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Discussion Starter #1
I've been thinking alot about our engines lately and the keys to tuning them to make it a viable option as a performance engine.

Back in the day I used to think that we were hampered by the factory equipment more than the zetec was. Ie: like our exhaust manifold resembles a crappy flowing log style turbo manifold while the zetec manifold would flow much more. That is partially correct but if our head is the real restriction to performance, opening up the intake and exhuast pipes isn't gonna help to much on a stock head. I have most of the bolt-ons and ran an egt header for a few days and yet still my car is slow and teh gains have been minimal. I used to think that we would see more gains since our motors are more restricted but nowadays I think bolt-ons should be bought last if your short on cash and the main problem should be fixed first and that is the head. The main thing that seperates the zetec from the spi in performance is the fact that it has twice as many valves. Dohc isn't as important as the fact that it will have better flow than we do becuase of a much bigger flow area.

I think we will benefit the most from porting and polishing the head first and dedicating the most attention to that to help level the playing field and increase the flows in and out. Getting rid of any restrictions from things like an exhaust should be done later. All the money that is spent on bolt-ons could easily get you a kick but p&p, 3-angle valve job and decking to raise the compression which is also a little lower than a stock zetecs.
 

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Ditto. Although I keep changing my mind alot on what I want I always come back to P&P of the heads and manifold and then to finish the rest of the ntake and xhaust work. Infact after my dampers that would be the next thing to do...only if I can find a spare head etc.
 

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Gig has something here...the stock CVH US spec head sucks for flow.. even the old 1.9 HP wasnt that great.

i will tell you this however, the SOHC CVH can be made to flow almost as much air as any similarly sized DOHC engine. the SPI has some very very nice sized valves, and larger ones can go in too; thing is, the intake runners are too restricted for the size of the valve, and the exhaust ports are usually so course its a wonder the exhaust can find its way out.

with moderate porting, keeping the stock valve sizes and just removing the excess casting from the valve throat, we can increase our power output by UP TO 20%. its been done before with other CVH engines. the stock cam at this point is getting to be the weak point too.. so a stage1 or better cam is highly recommended. another 8% power increase can be seen by matching the cam to the head, higher lift with moderate duration is key to a good "near-stock" engine.

after that, go to town on your intakes and the HO header, the 2.25" exhaust.. they'll have more impact and greater benefit now that the major restrictions are gone.

all said, intake, exhaust/header, with above mentioned head work will easily get us lots of 150hp n/a SPIs.

Don't believe me? ask the UK CVH tuners..they do it all the time.

Good topic Gig.
 

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As soon as I swap my car to manual transmission next year then the engine mods for me can resume. Frankly right now my auto scares the [censored] out of me...so I aint touchin it.


But...hopefully I will have AT LEAST located a spare head by then so I can just take it to a shop and have the port/polish/spit shine the damn...the key is in the spit shine


Then all of our power concerns will be tossed..haha
 

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Discussion Starter #6
Yeah gabe, gotta ditch that auto! I'm dying to do mine!

Pony, I couldn't agree more!
Btw, there might be some 150 crank hp spi's running around already, wink ,wink, nudge, nudge.
 

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If I were to do it again.....
Screw bolt on's, screw pot mod's, screw Split Port magic... When I look back on it, I spent so much time and energy trying to get 2 hp from a throttle body or spent $300 on a chip, I'm sure I can think or a bunch of little things I did in the quest for power. If I was to start all over again I would go right in to turbo charging. Yeah the SOHC dose'nt flow the best compared to a DOHC, but the SPI does have large valves for being a CVH. Boost fixes all the problems.

I would leave the head stock, it's not all that bad at all. Even the bottom end is strong, well yeah the pistons could benifit from forged.
I'm putting 6 psi to a stock SPI, I'm just at 1000 miles and not a thing has gone bad, I just g-tech'd this week end and pulled 154 Wheel hp!
dont know if I could do that again, but I just about pissed my self.
 

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there might be some 150 crank hp spi's running around already, wink ,wink, nudge, nudge.
guilty.

the head is the problem. Ive long thought about how to overcome the benefits of a DOHC. the biggest thing is being able to time the cams independantly. Right now I am doing some math to figure out what exactly I need from a camshaft. Since I cant tune independantly I need to get it right the first time. Ive seen a nice gain by taking the head to a race engine service shop and having them port and polish as well as do a 3 angle valve job. the valves seat nicer and seem to flow more. Im not sure exactly how much gain there was from this as I had the head decked at the same time. I posted before that it was 11:1. however after talking to Ray at Parks Engine Services, I discovered that after the addition of a new custom metal gasket, the real compression ratio is 10.3:1. I like that alot better because Im still running stock internals. so far Ive run 10K miles and had no trouble related to the actual engine componants. My last dyno yeilded 134/141 (if I remember correctly) NA and 128/190 with nitrous. I know the nitrous number seems odd. I question it too. I talked to gig about it and I have an appointment to dyno in Austin in the next week or two. I dont have the charts available because I just moved and most of my stuff is in boxes still. or I might have tossed it in the clean up. sorry. So I guess, believe what you want. anyway, head work seems to be the key. unfortunately Ford has decided to only sell fully loaded heads. so you'll have to find a used one if you dont wanna grind your current head. BTW, the whole job cost me 150$. thats less than a TB.
 

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SO glad mine is getting P&P'd as we speak.
 

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so whats everybody doing for headwork?

ive got a stage 2 cam and race tension valve springs going in soon.. but im having a valve job done first.

im thinking 3 angle is sufficient, and possibly have the machinist do some mild porting here and there.. especially where it needs it (in the valve throat and valve seats).

im expecting to be stunned after the p&p, valve job, higher rate springs and the (duh-nuh nuh nuh!) Crane stage 2 cam.
 

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Discussion Starter #12
I'm going to try and experiment with some magor intake port re-working and welding mixed with some combustion chamber smoothing and valve un-shrouding. Standard 3-angle job done with the efp springs and maybe an spi-lx regrind on the stock cam. Some stainless valves to cope with the heat. I want to try and see what I can do n/a before it's turboed. I was swayed away for a while and was gonna keep the head stock but I'm back on track now. It would take to much boost to get the power I want unless I do lot's of headwork.
 

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I have an Escort EXP turbo head if somebody wants to try it. It has a few small cracks across the valve reliefs, but I think they are repairable. No cam, but the valves and springs are included. The intake and exhaust ports are HUGE compared to the SPI ones.

Note: It will not work with our engine without major work. It MAY work with the Escort crowd, though.

Jim
 

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i doubt it will work for us either..
maybe a 1.9 or an older 1.6..
but it would probably just lower the compression..
i did some thinking and the whole idea of playing with my head
seems more feasable and less fuel-consuming than the turbo right now.. and I could always turbo later
i think what did it for the turbo idea was one of the ERDT guys saying that they got 25 mpg with 6 PSI.. not on my daily driver.
I would be SO
broke come winter.. if i get another car i'll go there but geez.. to go from 35+ to 25-
 

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ok, i'll sound like the dumb one. What exactlly is involed with a 3-angle valve job??
 

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Discussion Starter #18
You take the head off and send it out to place to cut different angles on the inside of the valve seat. This helps make the air flow past the valve better when it's open.

There are some pics of a multi-angle valve job at the bottom of this page. http://www.automotiverebuilder.com/ar/ar119854.htm
 

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I think we will benefit the most from porting and polishing the head first and dedicating the most attention to that to help level the playing field and increase the flows in and out. Getting rid of any restrictions from things like an exhaust should be done later. All the money that is spent on bolt-ons could easily get you a kick but p&p, 3-angle valve job and decking to raise the compression which is also a little lower than a stock zetecs.
This is not only applicable to the SPI. You can bolt on all day and the ZETEC is still puny. Headwork should be at the begining of the list not the end. Unfortunatly, we are all focaljet Zombies programmed to want 1000 bucks worth of mods that bolt on and give 15 hp.
 

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Discussion Starter #20
speak of the monkey devil...


How did your monkey head project go brad?
 
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