I need the info in a '66 or '67 Mercury Owners manual that tells the Owner what is the recomended minimum Octane for the 410 4v V8.

Many thanks, I made the mistake of building my 410 to the stock 10.5:1 CR. It is in fact a little higher than that since I also installed the C8AE-H heads which are aprox. 3cc smaller than the origanal heads.




Eric

 

Bummer, Dude!
You'll just want to get the highest you can find.
And 91 is about as good as it gets here in CA for most brands.
I'd feel better with at least 93, but you can always retard the timing a little.

--Matt

 

On the other hand, that thing will have NUTS!

 

I don't have owners manual. But, If you are running Cast Iron heads with more than 10.5 : 1, then I would use no less than 93 octane. You may even need to use an octane booster after that. That is pretty High Compression on todays ******y gasoline.

If push come to shove and you have to pull apart. I would still use the pistons you have . What I would do is have an engine builder, that you trust, polish the compression chambers. If you have a really good builder / machinist he may be able to mill them chambers out for a few more CC's. That along with polished chambers will decrease detenation greatly.


Scotty

 

well, as a last resort I'll pull the engine down and turn a larger depression in the top of the piston. I work at a Machine Shop and using a CNC lathe is my thing. Obviousely I'd need to inspect a piston to see how much could be taken off to drop it one point of C.R. without weakening the piston.
The other option is going with Aluminum Edelbrock heads. More $$$$ but I may not have a choice. Either way It'll be more $$$ if I can't get it to run on premium.



Eric

 

alpo23,
Is it knocking (pinging) now?
How well does it run on premium?
Answers to those questions will probably be your best guide.
If you never lug it or don't run much at WOT, you may be able to live with it.

In addition, higher compression gives better fuel economy.
But still, 10.5:1 seems a little excessive.

Chech out the following website:
http://www.chevron.com/prodserv/fuel...rgas/ch5.shtml

Look the table in Figure 5-9 and you can see typical effects of various parameters on octane requirement. For example, raising the compression ratio by a full number requires between 3 and 5 octane numbers to prevent knock.

Please let us know what solution you come up with.

--Matt

 

alpo23,

Turning the piston may work. It may, however, be nessesary to do both. That is turn the piston and polish the combustion chamber in order to keep detenation from coming on. All of that is some serious work. The easiest would be to put on edelbrock heads. Not only are they bigger Combustion chambers, but they are aluminum. Aluminum tends to disperse heat more evenly and better than cast iron. Allowing for a slightly higher comp ratio. Good luck on what ever you try.

let us know how it turns out.

Scotty

 

Before you do some expensive tear down, you might take a look at your distributor. On my 428 it was set inth 18r slot giving me 36 deg. of mech advance. Take a look at http://www.bob2000.com/dist.htm