Yes, 20-21cc approx. My equipment is not very sophisticated.....need to see if I can find a 100cc graduated beaker. Right now I use a big syringe.... Progress. Cam timing checked. Front end all buttoned up....even made a little pointer to set the timing. Head is on and torqued down, valves are set. Dizzy is in and approximately set. Starter and alternator on, just about ready to set it into the engine stand.....a lot more to do before I can crank up oil pressure, then see if it will make some (hopefully good) noise....
As engines go it has a purposeful no frills look. What combustion ratio do you believe you ended up with ??
Plugging in 72.1mm bore (60 thou over), 81.3 stroke, 20.5cc chamber, .04” x 75mm gasket, and .025” below deck gives 13.04/1 CR if I have the numbers right.
Yep, pretty much what I figured too.....but don't forget it's 70 thou over, and also the .3CC down to the rings from the top of the piston.....
Got the engine loaded into the stand this afternoon - today was PT day so that's about all I could do - but I got it mostly wired and plumbed. Filled it with oil, I'm letting it run down for a bit now to see how much it will hold with the added capacity. I already filled up the oil filter. Right now it has 4.5 qts in it, looks like 5 is about all it will take. I'm using the old header as I sent the new one off to be ceramic coated. Clancy came up with an old transmission case that I can cut the bellhousing off of and make a cover for the clutch and flywheel, but it will have to be for the next one I build. Too many projects to finish first and this one will be long gone in a couple days or less. Should be making smoke and noise tomorrow morning sometime.
It runs! Boy does high compression make a difference! We cranked up oil pressure - and at first it almost wouldn't turn over - but his carbs were leaking gas into the cylinders and once it got some lube on the rings it spun over fine - BUT - you don't want to use gasoline as a lubricant. I insisted that we pull his carbs off and put mine on. I used a shop rag to soak up all the gas in the ports - and there was quite a bit - then put my HIF44 on it and it started after it cleared out all the wet gas off the plugs. Once running it sounded great - good oil pressure, temp held right at 180 once it warmed up - I finally convinced him to put the muffler on it so we could hear ourselves think and it actually ran better with the back pressure, smoother and it returned to idle better. We let it run for 20 min or so to break in the cam and when he left he had a big smile on his face! He still has some work to do to install it in the racecar, and he needs to get his carbs sorted out before he tries to run it on them. Overall, I'm pretty happy with it now myself. I'll let it cool down overnight, then retorque the head and reset the valves then he can take it home. Sorry about the poor video, I was holding my phone while adjusting the carb.....I usually have the phone in a holder. First start of a 1275 Sprite Race Motor - YouTube
Very healthy, I saw it popped up to 5K, with authority. Is he running dual SUs, he might want to thinkusing a single weber, if his race group allows. Nicely done, video was just fine. Don
I'm sure he can run a Weber, but he's just getting started so he's going to run this while he builds up his experience and capabilities. Found the problem with the carbs, and it's embarrassing to say the least. The carbs had some AN3 fittings on the float chambers, and a hose with a hose barb on them too, connecting the two carbs. I hooked my fuel pump right onto that hose barb - not paying any attention to the fact that the AN fittings were the infeed, and the hose was the overflow. So, we pumped fuel in thru the overflow instead of thru the needle and seat - of course it overfueled! So, tomorrow I'll re-torque the head and reset the valve lash, then fire it up again and run it up to temp. After that I'll pull my carb off and put his back on, but I won't be able to run it with them cause I still don't have any AN3 fittings or hoses....that will be up to him to sort out.
It was 37* at 8 this morning and 61* at noon, so I waited till noon to finish this job.... I re-torqued the head, reset the valve lash, then I fired it up again, which it did easily and ran sweet - made lots of really good noises too! so it's ready to go home and get dropped into the car again. That will give him time to get all the little niggling bits sorted, plus he bought a Morroso Accusump and he can get that plumbed in too. Next race is at Eagles Canyon just north of Dallas at the end of April.
Since I completed this one he's run well at two different race weekends with no issues. Since I finished this one and the car seems to be running very fast, I now have a second race engine in the shop and a third on the way! Just waiting on a few parts to build this one, they should be here in a day or two. Everything is cleaned and ready to build
This one is more of a beginner's motor than an all out race motor, tho last time on the dyno it made 108 at the wheels. All out race motors are making more like 145 - 150 at the wheels. The black one I built has not been dyno'd but based on his race pace I'll bet he's close to 140 at the wheels. Kent Prather at Prather Racing is using E-85 ethanol in his racecar now, it required a lot of changes in fueling and spark, but he gained another 12 hp on his MGA motor - thats a significant number just for changing fuel. He's going to run it this weekend at Elkhart Lake (Road America) if anyone is in the area, it's a fantastic track to watch, lots of shade and great spots to see so much of the track. This weekend is a huge vintage sports car race....over 500 cars entered.
Well, DHL was as good as their word and delivered late this afternoon - BUT - unfortunately either I ordered the wrong rings or they sent the wrong rings. Either way, they don't fit. So, I've called an outfit in Ca to see if they have them (APT Racing) if they don't then I'll go to plans B, C and D.....7, Mania and Moss, not necessarily in that order. I also got in a Moss order today of gearbox parts, so I can build two of the three gearboxes I have waiting. I didn't order parts for the third one because I haven't torn it down yet to see if it's rebuildable and if so what I'll need. If it is and I can't get them from APT I may go ahead and order gearbox parts along with the rings. I spent the afternoon figuring out how to mount the engine in my stand, then cleaning the bores and rest of the bits to get ready for assembly. I also ran a tap thru all the holes in the block, and chamfered them too. I installed the lifters and cam, then laid in the crank and checked the end float. There are probably a few more things I can build at this point but not being able to put the pistons in is definitely going to hold me up.
Replacement rings still haven't arrived from California. I guess "Priority Mail" doesn't mean the same thing to me and the post office. Sent last Thursday.....
I had the rings sent that way last Thursday and they only showed up today! In the meantime I got a few things done in preparation - I made sure the crank end float was correct (3 thou on the dial indicator) I also glued in the cork gaskets in the oil pan, these are a royal PITA as they fit in a slot. but they come straight and you have to bend them to fit, then trim off the ends. If you don't have them completely down in the slot and you cut the ends off flush - it will leak. So I came up with a way to hold it in place while the glue set.....