SCAVMAN Posted August 18, 2009 Report Share Posted August 18, 2009 i have been looking around the internet for a while trying to find info on putting a 7afe head on a 4afe. i have a few questions as i can't find too much for myself is it a possible/easy thing to do? are any gains that will come of it worthwhile? i am well aware that it would be a better choice to put in a 4age, but I'm a uni student and am not too phased if i butcher this car so i want to play with the 4afe. Quote Link to comment Share on other sites More sharing options...
Hiro Protagonist Posted August 18, 2009 Report Share Posted August 18, 2009 i have been looking around the internet for a while trying to find info on putting a 7afe head on a 4afe. i have a few questions as i can't find too much for myself is it a possible/easy thing to do? are any gains that will come of it worthwhile? i am well aware that it would be a better choice to put in a 4age, but I'm a uni student and am not too phased if i butcher this car so i want to play with the 4afe. If it's a late-model 4AFE, then the heads are identical, thus no gains possible. Might as well just put the whole 7AFE in anyway Quote Link to comment Share on other sites More sharing options...
Sam_Q Posted September 8, 2009 Report Share Posted September 8, 2009 yeah we need to know the exact model of engine, got a pic? also what suberb are you in? Quote Link to comment Share on other sites More sharing options...
beerhead Posted September 8, 2009 Report Share Posted September 8, 2009 If the 4AFE and 7AFE have the same head does that mean the that 4AFE pistons in a 7AFE give you a bit of a compression gain? Quote Link to comment Share on other sites More sharing options...
Sam_Q Posted September 8, 2009 Report Share Posted September 8, 2009 no, because the 4afe uses an 18mm rod whist the 7afe uses a 20mm rod, both pressed in Quote Link to comment Share on other sites More sharing options...
beerhead Posted September 8, 2009 Report Share Posted September 8, 2009 OK, so early bigport with some recesses cut would be the way to do it. Quote Link to comment Share on other sites More sharing options...
Sam_Q Posted September 8, 2009 Report Share Posted September 8, 2009 the valves are so far recessed in a 4afe head the stock 4age pistons should be just fine. Quote Link to comment Share on other sites More sharing options...
Hiro Protagonist Posted September 9, 2009 Report Share Posted September 9, 2009 For the amount of effort, why not just skim the head instead for compression gain? Quote Link to comment Share on other sites More sharing options...
Sam_Q Posted September 9, 2009 Report Share Posted September 9, 2009 I have to agree with that one Quote Link to comment Share on other sites More sharing options...
beerhead Posted September 11, 2009 Report Share Posted September 11, 2009 I think you lot are taking my hypothetical thinking out loud as some kind of directive. All I intended it to help someone who wants to build a very hi comp 4AFE in the future. BTW, put in a decent enough sized cam in your car and all shaving your head will do is ruin your cam timing and make it 100% necessary to run cam gears. Quote Link to comment Share on other sites More sharing options...
Sam_Q Posted September 11, 2009 Report Share Posted September 11, 2009 I disagree, I worked out a while ago that on a 20V if you shave a whole mm off the head you only changed the cam timing 1.5 degrees or something like that. Depending on the model of 4afe they have a huge cam gear and there would be less of a difference again Quote Link to comment Share on other sites More sharing options...
beerhead Posted September 11, 2009 Report Share Posted September 11, 2009 When you shave the head of a clockwise spinning motor you retard your camshaft timing, pushing the power band further up into the rev range. It sounds good, but just makes your motor less ping safe, harder to tune, and drives your peak torque higher. I'm talking here about putting a big cam in a motor not about stock cams... Cam timing is one of the most crucial things to drive-ability when you're building a revver. If your fitting big cams to your motor you want to advance your cam timing to the point where you bring your peak torque back to a useable point of the rev range. My mechanic says you can get away with skipping a full tooth back on many applications when you're hitting 300+ duration cams (5 - 10 degrees advance). So 1.5 degrees of retard is probably fine on a stock motor, with close to stock compression. But the fact is a high comp motor with big cams needs the cam timing advanced to the point that you can take full advantage of the power band, or your not getting the most out of your motor. I really don't get with the "She'll be right" attitude when you're changing a variable that Toyota would have spent millions of dollars getting right. It's a little bit like the 20V motors running there water similar to a 16V. Does it work... yes, but toyota spent millions redesigning the water distribution of the head to cool the intake valves first to reduce detonation, allowing for colder intakes temps and more HP. Some people see replicating as close to factory Toyota conditions as possible crucial, some think they know better... Quote Link to comment Share on other sites More sharing options...
Sam_Q Posted September 11, 2009 Report Share Posted September 11, 2009 you know beerhead I know that you have more practical knowledge than me but I am really scratching my head with this one. I did some proper measurements and I found that the FE gear I have happens to have a circumference of almost exactly 360mm, which means for every 0.1mm shaved off the cams get retarded 0.1degrees. So for a 0.5mm head shave you advance the cams half a degree. I said nothing in my previous post that related to me having a "she will be right" attitude. I was actually using the reference of my own experience on an engine using a cam gear that I used to alter the advance/retard and the results I got with it and other experiences of people with 20V engines. I admit what I worked on had a stock cam but I found that less than a few degrees did crap all. I admit it's not an ideal comparison but I would of thought from my experience and others that half a degree of retard it would do very little. So a bit of an educated guess maybe but not a careless expectation that it would work. I only have a basic knowledge with cam results in the real world, can you tell me how advancing a high duration cam causes the power to shift lower in the rpm, shouldn't it do the opposite? Also why don't the aftermarket cams off the shelf have the grinds offset so they automatically have them with the additional advance with the stock gears? I mean isnt that the point of buying an upgraded set? or is it in regard to making the most of what you have in terms of a compromise for overall driveablity? You probably already worked it out but the static calculated CR of the 4afe using the later head would be 14.4:1 using the smallport pistons and a 1.2mm gasket. Same goes for the 20V cooling system, I know that the de-icing chamber gets the hot water instead of the cold and it was designed to be that way. So as a result the air has to go through about 150mm of a port that might be around 40 degrees hotter. I have done my own testing with this and calculations, I have done comparasins between my engine and someone elses who has very simular mods and I ran this type of cooling system for about 4 years before I sold any conversion parts. As I understand it I am using something a cooling system design thats similar to a 16V that Toyota also spent millions on. There was no guesswork here, no assumptions and has been proven on the road and off at the racetrack by multiple people. I have busted my balls making sure everything I sell works and I have a lifetime warranty against defective work/function on my cooling parts to back it up. I think its really disrespectful you take a cheap stab at what I am doing and I thought I knew you better than that. BTW my offer still stands on refunding/swapping that early model rear bypass you ended up with simply because I think it could be better. All that said I admit sometimes I am going to screw up and get info wrong, misjudge something or make a wrong educated guess. All I ask is a polite reason why I am wrong. Quote Link to comment Share on other sites More sharing options...
beerhead Posted September 11, 2009 Report Share Posted September 11, 2009 Apologies for the thread hijack... Not all motors respond the same way, I probably get things wrong sometimes because of being taught too much crap by 2V V8 people, but I've been told many times that advancing the cam gives you better bottom end torque, I wish I could have experimented on my own car though bloody chains! Here's a link I googled by some triumph lovers about cam timing, not too bad - Cam timing I'm not sure about aftermarket cam's having there timing offset from the factory, but I've never heard of people not finding drive ability in some cam gears, so I'd doubt it'd be very accurately timed in. Without a dyno run between each cam timing change it'd be hard to really notice any real gain or loss in power due to cam timing not really making or loosing power, just shifting it around a touch. I'm sure you would see the power move around a little on a graph. Who knows the head shave with the extra degree of retard may make more power, I'm sure the extra comp will cancel out any losses if the cam timing makes a loss anyhow... Even stock cams gain in driveabilty with cam adjustable gears from most accounts so factory timing isn't great to start with. Sam, I was talking about most modded 20V water systems in general, not about your kit, Yager motorsport have been fitting a similar setup to clubmans for nearly a decade now, I bet AE86's in Japan were wearing similar setups before we even knew 20V's existed :jamie: My biggest gripe with the 16V water system in a 20V is when I overlayed the 2 gaskets I saw that the layout of the small varying holes over all the water passages were not the same. To my understanding these are what control the coolant flow throughout the head, you put a small hole at the start of the chain and a larger hole as you go along as the pressure drops. If calculated properly the flow through each coolant port should be the same. The 20V gasket would not distribute the water pressure in the head the way a 16V gasket would, I'd expect that the head wouldn't be as evenly cooled. I'm sure day to day driving like a nanna and a quick blap here and there wouldn't be a change in reliability, but I bet you all the money in the world you put 2 20V's side by side, one with factory coolant flow one with 16V flow, both revving on the limiter with unlimited fuel and oil that's changed on the fly I know what one would blow up first. Quote Link to comment Share on other sites More sharing options...
Sam_Q Posted September 11, 2009 Report Share Posted September 11, 2009 your right all engines would behave different , I just can't see 0.5 degrees doing much but hey I could be wrong. That link looks useful, I will have a look once I have time to thanks. So with the 4afe would the guy fit a single adjustable cam gear? if it helps a 16v model fits straight on if you swap the bottom gear as well, after that you should be able to fit the 4ag belt also. Either that or modify the stock gear. Making an independent gear for the exhaust is possible but a massive pain to do. Your right the gaskets are different. The 16V has the holes staggered to have the bulk flow from the back of the head to then let the outlet of the water to the front of the engine. The 20V is the opposite, running a 16V gasket in a 20V head will let the rear cylinders get more cooling than the front. With the cooling systems like what I use only the water in the port behind the throttles gets changed in direction, so by rights the cooling system flow in the other side of the head should not be any different in having equal flow, does that make any sort of sense? Quote Link to comment Share on other sites More sharing options...
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