Dont worry i seached but i couldnt find anything on this… I was just thinking the other day what can i do to my engine that will give it realiable horsepower and efficiency without a turbo because Ima be swapping next summer. And i remembered that shaving the cylinder head will increase comp ratios but i Have no numbers for this, and i have a few question that need answering:) People who are knowledgable in this area can you shine a little light for me. Its all for a stock KA…with a short ram.
What comp ratio’s can I expect from a shaved head?( the highest possible that would be safe for the engine, no detonation or anything :S)
How much more power can I expect from this high comp ratio?
How much more efficient will my car run?
Does anyone know any shops that will do this? and and estimates on how much it will cost.
Would i need to change timing to do this properly?
and any personal input on this would be great, tell me what you think.
i belive youir best bet to raise compression is to use some sohc pistions , i know shaving the head will cause trouble with lining up the timing chains and timing marks , but if ur gonna go turbo next year dont waster your money, just save up and spend more money on extra goodies for your force fed plans
not that im tring to be a jerk, but you didnt search very hard. ive been researching something very similar for the past week. theres lots to be found here aswell as Zilvia. as hector said SOHC pistons will raise the compression to 11.5:1 or 12:1 depending on the pistons. alot of people think 10.5 is the best for NA so aftermarket foreged pistons would be your best bet, but much more money than SOHC pistons. I have also heard that you cant use too agresive cams with SOHC in DOHC setup because the valves will hit the pistons, anyone have more info on that?
There’s lots to be done in the N/A field, but generally speaking the motors available to us kinda suck at it. SR has awful valvetrain, KA is too oversquare. To make power you need to rev and keep revving (and ofcourse not have your torque die)
Couple of things for n/a EDIT: this is for DOHC KA
headers, high flow cat, catback, pulleys, ignition (msd 6a + blaster coil is a good idea), GSXR ITBs w/ velocity stacks.
And higher comp pistons, angrier cams (or just use two exhaust cams to save $) Some headwork too. If you get real cams, usually you need to do valves and valvesprings and retainers, you’re prolly gonna get into oversized valves, so you’ll need to machine your valve seats. VERY good idea to balance and heat treat and/or shot peen your crank and rods. Walbro fuel pump and SR injectors or better.
Finally run a standalone and tune it.
You’ll still prolly make less than 200whp, and you’ll be out 4 grand atleast. If you want to go fast, spend those 4 grand on coilovers & r-tires. Or get an SR-swap if you want straight line.
to go deeper in the cams, the two S13 exhaust cam swap (248/248), people said it was too agressive and that only up in tha high end has power. the best from people’s opinnions were to run 248/232. thats an S13 exhaust cam on the intake. and the S14 exhaust cam on the exhaust side. this will give you good mid to top range power. i heard that difference in max hp of 248/248 and 248/232 was only bout 2whp.
You said I can get sohc pistons that will make 11.5:1 and 12.:1 depending on the pistons… which piston will make which ratio. I think this is the best aproach I can do this myself. no machine shop needed… and sohc pistons should be cheap as hell. I will most likely go with this method… any suggestons?
and about getting coilovers… I have stiff lowering springs and adjustable damping… Should be enough for now. and for the post way up there I didnt mean im goin turbo with the KA… swapping for sr or if things go good… rb.
Back in the day I had an 86 Mustang GT… While researching a head swap, if I put certain heads on the 5.0L I would have to notch the piston for valve clearance. I’m sure there is a shop that will notch SOHC pistons for you if you get aggressive cams.
You should probably make up your mind about what you will want in the end, before you start spending money. Some of the things like raising compresion will not work with a turbo.
If you are willing to spend 4g’s on building up your car there are allot of thing that could be done.
Twice i said Im NOT TURBOING THE KA… ill want to raise compression because im sure I can get sohc pistons for cheap and I can do the work myself as i have access to a shop…I will be doing a complete swap afterwards for an SR or RB. that said. krgoodwin said “as hector said SOHC pistons will raise the compression to 11.5:1 or 12:1 depending on the pistons.” depending on the pistons? How many different Sohc pistons are there… sorry im not familiar with the sohcs.
From what i hear, some of the early SOHC engines had 9.1:1 compression instead of 8.6:1.
EDIT: Did some research and apperantly SOHC engines produced before February 1989 had 9.1:1 compression making closer to 150hp instead of the 140hp advertised.
huh… interesting there are 3 SOHC engine pistons? 11.5:1, 12:1 and 9.1:1? very interesting… Ill do some research too but this is getting confusing now…and an 11.5:1 ratio with 91 octane sould produce at least 180hp no?
94 from sunoco would be better. some say that you’ll get about 4% HP gain per compression point raised. so from 155HP at 9.5:1 to 167.4HP at 11.5:1. So no, it will not make 180HP. 180HP would probably require cams, full exhaust, ITB’s, maybe built up internal to rev higher and definatly a good tune. But ive never done it so what do i know? All of this adds up to more money and work than an SR that will make more power. Also from what i hear high comp KADE’s dont last all that long.
Actually its not a rustbucket… Its a black 92 coupe with spotless rails that have never been patched. there was 4 dime sized holes in the floor that have been patched and there was some suraface rust in the spare wheel well that i sanded and painted… so no its probably in better condition than most s14s…Anyway so people think its not worth doin the swap? that it wont be reliable… And is this 4% per point thing true? i always thought it was a bit more.
which pistons make the 10:1 ratio? the 9.0’s or the 8.5? they cant both make 10:1. you have any proof of this? everywhere ive looked all i see is theories and opinions. there was one guy who posted equations and came up with 11.5 and 12:1 compression.
frankly, you arent going to have the 88 sohc motor that came with higher compression pistons.
secondly 90% of the na ka shit on son was posted by me, there actually is a motor we built floating around someplace that was never used.
Brand new rebuild, rings, bearings, timing gides, tensioner, head gakset, all new head seals, springs etc etc etc. Entire thing was powdercoated the same purple as the d2’s.
talk to wayne, or Andrew about sohc pistons in a dohc.
Honestly, the marginal improvement in performance you will gain is not worth it. For drag/straight line, it makes so much more sense to save your money for boltons for when you swap to an SR, and for track it makes so much more sense to get wider wheels with R compounds and coilovers. It’s just really really bad value for the money. The only reason to do it is if you want to have a really cool experiment, learn how to build engines and have some fun in the process.
Thats acctually exactly what im doing over the winter. I havent decided if im going to put it in a car or not. probably not since it will be the first engine I build and wont last past 5 000km.
Put it in, and beat on it till it dies.
Honestly though, if you do it right, there’s no reason why it shouldn’t last. There’s guides on how to put a KA together, and just get someone else to machine your block and stuff. Powdercoat it in Cusco Blue to spite lucky :lol: