View Full Version : 1275 crankcase breather

Kevin Genoff
06-24-2003, 09:36 AM
Hey everyone, I am new to the LBC scene and this forum. graemlins/savewave.gif

I have a 1968 Sprite that I am currently working on. I'm a 22 year-old college student, so I am just doing a "spray-can" restoration on it. Won't be near concours or anything, but I want it to look like a nice, clean summer car. Anyways, on to the problem...

I am having a problem getting my idle set correctly. The car likes to surge, I can't get it to maintain a nice, steady idle. I noticed that the breather over the timing chain cover is open. Is this causing a vacuum leak? How is it normally routed? I noticed a plug on the upper side of the intake manifold...I am assuming it once had emissions deviced installed there. Is this somehow supposed to vent into that intake?

If this breather is irrelevant to idle, are there any other lines I need to check? I know there's the advance to the distributor. I'll check the manifold, make sure that is solid and sealed.

Any advice/input/help would be greatly appreciated. Thanks in advance!

06-24-2003, 10:05 AM
One of the common problems with a 68 Sprite or any car with old SU carbs is that the throttle shafts can become worn. After 30+ years the throttle has been opend and closed so often that the surface between the carb body and throttle have been enlarged and it allows extra air into the carb. Check the linkage; if it has play where it enters the carb, this might be the problem. Sometimes, dripping some heavy motor oil on the shafts at the point where they enter the carb will temporarily seal the leak and, momentarilly, cure the problem. This temporary cure can be used as a diagnostic tool to verify that leaking shafts are the problem. Remember: two carbs and the shaft goes through the body so oil all 4 places.

The air breather is not the cause of the vacuum leak. Generally air is flowing out of that hole and it is not directly connected to the air intake system. The car came with a cover for that opening and for the sake of keeping unwanted items out of the engine (bugs, dirt, water) you should replace the cover. I have seen many variations to the original cover: hoses vented to the ground, little "air" filters that match the cars paint color, old beer cans. They all seem to work and is really up to the personality of the owner.

I haven't looked under the bonnet of a 68 Sprite since my girlfriend sold hers (years ago). Are there other hoses attached to the intake manifold? If there are, remove and plug the manifold connections one at a time to isolate the surge. You need to "divide and conquer" to solve this problem.

good luck

Kevin Genoff
06-24-2003, 10:26 AM
thanks for the swift reply...

I guess it's back to the drawing board. I'm sure I'll get it.

As for the carbs, I shoulda mentioned - I replaced them. The plungers in the old carbs were hanging up, just not operating smoothly. I have replaced the gas tank, line, and carbs now.

I'll play with the timing. I know it's the first thing you should check, but without having the car idle nicely, I figured it'd be hard to set. The only vacuum line I saw was the ignition advance leading to the distributor.

Thanks for the input. I was almost hoping that was a leak, so I could route a line and have her purring like a kitten. I'll spend most of the 4th of July weekend working on it.

06-24-2003, 11:51 AM
The open vent on the timing cover isn't a great idea long-term, but it shouldn't affect your idle speed if the rest of your emissions stuff is plugged. I'm assuming you do not have the "pancake-shaped" PCV valve going over your valve cover.......these have a diagphram in them...if it's torn, the car will idle funny, but sounds like your's has been removed and the intake manifold connection is plugged (right?).

You may have a vacuum leak......an easy way to find this is to set the car at a reasonable idle speed and spray WD-40 at areas where you suspect a leak (use the extension straw nozzle). If the engine "sucks in" the WD-40, it will slow down a bit...and you've found your leak (the WD won't hurt the engine).

You may also with to "rock" the manifold while the engine is running...these sidedraft manifolds get loose (due to overhang): if you rock the manifold and idle speed changes, tighten it up (and may need a gasket too).

If none of this is useful, check float level and look for sticky floats. Sometimes, dirt will get in main jet and cause "lean-surge" too...an easy solution: remove top of each carb float chambers and carb piston/damper cover (and remove the sliding piston with the long needle). Blow down in the main jet (where the needle goes) and it should blow through to the float chamber (and will clean out any stuf in there). Use a spray can of WD-40 or carb cleaner (with an extension straw)....high pressure air might damage the plastic connector lines.

We'll assume your car has decent spark....good points and plugs etc. (and is not "loading up" due to plug fouling from weak spark).

I remember being a 21 year-old kid with a 1275 Sprite....be careful out there!

tahoe healey
06-24-2003, 12:24 PM
Good luck. Take your time and learn as you go. This is a real fun hobby and it is nice to see someone your age take an interest. You have advantages we didn't at your age. The computer! And this forum will be your study group. More answers than you may want but volumns of experience. graemlins/thumbsup.gif

Kevin Genoff
06-24-2003, 02:28 PM
Thanks everyone! I know what you mean about the computer helping...I think I am a member of about 5 car forums now images/icons/smile.gif I'm really into my daily driver - a '99 Grand Prix GT...there's a few GTP's running mid 11's right now - daily drivers too, no nitrous.

Anyways, this is my first carb'd, non-computer controlled venture. I am honestly trying to decide if I am going to keep it long-term, or finish it and sell it. I love the car, but tuition's killing me. We'll just play it by ear. It's not gonna sell easily if I can't get it to idle, and I certainly can't drive it. This car kinda fell into my lap, I couldn't pass it up.

As for the PCV...nope, just a plug in that hole. I never realized there was one until yesterday when I was browsing online and stumbled across someone's site. The pics showed it. As of now, there are no emissions devices on the car. I do have an air pump that was sitting in the trunk. I have no clue where it goes, how it was plumbed, and I have no interest in putting it back on.

Already reading through this forum I have seen tips on setting the timing better and whatnot. I'll have to go take another crack at all the ignition settings.

It has new plugs (probably fouled slightly now), new distributor cap, rotor, condensor, wires...new wiring (old was all pieced together, so I rewired the car. Also added an actual fuse box - I didn't like the constant and switchable only fuses). New Carbs, fuel line, filter, gas tank. Basically I need to finish up a little body work, paint it, put carpet in, and get it to idle. images/icons/grin.gif Hope to get it going soon so I can use it this summer.

Thanks for the advice and help!

06-24-2003, 02:50 PM
If you get a chance, come out to Waterford Hills for the races this weekend. There will be at least three Sprites running, and a bunch of us with lots of Spridget experience. If you have any questions, email me at jeffreydahn@yahoo.com
I'm about 40 miles west of you, and work in Sterling Heights. One way or another, we'll get you purring down the road.

Kevin Genoff
06-25-2003, 03:04 AM
Cool, thanks....I won't be around this weekend though, I am going up to St. Ignace for the car show with my girlfriend.

Do you go to Royal Oak to meet up with SEMAHC? I might try and stop in there one nite.

06-25-2003, 03:18 AM
OK, Kevin. I understand. We have another race weekend in July, two in August, and one in September. Or, if you're not busy tomorrow, from noon until 4 is practice and testing. I'll be there all day, and probably another Sprite or two.
If you want, email me at the address I posted, and I'll give you my phone number. I can talk you through a couple of things to look for on your Sprite.
I neveer have been to one of the Healey Club meetings. Maybe I should drop in on one myself.

06-25-2003, 11:59 PM

Several people gave you good sound advice.
On a 68 Sprite, (stock) the canister like thing on the timing cover was rubber hose piped to a Tee and piped to the inboard sides of each carb.
Check to see that those 2 carb tubes are either plugged up or they have a hose going between them.
This was the crankcase vent setup on a 68.
The airpump in the trunk is the best place for it.
Most are seized up anyway.
Another cause for a "mind of it's own" idel is the poppet valves on the carb throttle plates (butterflys) look inside, see if you still have a little valve with a spring on the throttle plate.
If so, remove the carb, get solid throttle plates or snip the poppet off and solder up the little holes in the plate. File them smooth.
Those springs weaken over time or instantly if the car ever backfired thru the carb. So with a weak spring, the idle does what it wants.
Also check the throttle shafts by spraying WD-40 or some ether at the shaft ends, and rock the carbs to see if the intake is tight to the block, they tend to loosen up.

Welcome to the LBC world. Carbs, vacuum advances, points, no computer controls, no sensors, and no relays images/icons/wink.gif
I hope we can help you with your Sprite.
And when my modern computerized sensored plastic car has problems, I hope you can help me figure it out images/icons/smile.gif

Kevin Genoff
07-01-2003, 09:28 AM
thanks spritenut...

I'll check it all out. I have two new SU's I just put on in Feb, so they shouldn't be work out yet. As for the canister vent...there are two brass inlets coming out of the carb at an angle. They are on the linkage side of each carb. Is that what I vent to? The old carbs didn't have them. I'll look at that in the next few days when I get over to work on it.

Thanks for the advice. I am going to make sure the manifolds are not leaking along the joint with the head. The carbs on are tight, since I just put them on recently. The car hasn't been really driven in 10 years. I had it running last summer with the old carbs, but not well. The plungers were sticking and just in poot shape, so I got the new carbs.

Thanks a ton everyone, and if you need help with that computer-controlled car, spritenut, just ask images/icons/smile.gif I'll help as much as I can.