Cam runs out early?
12-12-2011, 02:31 PM
#1
Cam runs out early? Ok so this is something id like to know as im looking into going a step up in my cam when i pull the motor apart next spring. Im running the cam in my sig and it pulls hard to about 6-6100 where it peaks and almost like it hits the limiter. This cam should keep pulling past that to easily 64-65. My dyno graph doesnt show any signs of float. My tune is set for 6500 so what can contribute to this issue? Just dont want to cam up and if there is an issue i need to worry about to get it figured out as the new cam will surpass the 6-61 peak rpm. My tuner thought it was odd to and he didnt know what to say as everything in the pcm seems normal. Ideas and what might cause this?
Thanks
Thanks
Last edited by 95mysticta; 12-12-2011 at 02:36 PM.
12-12-2011, 02:47 PM
#3
Im running the PAC 1518s which are a great spring set. Whats the issue i should be looking at... spring height and seat pressure? The seat pressure was around 130lb at 1.780. I know when my builder went over these heads they had a good size shim as they have been worked over a couple times from the looks of them. He also said if they posed an issue i would have to have a set of proper springs put in so there wasnt such a big shim. Im not to up to tech with my valvetrain so excuse me if im all over the place. Just trying to give as much info as i can with what my builder told me and how they are setup currently
12-12-2011, 02:54 PM
#5
So where does the problem lie with info ive given you about how its setup? I mean the springs should be more then adequate for this cam. Do i just need a set of properly sized springs to bring down the size of the shim or is it something else? Sorry again im not up on valvetrain tech.
12-12-2011, 03:01 PM
#7
I remember when i saw the heads they were all at or close to 1.780-1.800 from memory. I only have about 3-4k on them and if they were used from previous owner of the heads they had short use on his motor. So lets say maybe 5-6k at most and he bought them new.
Last edited by 95mysticta; 12-12-2011 at 03:11 PM.
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12-12-2011, 03:28 PM
#10
Im not saying it should be making more power but from llyods site it should peak at 6100. I just thought it was odd why it didnt want to pull past that which it should. Soxpuppet with the same le cam and cam only he spins his to 6500. i dont have the dyno sheet handy but i know back at the start up summer when i had it dyno tuned it pulled hard all the way to 6-61 where it made peak power and then felt like it hit the limiter and let off. I assume if whatever is causing it run out early it should keep pulling and possibly squeeze out some more power. I know when we were doing the logging with some WOT runs on the backroads he was telling to ring it out to 65 but it wouldnt pull anymore.
Like i said im not huge on my tech so bear with me.
Like i said im not huge on my tech so bear with me.
12-13-2011, 07:45 AM
#12
^^What he says, You know of how many cars I have tuned LT's / LS's that were heavily cammed, big heads and the customer would always say, My engine builder said it should pull to 7000 when in fact it was all over by 6100 or so. The only engines I have seen pull up to the 7+ mark are huge solid rollers, Sheet metal intakes ect, I'm not saying that a hyd cam cannot have power past or up to 6800 its that those are the exceptions. I has a LS car with a mild 224 cam , bolt ons that kept pulling up to 6800 and I let off due to all of the stock internals. My car has a bigger cam, slightly bigger heads and its all over by 6200 peak..
12-13-2011, 08:19 AM
#13
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if it falls off a cliff at 6100, valvesprings. if it simply noses over it may be done. seems like my 230/236 with self ported heads was done by around 6400 but cant remember for sure.
i will say 6100 seems to be the magic number for valve float. everybody's junk floats the valves at 6100 it seems.
i will say 6100 seems to be the magic number for valve float. everybody's junk floats the valves at 6100 it seems.
12-13-2011, 08:42 AM
#15
ok heres my question..........what are you baseing your rpm reading off of? your stock tach says 6200 when it feels like its nosing over?? what does it do does it sound like its on the limiter or it just noses over real bad? dont always trust that stock tach too........my buddies ls1 tach is off low.......says 6700 when hes on the limiter at 7200......
12-13-2011, 08:48 AM
#16
Really need to see the dyno graph like SS RRR said.
I have a very similar not very big cam (224/230-107) and mine easily pulls to 6.5K strong and hard.
If I had to guess at the problem assuming there is one, with the given information, I would say valve springs.
I have a very similar not very big cam (224/230-107) and mine easily pulls to 6.5K strong and hard.
If I had to guess at the problem assuming there is one, with the given information, I would say valve springs.
12-13-2011, 09:28 AM
#17
Using Datamaster while logging and tunning on the backroads. It pulls hard to where it should be but i would think it should still rev to 65 even if its not making anymore power should it not? Im not basing the that off my builder im basing it off a member on this board thats cam only with the same cam and he still pulls it to 65 which is why im bringing this topic up. My dyno graph is not the greatest as the dyno rpm reference was off and where i peaked at 6-61 the graph showed it make peak power at 5650 which is clearly wrong. When looking back at the log off the run it made peak airflow at 6-61 where it peaked off. When i first posted up my results after my dyno sessions i got chewed out cause people were doubting the graph etc and ended up in a shitfest bad talking my build. So with that being said dont look at the dyno as a very good tool but you can tell there is no float signs where it would dip off it were to. This is a older dyno and not very precise and more used as a tool then for numbers as they are up and down.
Here's a Vid....
Here's a Vid....
Last edited by 95mysticta; 12-13-2011 at 09:38 AM.