I'm looking to buy a set of heads off a 2000 land Rover discovery 2 with the 4.0 but the seller says its a "Bosch" engine. This won't make a difference on the heads' fitment for a 1964 Buick 300 right? I know theres a small casting difference that needs to be addressed but otherwise there shouldn't be an issue I don't think, but I want to double check.
Best bet is probably to find a set at a pick-n-pull. I scored a pair for about $160 that way recently. With the cast valve covers and rockers. Jim
I think all the Rover FI heads are the same, just the intake and fuel injection is different. Edited to clarify.
I found someone parting out a Rover and he'll get me the heads with rockers for $200 which i think is a good deal as well.
I posted this question on the Facebook group as well and got some more info there. Turns out they're similar enough to use, apart from a casting difference that is solved with a little JB weld. The combustion chambers are significantly smaller however, so they need to be enlarged to bring down the compression ratio.
I meant the heads are the same between Gems, Thor and Bosch FI motors. 300 heads have bigger ports and valves and 54cc chambers. The 4.0 and 4.6 heads are the same, 29cc chambers and better ports and valves than the earlier motors. The earlier 215 Buick and 3.5 and 3.9 Rover had 39cc chambers. Composite gaskets are around .040 thick. Steel shim gasket around .020 thick. Buick 300 2 barrel had around 8 to 1 compression advertised at 9 to 1. 300 4 barrels had 10.5 or 11 to 1 advertised and in reality around 9.25 to 1. The small chamber Rover heads with composite gasket and 2 barrel deep dish pistons will give around 11 to 1. Open the sides of the chambers a little to unshroud the valves and you would be around 10 to 1. Never heard of the use of JB weld. Jim B is putting Rover heads on a 300.
I just calculated my compression ratio and I would be looking at a 10.27:1 with the 29cc chambers. The felpro head gasket I'm using is 0.048 thick and the 26cc dishes in the silvolite pistons do pretty well to bring it down. Would unshrouding at this comp ratio still be beneficial or would the extra flow not be worth the drop? I know its different for every application, but I don't know how bad the shrouding on these heads is. Also its good to know for sure that the stock factory compression ratio was overrated, I did suspect it was a little lower than stated when calculating my rebuilt one.
The head gasket will compress down to about .040 when torqued. The Silvolite pistons may be lower compression than stock. You will probably be about 10.5 compression which is the practical limit for aluminum heads on the street with premium pump gas. Dynamic compression is what really matters, and that is determined by your cam choice. Are you using the 64 only aluminum intake and intake gaskets?
I actually subtracted 0.005 from the measured thickness, (0.053) as a machinist advised and got the 0.048. Using an online calculator I got 9.25:1 dynamic compression. Though I may be wrong about how much advance is ground into the cam so it might be a little higher than that. I was going to use the stock alu heads until I measured just how sunk the valves are which is why I'm swapping to a rover set. And I changed the 2bbl intake out for a 4bbl, also alu. I got a full gasket set from felpro so I'm not sure if the gaskets are aluminum specific.
I forgot there is a port size difference, thank you for reminding me. I'll need to get the correct gasket for that. As for the dcp, why does it need to be within that range? I think I can add about 6cc to the combustion chambers to get down to 8.5
To prevent pinging and knocking. Which is actually detonation. I'll post a chart for octane and Dynamic compression. It may help to retard the cam too. You really need to have your cam specs to be able to accurately calculate.
That's a helpful chart, but I talked to a machinist just now and he told me he's ran many engines with various setups in the low 9 dcp on pump gas with no issue and said the dcp does not have a direct relation to the octane required like shown here. I obviously don't know enough myself, but wanted to relay what a very experienced builder knows and told me. As for my own dcp, I realized I used the intake valve closing at 0.050 instead of 0.006 so I'm actually at 8.44 and not 9.25.
Very good article explaining Dynamic compression ratio: Discussing Compression Ratio And Pump Gas Compatibility (chevyhardcore.com)
After looking at your other post, I see you are using .040 longer 6" SBC connecting rods. You will have to deduct around 5cc from your combution chamber volume to compensate. With the stock pistons, that would bump the compression up about a point.
I just read through the article you sent, definitely a lot of questions i had were cleared up with it. Would the rover heads' combustion chamber be classified as a modern and more efficient one? Because the article does say up to 9:1 dcp is okay with pump gas for those. I am, however, using silvolite pistons with a huge 26cc dish so the static comp ratio would actually be a measly 7.7:1 with stock heads.
The smaller Rover chamber is more modern but you are still below zero deck for proper quench and will promote pinging. Piston level with block but deep dish. The open chamber of the 300 head is an older design. You can try slowing your mechanical advance curve to all in @3500 RPM and retarding your cam 4 degrees to help prevent pinging.
That's good info and I'll definitely keep it in mind, but most likely I'll be getting a custom ground cam instead of keeping the crower I have for it now. Someone had calculated an ideal cam for my combination and it's wayyy off from the specs i have now. You also reminded me i need to rebuild or replace the old stock distributor i have for it.
I know a guy with the Crower 50233 in his 300 that dynoed 300HP at the rear wheels. Another has that cam in a stroked 300 (350 crank). If you wat to put bigger valves in the Rover head look at the 75-76 Buick Oddfire V6, 1.62 IN and 1.42 EX. The biggest that can fit without changing seats. I used SBC Z28 valve springs years ago. SBC Small Block Chevy 1.26" Z28 Style Valve Springs .550 Max Lift Hydraulic Cam | eBay
