The V8 Owners Forum -

Very interested - am waiting to get to the top of the list for merlins, i keep telling myself that they are not a cost effective tuning option for me, but can help wanting them. Did you run standard head before the F85s? If so did you notice a difference with that modification alone? Are they standard or ported?

Mine are standard apart from upgraded springs as I was getting valve bounce over 5800rpm. My previous heads were stage 3 with the bigger valves on standard modified seats and self ported. If you look back through the thread you will see the dyno sheets for both heads.
The Mechanical 238 cam seems to work particularly well with this setup.
Comp ratio is 10.8:1.
To answer your question, Yes I noticed quite a difference.

One of my latest clips to give you an idea of the performance compared to other cars.
http://www.youtube.com/watch?v=-L3MXmiEJW4

Mark

I spoke to John Eales recently who informed me that he is the european distributor fot the new TA heads and that he has 10 pairs on order.
Likeley to be more expensive than the Merlins but possibly able to make more bhp.

Little tub, have you any idea about the current hp with the 500 carb ?

As for TA heads, sounds like many are on the waiting list but very few have actually received them. TA Performance seem to be too busy to even reply the mails.

I had my car on the same rollers before and after the head swap. I gained something like 11 hp with Merlins compared to thr previous heads. No other changes, not even the ignition advance or carb jetting.

DaviesDJ wrote:Very interested - am waiting to get to the top of the list for merlins, i keep telling myself that they are not a cost effective tuning option for me, but can help wanting them. Did you run standard head before the F85s? If so did you notice a difference with that modification alone? Are they standard or ported?

I spoke to John Eales 3 weeks ago he said he had a pile of Merlin heads that he couldn't give away !!

minorv8 wrote:Little tub, have you any idea about the current hp with the 500 carb ?

As for TA heads, sounds like many are on the waiting list but very few have actually received them. TA Performance seem to be too busy to even reply the mails.

I had my car on the same rollers before and after the head swap. I gained something like 11 hp with Merlins compared to thr previous heads. No other changes, not even the ignition advance or carb jetting.

I dont know what the power was with the carbs but have been told with the injection it is about 330bhp with 330ftlbs of torque but i will get that confirmed myself. The idea is to run a standard engine with loads of torque so that it doesn't have to be revved very high to perform and so should be reliable !!

mgbloke wrote:I spoke to John Eales recently who informed me that he is the european distributor fot the new TA heads and that he has 10 pairs on order.
Likeley to be more expensive than the Merlins but possibly able to make more bhp.

Anyone wanting the merlin heads should give JE a call, he says they are crap and has some that he cant give away !

Nigel dean built a Dax Rush V8 for a kit car mag, he chose the merlin heads maybe he can shed some light on their performance !

http://www.nigeldean.co.uk/Raptor%20F85.htm

330 hp is quite a number, I doubt that Piper 285 cam in in a 4,6 engine with 9.35 comp ratio would ever be that powerful (unless the rolling road is optimistic...) no matter what the induction system is.

minorv8 wrote:330 hp is quite a number, I doubt that Piper 285 cam in in a 4,6 engine with 9.35 comp ratio would ever be that powerful (unless the rolling road is optimistic...) no matter what the induction system is.

Fair enough i'll take your word for it and will post honest figures when i get the car on the rollers, in the new year.
Maybe it will be in between the 307bhp that RPI achieved on that rolling road youtube video with a standard 4.6l and the 330bhp quoted. I hope so anyway!
i am a novice tech wise, so please bear with me, i bought 4.3 LITRE V8 with quad 48mm dellortos brand new from TVR in 1998, they claimed it was 330bhp ??
the guys that have been doing my engine work consider anything larger than a 4.6 too big because the heads cant handle the air flow and actually get decreased performance with the bigger bored blocks ??
cheers

Yes I know the RPI video and to be honest I was expected similar increases in power. Take std 4,6 bottom end, fit Merlins and score 300 hp. Sure thing, piece of cake.

On thing to consider, factory 4,6 block may not even have the claimed 9,35:1. I know my half engine didn´t when I took it apart. Pistons are typically 0,040" down in the bore. Do the math and you may be closer to 9:0 or even less depending on the manufacturing tolerances.

Now, Merlins have larger chambers (31-32 cc) than 4.6 heads (26 cc). Fit the Merlins with no changes and your CR will be lower. The fact is that the Merlins flow better but they are not phenomenal. I had my heads tested in flow bench (as others also have) and the results are similar. The flow levels at about 10 mm lift to 180 cfm and that´s it.

TVR power figures are legendary, friend of mine bought a Cerbera with AJP V8 that is supposed to have something like 400 hp from factory. The previous owner spent £6000 on engine upgrades and the engine now as almost the quoted factory power (only 70 hp missing when measured before the upgrades...)

Yes, heads are strangling the Rover engine and TA heads look promising. Are they better than Wildcats ? Who knows, I am yet to see a power graph from a Rover engine with TA heads. The problem is that they may flow huge numbers at high lifts but where do you get cam and matching valve train that can support lift up to 0,700" ? The flow figures are irrelevant especially if you can´t reach those lift values And if the low lift power is killed the same time there really is no point.

I bet you will have serious traction power in your tub already at 300 hp mark.

But based on what I have tested with my engine and Merlin heads: 4,6 bottom end, CR around 9:0, std(ish) cam will probably see something like 280-290 HONEST ponies. Don´t fall for wheel hp + 25-30 % power loss in drivetrain crap if you have a manual box. I have typically seen 25-30 hp losses with LT77 + 3.08 diff from dyno to dyno.

little tub: 330hp with STD fuel injectors.. No way.. If it is TVR horsepower then maybe..

I made my friend 4.6engine with those merlin heads, good thinks what i saw those heads are combustion champer shape and exhaust port is rised slightly, but my home modded rover head exhaust port outflow merlin port..
Friend is installing this engine right now, and then it will go to rolling road.. Then we saw if those heads are any good..
ps: i made some porting those heads, in stock they are bad..

J.Eales say his CNC rover heads are slightly better than ported merlin heads.. CNC will give approx 10hp more than ported merlin..

TA-heads are quoted approx 10% more horsepower than J.Eales CNC heads.. So spending +3000£ on heads, is it worth?

minorv8 wrote:Yes I know the RPI video and to be honest I was expected similar increases in power. Take std 4,6 bottom end, fit Merlins and score 300 hp. Sure thing, piece of cake.

On thing to consider, factory 4,6 block may not even have the claimed 9,35:1. I know my half engine didn´t when I took it apart. Pistons are typically 0,040" down in the bore. Do the math and you may be closer to 9:0 or even less depending on the manufacturing tolerances.

Now, Merlins have larger chambers (31-32 cc) than 4.6 heads (26 cc). Fit the Merlins with no changes and your CR will be lower. The fact is that the Merlins flow better but they are not phenomenal. I had my heads tested in flow bench (as others also have) and the results are similar. The flow levels at about 10 mm lift to 180 cfm and that´s it.

TVR power figures are legendary, friend of mine bought a Cerbera with AJP V8 that is supposed to have something like 400 hp from factory. The previous owner spent £6000 on engine upgrades and the engine now as almost the quoted factory power (only 70 hp missing when measured before the upgrades...)

Yes, heads are strangling the Rover engine and TA heads look promising. Are they better than Wildcats ? Who knows, I am yet to see a power graph from a Rover engine with TA heads. The problem is that they may flow huge numbers at high lifts but where do you get cam and matching valve train that can support lift up to 0,700" ? The flow figures are irrelevant especially if you can´t reach those lift values And if the low lift power is killed the same time there really is no point.

I bet you will have serious traction power in your tub already at 300 hp mark.

But based on what I have tested with my engine and Merlin heads: 4,6 bottom end, CR around 9:0, std(ish) cam will probably see something like 280-290 HONEST ponies. Don´t fall for wheel hp + 25-30 % power loss in drivetrain crap if you have a manual box. I have typically seen 25-30 hp losses with LT77 + 3.08 diff from dyno to dyno.

Thanks for the informative reply ! i will definitely get it on a RR and let you evaluate the results for me.

The car is quick but i found inconsistent performance with the carb and ran out of gearing too soon with a T5 box and a 3.92 diff. When it comes back with the injection and the 3.14 diff, it will hopefully be transformed.

anyhow all this talk of BHP, is Torque not more important ??
Cheers!

kokkolanpoika wrote:little tub: 330hp with STD fuel injectors.. No way.. If it is TVR horsepower then maybe..

I made my friend 4.6engine with those merlin heads, good thinks what i saw those heads are combustion champer shape and exhaust port is rised slightly, but my home modded rover head exhaust port outflow merlin port..
Friend is installing this engine right now, and then it will go to rolling road.. Then we saw if those heads are any good..
ps: i made some porting those heads, in stock they are bad..

J.Eales say his CNC rover heads are slightly better than ported merlin heads.. CNC will give approx 10hp more than ported merlin..

TA-heads are quoted approx 10% more horsepower than J.Eales CNC heads.. So spending +3000£ on heads, is it worth?

Cheers for the reply !
it will be interesting to compare your dyno results with the home ported heads against my standard ones, especially if both engines are standard.
thanks Steve

DaviesDJ wrote:Very interested - am waiting to get to the top of the list for merlins, i keep telling myself that they are not a cost effective tuning option for me, but can help wanting them. Did you run standard head before the F85s? If so did you notice a difference with that modification alone? Are they standard or ported?

Heads are not ported, i did not have this engine with the standard heads but we should be able to find some dyno stats for a standard 4.6L to compare.

cheers