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| bradders |
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I have an EBI (3.9 MPEFI) and the other day i bought an EA (3.9 MPEFI) that had been in a prang. I want to rebuild that engine. What things will i probably have to replace. What is the best way to get a lil more compression?? Valves, springs, cam, port n polish. what should be included and why? also how do i understand cams? with lobe and lift n things like that. thanks for your time. I want to do as much as i can. Also any one in perth wanna give us a hand? that would be sweet......
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| SVO XR6 |
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cam's and injectors should be the last thing to choose with a motor build.
They all depend on the flow and power output(also regulated by what ECu you have). But from what i gather you want to get a nice amoutn of power for a good price and easly. So i reccomend you go for a nice lil gring from wade or sure cam. Both offer a cam to suit and without ecu upgrade which is a bonus. With the head, dont go to crazy with flow, too much you loose tourque which is what a street car thrives on. But a tidy up of the ports and the rest of the head and you'll benifit. Also look into some XR valves, you can also have these back cut and a nice radius cut on the seats. also dont shave too much off the head, more comperssion is the ECU's devil. so basicaly the only thing holding you back is the ECu and money, story of most ppl's life 
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ha ha ha, where can i get xr valves from? what does back cut mean? made to have a smaller diameter? cut the seats? make them wider? How do i know what cam to go with?
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you want to do a radius, or a 3 angel cut on the valve seats. Basicly it flows easier.
cut back means taking the meat outta the back of the valve, again making it easier to flow and cams, you dont want to go too big, have a look at the wade website
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So really what i should do is take my head to a head shop and say, "make my head flow better" Do they do all the valves and springs at a head shop? with tighter spings does that mean it'll have better throttle response? what head shops should i go to? and how do i know i am getting a good price?
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go to all tourque, there awsome
The springs are goin to snap your valves closed quicker at high rpm, no valve bounce. but im stressing, dont go to far with the head work, youll go backwards
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| bradders |
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whats valve bounce?
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| opto |
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Bradders do some studying into what you want out of your car first and what you have in your car and what it can do at the moment.
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Thats what i'm doing. Whats valve bounce? All i want is a sleeper, don't want super quantities of power but i want a nice tidy amount. Not too bothered about sound systems and asthetics, later on i'll have to upgrade the suspension and brakes to compensate for the power increases. looks like a wade 1604 profile is what i'm after but i still can't interpret what the
Cam Lift Duration Duration Valve Valve Cam Lift Phase Adv @050 Clr Lift tdc <) or any of that means can some one please tell me how to understand cams!!!!. I know what i want to get out of it i know that my car has potentual, i just got to get to it!
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| opto |
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Okay firstly IN MY OPINION YOU ARE GOING AROUND IT THE WRONG WAY.
Upgrade your suspension and brakes first. If you have an auto, types of cams are limited due to upsetting the ECU (Engine management) and the transmission going into limp home mode, while you are doing the first two mods
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| Spork |
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Valve bounce is when the valves are thrown clear of the cam profile becasue there is insufficient spring forces to hold them there against inertial forces. Leads to valve/head damage and uncontrolled valve movement = bad performance.
Obviously a standard car is properly designed this is not a problem. When you get a "big cam" With high lift and steep ramps then it can become a problem. Cam manufactures will specify if you need springs. Really with the complexaties of your engine you don't have to worry about what all the duration lift stuff is. Except that Lift is how much they open, and duration is how long they are open. But it's all so complicated without reading a big book you arn't going to grasp how a cam will affect your car just by looking at them. Best to go with what other people have said about it or dyno graphs or bum a ride in someone's car that has one.
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Finally an answere to my questions thank you very much. Yeah i might be going about it the wrong way, i took my car to 180 today and standard suspension and breaks seemed to do alright. with upgrades i doubt i'll be too fussed going any faster than that. I could have gone faster than that aswell. Really the plan is to get better fuel economy and maybe thrash the occasional person at the lights. Its an auto and when i put a new cam in i'll be putting a wade 1604 in along with valves n valve springs n things. but thats not going to happen 4 a little while because today i bought a TT250 moto bike so i can take it on the dunes in lancelin :d!
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