High throttle miss - Page 8

olddog · #**141** (**permalink**) 07-27-2016, 07:08 PM

Count yourself as lucky. If a keeper would have slipped off and let that valve drop, a calamity of epic proportions would have come your way. This is why I tried to steer you to look at this. It's a simple fix now, but would have made you sick, if you would have kept running it.

Good Luck moving forward.

Texasdoc · #**142** (**permalink**) 07-27-2016, 08:07 PM

Yes, I do. Back when we first discussed it, I checked them visually. I didn't have a spring compressor then but didn't see anything. It has steadily gotten worse on the drive to and from the shop. I wasn't sure I was going to make it home today. The mechanic said he saw the broken spring but it wasn't easily visible back then. On the drive home it got much worse and would barely hold the idle. I bet the spring was fracturing along the way. As soon as I took off the valve cover, it was obvious this time.

I am lucky.

Texasdoc · #**143** (**permalink**) 07-29-2016, 01:35 PM

I took all the springs off last night. The only two broken springs were #3 intake and #7 exhaust. AFR is sending me a whole new set. I verified cam lift, rocker ratio, rocker to keeper clearance, and coil bind clearance. Still no clue why they broke. AFR said these heads were two years old based on the serial number on the sticker. The springs did not have the colored ID stripe that their current springs are marked with. AFR switched spring manufacturers about that time, so maybe mine was an old set and maybe didn't get heat treated appropriately.

So a new set is going on and then we will see what happens.

DWRAT · #**144** (**permalink**) 07-29-2016, 01:46 PM

I hope this fixes your problems but I don't see how this can cause your misfiring.
Nice to hear AFR is taking care of the springs for you.

Gaz64 · #**145** (**permalink**) 07-29-2016, 03:59 PM

Quote:

Originally Posted by Texasdoc

I took all the springs off last night. The only two broken springs were #3 intake and #7 exhaust. AFR is sending me a whole new set. I verified cam lift, rocker ratio, rocker to keeper clearance, and coil bind clearance. Still no clue why they broke. AFR said these heads were two years old based on the serial number on the sticker. The springs did not have the colored ID stripe that their current springs are marked with. AFR switched spring manufacturers about that time, so maybe mine was an old set and maybe didn't get heat treated appropriately.

So a new set is going on and then we will see what happens.

Is this a hydraulic or solid cam?

Texasdoc · #**146** (**permalink**) 07-29-2016, 10:51 PM

It's a hydraulic roller. I know checking coil bind is inaccurate with the hydraulic system, but we are trying to come up with a reason of why I have two broken springs.

Gaz64 · #**147** (**permalink**) 07-29-2016, 10:57 PM

Ok, can you post your cam specs, rocker arm ratio, your current valve spring part number and installed height?

We should be able to work it out from there.

Gaz64 · #**148** (**permalink**) 07-30-2016, 02:36 AM

Quote:

Originally Posted by Texasdoc

OK, here's the damage. This is the Cylinder 7 exhaust spring. What's left of it anyway. It is the only broken one I've taken off so far. 7 intake is good. I'll get the spring mic and measure installed height later this week. I can see that the outer spring of Cylinder 3 exhaust is also broken.

There are no color markings on these springs anywhere to tell me what springs they actually are.

I've never seen an outer break into 3 pieces.

Do we know who makes this spring?

Texasdoc · #**149** (**permalink**) 07-30-2016, 08:35 AM

He didn't say who their previous manufacturer was. They currently use PAC racing. They are sending me AFR part 8019.

I have 1.6 ratio rockers, right at 600 lift, 1.8 installed height.

blykins · #**150** (**permalink**) 07-30-2016, 10:21 AM

I think that's the best recourse. Honestly, I think it was a spring QC issue, which shakes my confidence since I run a lot of PAC springs in my race stuff.

I talked with Tom for an hour or so over email yesterday trying to match up the specs and supply another valve spring, but with the size of the valve spring pocket, the size of the springs, the install height, metric valve stem sizes, etc., it was a little tedious.

Gaz64 · #**151** (**permalink**) 07-30-2016, 07:39 PM

Quote:

Originally Posted by Texasdoc

He didn't say who their previous manufacturer was. They currently use PAC racing. They are sending me AFR part 8019.

I have 1.6 ratio rockers, right at 600 lift, 1.8 installed height.

Looks like a step in the right direction, although it recommends a titanium retainer in the instructions?

http://www.airflowresearch.com/195cc...cylinder-head/

Texasdoc · #**152** (**permalink**) 07-30-2016, 09:32 PM

Can anyone who has AFR heads/springs tell me if the color stripe fades over time? I'm trying to decide what springs I have. When talking to AFR, the guy seemed puzzled that my springs don't have any color stripe on them. He did ask me if the inner spring is taller than the outer spring - which it is. They look like AFR's 8019 springs without the color stripe. However, if they were actually 8017, which has no color stripe and a max lift of 600, that would explain why they broke.

So, did mine have a pink/red stripe that faded, or do I have the wrong springs? Can anyone with AFR springs tell me if the color stripe fades over time? I only have about 300 miles on these heads.

Gaz64 · #**153** (**permalink**) 07-30-2016, 11:04 PM

The 8017s are listed as 1.290 O/D, the 8019s are listed as 1.270 O/D.

Is it possible to measure one of yours for O/D?

Gary

Texasdoc · #**154** (**permalink**) 07-31-2016, 01:18 PM

These measure 1.275. That 0.005 may be within the error of my calipers. So these are probably the 8019's.

I would still like to know if anyone else's AFR springs still has the color stripe after minimal use.

Gaz64 · #**155** (**permalink**) 07-31-2016, 04:19 PM

It seems they fitted with 8019s, and yours measure as near enough the same.

The stripe is obviously not a very good paint.

And if they are 8019s, what is the next step now?

2 out 16 is a bad failure rate.

Gary

Texasdoc · #**156** (**permalink**) 08-01-2016, 07:54 AM

I'm hoping it was a bad batch, that it was during their transition from one manufacturer to another. I'm going to install these and monitor it very closely. To use a different spring, I'd have to have the heads machined to fit a different size.

Texasdoc · #**157** (**permalink**) 08-22-2016, 04:44 PM

Good news - springs worked! Pulls up above 5000 rpm. No missing, however it does need tuning. It doesn't seem to be as quick as it should be. Seems like it runs out of steam around 4500 rpm. Still runs very rich off idle and stays rich throughout the run. Low power cruise at 40 mph around 1800 rpm, it is around 11-12:1. Seems like this would still be in the transition circuit. It leans out a bit (relatively to 13:1) at WOT closer to 4000 rpm, so I think the jets are fine.

DWRAT · #**158** (**permalink**) 08-22-2016, 06:25 PM

Wow, glad to hear your miss is now gone.

olddog · #**159** (**permalink**) 08-22-2016, 07:10 PM

Quote:

Originally Posted by Texasdoc

Good news - springs worked! Pulls up above 5000 rpm. No missing, however it does need tuning. It doesn't seem to be as quick as it should be. Seems like it runs out of steam around 4500 rpm. Still runs very rich off idle and stays rich throughout the run. Low power cruise at 40 mph around 1800 rpm, it is around 11-12:1. Seems like this would still be in the transition circuit. It leans out a bit (relatively to 13:1) at WOT closer to 4000 rpm, so I think the jets are fine.

11-12:1 at cruise is way too rich. It will wash the oil off your cylinder walls and wear out your rings, cylinder walls, and piston skirts. Your should be much closer to 14.7:1 at cruise.

WOT - most expert advice I read says 12.5:1 is about where maximum power is made. Some engines will make maximum power at 13:1, but a lot of engines will detonate this lean.

I would get the fuel right ASAP.

Gaz64 · #**160** (**permalink**) 08-22-2016, 07:41 PM

Quote:

Originally Posted by olddog

11-12:1 at cruise is way too rich. It will wash the oil off your cylinder walls and wear out your rings, cylinder walls, and piston skirts. Your should be much closer to 14.7:1 at cruise.

WOT - most expert advice I read says 12.5:1 is about where maximum power is made. Some engines will make maximum power at 13:1, but a lot of engines will detonate this lean.

I would get the fuel right ASAP.

Good advice here.

The carburetor needs a few changes to sorts this.

Now the engine is mechanically sound, some carb tuning should wake it up.