Ported Rover 3.9L heads

[Dan Jones]

Here are the pictures of the ported OEM Rover heads off of the Rover 5.0L.autocross engine that I purchased a while back.  I should have them on a flow bench next week.  They are 3.9L Rover castings (earlier 14 bolt version) and are fitted 1.782" intake and 1.450" exhaust valves with an overall length of 5.030" and I can see Ferrea on one of the valves so I suspect they are Ferrea F5012 and F5014 small block Ford valves.  The intake ports measure 1.11" wide by 1.91" tall (2.12 square inches):



The exhaust port exits are rounded on top and flat on bottom and fairly narrow at 0.865" wide by 1.525" tall.  They fit my header gaskets with only minor trimming to match the port roof so should match the Rimmers stainless steel tri-y headers that are currently on my Triumph TR8.



Minimum port cross-sectional areas (MCSA) are approximately 1.90 square inches intake and 1.23 square inches exhaust.  The chambers have been welded up to provide a quench pad but oddly the pistons are 0.050" down the hole at TDC so they weren't providing any sort quench effect.





The plan is to run those heads on a temporary engine (either a 4.2L or 4.6L Rover) along with an Edelbrock Performer Rover dual plane intake manifold while the Rover 5.0L gets rebuilt with the TA Performance Rover heads but I'm not sure how much cam I can run with the stock Rover pistons and larger valve heads.  The Extrude Hone process left the intake plenum very smooth:



I need to decide if I want to try to rough up the plenum and ports or leave as is.  Ports are substantially larger than an unported Performer Rover:



Dan Jones

[MGBV8]

Stock Rover pistons?  I just acquired a 4.2 crank to put in one of my 3.9 blocks. I can't bear the thought of those tomato soup can pistons.  I am hoping the block ca survive being bore to fit Chevy 305 pistons. Glenn Towery says to use an Isuzu piston with a 6.25 Chevy rod.  I'm looking into it. The higher rod ratio should be good for these engines.

[minorv8]

Interesting ! Which Isuzu pistons ?

[bigaldart]

We run the 305 chevy pistons in a 3.9 block bored to fit. Zero issues at around 480 HP. Chevy stock bore, stock stroke on a 3.9 crank needs a 6" rod for 0.003 out of the hole.

Alan

[Dan Jones]

> Stock Rover pistons?

Only for the temporary/back up engine and then only maybe.  The high RPM Rover 4.2L (cross-bolted block, Carrillo rods) and 5.0L Rover both have forged pistons.  Those engines get ported TA Performance heads.  However, my engine builder buddy is backed up and can't get to those engines (and associated dyno testing) anytime soon.  So the plan was to build a temporary engine to use this season and serve as a back up in the future.  I have a new-old-stock 4.2L long block and a used 4.6L short block that could be used.  Cheapest/easiest/fastest would be to use the 4.2L long block with steel shim headgaskets (to bump up the compression), adjustable pushrods, true roller timing set and a Crower 50232 hydraulic flat tappet camshaft that I have on hand, along with the Edelbrock Performer Rover intake and Rimmers stainless steel tri-ys that are currently on the car.  Better would be to use ported Rover 3.9L heads (has shaft mounted 1.6:1 roller rockers), Extrude Honed Edelbrock Performer Rover intake manifold and a hotter cam, perhaps a Schneider 274F but there may be piston-to-valve issues with the OEM pistons.  Also, the new-old-stock 4.2L long block has provisions but is not drilled for cross-bolted mains.  My engine builder buddy thinks it can be converted without having to align hone afterwards (would be checked and align honed if necessary).  That leaves the cast pistons as the weak link.  I've got a call out on a price estimate and lead time for custom forged pistons but haven't heard back yet.  If I use the 4.6L, I can also use a Schneider 280-F cam I have on hand and the block is already cross-bolted but it still has cast pistons that suffered piston-to-valve contact.  If I sprang for forged pistons for that short block, I'd likely use the ported Buick 300 heads and matching Huffaker intake.

I need to sit down and enter the options and associated costs into a spreadsheet, think about selling some spare parts and see what makes sense.  Feature creep is killing me here.  If I can put something together in my garage using mostly parts I have on hand, it makes sense.  If I have to pay for machining, forged pistons and wait 6 to 8 weeks, then have the block honed, crank balanced etc. it might make more sense to just jump to the high RPM 4.2L with the ported TA Rover heads but the intake for that one is set up for EFI which would delay driving it this year.

Dan Jones

[Dan Jones]

A quick picture of the roller rocker set up on the ported Rover 3.9L heads:



Dan Jones

[roverman]

FWIW. I have Icon forged sbc. 305" pistons, 3.736". They are "light",  but would need valve notches moved.  Too much bore ?  Cheers, Art.

[BlownMGB-V8]

Has anybody checked pricing on Diamond forged pistons lately? Seems to me not too long ago 350 Buick pistons were going for around $600 a set and they were somewhat flexible about things like compression height. Might be worth looking into.

Jim

[MG four six eight]

Has anybody checked pricing on Diamond forged pistons lately? Seems to me not too long ago 350 Buick pistons were going for around $600 a set and they were somewhat flexible about things like compression height. Might be worth looking into.

Jim




Jim,

It seemed like I paid around $1000-1200 for a set a few years ago.

When I first built my blower motor I used the standard Silvo-lite cast piston which I have had good luck with in the past. However I ended up having some ring seal issues, probably due to running to much boost ;-)
Anyway when I decided to tear it down to fix the ring seal problem, I decided to swallow the steep price and go with the Diamond forged piston. So far they have proven to be worth the money!

Bill

[mgb260]

These 305 pistons look like a good buy for a street motor. Max bore in later Rovers is .040. 305 is only .036 over.
http://www.ebay.com/itm/Speed-Pro-Chevy-305-5-0-5-0L-Hypereutectic-Coated-Skirt-Flat-Top-Pistons-Set-STD-/190829435979

[BlownMGB-V8]

I went with the Venolia custom pistons on my last build. They quoted  something over $700 but by the time I'd added everything I needed I was up to about $900. Anything custom is going to be a bit more than if you can get a set off the shelf, and forged are always going to be more than cast (hypereutectic). But if you figure the cost over the life of the motor often the extra is cheap insurance, especially as it usually lets you build the engine exactly the way you want to with no real compromises, (well, other than what rods to use)

Jim

[roverman]

"Isuzu piston with 6.25" Chevy rod"?  I've seen 6.125", but.... ?  roverman.

[MGBV8]

A 6.25" Chevy rod is available, even with the Honda journal size of 2.015"  I'm still looking for that Isuzu piston, though.

I did find some other options besides the Chevy 305 that I sort of settled on years ago, Holden V6 3.6L, Buick 3.3L, Chevy 265. Ford 255....

[mgb260]

Carl, The Honda size is outside of bearing shell. If I recall it is 1.85 crank pin size. Eagle makes replacement connecting rods that have small journal SBC rod bearing(2.00) in 6.00 length with 3/8" ARP rod bolts for around the same price as reconditioned SBC 283/327 11/32" rod bolt 5.7 rods. You would still have to take .050 off each side  of the big end to work. This is for stock stroke 3.9. .003 out of the hole gives almost perfect quench with the composition gasket. Check out 2.3 sohc Ford 1.74 intake, 1.5 exhaust valves.Will require new seats. Round top exhaust porting a good idea also. I still think the 305 Chevy pistons and the aftermarket SBC rods are the best bang for the buck. The 3.3 Buick pistons would be my second choice but then you have to deal with a dished piston and different pin size.