Hit rev limiter, now running rough
10-26-2015, 02:14 PM
#1
V8 Miata Fanatic
Thread Starter
Hit rev limiter, now running rough
I've got over a thousand easy miles on my conversion now. I really like this car.
It was a beautiful fall day in SW Ontario yesterday, so we took a break from yard work and went for a top down spin. After the car was thoroughly warmed up I started to put it through it's paces a bit. I stomped on it and got up to over 5k rpm in 2nd and the engine started making a different sound and stopped accelerating. I immediately let off the gas as I figured I hit the rev limiter....the tach is probably off in that range. Right after that both my wife and I noticed a fairly noticeable tick from the engine. I started to head back home to investigate, but at the next stop sign we noticed the tick was gone. Continued our drive for the next hr or so without issue. When I pulled into the garage though, I noticed it was running a bit rough. There is still a small tick, but it's not so bad that I can't be certain it wasn't already there. After it cooled down I checked the header bolts, they were OK, started it back up and it seems to still be running a bit rough at idle with a small hesitation when I punch the gas.
I'm going to change oil and filter again tonight. Last oil change was about 1k miles ago. I changed the first oil after about 100 miles of easy break in. Will also check for codes.
The engine was freshened up with new rings and bearings during the build, and ran perfectly before this event. Wondering if I may have damaged something, and wondering why it would tick after hitting the rev limiter and then seem to go away.
Any idea's?
It was a beautiful fall day in SW Ontario yesterday, so we took a break from yard work and went for a top down spin. After the car was thoroughly warmed up I started to put it through it's paces a bit. I stomped on it and got up to over 5k rpm in 2nd and the engine started making a different sound and stopped accelerating. I immediately let off the gas as I figured I hit the rev limiter....the tach is probably off in that range. Right after that both my wife and I noticed a fairly noticeable tick from the engine. I started to head back home to investigate, but at the next stop sign we noticed the tick was gone. Continued our drive for the next hr or so without issue. When I pulled into the garage though, I noticed it was running a bit rough. There is still a small tick, but it's not so bad that I can't be certain it wasn't already there. After it cooled down I checked the header bolts, they were OK, started it back up and it seems to still be running a bit rough at idle with a small hesitation when I punch the gas.
I'm going to change oil and filter again tonight. Last oil change was about 1k miles ago. I changed the first oil after about 100 miles of easy break in. Will also check for codes.
The engine was freshened up with new rings and bearings during the build, and ran perfectly before this event. Wondering if I may have damaged something, and wondering why it would tick after hitting the rev limiter and then seem to go away.
Any idea's?
10-27-2015, 08:17 AM
#5
V8 Miata Fanatic
Thread Starter
All stock except for 1.7 roller rockers. Stock heads were gone over at an engine shop during the build. New valves and seals, i would assume new springs too but not certain.
Well this could suck. Can't a stock 5.0 be revved to the limiter without damage?
I didn't get a chance to look at it last night, maybe tomorrow morning. Will any of those possibilities show up on a cylinder balance test?
Well this could suck. Can't a stock 5.0 be revved to the limiter without damage?
I didn't get a chance to look at it last night, maybe tomorrow morning. Will any of those possibilities show up on a cylinder balance test?
10-27-2015, 08:25 AM
#6
V8 Miata Fanatic
Should be able to in good condition. Lot of things at play there that could make a difference.
I built a pretty mean honda race quad a few years back. Lot of head work, high comp piston, nice cam, etc. etc. After getting it started I had a ticking sound that I couldn't diagnose based on the new parts I had put in. Finally pulled the springs out and as it turns out their full length was below spec by a few thousands. Put in new springs and I was good.
I didn't say that to guarantee thats your problem, just that it could be many things you don't expect. As has already been suggested, compression/leak down test is going to be a great place to start.
I built a pretty mean honda race quad a few years back. Lot of head work, high comp piston, nice cam, etc. etc. After getting it started I had a ticking sound that I couldn't diagnose based on the new parts I had put in. Finally pulled the springs out and as it turns out their full length was below spec by a few thousands. Put in new springs and I was good.
I didn't say that to guarantee thats your problem, just that it could be many things you don't expect. As has already been suggested, compression/leak down test is going to be a great place to start.
10-27-2015, 12:14 PM
#8
V8 Miata Habitué
I have had the odd valve hang up in my race car after a head rebuild, twice over the past 15 years. Both times head was freshly rebuilt and new bronze guides installed. Stock push rods and 1.7 rockers is pushing things a bit with stock springs. Oddly enough the stock springs are only rated to 5700rpm with a stock 6250 F0RD Rev Limit.
Compression test / leak down will get you started in right direction
Dean0
Compression test / leak down will get you started in right direction
Dean0
11-01-2015, 05:34 PM
#9
V8 Miata Fanatic
Thread Starter
Well I think we can chalk this one up to builder inexperience.
Last night I decided to investigate my ticking. A friend who gave me lots of advise during the rebuild said to check the easy stuff first...plugs, wire popped loose, air plugs in the backs of the heads working loose, popped header gasket etc.
So I pulled all the plugs to inspect, and number eight was really loose. Also noticed that they were all gapped to .035" which is weird because I was pretty sure I gapped them correctly during the build, which is supposed to be around .052. The plugs looked good, no moisture, all very similar in appearance. Tossed them back in, checked a few other easy things, started the car....ticking started immediately. A little rev of the gas and the ticking turned into a clatter. Shut it off right away. I did notice that it seemed to be coming from the passenger side.
Tonight I pulled the throttle body and egr spacer, pulled the valve cover to find #3 intake rocker sitting a bit cockeyed. It was really loose- bolt was just about out. Pulled the rocker and pushrod to inspect for damage and they seem fine.
I didn't use a torque wrench on the rockers during the build, I think my friend said to tighten the rockers (with pushrods down) just tight enough that you could barely turn the pushrods. I don't think that's tight enough. What is proper procedure for tightening pedestal mount roller rockers?
Looks like I was lucky here. Car goes away for the winter next week, so I will fix this side for now and re torque the other side in the spring....and avoid the rev limiter until I upgrade springs.
Last night I decided to investigate my ticking. A friend who gave me lots of advise during the rebuild said to check the easy stuff first...plugs, wire popped loose, air plugs in the backs of the heads working loose, popped header gasket etc.
So I pulled all the plugs to inspect, and number eight was really loose. Also noticed that they were all gapped to .035" which is weird because I was pretty sure I gapped them correctly during the build, which is supposed to be around .052. The plugs looked good, no moisture, all very similar in appearance. Tossed them back in, checked a few other easy things, started the car....ticking started immediately. A little rev of the gas and the ticking turned into a clatter. Shut it off right away. I did notice that it seemed to be coming from the passenger side.
Tonight I pulled the throttle body and egr spacer, pulled the valve cover to find #3 intake rocker sitting a bit cockeyed. It was really loose- bolt was just about out. Pulled the rocker and pushrod to inspect for damage and they seem fine.
I didn't use a torque wrench on the rockers during the build, I think my friend said to tighten the rockers (with pushrods down) just tight enough that you could barely turn the pushrods. I don't think that's tight enough. What is proper procedure for tightening pedestal mount roller rockers?
Looks like I was lucky here. Car goes away for the winter next week, so I will fix this side for now and re torque the other side in the spring....and avoid the rev limiter until I upgrade springs.
11-02-2015, 07:59 AM
#10
V8 Miata Zealot
18-25 lb/ft torque on the rocker fulcrum bolt according to the Ford service manual that I borrowed from work 25 years ago. Pedestal mount rockers are not adjusted like a stud-type rocker. If you are using a non-factory camshaft, you may have to compensate for that with a rocker shim kit. Ford Performance M-6529-A302, Ford Performance Rocker Arm Shim & Channel Kits | Ford Performance
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charchri4 (11-03-2015)
11-02-2015, 08:31 AM
#12
V8 Miata Zealot
In a factory-equipped engine you would just tighten them down. The valve lash is compensated for in the hydraulic lifter. I always just ran the bolts down with my 3/8' impact gun, no torque wrench needed.
11-02-2015, 09:04 AM
#14
Brad
I do not know what kind of 1.7 roller rockers you are using? My 1.6 scorpion roller rockers cant just be tightened down that way. The way it works is you rotate the engine until the lifter in question is all the way down (cam on base circle) then you tighten the bolt on the lifter until you feel a little drag when you try to rotate the push rod. then you put a torque wench on it and you must hit a specific torque value between 1/2 and 3/4 turn. Its this whole thing that even involves making sure the tip of the roller is centered up on the top of the valve stem. shorter or longer pushrods may be needed. Pedestal shimming may be needed. I spent about 2 weeks making sure mine were exactly right. (ok that is probably way more than what is needed) what I want you to take away from this is that setting up roller rockers is not trivial, I can send you some links to info.
I do not know what kind of 1.7 roller rockers you are using? My 1.6 scorpion roller rockers cant just be tightened down that way. The way it works is you rotate the engine until the lifter in question is all the way down (cam on base circle) then you tighten the bolt on the lifter until you feel a little drag when you try to rotate the push rod. then you put a torque wench on it and you must hit a specific torque value between 1/2 and 3/4 turn. Its this whole thing that even involves making sure the tip of the roller is centered up on the top of the valve stem. shorter or longer pushrods may be needed. Pedestal shimming may be needed. I spent about 2 weeks making sure mine were exactly right. (ok that is probably way more than what is needed) what I want you to take away from this is that setting up roller rockers is not trivial, I can send you some links to info.
11-02-2015, 09:46 AM
#15
Watching this video is a good place to start. Since I don't know what kind of roller rockers you have I am guessing this is the right info. When we take engines apart and mill the heads or use non-stock head gasket thicknesses we have to start checking pushrod lengths and verifying lifter pre-load ect. I have done this on (2) engines and am no expert but I can help to explain it if you want me to. dehines@txtav.com
11-02-2015, 10:40 AM
#16
V8 Miata Fanatic
Thread Starter
Good video. I watched quite a few but didn't see that one, but get the jist of it.
I've got the Crane/Cobra rockers, stock cam, stock heads etc. I'll torque with the lifters down and take note of how far I have to turn to get 20 ft/lbs.
Thanks for the info.
I've got the Crane/Cobra rockers, stock cam, stock heads etc. I'll torque with the lifters down and take note of how far I have to turn to get 20 ft/lbs.
Thanks for the info.
11-02-2015, 10:48 AM
#17
Make sure you have tightened the bolt just enough to stop the pushrod from spinning and then begin to count the turns until torque is met. This will get you the correct lifter pre-load. All in all it sounds like you are in a much happier place than it might have been. You will get this fixed without to much trouble and be driving again.
11-02-2015, 11:15 AM
#18
V8 Miata Fanatic
Thread Starter
For sure. I'm just happy to not have to pull the heads.
We have a nice week of weather forecast. I'll get the rockers done up tonight, tomorrow my intake gaskets will be here and I can button it up and drive.
We have a nice week of weather forecast. I'll get the rockers done up tonight, tomorrow my intake gaskets will be here and I can button it up and drive.
11-02-2015, 12:49 PM
#19
V8 Miata Habitué
Brad,
You must have been talking to a chevy man about valve train adjustment,lol. Looks like you got lucky om a loose pedestal mount. I assume you are using stock E7TE or F3 heads with stock mounting of the pedestal to the head with a bolt NOT a stud and jamb nut. Just torque down and go.
I use the F0RD MSport / Cobra 1.7 rockers and they just torque 18-25 ft/lbs. No adjustment needed for stock cam.
Dean0
You must have been talking to a chevy man about valve train adjustment,lol. Looks like you got lucky om a loose pedestal mount. I assume you are using stock E7TE or F3 heads with stock mounting of the pedestal to the head with a bolt NOT a stud and jamb nut. Just torque down and go.
I use the F0RD MSport / Cobra 1.7 rockers and they just torque 18-25 ft/lbs. No adjustment needed for stock cam.
Dean0
11-02-2015, 01:20 PM
#20
While it may work to just bolt them down and go, it is not designed to work that way. Rather than to argue with anyone. I went and found the installation instructions from Ford Racing for those roller rockers. Like I said before, when an engine is taken apart and rebuilt, you can no longer be certain that you pushrods are the correct length. Anyway, I am sure many people have been successful just bolting them down, and I have no interest in arguing the way people often do on the internet. Please read the instructions from ford,
https://fordperformanceracingparts.c...m_11_30_10.pdf
https://fordperformanceracingparts.c...m_11_30_10.pdf
11-02-2015, 06:42 PM
#22
V8 Miata Fanatic
Thread Starter
Got them torqued down. After zero lash each rocker bolt took less then a half turn to reach 20 ft/lbs. Glad I went ahead and did the drivers side too. This will work fine for now until I get some aluminum heads in a year or 2. -(ya who am I kidding...I'll likely do them next year if I can find a decent deal).
Anyways, thanks for all the replies, guys.
I should be able to button the rest of it up tomorrow night and hopefully take it on an out of town trip on Wed in this beautiful fall weather we're being treated to here.
Anyways, thanks for all the replies, guys.
I should be able to button the rest of it up tomorrow night and hopefully take it on an out of town trip on Wed in this beautiful fall weather we're being treated to here.
11-03-2015, 01:25 AM
#23
V8 Miata Habitué
MiataDoug
A little edgy are we?, You are right its not proper procedure. I assumed Brad would do what ever he was comfortable with as you had supplied a great link on how setting lash is done. I apologize if I suggested otherwise.
Brad,
I only suggested the "bolt and go" option as I am very familiar with those rockers and I have been following your build, great job, and felt the boltngo option would work fine until you had time this winter in the shop to double check . Glad you did check both sides and using the method MiataDoug suggested, now without a doubt you know your valve train is adjusted with in spec.
Now time for the testing.
Party on
Dean0
A little edgy are we?, You are right its not proper procedure. I assumed Brad would do what ever he was comfortable with as you had supplied a great link on how setting lash is done. I apologize if I suggested otherwise.
Brad,
I only suggested the "bolt and go" option as I am very familiar with those rockers and I have been following your build, great job, and felt the boltngo option would work fine until you had time this winter in the shop to double check . Glad you did check both sides and using the method MiataDoug suggested, now without a doubt you know your valve train is adjusted with in spec.
Now time for the testing.
Party on
Dean0
Last edited by movieboy4fun; 11-03-2015 at 01:29 AM. Reason: bad spelling
11-03-2015, 10:31 AM
#24
V8 Miata Fanatic
Thread Starter
Well, I noticed while the upper was off that my PCV grommet was really loose. So what the hell, I'll put in a new Motorcraft grommet, filter and valve. It a bugger to get at with the upper in place. Wish I'd noticed that earlier so I could have ordered the parts yesterday....now I have to wait till tomorrow morning to button it up. At least my intake gaskets showed up today.
11-04-2015, 11:54 AM
#25
V8 Miata Fanatic
Thread Starter
update:
Got it back together this morning, started it up.....still ticking a bit. Changed oil and changed to a Motorcraft filter, started up -ticking disappeared after a couple seconds. Went for a quick spin and all seems good. Driving to an out of town job today. Beautiful top down day.
I did notice only about 3 quarts and a bit drained out. Will have to keep an eye on the oil level. It's not smoking so it must be my small leak.
Got it back together this morning, started it up.....still ticking a bit. Changed oil and changed to a Motorcraft filter, started up -ticking disappeared after a couple seconds. Went for a quick spin and all seems good. Driving to an out of town job today. Beautiful top down day.
I did notice only about 3 quarts and a bit drained out. Will have to keep an eye on the oil level. It's not smoking so it must be my small leak.
