215 vs 300 flow differences, exh. port spacing and size question.

[Wilitrun]

Hello,
Based on a phone call with Mark LaGrou today, I was hoping someone has a definitive answer to this question:
How significant are the dimensional differences between the exhaust ports of a 215 vs 300 head, and how much more flow is being handled below the 5000RPM range between these two engines, in their stock form?

[BlownMGB-V8]

Best thing would be to look up Dan Jones' reports on head flow. But the short answer is that yes it does make a difference. The ranking basically goes 215/3.5 R, late R, 300 alloy, 300 iron, Merlin, TA. Not sure whether the Merlin or the iron 300 flows more.

But that's only half the story, the other half is chamber volume. You can't just pull a set of 215 heads and bolt on 300 heads.

Jim

[Wilitrun]

Thanks Jim, I do seem to remember a report like that being discussed here before. I'll look it up.
I should add the reason I'm asking about this is that Mark advised strongly against using the D&D Block Hugger headers on a 300 full stop because he felt they were too restrictive and the differences in port size between the two heads likely meant I would not be able to keep exhaust manifold gaskets in place with that manifold.
While I don't dispute his expertise there don't seem to be any other options other than RV8 style (are they optimized for the 300 either?) or making my own, which is simply far beyond my expertise - or budget to hire someone else to do it. So I'm hoping someone has some raw data that'll help inform me on how bad these manifolds will actually be on my car.

[mgb260]

TSI has blockhuggers for $325 and "big bore RV8 style" though the fender well header for $525. The big bore headers are what Ian has on his car..

http://www.tsimportedautomotive.com/MGBv8conversionparts.html

[MGBV8]

I posted this on that other forum.  

However he did say that he doesn't recommend these headers for the 300 as the ports are not a match to the 215 (which they are meant for) and not only will they be restrictive to flow, but I may have an issue keeping the gaskets in place. His only other suggestion was to build a custom set of headers myself.
      
      
   

   Sounds like he has never really used them on a 300.  Mike Moor swapped out his 215 for a 300 back around 1997-1998.  He used the 215 block hugger headers on the 300 until just a few years ago.  They are surely a bit restrictive (for any engine), but I witnessed that 300 with the 215 block huggers rear wheel dyno at 306 HP.  I was impressed.
   
   http://www.britishv8.org/MG/MikelMoor.htm
   
   
   Mike has since replaced them with a custom set of bigger tube RV8 style headers built by his good friend Terry Senneker.  Not sure if they are available at Senneker Performance.
   
   https://www.fastcarsinc.com/.
   
   
   BTW, I bought my ceramic coated block hugger headers & ceramic coated Y-pipe from Dan LaGrou in 2001.

[Wilitrun]

Thanks Jim and Carl,
I saw the other post, I'm just trying to cast my net as wide as possible so I can be the most informed before making a final choice. Your argument (and long experience with the headers) is very compelling.
Carl, in the 21 years you've had this combination on your car, and by your picture you're doing spirited track driving as well as daily trips, have you ever had a problem with the gaskets separating or leaking at the head-to flange joint? Is the mismatch of port size and spacing enough to compromise its integrity?
Jim, thanks for that link - the headers shown in the list look almost identical to the D&D units, and if the lead-time is shorter the price is extremely convincing - it looks like there are a number of other items in the list that I could tack on and save hours of time with for the same price. I will give them a call. Even if they don't fit perfectly, the risk is low enough to warrant a try.
Again, the input is much appreciated - if anyone else has any thoughts, they are more than welcome.

[BlownMGB-V8]

I highly recommend the OEM Rover multi-layer stainless exhaust gaskets. BUT they are beaded for the Rover ports and don't quite match the 300 ones. This is fixable, I have the dies to re-stamp the bead and could probably be persuaded to do that. It then becomes a permanent re-usable gasket.

Jim

[Wilitrun]

Wow, that sounds amazing! Once I've secured a set of headers I'm sure I will ask you for that. Thank you!

[MGBV8]

I've not had any header gasket issues beyond the normal retightening a couple of times as they settle in.

[MGBV8]

Took a bit to find it again, but I thought this might help.

http://www.roversd1.nl/sd1web/capacity3.html

[Wilitrun]

Thanks for the link Carl, the exhaust port comparison was particularly useful.
Jim, does Ian have pictures of his setup anywhere? I don't recognize the name but I'm relatively new here.

[mgb260]

Ian has Chris's old car. He has the Big Bore RV8 through the fender style headers. Here's his page on the MGExperience site.

https://www.mgexp.com/member/BC-MGB.120492/