continued use it's memory took it back to the original group. The new ones are more than worth the money.
Ray in La Mesa is offline   Reply With Quote
Old 02-19-2020, 10:31 AM   #7
redmodelt
Senior Member
 
redmodelt's Avatar
 
Join Date: May 2010
Location: Portland OR
Posts: 5,365
Default Re: Manifold Decking

Sagging exhaust manifolds, partly can be blamed on lack of gland rings. Except for a very very short window, that is why Ford installed them.
__________________
I know the voices aren't real but damn they have some good ideas!
redmodelt is offline   Reply With Quote
Reply

Thread Tools
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 Off

Forum Jump

Sponsored Links (Register now to hide all advertisements)


All times are GMT -5. The time now is 01:35 PM.