Gollum Posted February 22, 2012 Share Posted February 22, 2012 So your saying a maxima N47 head will get you that compression ratio?? No, he's lying to you. This thread smells like the trash to me... Quote Link to comment Share on other sites More sharing options...
Zguy91 Posted February 22, 2012 Share Posted February 22, 2012 If you use the engine calculator it says a flat top block with an n42 head with 1mm head gasket yields a 9.97 compression ratio. Is that not right? Quote Link to comment Share on other sites More sharing options...
Gollum Posted February 22, 2012 Share Posted February 22, 2012 If you use the engine calculator it says a flat top block with an n42 head with 1mm head gasket yields a 9.97 compression ratio. Is that not right? Well Mack was talking about the MN47, or maxima N47, which is a different head than the Z N47.... Besides, most of the calculators are OFF, which is why Josh originally posted how to CC chambers and calculate compression, as it's much more reliable than a program on the inter webs. Quote Link to comment Share on other sites More sharing options...
Zguy91 Posted February 22, 2012 Share Posted February 22, 2012 Oh ok see I always say people call the maxima head the MN47 and the Z head the N47 so i was confused which one they were talking about. I agree that the calculators seem a bit off Quote Link to comment Share on other sites More sharing options...
Josh280z Posted February 22, 2012 Author Share Posted February 22, 2012 I don't know what is trash and what isn't. I'm just trying to learn is all. I have P79 head that I'm going to shave for high compression. I know I have to shim everything to keep geometry right, but do I have to get the longer valves? Quote Link to comment Share on other sites More sharing options...
Josh280z Posted February 26, 2012 Author Share Posted February 26, 2012 I have Bosch 0280155811 that flow 375cc/min, I am rebuilding an engine with flat top pistons and the P79 high compression head mod. I know I will need MS. It is going to be a daily driver while still also being able to be a weekend cruiser. My build will consist of: P79 head compression shave F54 flat top piston w/block 375cc/min injectors Megasquirt Lightened flywheel MY QUESTIONS: Will I need the T5 transmission to handle the power, I have 2 NA 5 speed transmissions? What kind of cam will suit my needs? Should I switch to an LSD? Will it idle properly with MS? Will a return less fuel system cut power to the fuel rail? Who still makes some good headers for my car? Should I upgrade the valve springs? I want to reach the 200+ HP mark, which should be easy with that set up. I know about the chance the engine has of pinging. Is there anything I should be concerned about? Could you please help me with some of my questions. Quote Link to comment Share on other sites More sharing options...
steve260z Posted February 26, 2012 Share Posted February 26, 2012 Are you installing the longer '75-78 valves? ss Quote Link to comment Share on other sites More sharing options...
Josh280z Posted February 26, 2012 Author Share Posted February 26, 2012 I'm installing the N47 valves which are the same length. Quote Link to comment Share on other sites More sharing options...
Pyro Posted February 26, 2012 Share Posted February 26, 2012 Redo the compression calculations with the piston sticking up 0.010" out of the block. Because.... That is what the stock setup does. (sticks out of the block). If you use a mild cam with stock valve springs you don't need to resurface anything. Get the stock cam reground, add some thicker lashpads, and go. Increase duration but keep the lift low and the lobe ramp slow (like a stock cam). The later the intake valve closes (bigger cam) the eaiser it will be to run high compression with pump gas. That is why I mentioned it. Quote Link to comment Share on other sites More sharing options...
Josh280z Posted February 27, 2012 Author Share Posted February 27, 2012 Pyro, I appreciate your input but this is the way I've decided to go. If I didn't shave the head, then it would just be stock compression, which is not what I want... Before anyone says anything, I also know about the beadwork that needs to be done, and have plans in the works for that. Pyro, you didn't answer any of my recent questions though. Quote Link to comment Share on other sites More sharing options...
calvin280zxt Posted February 27, 2012 Share Posted February 27, 2012 (edited) Im pushing 240-50 hp on my na 5 speed i wouldnt worry about that. Especially with a spare. As long as your not drag race starting. Try and find a 2+2 flywheel they have a bigger clutch and pressureplate Edited February 27, 2012 by calvin280zxt Quote Link to comment Share on other sites More sharing options...
Josh280z Posted February 27, 2012 Author Share Posted February 27, 2012 (edited) Ok thank you for letting me know that about that transmission. I'll be getting a lightened flywheel and a performance clutch. Edited February 27, 2012 by Josh280z Quote Link to comment Share on other sites More sharing options...
Gollum Posted February 27, 2012 Share Posted February 27, 2012 I have Bosch 0280155811 that flow 375cc/min, I am rebuilding an engine with flat top pistons and the P79 high compression head mod. I know I will need MS. It is going to be a daily driver while still also being able to be a weekend cruiser. My build will consist of: P79 head compression shave F54 flat top piston w/block 375cc/min injectors Megasquirt Lightened flywheel MY QUESTIONS: Will I need the T5 transmission to handle the power, I have 2 NA 5 speed transmissions? Answered What kind of cam will suit my needs? I'd go with the isky stage 3 cam, or if you want to go crazy go with their .530 lift competition cam. Should I switch to an LSD? Not unless you're going to be competitive racing. Casual racing and street driving, open diffs are fine. Will it idle properly with MS? I don't see why not. MS has decent idle controls that will help the cam idle smoothly with much more radical cam than carbs would ever allow. Will a return less fuel system cut power to the fuel rail? Huh? Come again? What do you mean "cut power"? A return less system relies on a variable voltage signal to the pump to regulate flow. Who still makes some good headers for my car? MSA ones aren't bad, and if you're going all out just have some made if you don't like the common offerings like theirs. Should I upgrade the valve springs? Not a bad idea if you're going with a radical cam, but remember that the crank has nasty harmonics between 7-8k that shouldn't be lived in. Having a cam that doesn't "turn on" until 3k can be mighty boring if you're stopping at 7k. That said, many just make sure to pass through those ranges instead of sticking around and have reported years of fail-free service from their cranks. I want to reach the 200+ HP mark, which should be easy with that set up. I know about the chance the engine has of pinging. Is there anything I should be concerned about? At the HP and compression levels you're talking about, ping should NOT be an issue. If it is, then there's something WRONG. I'll even go as far as to say this, if you're running a programmable EFI setup, and running less than 11:1 compression and you're pinging then you need to either figure out what's wrong with your tune, or find out what's wrong with your ignition setup. Too many blown engines have been from faulty ignition parts, not too high of compression like people want to assume. Yes the L motor doesn't like high compression and tends to ping, but there's lots of factors there and having programmable ignition is the first step to solving some of those issues. Could you please help me with some of my questions. Quote Link to comment Share on other sites More sharing options...
Josh280z Posted February 27, 2012 Author Share Posted February 27, 2012 Gollum, you rock thanks for answering the questions I asked. Quote Link to comment Share on other sites More sharing options...
Josh280z Posted April 16, 2012 Author Share Posted April 16, 2012 I've decided to go a different route with my build... Will the N47 cooling ports match up with the F54 block? Also, will the OEM flattop pistons be alright in the 200-300 hp range, or should I go for forged pistons? Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.