PAC 1243 Valve Springs
 

Got a new set of PAC 1243 springs and I checked half of the springs and decided to stop because I think I will be returning the springs.

Installing them at 1.850 and 2.215 open

On the seat they range from 220 to 272
Open they range from 608 to 618

The open pressure is pretty consistent but on the seat the pressures are all over the place. An interesting thing is the spring that had the lowest pressure on the seat had the highest open pressure. Has anyone else had this problem?

I've used them before. Both Bullet and Crower recommended them for my intended use, that said my installed height is 1.900-1.910".

The springs are rated 240 at 1.900"
With that spring PAC recommends the distance from coil bind at max lift to be from 0.060" to 0.100"

( A fwiw, the Comp 943 is the same spring )


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Tim: How's the retainer fitting against the spring inner and outer? Especially the inner. My understanding is the inner spring is .100 shorter than the outer.
I'm curious. What is the height of all your valves from the spring pad to the upper side of the retainer with no shims under the spring pad using your Micrometer? So that would be your installed height to start with. I understand your suppose to pick the shortest one and work from there.

Back when I adjusted mine I used +/- .050 keepers and shims, to achieve desired spring pressures on the intake and exhaust. Gotta keep in mind distance to the valve stem seal on full open. I read .090 distance. Checkout PSI 1500 series springs. The website has a calculator for messing around with installed height to give you an example.
https://www.psisprings.com/
https://www.psisprings.com/calculate/

Another tid bit, and another reason one should make efforts to verify what you read in catalogs.

At the time I was using that spring PAC listed it with 1.100" coil bind distance, but in discussion with their tech rep he said it was actually 1.070".

It was in this conversation he told me they wanted that distance to coil bind I mentioned above.

Edit: I went back to look at my records to see what they measured new with their retainers in place at the actual verified installed height. Sorry, I cannot find the results as it was about 15 years ago.


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A fwiw, regarding PSI springs. Watch the distance from coil bind, try to keep it under 0.100".
That's what PSI tech recommends regarding the coil bind distance with their springs.
Again, this was years ago.

Improper distance from coil bind at net valve lift may cause spring surge, which can greatly reduce the available spring load needed to close the valve.

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Hi Steve: I just received information from PSI tech on my springs and they are more than .100 from coil bind, and he said if you have no issues such as break up, valve float, broken springs, valve seat wear, at higher rpm to carry on. He did say we recommend .060"-.100. He said you would be just adding extra load on the valve train.

Thanks. I appreciate the info.

The distance from coil bind, a very interesting topic....

How Much Valvespring Coil-Bind Clearance Is Safe?

https://www.motortrend.com/articles/...rance-is-safe/


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Chuck
First off Bullet Cams knowing Ultradyne cams and having specific knowledge of my cam recommended the PAC 1243 springs installed at 1.85 with 1.65 rockers. Bullet also said .070 is the ideal distance from coil bind. After accounting for the .016 lash I have .085 distance from coil bind at net lift. I didn't calculate the distance from coil bind based on what PAC says it is supposed to be I measured it.

The retainers fit correctly, they are stepped to account for the shorter inner spring. I don't like to put the springs directly on the head and/or the shims as it tears things up and the springs can move around. I am using a hat style spring locator and shims are installed under the spring locator.

Installed height with spring locator installed is between 1.826 to 1.840 on the exhaust and between 1.885 and 1.898 on the intake. I am using -.050 retainer locks on the exhaust valves so that I can meet the 1.85 installed height on the exhaust valves.

I am fine with the open and closed pressures provided the PAC springs have meet the pressure they advertise. My issue is some of the the new PAC 1243 springs I have do not meet the correct pressure at 1.85. The pressure at should be in the 265 neighborhood but the pressures are all over the place ranging from 220 to 272. The spring rate is inconsistent and not correct for about 40% of the springs because they look pretty good at full lift but on the seat not so much.

I was looking at the Comp 943 springs and may exchange the PAC springs for the comp's. If I got another set of the PAC's I probably would end up with the same issue.

I want to think I have a new set of 243s and want to think they had some variability also.

Thanks Tim: Sounds like you got a good handle on things. PAC does make some very nice springs. I would work with them first to see if they can accommodate you better.

I bought them through a retailer and not sure if I should go through the retailer or go to PAC directly. I will call PAC on Monday and see what they say. I just don't want to go through the trouble of returning the PAC springs for a new set and having the same issue with the new ones.

Tim just make darn sure that the retainers your using drop right into the spring and have some side play to allow for expansion of the parts when hot.

Tim, it’s a great work out many times over but I have found that if I take the higher pressure reading springs and cycle them up to near coil bind in a vise 20 times they drop down a fair amount and make it easier to match them up for seat pressure.

Use the higher pressure ones on the intake valves.

after cycling them all be sure to check for ball park equal open pressure at your valve lift your running .

Also clamp the springs in the vise between wood.
If your vise jaw’s put marks in the spring bases you will have to polish those out ( a pain ) or consider that spring garbage.

Keep close track of the change in pressure.

If the low reading springs in terms of seat pressure drop off more percentage wise then the higher ones after cycling them then you truly have a turd set of springs and should send them back.

I know this all is a ton of work, but these days this is what it takes to have a long life stable valvetrain that does not loose control of itself nor break rockers or bend push rods .

Yes I know I sounds like i am a fanatic and this is a full afternoon’s worth of work, but have a few real bad issues like I have had by assuming that out of the box parts where ready to be put into use and you are likely to feel they way I do.

Tim I also have a set of high end Manleys that were all over the place, picked up a NIB set of the same ones here and all were really close. I think it is the luck of the draw!

And one time I had some dual roller springs form Comp box was a set of singles!

All the open pressures are pretty much in the ball park. But the pressure on the seat varies from 220 to 268. If I shim up the springs that are low on the seat then the open pressure will be inconsistent. They are supposed to be 240 @1.9 and at 1.85 I got some in the 2.20's. I expect better than that. It's not just that the pressures are low but the rate is off on some but OK on others. The spring that is the lowest on the seat is the same spring that is the highest open, the rates are off on some but OK on others. This tells me that PAC never tested these springs before they put them in the box. I am disappointed in the quality of parts these days. I will call PAC tomorrow and see what they say. I don't want to warranty these and get a new box out of the same batch.

Tim,
When you get them on the phone ask them what the actual coil bind number is.

As I mentioned years ago their rep told me in conversation it was 1.070

As shown here:

https://cnc-motorsports.com/pac-circ...pac-12432.html

Example, Oher sources state 1.100 and 1.150

A post I made on the subject from 4 years ago....

never trust what's stated in a catalog. Example...when I bought my PAC-1243 valve springs they were rated with coil bind at 1.100".
Now their online catalog says 1.053". I recently called them and asked about the original figure. The response, well we found the springs were actually a bit shorter than when we figured it so we changed it.
But he went on and stated they use something different today than the current catalog, he said it's 1.070".

I asked him how often do you change the web site and he stated not often enough !

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Here is a good video on spring to retainer clearance. This is not meant to contradict any other post. I watch and read some very creditable folks on the subject and some say .005"-.010" clearance. Some say snap retainer into the spring. My Outer spring I.D is 1.060" and my retainer is 1.060" One other thing to make sure is the retainer step height on the inner spring.
https://www.youtube.com/watch?v=wZOGHjEKvZg

OK here's the deal. I went back and checked every single spring and at 1.85 (IH) I'm getting between 258-268 and at net lift from 608-618. I am very happy with these numbers, not sure why I came up with different numbers the first time but I must have been doing something wrong. In the PAC catalog it has coil bind listed as 1.150, but on the box it says 1.070, and I was measuring it at around 1.130. I called PAC and asked them what the coil bind was and he said it was 1.150. I told him I was getting around 1.130 with my measurements and he said my numbers were probably correct. Due to variations in coil bind from spring to spring they list a conservative number. Anyhow all is well with these springs and I am happy. I appreciate everyone's advice and info, I am not a professional and I appreciate this forum and the smart guys that give advice freely to guys like me.

I could live with 10 lbs difference and get on down the road.