Engine and Transmission Tech

How large a quench area can be achieved is a function of the piston and head design. A dished piston and a small chambered head can usually achieve a larger quench area than an large chamber. The 300 could be characterized as a larger chambered head, however it isn't really right to say that no meaningful quench area can be achieved. You would have to take a pattern of the chamber and overlay it on the piston to see how much quench area there is. The quench area is essentially restricting the flame to the chamber and the piston dish. There is a good bit of theory on why this is a good thing and how much is desirable, but conventional design leaves .040" between the piston and the head to avoid contact under any conditions. A piston dish allows this close contact around the outer edge of the piston, that area may be up to about 1/2" wide. The volume of the dish determines the compression ratio, along with the chamber volume and head gasket thickness, often with a zero piston height and a .040" head gasket.

All heads reduce this squish area by the area of the valves over the piston rim and by the area over the spark plug. 300 heads are no different here except possibly in having more area around the plug.

Obviously more modern head and engine designs will be a bit more refined, but I built my 300 headed 340 for .040" quench. You don't have to bother with it of course, it is really one of those smaller things that can make a little difference. Read up on the theory if you are curious, a web search will bring up plenty of study materials.

Jim

I understand quench. I had no trouble when building my 400hp 350 in my Camaro. It is a real challenge with the Buick 215/Rover V8 engines. Plus there is very little quench area anyway. Not sure it would be worth much.

Jim, an 89 Buick 3.3 V6 piston has a bore of 3.700", compression height of 1.31", pin diameter of .9054". I calculate the dish at about 20cc.

So, a Rover 3.7" block, with a Buick 340/350 crankshaft, Chevy 5.7" rods and Buick pistons ought to come within about .025" of zero-deck. Steel shim gasket. That makes about 331 CI or 5.4 liters.

I expect you'd want to use aftermarket cap-screw rods to clear the camshaft.

Pistons with compression heights as low as 1.1" are available, so rod lengths of 5.9" can be fitted.

Paul, I'm not sure the crankcase on a Rover is big enough to accept a 340/350 crank.

Jim

I think I may have discovered a new problem. The TA heads have a slightly relocated oil drain as compared to a stock head. I bought a set of Cometic gaskets and in test fits I'm seeing a problem with the alignment of the gasket to the oil drain. In the attached photo you can see that the hole provided in the cometic gasket doesn't line up well with the block or TA head. If this were a composite gasket I wouldn't worry about it, but since these gaskets rely on the raised embossment to create a seal I'm afraid there might be oil seepage out at the joint near the drainback. You can see in the pic that only a portion of the embossment is captured in the block/head joint. I did put the cometic on a stock head and it's a different situation - the production head has cast material all around the oil drainback hole in the gasket, however there still won't be anything on the block side of the joint.

Maybe I'm over thinking this but the last thing I want to deal with is leaky heads when i get this thing running. I'm on a tight timeline to get to the Brian Redman at Road America next month and don't have time to change head gaskets after firing it up. Anyone else seen this with Cometics or had any similar problem?

Ive had problems with the oll drain backs,I'm probably going to put in exterior oil drains from the head to the sump,watch this space as it's an ongoing build !
Have you blocked your oil feed holes in your block ? You will need to do this if you're using MLS gaskets.

"Have you blocked your oil feed holes in your block ? You will need to do this if you're using MLS gaskets."

Argh, didn't think of that. One more reason to switch to the composite gaskets. With no boost I don't think there's much risk there.

So you're having trouble with oil drain back in just normal running?

Yes,that's why the dyno session was cut short,wasn't getting the oil back to the sump quick enough,
I will be doing a full write up when sorted

I started a new thread since this isn't about TA heads. I just chimed in because Dan is using a similar short block.

I moved some posts. Some are shown as quoted instead. New thread started here.

[forum.britishv8.org]

Do you guys know if a stock type composite gasket will be sufficient to seal off the oil passage on the block face? My shortblock is already assembled so I can't really go in now and put a plug in it. I'm hoping that the seal ring and composite main gasket body are sufficient to contain the oil pressure.

You could try driving tapered pins into the holes.

The saga continues for me... I was close to firing the engine, went ahead and built it up with Cometic MLS gaskets but upon filling the cooling system and pressure checking it I've got major water leaks at the block/head interface into the valley and a little on the exterior. The surface finish on the block deck face was not horrible but I was a bit concerned, guess I should have trusted my gut on that one. Heads are coming back off and composite gaskets going on in their place.

Using Rover heads, home ported due to no flow bench access. I pay a lot of attention to squish and as we run a flat top piston the Rover does have a decent amount of squish. The motor we run now is specced as a 3.9 block overbored to stock 305 chevy size, 0.037 overbore if I remember correctly. Stock bore and stroke Keith Black Ikon forged pistons, Scat 6" rods narrowed on the big end to suit the Rover, piston ends up 0.003 out of the bore, we run a 44 thou Copper head gasket. Works great and I think would be manageable on decent gas normally aspirated with the right camshaft. We run the Real Steel blower cam, 4-71 blower, enderle bug catcher on methanol. Best guess on HP based on times and speeds suggests 470-490HP at 5% overdrive giving around 12-16 lbs of boost. We ran 20 lbs plus on a 3.5 with cast Volvo pistons so next step is more boost. Best ET 8.84 @149.3 but I am sure there is a fair amount to come.

Alan