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AL WULF
Allen Wulf
Wheat Ridge, CO
(37 posts)

Registered:
01/18/2008 12:48AM

Main British Car:
'67 MGB-V8 '62 MGA MKII Deluxe Rover 3.9 EFI

Rover 3.9 Camshaft Specs
Posted by: AL WULF
Date: November 07, 2009 11:52AM

I just bought a low mileage 3.9 short block. Does anyone know the specifications of the cam for a 3.9 with 9.35 compression?
The lifters and camshaft are in great shape and I think they are original.
The engine in my car is a Buick 215 bored over .040 and I am using a Crower 50228 which works well with the Hotwire fuel injection. Sometime before spring I plan to replace the 215 with 3.9.

Thanks,

Al Wulf


castlesid
Kevin Jackson
Sidcup UK
(361 posts)

Registered:
11/18/2007 10:38AM

Main British Car:
1975 MGB GT Rover V8 4.35L

Re: Rover 3.9 Camshaft Specs
Posted by: castlesid
Date: November 07, 2009 12:53PM

Al,

The standard 3.9 cam if used in a 3.5/215 will give approx 6 BHP increase over a standard 3.5 Rover cam.

It has fairly limited lift at .390 so would assume the crower might be a little stronger and if it works well with the Hotwire system I would be inclined to stay with it.

If you switch the cam it is important that the same lifters go back onto the same cam lobes or excessive wear of the cam will occur so suggest you number them as you take them out and then replace in the same order.

Kevin.


AL WULF
Allen Wulf
Wheat Ridge, CO
(37 posts)

Registered:
01/18/2008 12:48AM

Main British Car:
'67 MGB-V8 '62 MGA MKII Deluxe Rover 3.9 EFI

Re: Rover 3.9 Camshaft Specs
Posted by: AL WULF
Date: November 07, 2009 07:20PM

Kevin,
Thanks for the prompt response. According to my cam card the Crower 50228 has a intake lift of .424 and exhaust lift of .430. My 1961 Motors manual says the stock Buick has a lift of .383, so the Rover is a little better. A number of the V8 guys in North America use the Crower 50232, and I may consider that. The engine could probably be used as is, but I may replace the 9.35 pistons with 10.25 or 10.5.

Al


castlesid
Kevin Jackson
Sidcup UK
(361 posts)

Registered:
11/18/2007 10:38AM

Main British Car:
1975 MGB GT Rover V8 4.35L

Re: Rover 3.9 Camshaft Specs
Posted by: castlesid
Date: November 07, 2009 08:40PM

Al,

I have the 50232 and like it a lot, my engine is 4.35L but the Crower 50232 should be ok in a 3.9.

I find I can run down to 1500RPM in 4th gear and it will still pull away cleanly but drop below 1500RPM and it does not like it.

You will need to do a bit of headwork to install that cam, it has a lot more lift at .488" you willl need to have the tops of the guides machined down 100 thou. and the installed spring heights should be checked and set accurately.also if you are running standard heads I think you will be wasting your money on the 50232, it's the heads that hold these engines back more than anything and a stage 1 job on the heads will release another 35 BHP or so.

Just remembered you have Hotwire and although the 50232 has 112 lobe seperation angle it may not like this cam, I'd check with D&D as they will definitely know as they use it a lot.

Kevin.


bsa_m21
Martin Rothman
Vancouver, Canada
(216 posts)

Registered:
01/06/2009 11:41AM

Main British Car:
1980 TR7V8 Rover 3.9L

authors avatar
Re: Rover 3.9 Camshaft Specs
Posted by: bsa_m21
Date: November 10, 2009 09:58PM

Al,

You may want to recheck your Rover block. 9.35 piston blocks are fairly scarce this side of the pond. Mid way along one side of the top of the block will have the comp ratio stamped into it. Normally over here it's 8.13:1, not 9.35:1.

Martin


castlesid
Kevin Jackson
Sidcup UK
(361 posts)

Registered:
11/18/2007 10:38AM

Main British Car:
1975 MGB GT Rover V8 4.35L

Re: Rover 3.9 Camshaft Specs
Posted by: castlesid
Date: November 11, 2009 11:59AM

Al,

The 3.9 is the larger 94mm/3.7" bore, so you will not find standard pistons for the the ratios you mentioned above.

You could have a max of 20thou. off the heads with tin gaskets to give an additional .5/1 to approx 9.85 but if you use composite gaskets which are thicker you will be back to where you started.

If you do machine the heads you will need to check the lifter preload as this will increase by approx 30tthou.

Kevin.


AL WULF
Allen Wulf
Wheat Ridge, CO
(37 posts)

Registered:
01/18/2008 12:48AM

Main British Car:
'67 MGB-V8 '62 MGA MKII Deluxe Rover 3.9 EFI

Re: Rover 3.9 Camshaft Specs
Posted by: AL WULF
Date: November 11, 2009 11:42PM

Martin,
The block has 9.35:1 stamped on the left side underneath cylinders 3 and 5. Also, the numbers stamped below the compression ratio are 29G00193A. The previous owner replaced this block with a 4.6 and kept his heads, front cover, and distributor for new engine. This 3.9 is has a little over 55,000 miles on it, the cylinder walls show practically no wear, nor do the rod and main bearings. The camshaft and lifters are good, too. So the engine wasn't even close to being worn out, he just want a bigger one.

I have a set of Rover heads numbered HRC2210 on my 215 which I'll put on the 3.9, as well as the front cover and Delco distributor. Eventhough the stock 3.9 cam looks prefect, I'm thinking this would be a good time to replace it with one with a little more lift.

Thanks Kevin and Martin for you input.

Al



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