The V8 Owners Forum -

Ok, what is worth the money and what is not ?

Take a set of std heads, have it ported, fitted with new valves and guides and machined and you will pay what ? xxx quid. I have ported my old heads and have it machined and yet paid something like 500 quid for work and parts. That figure excludes my own work and supplies etc. With Rover sourced heads the valve size is limited given their location to cylinder CL. It is possible to do serious porting if one is ready to weld some material here and there.

Add the costs and you are close to what Merlins cost provided if you can get them. Sure, had I known that on my specific engine they only give that 11 extra I might have thought twice. I had the money and decided to get them. To be fair the current spec is far from optimized compared to the former spec: less CR and valve geometry is crap.

I doubt that Timo is happy with his current 5,2 engine output but it also needs some work. I just wanted to measure the changes at same rolling road so someone else may or may not benefit from them. It would be fun to fit the old heads back and use the single plane manifold with them but that is unlikely to happen... unless... Another interesting thing would be a modified EFi manifold sitting in the garage. I have not decided yet what to do next but the spec will be definitely different the next spring.

One thing is certain, if you buy Wildcats or TA heads, do not expect miracles at lower revs. They will excel at high revs but it also means that the rest of the engine must be treated equal: big cam and sturdy bottom end.

kokkolanpoika wrote:
merlins flow only 191,4cfm as rover stage 4 flows 183cfm at the same flow bench @ 28" Thats why they aren´t so popular.. And if they are good heads, why there is no more dyno sheet available? Because they dont give power. I dont belive..
.

Well you just hit the nail.............not
Tell me why are they sold out every time.......cause they don't work ????

You can not compare apples with pears. Its the engine combo that makes the horsepower, not the heads alone.
Stage 4 heads on a mild combo will loose horsepower and drivebilety.
But after reading all your post on this subject Ill guess you are an experainced engine builder so you know where you'r talking about.
So you also know how much horsepower increase stge 3 heads will give on Minors engine combo compared to the Merlin heads he have.

Then costwise not shure about Finland but here in Holland it cost a fortune to build stage 3 or 4 heads out of standard heads. I had just to pay Gbp 1000 for my full Merlin kit including springs, wasted stem stainless steel valves, valve springs all fully assembled and ARP head bolds.
I can not even rebuild standard heads with new guides at the machine shop overhere.

Next dyno figurs.............don't mean nothing if they are not made on the same dyno. We both can build the same engine combo while Ill dyno it here and you dyno it in Finland. I am shure we will have differend readouts. And the difference will be more than 10bhp. As long as the dyno sheets aint from the same company, you can not compare them at all.
Thats the reason I wont show my dynosheet cause its worth nothing more than an indication.

So yess I am happy with the 10 bhp improvemend you think I have

Well someone has a flow figure so. . . 183 for fully ported rover heads against 191 for as cast aftermarket heads to me that seems a pretty good start for a performance engine from the look of the chamber you have a decent squish area which means you can use flat top or reverse crown pistons and increase CR and if the flow of the merlins is continued beyond .450 of lift (where rovers usually max out because of port turbulance) you can use a faster higher lift cam and you are looking at a good gain. 11BHP just for a head change on a 4 litre engine that is otherwise in a mild state of tune is actually pretty good when it is not otherwise optimised to benifit from the extra flow.
Full Flow figures would tell far more of the story.
As said above it is the combination of parts thst the heads allow that counts and I think with a starting point of 191 cfm you could see well over 210 with a basic clean up of the castings, a figure far out of reach of the rover castings, then you will see much better power figures.
Best regards
Mike

I am following this with interest. one thing sticks out as mentioned above we are comparing apples and oranges here. One a fully maxed out hand ported cylinder head, the other is a basic raw casting. Yet, the raw casting still gives a HP improvement. The potential in these heads is obvious, given some thought and work by a decent head porter who understands airflow the future is bright. At the price they are a bargain in my mind and as soon as funds allow they will be on the car.

Alan

JP. wrote:

kokkolanpoika wrote:
merlins flow only 191,4cfm as rover stage 4 flows 183cfm at the same flow bench @ 28" Thats why they aren´t so popular.. And if they are good heads, why there is no more dyno sheet available? Because they dont give power. I dont belive..
.

Well you just hit the nail.............not
Tell me why are they sold out every time.......cause they don't work ????

You can not compare apples with pears. Its the engine combo that makes the horsepower, not the heads alone.
Stage 4 heads on a mild combo will loose horsepower and drivebilety.
But after reading all your post on this subject Ill guess you are an experainced engine builder so you know where you'r talking about.
So you also know how much horsepower increase stge 3 heads will give on Minors engine combo compared to the Merlin heads he have.

Then costwise not shure about Finland but here in Holland it cost a fortune to build stage 3 or 4 heads out of standard heads. I had just to pay Gbp 1000 for my full Merlin kit including springs, wasted stem stainless steel valves, valve springs all fully assembled and ARP head bolds.
I can not even rebuild standard heads with new guides at the machine shop overhere.

Next dyno figurs.............don't mean nothing if they are not made on the same dyno. We both can build the same engine combo while Ill dyno it here and you dyno it in Finland. I am shure we will have differend readouts. And the difference will be more than 10bhp. As long as the dyno sheets aint from the same company, you can not compare them at all.
Thats the reason I wont show my dynosheet cause its worth nothing more than an indication.

So yess I am happy with the 10 bhp improvemend you think I have

As you JP. say in the another topick witch link i posted here "above".

Cause those guys running them turned away from this forum. Why?

I had more than 10bhp increasement when switching over to Merlin heads. Dyno sheet please.

But hey I won't even bother to scan my sheet and post it here.
Why? Because it wont make any serious increment?

If they are sold out, where all the guys are who own them? Also more dynosheets..

In Finland stage 3 3angle valve seat job, inc milling heads ïs approx 200£ inc vat + valves and guides excample v8 tuner?
Stage 4 valve seat job, new bigger seats, milling heads + manifold face, pressure test to heads, fitting new guides (also old guides pressed away) cost approx 650£ inc vat + valves and guides etc. total is near merlins price? + my local flow bench guy wants 200£/pair, but i always port my heads and manifols by my own hands.

Well finally got my merlin heads fitted and managed to keep the 10.8:1 CR. Had a RR session today and the results are promising. Spec 4.6, 4.0L pistons 238 mechanical cam. Very happy with the result.

Mark,

Don't keep us in the dark i'm sure we would all like to see the dyno read out with the M238 cam.

What hasn't been mentioned in the previous threads is the nice flat torque curve from 2000 RPM upwards shown on the Real Steel engine dyno.

Quoted peak power figures can be very misleading if they are only achieved over a very narrow rev band.

The Merlins raised exhaust ports and Weslake style combustion chambers point towards an efficient design and if there is room for further development then they must have a bit more potential.

Kevin.

I guess Ill have to confess Havent fitted heads yet.
As there seem to be some wind up merchants I thought I would join in. Lol

Wont actually get the engine running until Feb 10 but hope to have the same CR and will use the same rolling road as before.

Interestingly RS claim that the Merlin heads are not suitable fo the 3.5 could this be because they flow too well?

Mark

mgbloke wrote:
Interestingly RS claim that the Merlin heads are not suitable fo the 3.5 could this be because they flow too well?

Mark

Thats exactly what Charles @ Real Steel told me, they flow to well for a naturaly aspirated 3.5 resulting in to low air speed.
But on a supercharged 3.5 it works very well cause the supercharger keeps on pumping air even while its not boosting so at all times there's enough airspeed in the runners.

So to compare, do stage 3 rover heads work OK on the 3,5?

Anyone?

mgbloke wrote:So to compare, do stage 3 rover heads work OK on the 3,5?

Anyone?

Well they will if all the other parts suit the application, would be a waste with a stock cam and SUs though.

The Merlins must be considered not only as a good head out the box but also as a good base from which to start. Real Steel have managed to center the valves in the bore with the Merlin heads and for that reason alone they have more ultimate potential than ANY stock casting ever, period. They have done this while retaining a pretty standard valvetrain arrangement.
They have not been made in great numbers as they seem to be being made up as and when they have been paid for, understandably, in these times, Real Steel does not want a lot of cash sitting on their shelf in rover parts.

I would imagine that TA heads nor Wildcats are not produced in big batches for the very same reason.

HairbearTE wrote:.. for that reason alone they have more ultimate potential than ANY stock casting ever, period.

Whilst I agree in principle the problem is there is only a very minute percentage of the stock castings that have been taken to their potential - and in terms of how many / how long for those it makes you wonder?????

Lets review the figures. All the numbers I have seen for stock heads are around 105 cfm, fully ported around 180-185 cfm, untouched Merlins are 190+ cfm. In terms of bang for buck they are a screaming deal. Ok you may be able to port stock heads to match for a similar price, its not going to be much cheaper, then you have thin walled ports and all the issues which can occur with ported heads. These can range from porosity, cracking, hot spots in the water jacket etc. To be honest I cannot see the issue here. OK at present a small gain over fully ported stock heads, but a huge improvement over stock heads. Anyone not already having ported heads is going to see a massive improvement. It just remains for the supply to improve.

Alan

Mike