S4 E30. MPG & We modify the 670 cc Predator camshaft by removing the compression relief.

In this video, we're going to take the 670cc V-Twin Harbor Freight engine out of this vintage French car and modify the camshaft to disable the compression release and that way we can lower the idle speed of the engine. We'll also make a few custom made parts and take the car out for a road test so we can measure the fuel consumption. And as a bonus, we'll discover a new and potentially disastrous problem with this car. So let's get started. Okay, let's pull the engine out so I can get inside it and fiddle around with the camshaft. Now as you can see, I've already pulled the twin carburetors and installed the lifting chain. The next thing I need to do is zip out the four screws that secure the drive belt shield that's underneath the car. And the shield is off. This thing helps keep the road debris from getting on the drive belt. Now we need to remove the exhaust system and to do that we need to zip out these four nuts. Then we need to pull this spring that holds the muffler to the rest of the exhaust system. And just to be on the safe side, let's remove the wideband oxygen sensor. And there you have it. The entire exhaust system is off the car. Now we need to remove the four bolts that hold this monster of a motor to the custom engine cradle. At this point, I can tilt the engine backwards just a little bit to remove the alternator belt. And finally, I can tilt the engine forward to remove the CVT drive belt. With all the obstacles removed, I can then hook the engine onto the hoist. And for this job, I'm using a two ton hoist to lift a tiny 100 pound engine. Meh, I use this lift for just about everything nowadays. The only thing easier than using the lift is to have someone else use the lift while you watch. And the engine's out. The engine bay seems empty and we'll get back to that in a moment. Let's drop the engine on the work table first. All right, this guy's ready to carve into, but let's take another look at that engine bay. So this orange wire is from the battery and feeds power to the starter. Now on this car, the battery's located all the way up front. The battery that we're using is out of a Mazda Miata and it's a very good battery and it's really small. Anyway, as you know, the engine's in the back of the car and this battery has to send juice through an incredibly long 55 year old cable that's seen better days. Now a few episodes ago, we did an experiment to simulate what would happen if we removed the compression relief mechanism. It was a simple experiment and all we did was increase the lash on the exhaust valves, thereby causing the compression relief gizmo not to work as intended. Anyway, when we cranked the engine over, we had this happen. Well, this proved that the starter would have difficulties cranking the engine over without the compression relief mechanism. So that was a concern. Now here's something I didn't show and it's because I completely forgot about this issue. Anyway, watch this voltmeter. Now to avoid any confusion, this video was obviously shot before we removed the engine. And for reference, this voltmeter is measuring the voltage at the starter on the 670 engine and that's because it was a convenient place to make the connection. Oh yeah, and the voltage being displayed is indicating the battery is very much discharged. I'm aware of that and keep in mind, electricity and electronics are my specialty. You know, everything I say or show has to be mitigated in some degree in order to keep the audience on the right track. Otherwise, the comment section gets way out of hand. In a way, that's a good thing because it means my audience really pays attention to the details and for the most part, they're problem solvers. But this time around, just ignore the low voltage for the moment. Anyway, when I press the start button, you can see the voltage at the starter immediately drops to about 7. Now of course, some of the reason we see this voltage drop is because the battery is discharged. But even when the battery is fully charged, I still get a massive voltage drop from the battery to the starter. Meh, this is something I never really cared about because the engine always cranked over fine. Now that we're increasing the load on the starter by removing the compression relief mechanism, we'll need to address the voltage drop that's plagued this car since I first put it on the road. Now would be a good time to move the battery from the front of the car to the back of the car. And since we're using a high quality battery that's made for a Mazda Miata, the battery is tiny and we can tuck it into an unreasonably small space. I reckon with the shorter cables from the battery to the starter, we should completely eliminate the voltage drop and this should help the starter crank the engine over. So, our simple project got slightly more complicated. In order to gain access to all the thingies and gizmos inside the engine, we first have to remove the CVT type clutch. I really wish removing this retaining bolt was all that was needed, but that's not the case. As you can see, the clutch is not coming off even if I actually give it some effort, which is rare. So on this Comet 94C Duster clutch, there's an extra step required in order to remove the clutch without damaging it. And you have to use this clutch puller thingamajig. Now, this special bolt came with the clutch. However, the rod was something I had to make myself. This method ensures that no damage will occur to the lightweight aluminum sheaves on this clutch. A hammer or a crowbar would instantly damage this very expensive part and that's something most people want to avoid, including myself. Okay, the clutch is off. Now we can go ahead and drain the crankcase oil. This engine's on its third or fourth oil change already and I believe it's on its third oil filter as well. This oil only has a few hours on it and in my book, that's brand new oil. So we're going to empty it into this coffee container, which still has a few grounds in it, but that's fine. Anyway, we'll use this fresh oil to do an oil change on the lawnmower because, well, I don't think the oil's ever been changed on that beast. So while I drain the oil, it's time for my first coffee break. So the highest tier that I offer to my patrons is the collector tier. And when you become a collector, you become eligible to receive something that was used in the production of the video series. This month, well, I'm giving away this ultra rare second generation coffee cup to a lucky member. This cup was one of the six that were commissioned when we hit the 100,000 subscribers a few years ago. We don't sell these cups. Instead, they're always given away. Actually, by the time this video drops, this coffee cup will be on its way to its new home. I certainly appreciate all my patrons, and I'm working on other benefits for those who join and provide support for the channel. But it takes time for me to figure out stuff because, well, I'm an idiot when it comes to social media and whatnot. Looks like we were able to harvest two quarts of fresh oil. Now I'm sure the Briggs & Stratton will love this stuff. Now even though I just emptied the engine of all its oil, there's still plenty of oil left in the crankcase to make a mess. So I jammed a block of under the engine to tilt it back a little bit, and this will keep any remaining oil from gushing out once I remove the bolts on the cover. Now before I do anything, I'll shoot a little bit of lubricant around the crank seal, and this will help when I pull the cover off in a few minutes. Oh, since this is a small engine, well, this is my version of blue. I reckon some of you folks will get that reference, and if you don't, well, check the comments and find out who blue is. Anyway, I never miss an episode. Well, it looks like the gasket was destroyed, but no worries. I went ahead and ordered a new gasket before we started this. For some reason, I felt compelled to line up the timing marks before removing the camshaft. I'm not sure if this is necessary. However, it is necessary when reinstalling the camshaft. And the camshaft's out. Let's take a better look at it. Hmm, okay. Well, this is different. Now this sort of half-moon thingy attached to the cam gear is what controls the compression relief. When the engine spins fast enough, well, the centrifugal force acts on this half-moon thingy, and it's attached to some kind of a linkage that will retract these ball bearings. These ball bearings protrude slightly, and when the engine's spinning over slowly, well, they'll bump into the exhaust valve lifter and open the exhaust valve slightly during the compression stroke. This is a very interesting mechanism. Now, some folks have suggested I modify this gizmo instead of completely removing it, and well, that's not a bad idea. My only concern is, it may take a few attempts to figure out what works, and that means I may have to pull the camshaft a few times in order to successfully modify it. Frankly, I don't think I have the time to fiddle around with weights, springs, and whatnot. Perhaps that's a job for someone who has a lot more time. I think we'll go with the brute force method and just remove all this stuff and take our chances. It would be nice if we could pop these rivet thingies out with a punch, but that doesn't seem to be working. Of course, the answer in this situation is to use more violence. So, the trick is to sneak up on the camshaft and attack it before it knows anything's going on. Here, let me show you. Alright, that should do it. Now, we have to pull this pin to release the internal shaft thingy. This may be the hardest part. I wonder if we can just use some vice grips to pull this pin out. Let's give that a try and see what happens. I don't know. Oh, blue! This may or may not work. Okay, the pin's moving. That's awesome. And there we go. I didn't think this would actually work. Let's see if the junk will come out of the cam now. Hmm. Hey, get back here! Okay, that's better. So, it looks like we have a shaft and two balls. Hmm. I'm not going there. This is a fascinating arrangement of parts. Very interesting. Now, as you can see, with all the junk removed, that leaves two large holes in the camshaft. I reckon these holes may damage the lifter, so I'm going to countersink them slightly. Now, the good news is, these holes are on the bottom of the cam lobe and there isn't any pressure from the valve springs pushing on the lifter as they pass by these holes. A slight chamfer should prevent any damage to the lifters. Now, there's no guarantee that this will work, but keep in mind, there's absolutely nothing on the internet that shows how to do this on a 670 and this is the first video. We'll try this and monitor the situation. The good news is, the engine has an oil filter and I guess that's the good news. I reckon if we're going to have problems, we'll notice that the lash on the exhaust valve will start increasing over time. So, we do have a way to monitor the condition of the camshaft and the lifters. Off-camera, I thoroughly cleaned the camshaft and now I can put some assembly lube on it and reinstall the camshaft. And again, off-camera, I removed the pushrods to make installing the camshaft easier. Of course, this guy cannot be installed willy-nilly and the timing marks have to be lined up. I think most people know this, but in case you didn't, well, there you go. Oh, before I forget, I need to install this shim or thrust washer. The rest of the assembly is straightforward and the only thing to keep aware of is the oil pump gear needs to mesh with the crank gear. So, don't force the cover on if you feel some resistance. Now, off-camera, I did torque the side cover bolts to spec, which is 17 foot-pounds on this engine. And we're done! I'll adjust the valve lash once the engine's back in the car, but before we can install the engine, we need to mount the battery in the engine bay. This area here provides more than enough space to mount the tiny Mazda MX-5 battery. For reference, we'll be putting the battery in this area on the other side of this rear panel. As it turns out, you just can't buy a battery relocation kit to mount a Mazda Miata battery in a 1969 Renault R10 with a Predator 670cc engine. So, we're going to have to build something to fit it in the limited space behind the right-side taillight. For the battery box, I'm going to fabricate it from a single chunk of angle iron. This should speed up the process, brackets and doohickeys on to complete the package. This is the only battery tray in the world for a 1969 Renault R10 equipped with an air-cooled two-cylinder engine from Harbor Freight. Let's install it and see how it fits. Now, relocating the battery on a normal R10 to this location won't work because this area is normally reserved for the radiator and cooling shroud and all that other crap. Anyway, it fits perfect and the battery cables will only be about 20 inches long. I reckon that should make a huge difference. Let's install the engine and get this car back on the road. In this video, I want to put some miles on the car to verify everything works. And while we're at it, I can also check the fuel economy because a lot of folks find that interesting. But keep in mind, this is not a fuel economy project. It's more of a race car project. So, the valve lash on both sides of the engine have been adjusted. The exhaust valves were adjusted to 8 thousandths of an inch and the intake valves were set to 6 thousandths of an inch. Now, off-camera, I did go ahead and reassemble everything else to speed things up. Last year, we made about a dozen or so videos on how this car was constructed. If you're interested in some of the details, you have all the videos you need to satisfy your curiosity. The engineering that went into this car was derived from past experience when we put a tiny 212cc Harbor Freight engine into a Honda Insight. And of course, all those videos are available as well. What I'm trying to say is, please watch the older videos if you have any questions. Unfortunately, I can't answer every question in the comments section, but you can certainly help yourself to any video you want. Okay, it's done. Let's take a closer look. As you can see, the tiny battery tucks away nicely in its little corner of the engine bay. And best of all, the cables that go to the starter are only 20 inches long. And in case you're wondering, we also installed new ground cables. So now, the starter will have all the juice it needs to crank this engine over. Now, the original battery cable, well, that was left in place and we actually hooked it back up. Because that somehow provides all the electrical power that the rest of the car needs. Of course, we made the loose end of the battery cable in the trunk safe and there's no chance of it shorting out. Now, another thing about this engine bay is, it's a lot cleaner. Now, I'm not against having a clean engine bay. Actually, I prefer it. However, the reason we cleaned this engine bay was to scrub off all the remains of the countless CVT belts we ruined last summer. Now that the engine bay is clean, we can keep track of the new belt. Now, this belt is significantly thicker and better in every way, so we don't expect to see any significant wear for quite a while. But, in case we do develop any problems, the belt debris tends to show up here first, and by the time it ends up on the inner wheel wells, well, that usually means it's time to panic. So far, so good. I reckon we should start the engine and see what happens. All right, well, it sounds like the starter had zero issue spinning the engine over. And that's amazing when you consider the battery is kind of low. Anyway, as you can hear, the idle is a lot lower than it was before. Actually, it's a little bit lower than normal because, well, the engine is stone cold. Now, once again, I did set the idle adjustments by ear. You see, the nipples that we need to install on these carburetor bosses haven't arrived yet. So, I went ahead and did something one of the viewers suggested and used a vacuum hose to my ear to synchronize the carburetors. Well, it's a great idea, and for the most part it seemed to work. But, as a lot of you folks know, I'm partially deaf, so this was a bit tricky, and it's good enough for now. I really need to put gauges on this contraption because my eyes work better than my ears, just barely. All right, let's hit the road and just cruise around, burn some gas, and have some fun. So, it looks like we still have a minor voltage drop at the starter, but the engine cranks over without any issues. Let me goose the throttle to get the alternator working. All right, that's better. Let's see if the new lower idle speed helps in putting the transmission into gear. Yeah, it's like butter now. That's so much better. Now, unfortunately, the audio on camera B has failed, and we can't hear the glorious sound of the big V-twin. I reckon it's time for yet another new camera. Anyway, I'm sorry about that. Now, at the beginning of this video, I did mention we'll have some sort of disaster. Well, destiny awaits us. Let's meet it head-on. Now, on this ride, we're going to be checking the fuel economy of this big V-twin engine when the car is driven normally. And that means we'll be driving with the windows down, and we'll try to keep the speed between 50 and 55 miles per hour. This will give us realistic fuel economy data. Now, it's super easy to jump to conclusions and assume we built this car for fuel economy, especially since we have such a tiny engine. But that's certainly not the case, and this car was not built for fuel economy. It's just a fun project that makes awesome noises. Just prior to leaving on today's adventure, I went ahead and replaced the El Cheapo spark plugs with a fresh set of NGK plugs. The engine seems to run the same with the better spark plugs, and I really wasn't expecting anything different. Overall, the car runs great, and it doesn't seem to have any problems maintaining cruising speed. Today, the ambient temperature is in the 90s, and we do have a bit more wind than normal. Now, as you can see, I've sped up the video quite a bit, and I've edited out a large portion already. So, at this point in the road test, we have about 20 miles on the car, and everything is going fine. And right about here is when I started to notice a strong aroma of oil. Now, this is nothing new with this car. It does have a minor transmission leak, and it will drip oil when the car is in motion. But, just to be on the safe side, I figured I'd pull over and check the engine bay, plus shoot some b-roll of the car out in the middle of nowhere. So, I'm not a farmer, and things like this confuse me. It looks like they're building some kind of a wall with grass clippings. Eh, I guess it makes sense to somebody. Let's have a look at that engine bay. So, right away I can see that there's oil on the recently cleaned wheel well, and it doesn't smell like gear lube, so that's good, I guess. But, if it's not gear lube, then it must be oil from the engine, and that's bad. Yep, we have oil all over the place. Wow, the more I look, the more oil I see. Hmm, it's definitely engine oil. This thing must have been flinging a ton of oil, but I'm not sure where the oil's coming from. Now, prior to this road trip, we ran the engine for about 30 minutes and drove the car around a block a few times. Everything seemed fine. Well, hopefully we still have enough oil to get back to town. Yep, that's engine oil and a lot of it. This engine holds about a half gallon of oil, and it's hard to say how much oil we lost already. But, as you can see, everything is just covered in oil. It'll be interesting to find out what the problem is. The good news is, well, the drive belt seems fine for now, and hopefully it didn't get much oil on it. So, we're on the road again, and obviously we're heading back to the shop. I did check the dipstick, and it indicated the oil was low, but we still have oil in the crankcase, so that's good. The drive belt feels fine, and there's no evidence of the clutch slipping, so that's also good. And we're back. Let's take another look at that engine bay. Now, according to the odometer, we covered 23.1 miles on this trip. Oh, now check this out. The rear window is covered in oil. That's interesting, and possibly a clue. As for the rest of the engine, well, it's still covered in oil. I'll let everything cool off, and then we can take another look. So, given that this car is equipped with such a small fuel tank, we should be able to determine the fuel economy with a high degree of accuracy, even though we traveled only 23 miles. And it looks like this car consumed 2.55 liters of gasoline, and that works out to 34.47 miles to the US gallon. Now, I don't exactly recall what the last fuel economy figure was, but it was close to 34 miles to the gallon, give or take a little bit. So, that's interesting. The twin carburetors provide basically the same fuel economy as a stock carburetor, but the overall performance is significantly better. If you want, check out the previous video where we test the acceleration performance on this rig. It's actually funny to see this car accelerate as fast as it does with such a small engine. Well, it's the next day, and prior to putting the car away last night, I spent about an hour or so scrubbing and cleaning all the oil from the engine bay. And as you can see, the engine and the surrounding areas are clean again. I also went ahead and added more oil to the engine. Now, after I cleaned the engine, I did start it up to dry it off, and I saw some liquid shoot from this crankcase breather. You know, I'm not sure if that was just a bit of water that got into the breather, or it was oil. Now, given the mess we saw yesterday, it kind of makes sense that if oil was sputtering out of this crankcase vent, it would hit the rear panel and bounce back and cover the engine. At least, that's my theory. Now, keep in mind, this open crankcase vent hasn't dripped any oil in the past, and if the oil is coming from this hose, well, that would be bad news. Okay, just to be on the safe side, I went ahead and connected the crankcase vent to a hose and routed it to a plastic container. That way, if this is the source of the oil leak, we won't make a huge mess again. All right, let me start the engine. Well, it started right up, and it sounds terrific. So far, nothing's coming out of the vent tube, so that's good news. Let me goose the throttle. Oh, wow, that's not good. The crankcase vent is starting to push oil. So, on an air-cooled overhead valve engine, a blown head gasket will pressurize the crankcase, and any oil caught near the baffle for the vent will exit the engine with authority. I've seen this plenty of times in the past. Let's pull the oil fill cap and see how much pressure is in the crankcase. Oh, yeah, that's way too much pressure. Well, my best guess is we have at least one blown head gasket. I reckon I could do a compression test and a leak down test to isolate which cylinder is blown. Now, I don't have a problem with stuff like this. It's actually a fairly simple repair if it's one or both head gaskets that are damaged. My concern is, why did it blow a head gasket? Now, according to the logbook, this engine has over 40 hours on it, and, well, we haven't been so kind to it. Could this be a result of the constant abuse, or is it somehow related to the camshaft modification? Hmm, I think before I do any more speculations, I need to actually confirm that it's a head gasket, and then we can do some more speculations. Anyway, it's Saturday morning here in Kansas, and I have to get this video uploaded in a few hours, so I reckon we'll end it right here. As always, I had fun today, and I hope you did as well, and we'll see you next time. Until then!