Merlin Head flow datas

[kiwicar]

I think the above says it all, 20% increase below .4" lift is a very large amount of increase and would favour shorter duration cams and cams with ramps designed for road use. for a race engine I would think a relativly short duration mechanical roller cam with lift around .450 to .480" lift would be stunning with these heads, with a wide LSA say 112 to 114 degrees, say 210-215 degrees duration. It would also be consistant with the 230 duration mechanical flat tappet cam working well while the 240 degree version with more lift not working so well.
With so much extra low lift flow, but close to the same peak flow they really demand a different aproach to the tuning and porting of the heads. I woulld be very interested in seeing how these heads compared on a pulsed wet flow flow bench, I bet that is what they were developed on and probably give even more dramatic results compared to ported rover heads.
Best regards
Mike

[Wotland]

Anyone wanting to develope a pair of ali buick 300 heads can find mine on ebay right now, complete with set of Titanium big valves.... pm me forum members if you want to finish auction early

Marcus,

do you know the weight of your valves ?

[kokkolanpoika]

I had a Merlin head compared to my homeported big valve 4,6 head on same flow bench. The merlins flowed up to 20 % more than the modified 4,6 head up to 0,4" lift where the Merlin flow just leveled. They still flowed more than the Rover head. I need to find the chart for exact numbers. I also took the car to RR session with both heads and Merlins were better at low revs, mid range was about the same and again Merlins were better at higher revs. With Performer manifold and 500 cfm carb the power increase was 12 hp. Swap to Wilpower manifold gained another 20 hp. In retrospect I hoped more but there are still details that need attention so hopefully there is some room for improvement. Single plane manifold did ruin the low rpm response compared to performer manifold which was to be expected. I am thinking about fitting EFi so that may changes things considerably. Real steel dyno chart in their catalogue is with single plane manifold and carb, not efi.

Your ex heads valves are 41,5mm/35,5mm. If you put 43/38mm valves on your head, i think flow capacity will increase slightly = same results as merlin?
You have to try put your old heads back to your engine and get RR session again with Wildpower manifold.. I will estimate that Results is 12hp more than Performer manifold.. I understand that performer is designet to approx with 250-270hp..

[kokkolanpoika]

The trouble here seems to be there are still no proper back to back flow figures for merlin heads and other "ported" RV8 heads, done on the same flow bench under consistant conditions. It is pretty obvious that the various bits cast into the heads are intended to optimise flow on pretty standard mmanifold (I suspect EFI, but again little information to confirm this) so for a result that means somthing it would seem to me a good idea to flow test these heads with a manifold bolted on, just a narrow radius on the gasket face of the port will be meaningless. Secondly these heads seem to be optomised for low lift flow, so lets see some figures for low lift flow to compare. finally some results were obtained with the valves removed all together, these are totally meaningless as the valve in any head iis key to getting the flow over the seat, pulling the valve out can result in a reduction of flow in the order of 35%.
The couple of guys who have built engines using these heads don't report results "similar to stage 4 heads" they report results a very large amount better, MGbloke reports 320bhp out of his engine, looking at the rest of the spec of his engine, especially the cam figures suggest that under certain circumstances these heads produce quite remarcable results. It is very interesting that another tuner using a cam he believes to be better that has about another 15 thou lift cannot get these heads to work, that would suggest to me that moving the valve too far from the seat on these heads causes the flow to become turbulent over the seat and flow suddenly drops away and these heads are designed to work with a specific aproach to tuning.
As I say results from engines built by people who I have alot of respect for (members of this forum) definatly suggests that these heads are good when used inteligently in a well ballanced package not too far from standard rover and that there is more to the story than peak flow figures.
Sorry rant over
Mike
edited to replace MGBV8 with MG Bloke

MGbloge has got similar engine as mine, but only 4.6litre as mine got 5.2litre. I think cam is same M238, not sure for CR and exchaust manifold size.?

He has got stage 3 heads before RR session, I´n my mind it is not comparable to stage 4 heads flowing capacity.

http://www.v8forum.co.uk/forum/viewtopi ... &start=150

MGbloge 277.6hp @wheels/326@flywheel.. 17,5% power loss
My 5.2litre made 301hp @wheels/336@flywheel.. mine has got 12% power loss.
I have got home ported heads with stage 4 valves 43/38mm. + siamesed plenum witch may give slightly worse results than single/twin/triple plenum (spoke to John Eales)

Those dyno results are not comparable because we have got those result from dffrent dynos.. Not sure if i have got slightly smaller cubic capacity, results may be almoust identical with Merlin results..? -23hp difference with 600cc engine size?

My Ex 4.6engine made approx 242hp@wheels/280@flywheel (cant find graph now) torgue was same as MGbloge with Merlins 323lbft but only 3820rpm..

I think i can quarantee that if we made 4,6engine first stage 3 heads, then we change stage 4race, it will give 30hp more than stage 3heads? Because those small valves dosent flow enought air for that size engine.. Bigger the engine = hard to get more power with those heads.

http://mez.co.uk/TuningTheRoverV8-pt4.html 35hp difference between 4.6 and 5.2litre

[mgbloke]

Timo
What specification was your 4.6 when you made 242bhp at the wheels?

Mark

[kokkolanpoika]

Timo
What specification was your 4.6 when you made 242bhp at the wheels?

Mark

Home ported heads, std valve guides/springs, with stage 3 valves 41,5/35,5mm.
Kent H214cam,
10,5CR,
std 65mm plenum, std 38mm trumpets,
std 3,9efi ECU "no chip"+ injectors, fuel pressure 3bar + (faulty fuel pump, pressure drops 0,5bar at full throttle)
4-1headers primaries are 1,5" tube + 2.35" secondary pipe feeding into 3" tail pipe/outlett.
I´t made this 242RWHP dyno testing with my friend race 4,5litre engine ECU JE-motors promise 299hp at flywheel.. With std ECU it will made 238RWHP.. So it will run lean..

I estimate that it will give close to 300flywheel horsepower when i sell it.. Modifications are home made 45mm trumpets, home made 72mm plenum + Bosch big fuel pump + 315cc injectors and Bosch red coil.. + Haltech engine magnament.

Now i found a dynosheet, but i just bought new computer and my scanner dosent work with this.. So i cannot prove it yet.. Have to call my nerd friend..

[350matt]

so basically the Merlins are still a good buy is the upshot of all this

[kiwicar]

Hi
Yes for a fast road/ moderate competition engine definatly, if it is for the ultimate big displacment all out for the last BHP drag/ sprint/ circute engine engine then it would be Tomcats
Best regrads
Mike

[minorv8]

I took my Merlins apart and attacked them with a grinder. I got some info from USA where a guy bought Merlins and took them directly to a Buick V6 specialist. They made some worthwile improvements, getting the intake flow to around 220 cfm along with improvements throughout the lift range. Similar results with exhaust also. Mods included port work, removing the fillet in the intake corner and the fin in the port, deshrouding the chamber, attention to throat area etc. I also had them machined 0,020" with the final CR at 10,5:1.

The engine is now back together but since there is 2 ft of snow and ice you need to wait for additional info.