Did a compression test on my stroked Olds 215, not good. #4 cylinder at 50 lbs.

Gswest236 · September 11, 2026, 08:36:16 PM

Yes, learning by my own mistakes. We're getting the fuel line, filter, pressure gauge and return line back in. Starting to connect wires, hoses etc. I got the drivers side header back on and once I know where the wires are going on the other side I'll get the other header back on. I'm going with some new NGK plugs that are a setting cooler as the old plugs were standard heat range. I'm learning that with the mods in this engine and being all aluminum, the heat range should be 1 or 2 settings cooler. If there's a consensus on best spark plugs for these stroked motors, I'm all ears.

mgb260 · September 11, 2026, 09:32:49 PM

NGK one range cooler should be perfect. I gap at .040 for Electronic ignition. When you go to start, unhook the top radiator hose from the radiator and fill there to eliminate air pockets. Run for 20 minutes at 2000+ RPM to breakin cam and lifters. It may get hot and you may have to shut down and try again.

MGBV8 · September 11, 2026, 09:39:05 PM

Hmm. Buick specs were a bit hot.

Gswest236 · September 12, 2026, 09:44:20 PM

I went with one step cooler than what was in and will gap at .040. They had Champion RL95YC's in and I'm now going with NGK BPR6HS. It has a projected tip like the Champions and it matches the tip length 1/2". I put one in and rotated the engine back around to TDC to make sure it didn't hit the piston. I think we're good there. I guess I can put all the plugs in since I shouldn't have to rotate the motor manually again. Knock on wood! Good advice on the JetHot coated headers Jim!

Gswest236 · September 15, 2026, 08:58:52 PM

At this point I'm looking at the PCV system I was using with the stock Olds valve covers. When I was using the Offenhauser covers, oil was coming out of the vented valve cover caps. It was a mess. Significant blow by didn't help. The Offy's aren't baffled and there's no provision for the PCV valve. Here's my question; Can I install a PCV on the cap with a vent tube and route it to the intake manifold? With the other cap being vented, will this keep the oil from coming out the caps being there's no baffles in the covers? I had a catch can setup with the stock (baffled) covers and oil leaks were reduced and no oil was coming out of the valve cover caps. I love the Offy valve covers, but if oil is going to be everywhere, I'll need a fix.

mgb260 · September 15, 2026, 09:31:13 PM

That is the idea of the parts I recommended. Open vent on driver side and vent with tube to PCV on the passenger side is commonly used. If you have a little oil around the open breather you could go to another one with tube to go to the bottom of the air cleaner with a hose. The open breather should have what looks like a kitchen scrubber inside it. With no blowby, should have suction there.

mgb260 · September 15, 2026, 09:43:06 PM

PCV diagram:

BlownMGB-V8 · September 16, 2026, 11:40:30 AM

215s are commonly prone to blowby regardless of how meticulous you are in the build. It has to be allowed for in the crankcase vent system.

First and foremost, provide an escape path for the combustion byproducts at max load and speed. Only then can you assemble an effective evacuation system for midrange and idle. The bare minimum is a clear and unobstructed 5/8" inner diameter and this will not be enough as the engine inevitably wears. It doesn't matter a lot where this line goes as long as it is open to atmosphere. Some choices are better than others. Road tube: not great. Valve cover vent: slightly better. Through the air cleaner base inside the filter with a flame trap: better. 3/4 ID tube: better still. Catch can: OK but completely unnecessary.

I like to come off the fuel filter mount block off plate with a 90 degree street L pipe fitting (stainless is available) and go vertical with a 1" ID hose. The cut off end of a threaded pipe of a suitable length works quite well here. That's big enough in cross section to pull half of a pot scrubber inside as a trap and drain the oil that condenses back into the crankcase and still have enough flow area. This configuration has worked well. Placing the outlet where the fumes follow the intake path is good practice but the outlet should not be obstructed in any way.

Once you have that in place it's fair game to configure the positive crankcase ventilation system. That's where the small line with the PCV valve comes in. It also can go anywhere although it is common if a valve cover vent line is used to plumb it to the opposite side. Other engines such as the B series use the tappet cover, etc. It needs to restrict or stop the flow at idle under high vacuum and allow full flow at moderate vacuum during cruise, whatever that happens to be for your engine. The carb or EFI is then calibrated for that air leak.

In practice this then blocks off air flow at idle so you can control your idle speed. It allows vacuum to pull vapors out of the crankcase at cruise and compensates for the airflow, and it allows the engine to ingest the blowby gases, with the fuel system tuned to accommodate the blowby content. Oil vapors are condensed and/or kept inside a sealed system.

Jim

Gswest236 · September 16, 2026, 08:47:36 PM

Thanks guys! Jim are you talking about the fuel pump block off plate. Because I do have that plate with a 90 fitting. So I'll put that back on and run the hose under the air cleaner where I had the original valve cover vented to. Then I can attach a PCV valve to the cap with the tube and run it to the intake. Sound reasonable?

BlownMGB-V8 · September 17, 2026, 09:02:01 AM

It does but you also need a flame arrester/vapor trap in that line because without it a backfire can ignite gases in the crankcase and blow out the lifter valley tin. BTDT

There is enough room in the plate to go up to a 3/4" NPT thread which has a 1.050" OD. This gives room for the pot scrubber pad and the only down side is routing the hose. Silicon and pre-bent hoses are available though. With the pot scrubber nothing special is needed on the air filter end and oil drain back is very much downhill.

You can go smaller on the sizes and some will probably recommend that. I won't. It's no harder to make it larger than it is to make it smaller and this is a case where too large is only an issue if you can't fit it in the space available. Too small otoh can cause oil leaks.

Jim

Gswest236 · September 17, 2026, 01:52:58 PM

Thanks Jim! I'll look at what hose sizes I can get routed to the air filter housing underside.

Gswest236 · September 17, 2026, 08:41:39 PM

I think I have what I need except the 3/4" hose for the fuel pump block off plate and 3/8" hose for the PCV valve to intake. Coming tomorrow. I found the right cap for the PCV in my stash of parts. I did get the spark plugs gapped and installed with anti-seize.

Gswest236 · September 18, 2026, 06:34:23 PM

So, the question is how much of the mesh and how far up the hose to place this stuff? Looking online, there are warnings that it could restrict flow if done incorrectly. Also its stated that it should be cleaned out periodically with solvent.

BlownMGB-V8 · **Today** at 09:54:33 AM

If you stick a wire through the hose and tie it to the end of the scrubber pad to pull it back through you will figure out pretty quick how much you can get in there.

Jim