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MG MGA - ram tubes & roller rockers

I would like to get the most of my std. 1500cc A and I am considering short ram tubes to fit inside the std. air cleaners. Also, maybe roller rockers to give more valve lift. Any advice will be appreciated Thanks Sean
S Sherry

I use both on my 1800.
I installed Harland Sharp (www.harlandsharp.com) 1.5 ratio rockers that mounted on the MG shaft from APT (www.aptfast.com) Only a little more lift than stock. I proably could have gone to a 1.7 ratio but I really could not find anybody familiar enough with that mod. They work just fine, quite & smooth, with an APT 2ed stage street cam.
I also have stub stacks mounted inside K&Ns. Who knows what difference they make. A lot of people who make sense to me say they help and there so cheap, about $40, there's not much reason not to use them. The car goes fine, I'm happy with it. The mileage is not great for some reason.
Steve
Steve Meline

I have the Moss 1.6 ratio rollers and they are great, but very expensive.

Before that I went with the considerably cheaper option of offset bushing the standard rockers, this gives 1.5 easily enough.

Remember though that the standard rockers really vary in ratio quite a bit, so get several old sets, push out the bush then measure them first. Then use the best ones

Cheers
Mark.
Mark Hester

I saw a demonstration in a class on designing road culverts that absolutely convinced me ram stacks work. A pipe with a flared end (like a ram stack) flowed full of water, where a pipe without the flare generated turbulence and would not flow full regardless of the head or pressure on the inlet. Since air and water flow in similar ways, I'm sure a carburetor stack also must work in the same way by reducing turbulence. I don't know how well it works inside an air cleaner, but I suspect that it would work best in an oversize, free flowing air filter like a K&N.

Ken.
k v morton

Mark, thanks for your reply. Did you have any valve head clearance issues with the 1.6 ratio, or any push rod length or clearance issues. I'm loath to disturb the cyl. head as it is trouble free and just want a bolt on modification. Sean
S Sherry

Hi Sean,

I never replace rockers without renewing the head gasket. They only cost £10, so not worth a failure in the middle of know where.


The moss rollers seem to be OK with standard and modified heads, I've used my set on both.

My race head is 35cc so has been skimmed quite significantly.

The only real test is to turn the motor over by hand and make sure you have clearance or build it without the head gasket, although the composite ones are quite thick.
I build them with an old thin copper one and then run the ticker composite gasket.

I run the much lighter mini cam followers (make sure you get the one's with the drain hole) and 18v pushrods. got for an extra 500 RPM over the lead sinker early type.

Cheers
Mark.
Mark Hester

This thread was discussed between 18/03/2008 and 19/03/2008

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This thread is from the archive. The Live MG MGA BBS is active now.