Jump to content
HybridZ

MN47 Maxima Head


datzun90

Recommended Posts

Hey guys, I have been doing a lot of reading on the site regarding the maxima head on an N/A L28 w/ flattops. I was just looking at getting some feedback from the people who are currently running this setup. I.E. detotnation problems you encountered, valve clearance issues, etc. I should state that i have an N42 block w/ STD bore flattops, a 490/280 cam, tiple DCOE42 webers, and an aftermarket header. I plan on building this as a hot street motor that i will use ocasionally at track days. As well, where i live i can easily get 94 ocatne fuel @ the pump, so i am hoping this setup is capable at running pump gas w/ a full 36deg advance on the timing. Any input would be greatly appreciated. Thanks.

Link to comment
Share on other sites

With a flat-top n42 block and a MN47 head, you're pushing close to 11:1 comression with a 39cc combustion chamber, which is really pushing the envelope on pump gas in an l series engine. [small](You could drop this with a thick head gasket, but then you're losing quenceh and that's an entirely different discussion.)[/small] The 94 octane you get in Canada isn't the same as 94 octane here in the US (RON measurements vs. AKI measurements. 95 octane in Canada = 91-92 octane in the US), so you're really looking at the same gas we have available here.

 

The l series engine is a relatively hyper-sensitive one when compared to other engines, and I know the mn47 head on pump gas is a pretty widely debated topic. From my reading, I've gathered that the general consensus us that you won't be able to run full advance on pump gas and get the most potential out of your combo. You might want to do some very detailed research about how low you can get your dynamic compression ratio with a monster cam, but that would defeat your goal of primarily driving on the street.

 

My opinion (which should be taken with a large grain of salt, as it's purely from reading here, and not from first-hand experience) is that you'll be able to make more power with a lower compression ratio that you can run a full ignition advance on before you get into detonation. Look into what people have been doing with an E31 or E88 head with their slightly larger 42cc combustion chambers.

Link to comment
Share on other sites

I am trying to avoid a head w/ square exhaust ports because i already have a round port header and i am on a very tight budget. I was thinking of a shaved P90 but the cam tower shims and the machining work make it kind of a pricey option. As for the gas i can always get the 93 octane in NY state considering i buy almost all my gas there anyways. But i appreciate your input. thanks -Riley-

Link to comment
Share on other sites

a $100 used header is cheaper than a head/headwork....isnt it??

 

Yah i guess thats true, but i was hoping to have to not get a head i have to spend any extra money on wether it's a header or machine work. Thats why the MN47 caught my eye. I am pretty sure either mack or 1 fast z said they were running their setup with full advance on pump gas but i couldn't find the post it was in again. Plus if i get one of the older heads won't i have to put hardened valve seat in it?

Link to comment
Share on other sites

Get a P79, if you're worried about the exhaust ports being round.

 

shave/shim like P90, or get an MN47 and open the chambers up to what you need.

 

I was considering the P79 too so if a Maxima head is just not practical to run i'll probably end up getting one of those. With a maxima head would unshrouding the valves lower the C/R a bit? because that may be a little more reasonable cost. The ain point I am getting at is that i am looking for the best bang for my buck in a cylinder head and from what i read the maxima one seemed to be it. I am just trying to get more info from people with that setup to reinforce my decision because it seems not too many people are running it. Thanks again for the input guys.

Edited by datzun90
Spelling + Grammatical Errors
Link to comment
Share on other sites

  • 3 years later...

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...