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chad123

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Creating an HF All-Motor Monster


Overview:

This is dedicated to everyone driving around in an 88-91 CRX HF getting 50 miles to the gallon. Honda’s little 8-valve motor is great for fuel economy, but as you HF drivers will attest lacks the power to chirp the tires when driving spiritedly. For those wanting a very inexpensive solution, keep reading. For fewer than 500 dollars you can transform your CRX HF into an all-motor beast that’s capable of running high 14’s.



The Setup:

For starters, you’ll want to find a DX head off of any Honda motor. Newer heads are better for the obvious reasons and they can be found everywhere. Look to spend no more than 50 dollars on a clean DX head. Next, search the local junkyards for a 4th Generation Si intake manifold. This should cost around 25 dollars, although friends with Honda’s will probably have a few lying around so this could be had for even less. Ideally you’ll want a CRX Si Distributor, CRX Si Ecu and CRX Si transmission for the setup, along with a timing belt the same year as the head. For example, if it’s a 95 DX head, you’ll want a 95 DX timing belt. Other belts will probably work, but its guaranteed to work if you use this setup, although you can match parts numbers to make sure everything is to OEM specs.

What Makes the Power:

Well, if you’ll remember the HF motor has an 8-valve head, which is great for fuel economy and miserable for performance. The 16-valve head will raise compression substantially creating a surprisingly powerful hybrid. Now, what kind of numbers can you expect from this setup? A friend of mine recently used a similar setup and put down 112, 109 to the wheels. With this type of power, look to be pulling on GSR’s, Civic Si’s and even the occasional unsuspecting Type R owner.



Conclusion:

Remember, this setup should cost no more than 500, and if you have a CRX Si parts car sitting around this should cost no more than 150. Using Si parts will yield the best parts but if you’re trying to keep a budget a DX transmission/ECU will work if their readily available. And the best part, when you blow up this motor you’ll have saved enough money to buy a ZC, D16Z or even B16A. (SO HERES MY QUESTION ...WOULDNT I GET MORE POWER IF I USED A SI HEAD INSTED OF A DX HEAD OR WOULD I HAVE A PROBLEM WITH THAT HEAD ?? I HAVE ANOTHER QUESTION WOULD I REALLY BE RUNNING IN HIGH 14S WUTH THIS SETUP...ANYONE THATS DONE THIS SWAP PLEASE TELL ME ..THANKS!!)
 
umm, Si head and IM might give u a slight edge, but not to much, also ... dont use DX, its dual point, when HF is multi, just go straight for the Si IM and Head, then put i/h/e and u might be running mid 15's. no way in hell ur gunna run 14's tho. also , most likely ur engine will blow up sooner b/c of increased load on parts not made to take the higher compression.
 
the dx head has nothing to do with the fuel injection that is why the article states but an si intake manifold which would be a multi point injection setup
 
the 4th gen DX and SI heads are identical.... The difference is the valve train including cams, and the intake and exaust manifolds... if you want to do this swap, get an DX or SI head, the si head, either way you will need an adjustable cam gear to use the SI cam (DX cam will work reguardless) the si cam gear is half a tooth off. also you may need to get a taller head gasket or clay the motor to make sure that the valves clear the pistons...
 
OK you don't have to get an adjustable cam gear, and there are no clearance issues. If you do it right it will be very reliable. You are basically building a MPFI 1.5, Honda did the same thing with a 1.6 block. You can even use a head from a 92-95 1.5 Civic (D15B7), it should be in better condition. Use the 88-91 Si Intake manifold and you are set.
 
do i have to have a SI disributer for this setup?? or would i need that for more power
 
Required, you are going from 2 injectors to 4, it has to spark with each of them. The Dx one just won't work.
 
HF dizzy should work then.

Why Mini Me? VTEC isn't everything. Get a cam from Deltacams.com and a Y8 IM with a B series TB.
 
sorry for jacking your thread, but, im in the same situation right now, and if you did go to the y8 im could u use that hondata gasket to lower temps? Also the pistons, i have a 90 and could the pistons possibly have 16 valve reliefs? and if not, could it still be ok or what should i do? and finally have very little experiance, i changed my timming belt, other belts, and h2o pump when i got hte car, should this be enough knowledge to successfully pull this off? thanks and sorry again.
 
i read that the si head woudn't work on a d series block :wtf: is this now saying it will?
set this straight someone....both crx and civic dx have the same block, correct? - therefore doing this in a dx is the exact proceedure, when you do the mini me modification why the hell not just do the mpfi mod while you are at it, when you do the mini me you have to replace the IM right? if so why not therefore get the mpfi IM?, also mpfi says replace the distributer right?, so why not go with an si one?....isn't it possible to bolt on an integra throttle body, pretty sure they are 60mm - wouldn't you have to port the IM?

there should be an article placed on here about doing an MPFI conversion, also with the mini me - both have bin a very talked about mod lately
 
biglee

Yes Yes and Yes. Yes you can use Y8 IM and Hondata Gasket, Yes you could have 16 Pistons ( if not you can grind some valve reliefs into your current pistons, or get a used set of 16 V ones for $25 from a yard or new for $150 ish from Honda), and yes it's about the same difficulty as a timing belt change.

93dxKID

Any SOHC D series head will bolt onto any SOHC D series block.
 
you can't go vtec on an HF. it will hit the pistons.
you can't use a 4th gen si head either. the valves will hit.

the reason the dx works is because it DOESN'T hit the non-reliefed piston (remeber, the hf is an 8 valve), and thats what creates the super compression, and hence power.
 
The DX / Si heads are the same. The cams are different.

Not all the HF's have non relifed pistons. Like I said if not change them.

The power comes from changing the cam and getting a better flowing IM. NOT compression.

Have you seen a HF intake manifold and throttle body? They are half the size of a Si one.
 
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