Merlin heads anyone?
Discussion
I wish 
Excuse my ignorance on this one but can you use the standard inlet & exhaust manifolds with these heads?
Even if the inlet manifold fits, if you've got to build new exhaust manifolds it's going to get very costly, in that case wouldn't it make more sense to go with decent set of modified standard castings?
Anyone know the definitive answer to the Merlin heads manifold question?
Even if the inlet manifold fits, if you've got to build new exhaust manifolds it's going to get very costly, in that case wouldn't it make more sense to go with decent set of modified standard castings?
Anyone know the definitive answer to the Merlin heads manifold question?
ChimpOnGas said:
Excuse my ignorance on this one but can you use the standard inlet & exhaust manifolds with these heads?
Even if the inlet manifold fits, if you've got to build new exhaust manifolds it's going to get very costly, in that case wouldn't it make more sense to go with decent set of modified standard castings?
Anyone know the definitive answer to the Merlin heads manifold question?
Far as I know dave the exhaust manifolds are very slightly higher (not a problem) and the intake does have to be modified slightly inc porting etc Even if the inlet manifold fits, if you've got to build new exhaust manifolds it's going to get very costly, in that case wouldn't it make more sense to go with decent set of modified standard castings?
Anyone know the definitive answer to the Merlin heads manifold question?
I only posted it up I am not saying they will go straight on etc they don't interest me 
From what I've seen this seems to be the definitive post on Merlin heads:
http://www.v8forum.co.uk/forum/viewtopic.php?t=550...
If you can be bothered to read all 27 pages
If not I'll do my best to summarise by unpicking the key bits of info that seem substantiated and relevant, please do correct me if I've missed anything or have misrepresented what I've surmised from this post.
Firstly there's a bit of typical forum sniping going on, there's a pro camp and a very vocal camp that throws a lot of doubt over the benefit of Merlin heads when compared with a decent set of ported standard castings with the 43mm inlets & 37mm exhausts.
Certainly it seems John Eales doesn't rate Merlin heads although he perhaps has commercial interests elsewhere that may or may not play a part, however there is a recurring statement from another poster stating a set of JE CNC ported heads flow one more CFM than the Merlins.
But it does seem the OP "Mark" has the best overall first hand knowledge of the Merlin heads as he's developed them on his extremely quick 4.8 litre MGB, so I'll mostly stick with his feedback in my summary.
Firstly there definitely is some work required on both your existing inlet & exhaust manifolds to use them on these heads, so there's a cost from the outset that perhaps you wouldn't have with ported Rover castings.
While Mark did eventually make an excellent 356.5hp from his 4.8 build, he did end up doing some porting work to the heads to remove some strange detailing in the port castings, further modifications were required to accommodate his roller rockers.
It should also be noted that the big jump from Mark's 326hp he originally made with these heads to the 356.5hp final figure coincided with the move to Canems and throttle bodies, it seems likely to me these are the two changes that brought the extra 30hp more than the porting work?
Without the Canems & throttle bodies the engine was making just under 68hp per litre, as we know a well built 5 litre RV8 with a set of decent heads from V8 Developments regularly make 70hp per litre.
So for comparison we really need to see what one of JE's or Rob's engines on throttle bodies can make before we get too excited about Merlin heads.
The post seems to end with two key points from the OP Mark that stand out to me:
1) He ends by taking about an engineering company in Slough that could possibly solve his porosity problems, this suggest to me the issues may have been ongoing & never fully resolved by the laser welding paid for by the original supplier Real Steel
2) Mark also makes a final statement that he's going to sell his Merlin heads & replace them with a set of TA heads
All the above and Mark's last two statements seem to suggest the Merlin heads aren't the full shizzle they claim to be
In summary perhaps this means the most cost effective & trouble free solution to better heads on your RV8 still lies at the door of John Eales or Rob Robertson?
Discuss
http://www.v8forum.co.uk/forum/viewtopic.php?t=550...
If you can be bothered to read all 27 pages
If not I'll do my best to summarise by unpicking the key bits of info that seem substantiated and relevant, please do correct me if I've missed anything or have misrepresented what I've surmised from this post.
Firstly there's a bit of typical forum sniping going on, there's a pro camp and a very vocal camp that throws a lot of doubt over the benefit of Merlin heads when compared with a decent set of ported standard castings with the 43mm inlets & 37mm exhausts.
Certainly it seems John Eales doesn't rate Merlin heads although he perhaps has commercial interests elsewhere that may or may not play a part, however there is a recurring statement from another poster stating a set of JE CNC ported heads flow one more CFM than the Merlins.
But it does seem the OP "Mark" has the best overall first hand knowledge of the Merlin heads as he's developed them on his extremely quick 4.8 litre MGB, so I'll mostly stick with his feedback in my summary.
Firstly there definitely is some work required on both your existing inlet & exhaust manifolds to use them on these heads, so there's a cost from the outset that perhaps you wouldn't have with ported Rover castings.
While Mark did eventually make an excellent 356.5hp from his 4.8 build, he did end up doing some porting work to the heads to remove some strange detailing in the port castings, further modifications were required to accommodate his roller rockers.
It should also be noted that the big jump from Mark's 326hp he originally made with these heads to the 356.5hp final figure coincided with the move to Canems and throttle bodies, it seems likely to me these are the two changes that brought the extra 30hp more than the porting work?
Without the Canems & throttle bodies the engine was making just under 68hp per litre, as we know a well built 5 litre RV8 with a set of decent heads from V8 Developments regularly make 70hp per litre.
So for comparison we really need to see what one of JE's or Rob's engines on throttle bodies can make before we get too excited about Merlin heads.
The post seems to end with two key points from the OP Mark that stand out to me:
1) He ends by taking about an engineering company in Slough that could possibly solve his porosity problems, this suggest to me the issues may have been ongoing & never fully resolved by the laser welding paid for by the original supplier Real Steel
2) Mark also makes a final statement that he's going to sell his Merlin heads & replace them with a set of TA heads
All the above and Mark's last two statements seem to suggest the Merlin heads aren't the full shizzle they claim to be
In summary perhaps this means the most cost effective & trouble free solution to better heads on your RV8 still lies at the door of John Eales or Rob Robertson?
Discuss
ChimpOnGas said:
So for comparison we really need to see what one of JE's or Rob's engines on throttle bodies can make before we get too excited about Merlin heads.
Discuss
I have one of Rob's 5.0 litre engines, running an ACT triple TB plenum, and my old 500 heads heavily worked by Rob. If you guys want to chip in and buy me a set of ITB's with JE xover manifold I'd be quite happy to dyno and test this setup, and provide a full written report, motoring journo stylee at no extra charge Discuss
..Guys? hello? where's everyone gone?
ChilliWhizz said:
I have one of Rob's 5.0 litre engines, running an ACT triple TB plenum, and my old 500 heads heavily worked by Rob. If you guys want to chip in and buy me a set of ITB's with JE xover manifold I'd be quite happy to dyno and test this setup, and provide a full written report, motoring journo stylee at no extra charge ..
Guys? hello? where's everyone gone?
..Guys? hello? where's everyone gone?
Nice try Chilli
Bobby Shaftoe said:
I'm not sure why the Merlins get such a bad rap.
Perhaps because some people who've used them have reported porosity issues, and for various reasons have ended up needing to fettle them a bit.And because in the real world they don't necessarily seem to give much more power (if any) than a set of JE CNC or V8D heads, well nothing properly proven that I've seen yet.
Bobby Shaftoe said:
They're also ~£350 cheaper than Eales CNC heads, and the Merlins still have additional porting potential, supposedly upto around 210-220 cfm, wheras the rover castings are at the limit without welding additional aluminium on to the head.
Point taken, but I'd be very disappointed if I bought a set of Merlins only to find they were porous. Bobby Shaftoe said:
As for V8 Dev/Rob heads, again £300 more expensive and i've never seen any flow figures for them, so a complete unknown quantity and will vary on who the porting has been subbed out to and the quality of the original casting.
But I'd balance that by saying Rob always seems to totally stand by what he does & that counts for a lot in my book, who actually makes these Merlin heads anyway and what come back have you got of they start leaking coolant after a couple of years of use?On the cost question, I believe these Merlin heads are £1405.55 new.
Does that mean the Eales CNC heads are £1750 & Rob's are £1700 ?
So the Merlins are cheaper but you do have to fettle your manifolds to make them work, so that's going to close the gap a bit.
And what can you expect from any of these heads anyway, 40hp perhaps?
How long will it take before you get used to 40hp, not that long I'd guess?
I'm not suggesting they are bad value as undoubtedly there's a lot of work in these worked on heads, but even the cheaper new Merlin heads cost you £35 for every pony you gain.
Still they are all a bit cheaper than an SC Power supercharger once its up & running properly, which by my calculations could cost as much a £50 per additional nag, mind you're adding 100hp there & you're definitely going to feel that.
I think I'll keep saving for the blower
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