As i said, a zetec bottom end actually cures the camshaft problems in the cvh head as they get good oil pressure for a change

 

The zetec was originally designed as a "lean burn" engine, but the govenment changed its mind on emmisions laws and ford were forced to put it into production as a lambda1 cat emmisions engine

 

There does seem a strong arguement for both the ZVH and Zetec turbo's... Ive seen alot of so-called 300bhp+ Zetec turbos and ZVHs which have been easily dismissed by a well running CVH turbo. But then of course theres loads of BIG BHP ZVHs and Zetecs out there, esp when you look to the likes of Area Six and Sitech.

Surely if the zetec bottom end has better oil pressure then that will help the CVH head loads. But then again, if your gonna go through the agro of buying a zetec engine and fitting it in the engine bay then skimming the pistons etc you may as well put the Zetec head on it and save the cost of machining work for the block etc to match the CVH head. Theres adaptor plates out there for zetec-cvh manifolds! So even a full zetec can be put in reasonably cheaply. Its all down to opinion isnt it?

 

correct

 

I dont think it's misinformation Simon, we are comparing the cost of building a 300bhp ZT to a ZVH.
Both need pistons and rods which cost about the same but the ZVH needs far more money spent on the head as you've said above, porting, cam, solids, port work and even if you spend that money it will still not be a responsive as a ZT, where as the ZT just needs valve springs.

If you want to compare stock engines...
The CVH bottom end may have a poor oil system but it can take more power than a Zetec, the CVH head flows badly.
The Zetec bottom end may have a better oil system/pressure but the pistons and rods cannot take much for a turbo application, the Zetec head flows far better not only for max bhp but for response too being 16v.

So by sticking a stock CVH head on a stock Zetec bottom end you get an engine that cant take much BHP and that cant breathe over 5000rpm.

IMO there is no performance advantage to building a decent ZVH over a decent ZT, it will cost more for the same power and not be as responsive or as economical.

 

It may help but it cetainly doesnt cure it!
Part of the cam wear problem is poor oiling yes, but the other factors are the very heavy valve train putting massive pressure on the lobes and lifters and of course the trend of por quality blanks being uesd to produce CVH cams in recent years.
Karl Norris fitted a oiling rail of some description to a CVH head to try and help the cam wear issues and it made no difference, you can also fit high pressure relief springs to the stock pump, or shim them to the point where the oil pressure is so high it blows out the side of the filter but the cam/lifters will still wear.
It's a combination of all those factors and really the point here is that a Zetec head will flow better and it has none of the CVH heads problems, flow, cams, rocker studs pulling out, rocker arms snapping.

 

The only reason i can think of is originality and old skool looks, with the reliability/torque of the zetec. Plus its easy to use the original CVH management/fuel system with a zvh, plus zetecs are easier to find than cvhs these days. But dont get me wrong i think its great people are still pushing the boundarys of the ORIGINAL rs turbo engine.

 

cheap set of £30 c20xe mahle pistons and the zetec is good for around 310

no the zvh is more responsive than the full zetec

 

Originality and old skool looks is not a "performance advantage" though is it? If you do it for that reason though then of course fair play!
It is great that people are still developing the old CVH like Stu Collins for example pushing massive power out of his.
If I were to build a new engine though it would be a ZT for sure.

 

These fit on stock rods and the stock rods can take 310bhp?
How can a ZVH be more responsive than a ZT? It has an 8v valve head with massive ports if done properly lol

 

have you not heard of "go faster stripes" karlos?

 

The C20XE pistons are better than the LET pistons, then as Karlos points out don't the rods become the next weak spot.

I think what is needed is a CTec, CVH bottom end with a zetec head lol...?

 

have you ever seen the likes?

 

lol
See now if they actually bolted up in theory you would have an engine good for 250bhp (bottom end), responsive, economical and reliable (top end) with no mods at all! lol
The exact opposite of a stock ZVH!

 

yes the rods on the zetec at 310 are at the same stress has a cvh at 250

a zvh with a good big port head makes it even more responsive

i have driven and modified all 3 engines

most who call the zvh has never drove one or it has been cheaply built

 

No they're not mate, a CVH at 250bhp is 62.5bhp per cylinder and a Zetec at 310bhp is 77.5bhp per cylinder, but your point is that stock rods can take 310bhp yeah?

A 16v head that can flow 300bhp compared to a 8v head that can flow 300bhp will always be more responsive as the ports and valves are smaller increasing gas velocity, so a ZVH will not be more responsive than a ZT all other factors being equal of course.

 

People say ZVH cant rev because they leave it on the puney T3 and poor head work. That your ZVHs dont rev quote.

The standard Black bottom end takes 250bhp then the rods give up.
The standard CVH take 230bhp reliable then the rods give up.

ZVH cam £150
Solid followers £150
Std valve std springs.
Sitech ZVH head gasket simular to cometic price.
Porting.
Sorry? how expensive?

Thing is I like Zetecs, my last one done for a customer 505bhp

 

Ive had 300hp going through mine for the past 2750 miles with no probs ,

thats also including 3 track days 3 trips to the strip and 2 bruntingthorpe thrashs

silvertop zetec

 

lol
Simon I notice you didnt put a price for porting, to you that may be free but to the rest of us it isnt, my NMS head cost around £580 without a cam and lifters so thats £880 in total and that is the sort of quality headwork you need for a ZVH to work well as you know.

I dont agree that 230bhp is the limit of CVH rods, Jimbo Gibbs for example runs just over 250bhp and gives it hell with no problems, it's raising the rev limiter that will send one through the block.

None of this really matters anyway my point was just that unless you like the look of a CVH head in your bay for oldskool value or just fancy a ZVH or whatever, there is no reason to spend the money needed to make a good one when for similair or less money a ZT is a better engine, performance, economy and reliability.

 

I was pointing out it does make sence. However I can now see it your opinion we are discusing, which makes it pointless to carry on.

I have put my experiance into this tread, feel free to use it or ignore it.

 

it's a bit daft this "zvh is shit crap".
Karlos, build one and drive it, then comment.
i have run cvh turbo's and zvh turbo's, now building a zetec turbo.
i liked the cvh turbo but thought it was missing something, i loved the zvh turbo as it gave a big torque surge from low don that the cvh didn't have and you just need to hold the steering wheel tight lol!
however the zvh didn't have the revability of the cvh due to the head being way too restrictive as the VE was lower.
so now i want an engine that can rev well and give great power and top speed due to the extra useable revs

the way i see it it costs about the same to get a zvh and a cvh to 300bhp (probably the cvh costs more), certainly will cost less to get a zvh to 350bhp (ask bomber about his 369bhp zvh and say it's crap) than a cvh 1600.

the age old saying of "no replacement for displacement" has so much truth.

 

Yes mate it is only my opinion, there is no right or wrong, always good for others to see differing opinions and options though.

 

Late response as I've been busy at work with a big contract whilst trying to redecorate my office at the same time. 9.30am till 11.30pm at night leaves little desire to browse PF!!

My post is based on my experiences of building and driving RS's over the last 12 years and I agree with Karlos completely.

First off, the CVH head.

Large heavy valves that can't dissipate heat quickly leading to premature valve head failure when used hard. The weight of such large valves require big springs to make sure they close properly, adding stress to the valve train. The heavy springs cause large amounts of pressure onto the cam lobes and rocker studs, leading to premature wear of the cam lobes, followers, and pulling out rocker studs from the soft alloy head.

The Zetec bottom end.

Long stroke with poor rod ratio making it produce decent low down torque, but hindering it's ability to rev as well as having a weak oil pump. It may have decent flow but if you suffer a set of cracked gears in the pump, it can wipe out your expensive engine. Luck of the draw whether it lasts or not. Thinner bore walls than the CVH. The rod ratio was revised on the black top making it better to rev.

The ZVH.

I've driven a few of varying spec, and every one irritated the shit out of me. Tons of torque all at once (with massive wheel spin, followed by a disintegrating gearbox) then nothing after 5.5k rpm. With a T34 they are marginally better but still fell flat on it's face. They just feel like they want to produce shit loads of power and then don't.

The CVH.

The bottom end is good although quite harsh and needs good balancing. Oil pump is ok although I have found that they can be a bit hit and miss as to producing oil pressure on older engines of seemingly good repute. Strong as an Ox with steel rods. Just lacking in capacity required to spool larger turbos.

A decent spec Zetec is a long way from a ZVH as is a decent spec CVH. I would ultimately like to combine a Zetec head onto a CVH bottom end but lack of front oil returns causes big issues.

 

back to the porting thing, for a cvh to hit big power it needs good porting and bigger valves, just as the zvh does.
IMO and i mean mine alone, the zvh is a good compromise for getting bigger power than the average cvh turbo, but the ability to rev doesn't make it the most practical.
doesn't matter to me now as i'm going full zetec, but i did enjoy the zvh (till it's out this week ready for selling on to it's next owner or sitting in my garage waiting

 

I had a 2.0 zvh turbo in an escort with a t34 turbo which i didnt like! the same engine has now been fitted to my xr2 with a stg 3 hybrid turbo and larger exhaust housing and it goes like fook! im happy enough with the way it is and will do for just now! if i change my mind and decide to keep the car i would go with a frs engine with gt28r! too much hassle mucking about with spending money on pistons,rods etc when you can just buy an engine which is ready to go in!

 

ive got a mtx75 gearbox sat at work. its off my old 2.0ltr zvh turbo. you can have it if you want it mate.