cobraz240z Posted January 16, 2006 Share Posted January 16, 2006 what is the biggest valves i could put on my e31 head and will larger valves hit the pistons on a 1971 2.4 block? and can i make 220 horsepower on a stock 2.4 block with 3x2 carbs setup 40's ported e31 head large tube headers and a cam? Quote Link to comment Share on other sites More sharing options...
RedNeckZ Posted January 16, 2006 Share Posted January 16, 2006 You can install the L28 valves in the head. You can use both the intake and exhaust valves. Be sure to install the hard seats with it. It will require you to get some machine shop work done on it for the seats and a three angle valve job after the hard seats are put in. But I have done this to my head. After finding out that I had three cracks between three sets of valves. With the new welding systems that they now have, they were able to fix the problem and install the bigger valves. Then I then had the head ported and polished by Heads by Paul in Denver, CO. This was done back in the 90's and is still going strong today. Good Luck, Rich. Quote Link to comment Share on other sites More sharing options...
RedNeckZ Posted January 16, 2006 Share Posted January 16, 2006 With a new rebuild of motor (L28 block) and E31 head. Depending on piston size (40 over) and compression (12:1) and what crank (stroked or not stroked) you will be using. You should be able to see that much power. The valves will not hit the pistons if the time chain is put on right (42 links, dot to dot). But it depends on what you have going on with it mostly. Depending on a lot of info we don't have, we can only guess at this. But yes, under normal conditions you should see that much power from it. Good Luck, Rich. Quote Link to comment Share on other sites More sharing options...
madkaw Posted January 16, 2006 Share Posted January 16, 2006 I am doing a e-88 the same way on a 2.4 block with .40 over pistons with a 480 lift cam and you have to put reliefs in the block or the exhaust will hit the cylinder. Be careful because a lot of guys are using the 2.8 block so mention of relief is needed but you WILL have to relief a 240 block with bigger valves . This is also verified in How To Modify Datsun book. Good Luck Quote Link to comment Share on other sites More sharing options...
JMortensen Posted January 16, 2006 Share Posted January 16, 2006 He is specifying a stock 240 block, so I'm thinking that getting 220 whp is probably not going to happen. 220 bhp is within the realm of possibility if everything was done well which equals roughly 187 whp. I have reservations about putting big valves in when you have to notch the block for them to fit. Always seemed like a bad idea to have the valve that close to the cylinder wall. If there is no room or very little room between the valve and the wall then how is the air/fuel mix going to flow around that side of the valve??? Not very well I don't think... If you got a 2.8 block with flat tops that would give you a big boost in compression and displacement. 16% in displacement and 22% in compression by my calculations. That would make it a lot easier to hit the numbers you're looking for. Then again my L28/E31 takes 95 octane to keep from pinging so there are other problems to deal with if you go that route. Quote Link to comment Share on other sites More sharing options...
cobraz240z Posted January 17, 2006 Author Share Posted January 17, 2006 ok i know if i put bigger valves i will need to do some piston work do the bigger valves make that much of a difference and is it worth the differnece or should i just get the 280 block I would think the L24 would be more rpm friendly but i may be wrong i just want 220 hp at the flywheel what is the cheapest way to get that power i would like more but i lost my job and cant afford to spend alot of money on a motor i will do all my mechanical work what is the best combo for hp for the price Quote Link to comment Share on other sites More sharing options...
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