Rover/Buick head interchangability

Discussion in 'Small Block Tech' started by WV-MADMAN, Nov 5, 2017.


    WV-MADMAN Well-Known Member

    I was wondering if anyone has tried using Rover 4.0/4.6 heads on a 300 Buick.

    Did Rover make any worth while improvements in their 40 or so years of production?

    I ask because electrolysis has not been kind to original aluminum 300 heads, I've got several sets and the water ports are ugly on all of them and I got to wondering, for a budget rebuild would you gain, lose or break even performance wise with Rover heads.

    You can grab nice sets of these for $500 or less is what got me thinking;)
  2. Jim Blackwood

    Jim Blackwood Well-Known Member

    I'm sure they'd work, but the Brits never did seem to be as aggressive in terms of port and valve sizes as we are and the only factory Rover heads that I would think might have a chance of pulling even might be the ones used in the 5 liter versions sold to TVR, if they are in fact any different. My guess is that Dan Jones would know for sure though.

  3. Dan Jones

    Dan Jones Well-Known Member

    > Did Rover make any worth while improvements in their 40 or so years of production?

    Rover made only minor changes over the production run. The 4.0L/4.6L heads changed to 4 bolts per cylinder like the Buick 300 from 5 like the Buick 215. The combustion chamber volume was reduced and the ports are slightly larger.

    > I was wondering if anyone has tried using Rover 4.0/4.6 heads on a 300 Buick.

    You'd likely need custom dished pistons. The Rover 4.0L/4.6L heads have 28 to 29cc chambers versus 54cc chambers for the Buick 300. If your current Buick 300 has 9:1 compression and you swapped on Rover 4.6L heads with no other changes, it would result in a nearly 13:1 compression ratio. You could drop that somewhat with a thicker headgasket. Also, you'd have a port mis-match on the intake side as the Rover ports are much smaller than the Buick 300.

    > I've got several sets and the water ports are ugly on all of them and I got to wondering,
    > for a budget rebuild would you gain, lose or break even performance wise with Rover heads.

    I've flowed a number of Rover and Buick heads. The 4.0L/4.6L heads are the best flowing of the production Rover heads, flowing 135 CFM intake and 106 CFM exhaust through 1.575" diameter and 1.350" diameter valves. An unported set of Buick 300 aluminum heads (1.625" intake and 1.312" exhaust) flowed 154 CFM intake and 116 CFM exhaust. My ported Buick 300 heads flow 200 CFM intake and 153 CFM exhaust through Stage 1 Buick V6 valves (1.775" intake and 1.5" exhaust). Depending upon how much power your engine makes, the smaller intake port minimum cross-sectional area of the Rover heads can become an power limiting issue.

    > I ask because electrolysis has not been kind to original aluminum 300 heads,

    I have several sets of aluminum Buick 300 heads that I'd sell, including bare, assembled and unported and ported with over-size valves. The bare set (have valves, rockers etc but they are disassembled) are virgin with no corrosion. The rebuilt set has had the water port on the combustion face ground out and welded up. The ported set have been externally polished and milled to clean up the decks. IIIRC, they came in around 46 or 49 ccs. Let me know if you're interested and I can get some pictures.

    > TVR, if they are in fact any different.

    As I understand it some/most of the 4.3 and 4.5L TVR engines got larger valves while the 5.0L got ported heads with larger valves.

    Dan Jones
    300sbb_overkill likes this.
  4. alec296

    alec296 i need another buick

    Depending on where problem area is I seen aluminum heads welded up after major catastrophe. I don’t see why you can’t get them repaired.
  5. 8ad-f85

    8ad-f85 Well-Known Member

    I'm guessing that the electrolysis damage is in the water jackets and probably quite excessive.
    So...yes aluminum castings can be nearly infinitely repaired, but these you'd possibly be slicing the head in half and re-carving them from the inside back out and welding it back together, then heat treating them.
    It 'could' be less work to carve up a new one on the mill.
    I've never explored using chemical means to reverse the damage, and I'm not sure it could be safely done.
  6. 8ad-f85

    8ad-f85 Well-Known Member

    Edit...unless the castings are reeeaallly expensive, it's often cheaper to get different ones.
    Maybe bandsaw these up for a head porter?

    WV-MADMAN Well-Known Member

    I was asking more as a ''what if'' kind of thing, since I don't remember having heard the answer.

    The rover heads are crazy cheap & plentiful and '64 300 heads are loosing the war of attrition to time.

    Shame that the 4.0/4.6 heads sound useless...
  8. 8ad-f85

    8ad-f85 Well-Known Member

    What I read above states that you would have to re-drill the block's head bolt pattern after assessing the situation, cut more dish into the pistons or swap them, add intake spacers or other fabrications and at the end of the day your powerband would be drastically affected by the smaller CSA of the ports lowering peak torque and hp rpm's unless they are heavily re-worked there too.

    The machining part is a walk in the park.
  9. Jim Blackwood

    Jim Blackwood Well-Known Member

    No changes to the head bolt pattern, just use fewer studs, same as Buick did.
    It could make sense if you were doing an econo build. The small ports, valves and runners would be good for that. If you found the right cam you might be able to get the DCR down to something reasonable, I have no idea if that could even work, but there could be a use for such an engine I suppose.
  10. 8ad-f85

    8ad-f85 Well-Known Member

    Thanks, I definitely read into that wrong!
    Makes perfect sense.

    I suppose if a fellow wanted to run 13:1 and E85 it might be a good idea to add a bolt boss back into the casting :)
    That also...might be an easy ride.
  11. Jim Blackwood

    Jim Blackwood Well-Known Member

    Yes, it could be a decent E85 engine at that. Just use the 10 head bolts and leave the extras open or stick dummy bolts in them.

    WV-MADMAN Well-Known Member

    On the head bolt thing...

    I heard, (I cant remember where but it was reliable, or I wouldn't mention it, I just cant accredit it) that when Buick was testing the 215 they had more head gasket failures with the 5 bolt configuration and went with 4 instead. (uneven clamp load issues I believe)

    The change came so late in development that Buicks were cast with the extra bolt locations they just didn't drill them.

    When Olds started using the 215 they made some miner changes to the heads to make them more ''Olds'' and also started using the 5 bolt configuration.

    Then GM made one of their many bonehead moves and sold the 215 to Rover and the brits used the Buick style heads but also followed Olds and used 5 head bolts.

    The gasket failures still reared their heads when ever the 215 was hopped-up so TVR and others pushing the 215s limits used the 4 bolt setup that buick had figured out decades before. on an engine they developed lets remember, so if they didn't use 5 bolts why would anyone else think it was a good idea?

    The brits are veeeeerrrryyyyy slow learners and finally stopped using the 5 bolt setup for about the last decade or so of production.....Due to a long history of head gasket failures :rolleyes:
    8ad-f85 likes this.
  13. 8ad-f85

    8ad-f85 Well-Known Member

    Good info!
    I wonder if there were heat treat and casting issues back then that have been overcome with better foundry processes.
    Also wonder if they played with 13:1 cylinder pressures, and at what point in it's life the failures occurred and why.
    I would want these factors on the table to decide like any other engineer, machinist or builder (not 'assembler') .
    There are so many times the factory process gets scrutinized in projects like these.
    Other brands that add head bolts often use a smaller diameter fastener, just to add some rigidity to a long span needing some support.

    WV-MADMAN Well-Known Member

  15. Jim Blackwood

    Jim Blackwood Well-Known Member

    That vendor you mention has suffered some hits in recent years and some would say deservedly so. That's as far as I'm going to go because they were a solid long time supporter of the LBC conversion crowd and were therefore deserving of the benefit of the doubt. The business has passed to the son.

    A few errors though. The Buick 215 was produced with 5 bolts/cylinder throughout its production. Olds used 6, evenly spaced. The 300, 340 and 350 all used 4 IIRC as did the late Rover engines. So although Buick might have recognized the uneven clamping they did nothing about it until they went back to an iron block. Head gasket failures were not rampant, but not infrequent either.

    WV-MADMAN likes this.
  16. 8ad-f85

    8ad-f85 Well-Known Member

    WV madman, thanks for the link.
    I'm not looking for the info, more like suggesting that people should go ahead and explore solutions to problems, rather than accept the limitations they are working with.
    Anything is solvable. Maybe not practical, but still...

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