Merlin Heads

[kokkolanpoika]

Why to hell they make merlins, it hey are any better than stage 4 rover heads. As i understand before they cast them that merlins should be better than stage 4 race heads, and slightly worse than wild cats, so they should be flow approx 210cfm? If wild cats flow 237cfm and rover 183cfm..

I i need heads, i will go for John Eales CNC ported heads or V8 developments.. Or wild cats.. But this is my opinion..
I think Rover heads will give better dyno readings hole rew range..

[bigaldart]

But they match the stage 4 heads now as cast, therefore the potential when ported is much more. I still see no problem with them and they are a very good price. Compare the price for a new pair of heads, rocker covers and outrigger rocker stands and then pay for stage 4 porting, new valves etc.

Alan

[kiwicar]

And that flow increase is at low valve lift where it is difficult to improve by normal porting techniques and on an engine with a flat tappet cam like the rover, where the flow really counts.
Mike

[HairbearTE]

Think of the benefit on say Ian S' engine.. Group A can, low lift, long duration. Already revs like a nutcase.. could make for an awesome combo

[bigaldart]

I would certainly love to try a set under the blower on the dragster. 9.45 on totally stock heads, what do you reckon with a set of these?

Alan

[kiwicar]

I recon you may have the most to gain, you are running alcahol aren't you? just the bigger droplet size should really benfit from the more modern chamber shape.
Best regards
Mike

[kokkolanpoika]

But they match the stage 4 heads now as cast, therefore the potential when ported is much more. I still see no problem with them and they are a very good price. Compare the price for a new pair of heads, rocker covers and outrigger rocker stands and then pay for stage 4 porting, new valves etc.

Alan

As I understand that John Eales has got ported merlin heads, and they dont flow anymore than stock merlins?
If you guys want more power, why dont you port merlins ang give the dyno results here?
Minor v8 has got ported inlet track, but dyno results are not very impressive to me..

[Darkspeed]

I need to do some further checks and tests on the bench this weekend to see if the results I got on the exhausts on the Merlins are correct - It would be nice if I still had them.

The numbers I ran on the Merlins for the exhaust flows were lower than I expected - subsequent tests on a stock SD1 appear to match up with flow results from other sources so my initial thoughts of suspecting a bench issue appear unfounded.

Rules of thumb for people with far more experience than I state to get good results the exhausts should flow about 70% of the inlets

.7 x 185 = 129 CFM - the test on the Merlins came up as 108CFM - less than 60% so something I need to check.

On the ported Merlins front Eppo reported that John was seeing more flow after working the heads - 120CFM @ 10" compared to 110CFM @ 10" stock. £1200 for the base heads then another £x00 to get them to flow nearer to what they should for the valves fitted does seem a bit odd.

The issue appears to be that they are not a simple bolt on and go big flow package. They do appear good value but with reported problems with rocker gear - rocker covers - exhausts - and having flow no better than a good Stage 4 does raise some questions.

Of these 40 sets that repoted to be are out there I need someone to have a piston let go and destroy one so that they can send it to me to do further tests and take the carbides too.

[kiwicar]

I cant see a graph of stage 4s against merlins bus I cant imagine they are much different from the stage 3s at low valve lifts the stage 4s may peak at similar levels to the merlins, however as repeatadly stated the valve actually spends little time at full lift with a flat tappet cam and low lift flow is far more important to performance and here the merlins show gains in the 12 to 14% range, this is a big differance, and as I have said several times is very difficult to get using standard porting techniques, and is rearly achieved with bigger valves and port pollishing. Interpreting these graphs is key to understanding how to gain performance and selecting other modifications. Flow figures at peak lift in isolation do not tell you what is going on.
Best regards
Mike

[spend]

Is stage 4 a well defined enough product to be able to be sure you have representative data anyway?

I know plenty that port to the detriment of flow due to other factors, and minor differences give significantly different results.

I agree with Timo good heads are not a detriment, there have been plenty of 400+bhp examples.

[HairbearTE]

Is stage 4 a well defined enough product to be able to be sure you have representative data anyway?

I would say yes, the griff 500 head is widely accepted to be stage 4. I understand your angle though, all this stageX nonsense means different things from different manufacturers. I've heard that Real Steel used to do a stage 2 rover head that was better than other suppliers stage 3. This of course is where having a flowbench is so useful, helps to step around all that BS and work with some solid figures.

[spend]

I would say yes, the griff 500 head is widely accepted to be stage 4.

The TVR 500 heads have full size guides, and there are other significant areas that can be improved. Dom, V8D and Jamie all do it slightly differently as well from what I've seen. By your definition then would you class all those modified heads as stage 5! or is it just UBV must be stage 4 - back to my original point.

With the advent of better efi and ignition control many of us have started to use race cams and I suppose what you would call race heads - TB's allow even more radical things to be done. We've not even started to consider the 1.75/1.55" valved variants..

[kokkolanpoika]

I cant see a graph of stage 4s against merlins bus I cant imagine they are much different from the stage 3s at low valve lifts the stage 4s may peak at similar levels to the merlins, however as repeatadly stated the valve actually spends little time at full lift with a flat tappet cam and low lift flow is far more important to performance and here the merlins show gains in the 12 to 14% range, this is a big differance, and as I have said several times is very difficult to get using standard porting techniques, and is rearly achieved with bigger valves and port pollishing. Interpreting these graphs is key to understanding how to gain performance and selecting other modifications. Flow figures at peak lift in isolation do not tell you what is going on.
Best regards
Mike

Excample real steel 5.0 made 336hp and 352ft/lbs of torque, Is this carb or injection?. Cam is guite agressive 224/231 @ 0.05" lift 0.508/0.512 ? Cr 10.5:1. And i think fuel curves and ignition timing is optimal..

My 5.2litre engine HOME ported "stage 4 heads" 43/38mm valves 8mm steam. CR 10.7:1. Mechanical Cam 238/238 @ 0,05" lift 0.50" - clearance It made without any adjustments 324hp @ 4970rpm when lamda is over 15.. torque 382ft/lbs.
So my heads ar ported like piece of shi..t and ever see a flow bench, and all parts are ordered spending my own imagination.
It will give guite impressive results in my mind.. Ì´m hoping to see 360hp when i can get fuel mixture correckt.. and over 370-380hp when i fit throttle bodies..

I think 200cc dosen´t mean anythink, maybe more torque? (bottom end is 5kg heavier than normal 5.0/5.2litre engine, i have got forged crank)

[HairbearTE]

I would say yes, the griff 500 head is widely accepted to be stage 4.

The TVR 500 heads have full size guides, and there are other significant areas that can be improved. Dom, V8D and Jamie all do it slightly differently as well from what I've seen. By your definition then would you class all those modified heads as stage 5! or is it just UBV must be stage 4 - back to my original point.

With the advent of better efi and ignition control many of us have started to use race cams and I suppose what you would call race heads - TB's allow even more radical things to be done. We've not even started to consider the 1.75/1.55" valved variants..

As I said above I don't like to describe any heads as "stage" anything. There are a series of popular mods that are included on rover heads that people associate with a certain "stage". Can you imagine seeing a pair of "stage 3" SBC heads on ebay? It'll never happen. Likewise a head that could be used on one race engine could equally be used on another street engine. In the rover Market I guess you could legitimately refer to a fully ported Wildcat as a race head but that's about it. I'm building Buick300 heads with Ti valves (1.73/1.55) and I'm welding up the chambers to get some good CR with my large overlap cam. Do I consider them race heads? No.

[poo slinger]

I would say yes, the griff 500 head is widely accepted to be stage 4.

The TVR 500 heads have full size guides, and there are other significant areas that can be improved. Dom, V8D and Jamie all do it slightly differently as well from what I've seen. By your definition then would you class all those modified heads as stage 5! or is it just UBV must be stage 4 - back to my original point.

With the advent of better efi and ignition control many of us have started to use race cams and I suppose what you would call race heads - TB's allow even more radical things to be done. We've not even started to consider the 1.75/1.55" valved variants..

As I said above I don't like to describe any heads as "stage" anything. There are a series of popular mods that are included on rover heads that people associate with a certain "stage". Can you imagine seeing a pair of "stage 3" SBC heads on ebay? It'll never happen. Likewise a head that could be used on one race engine could equally be used on another street engine. In the rover Market I guess you could legitimately refer to a fully ported Wildcat as a race head but that's about it. I'm building Buick300 heads with Ti valves (1.73/1.55) and I'm welding up the chambers to get some good CR with my large overlap cam. Do I consider them race heads? No.

so what you are saying is that some heads that work well on a race engines will have no posotives on a fast road street engine?