Spitfire & GT6 Forum

Hello all,

I would love to tap into some Weber experts on this one. I've just restored my '79 Spitfire, and it's running better than ever. The engine is all rebuilt with new pistons, a turned crank, machined head, a Weber Carb (& Pierce Manifold), PaceSetter Exhaust Header, new oil pump, new fuel pump, new dizzy and coil, etc. etc. I now don't have trouble with the engine stalling. However, I have new problems now.

My biggest issue is that the engine sputters a little bit when I'm cruising. When I accelerate hard, the engine purrs just fine. It revs up nicely and doesn't skip at all. However, when I'm down at idle, or, when I'm cruising in 3rd gear (around 2500 - 3500 rpm) the engine will sputter of skip. I can make it do this in all gears actually, but it's most noticeable in 3rd. In addition, when I turn the car off, there is a loud backfire.

I've played with timing. It's pretty advanced right now. Basically, I've done the timing by listening to the engine (as was reccomened in another post). I just played with the idle mixture screw. I leaned out the mixture (with the idle mixture screw on the Weber) by a quarter-turn. At first I tried a half-turn, but the engine bogged down a ton. I fiddled a little with the timing, but can't hear much difference with the small rotations of the distributor.

Currently, I have the vacuum advance on the Flamethrower dizzy hooked up to the vacuum port on the Weber. Should I just get rid of the vacuum advance? I feel like it's helping on acceleration, but maybe it's hurting at cruising speeds? Do I need to change one of the jets in the carb? Is this as simple as re-gapping my plugs? I checked the three easy ones about a month ago.

Any help would be much appreciated. Please reference the figures below if you need some additional info. Those pics are a little old. The only changes to the engine that I can see are that those pics don't show the vacuum pipe running from the dizzy to the carb. I have also wrapped the exhaust manifold. Finally, the choke has been adjusted. I don't know if that has anything to do with my problem. But basically, I have the choke so that it is barely cracked open when cold. This way, the car doesn't need to warm up much at all before the choke is fully open.

My other problem is that it's hard to start when its warm. But I know why. So I'd mostly like some help with this skipping/sputtering issue.

Thanks guys! Looking forward to your suggestions.

How did you determine which way to put in the dizzy? I never saw one with No. 1 over there before. Usually 1 is right beside the No. 2 plug or just behind the alt. It doesn't sound like a big deal on the way it is in, but when you are troubleshooting it helps fro a base setting. So, try switching the whole dizzy 180 degrees, the drive cog too. Did you check your valve clearance?

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'S all for now
Vic

I did check my valve clearances. They're all good. The engine is running really quiet. No top end noise.

Could it be water or the ethanol in the fuel? Would that cause the engine to sputter a little?

As far as the sputter, have you double checked for vacuum leaks around the intake/exhaust manifolds?
(I think that might explain why you have smooth acceleration, but sputtering when you level off?)

Also, what about your fuel pressure?

-aaron

You know, if you shaved the head the compression is going to be higher than the octane we have now-a-days runs on. That car was made to run on 100 oct and now it is only 80 i believe. so ... On that mixture don't get carried away. Just do it one flat at a time.



Edited 1 time(s). Last edit at 2012-07-21 05:06 PM by 69MkIII.

Hello Aaron,

Thank you for your comments. I have not checked for any vacuum leaks around the intake/exhaust manifolds. That could very well be the problem. How do you check again? Is it carb cleaner that you spray around the manifolds? If the engine bogs, then you have a leak, correct?

If there is a leak, then I supposed the solution is to just tighten up the manifold bolts, right?

As far as fuel pressure, I once put an in-line regulator on the gas supply. This only hurt performance. The car almost wouldn't run. It was an adjustable regulator from NAPA. Then about 2 days into using it, it burst and gas spilled everywhere out of the regulator. I threw it out. I have a new mechanical fuel pump, so I believe it's putting out 20 psi or so. I have not checked, but this is what I have read. Any thoughts on this?

Darrell - I agree with you on the octane rating of the fuel. I am using the highest octane gas at the pump. Would you recommend an octane booster or another additive?

Thank you all for your comments.

use a hose and just a little bit of water over the area you're looking for leaks and it will run bad if the water gets in - or die. carb cleaner - not sure. do it when the engine is just started cold. possibly gasket time.



Edited 1 time(s). Last edit at 2012-07-23 10:14 PM by 69MkIII.

I don't recommend an octane booster but i do recommend a lead substitute if you are doing a lot of hard pulling up hills etc.

To check for a vacuum leak, you can use a propane torch, and go around the gasket (w/o it being lit of course)...if you the engine revs up because of the extra gas, then you have a leak.

Thre distributer looks to be set 180 deg off, but if it's running that won't matter. So be it. Sounds like you may be a little bit on the lean side. The backfire would tend for me to think so.

Sir, if you flip the drive cog I think you'll find it will break, am I right? Is it not off center?

The drive gear was installed 180 degrees off, while the engine was apart. Yes it's offset and the distributer can only go on one way. Again, if it's running it's running and can be left that way. Vic is reefering to the common way the wires ought to appear. Here's mine the day we brought it home. A 1300 '71 by the way



Edited 1 time(s). Last edit at 2012-07-18 07:05 PM by Falkon.

I like my dizzy to look like the manual, but only for problem solving. Yes the drive cog is off center and the whole thing has to be switched if you go 180 degrees. As Al says if it is running, so be it.

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'S all for now
Vic

The engine looks great. I put that Weber on my spit and did not like the way it performed. I heard that fuel could pool in the manafold. When you are excelerating hard the fuel has no time to pool, when you are cruising and at idle it does. I am restoring mine right now but will not be putting that carb back on.

Well I guess that answers the question regarding my motor.. At some point it was apart. As you can see I'm also off 180deg. Runs, or was before I stripped things down. So if I'm undertanding you guys it's OK the way it is (180 off) as long as it's running fine... ?

Sorry to Hi-jack the thread...