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When you add 23 degrees of Intake duration @ .050" and 37 on the Exhaust side to a 9.5:1 compression engine you will easily lose 6 inches of manifold vacuum since the cylinder pressure (cranking compression) has dropped dramatically.
The Hot Rod article that tested every GM factory cam in a stock 5.3 determined that the best one (losing no low end torque and only gaining) was the 01-04 LS1 cam
It's like a two-up from the stock 5.3 cam but where the lobes are, it maintains great cylinder pressure
I'd say your combo is doing pretty decent for the magnitude of cam increase.
I've heard of that. But Companies sell pushrods listed as the length (caliper) They don't list them as a full length (without the top hole cutout). You can call a company and say Ive measured a certain length in Caliper and they can add the .017 difference or whatever the measurement is for the oil holes.
But my Cospeed 7.4s measured almost exactly 7.4", And I'm sure the BTRs listed as 7.375 will hopefully measure that much with a caliper. I ordered the Manleys through summit and they had it listed as t 7.375" and the Manley had that engraved on them as well.
It doesn't matter how he measured them. The pushrods he got were all over the map. NO excuse for that. If he ordered ONE length measurement, he should have received ALL pushrods at that measurement.
When you add 23 degrees of Intake duration @ .050" and 37 on the Exhaust side to a 9.5:1 compression engine you will easily lose 6 inches of manifold vacuum since the cylinder pressure (cranking compression) has dropped dramatically.
The Hot Rod article that tested every GM factory cam in a stock 5.3 determined that the best one (losing no low end torque and only gaining) was the 01-04 LS1 cam
It's like a two-up from the stock 5.3 cam but where the lobes are, it maintains great cylinder pressure
I'd say your combo is doing pretty decent for the magnitude of cam increase.
Thats what I figured. Stock 5.3 cam is 191/190, so my 214/228 is like you said increased 23* intake and 37* exhaust. I'm sure there is a trade off in vacuum signal but I wasn't sure 6" was what it should be. I would be happy with 16-17" of vacuum. Since I run a hydroboost vacuum isn't an issue for brakes. But idle quality is important for me.
Ive read that hotrod article multiple times, the LS1 is the same as the LQ9 cam right? I purchased a low mileage LQ9 cam (the one that lost no power but gained 40hp over the stocker) and its sitting on my shelf. I was told to do the custom as I'm leaving another 40-50hp on the table. Steven at Cam motion ensured me that I should be pulling 19" of vacuum with my stock 5.3... which almost seemed too good to be true when I only pulled 19-19.5" with the stock cam. Everyone else Ive spoken to seem to think I'm low on vacuum as well.
I'm no cam expert but Im in the middle between the 210 & 224 so I should pull 18-19" on a 5.3 with a 214/228 and I have a 115.5+4.5 lobe so I should make a little more vacuum.
if you are really that concerned with the setup, going "Dot to Dot" on the timing set may not be what you want..... Degree the cam if you want it right
Also, I dont get the warm fuzzy checking the push rods with a caliper, seems to me that they ride on the ball ends and that it would take a fixture of some sort to really get a good number..... but then again its a hydraulic lifter and a few thousands isnt a big deal
I ended up swapping all the pushrods with the BTR... figured I would run them and see if the little bit helped. If not I can always drop to 7.350 and call it a day, just worried about valve train noise.
I ended up measuring the cospeed 7.4s and they all are very close to each other... like a set of pushrods should be. See pic below. Why couldn't i get a set that all matched... I think it's crazy for precision parts to be this far off. If any of the 7.375 sets actually measured that I wouldn't even be considering the 7.350. Most of my preload turns are now 5/8 turn through 1 turn. I think the 7.350 would get me to the 5/8 -3/4 turn. $100 is cheap vs having to yank the plugs, wires, coils, valve covers, intake tubing etc.
Anyone got any better ideas to the loss of vacuum?
Do you need to do a crank relearn or Cam relearn after doing a cam swap?
Did you install that cam yourself? Why couldn't the Morel lifters work with less than .060 preload? by( using the 7.350) How much loading the lifters with one full turn from zero lash?
It doesn't matter how he measured them. The pushrods he got were all over the map. NO excuse for that. If he ordered ONE length measurement, he should have received ALL pushrods at that measurement.
Got the BTR 7.375 pushrods in. Measured them and the same crap as the manleys.
Thought maybe the caliper was off but then measured it against my 6" dual caliper and it's pretty much dead on at different lengths
They are within .008" of each other. That's pretty close. I know, I know. But they are.
Also, they aren't 7.375" because that's the gauge length. You have to add about .012" to it to get total length. I'm not sure why the CoSpeed ones are like that unless they use a different manufacturer.
Manton measures their pushrods total length. It's a little less accurate because of how the caliper can rest on the ball joint end. Which is part of the variance you see. But I saw variance of up to .005 on my Mantons as well. You almost have to create a jig to hold the pushrod in the same place every time on the caliper to eliminate some of the variance. I would test though by putting two next to each other and the shorter one would always drop out. So I knew I wasn't crazy.
Did you install that cam yourself? Why couldn't the Morel lifters work with less than .060 preload? by( using the 7.350) How much loading the lifters with one full turn from zero lash?
Yes, installed straight up, dot to dot.
Morels will work with less... they just get noisier. People run as low as .020-.030 and they are fine however they are noisy. Most shoot for .040-.060 and .050-.060 being the best compromise of noise vs performance. Straub tech recommends .050-.060. I read a thread where a guy was running .080-.100 on the morels and it was holding the valves open so he dropped the preload and the motor ran much better. The issue is most motors run LS7 lifters which require .080-.100 preload recommended and I would have been perfect for that, but the morels are .050 taller.
The crank relearn is only about misfire detection. It won't help with anything else.
Yea I read up on that last night. So it's not an issue then. Personally I think thick oil 15w40 and too much preload could be contributing to my issue.
Interesting u got those measurements. I wish mine were... but it looks like I got a mix of 3 batches. The same batch was close but too much difference between the 2.
They are within .008" of each other. That's pretty close. I know, I know. But they are.
Also, they aren't 7.375" because that's the gauge length. You have to add about .012" to it to get total length. I'm not sure why the CoSpeed ones are like that unless they use a different manufacturer.
Manton measures their pushrods total length. It's a little less accurate because of how the caliper can rest on the ball joint end. Which is part of the variance you see. But I saw variance of up to .005 on my Mantons as well. You almost have to create a jig to hold the pushrod in the same place every time on the caliper to eliminate some of the variance. I would test though by putting two next to each other and the shorter one would always drop out. So I knew I wasn't crazy.
lol I get it. Agreed it's more accurate than the manleys.
Yes, the recessed ball end or gauge length is or should be less than the actual advertised pushrods. So the recessed part or oil hole is shorter than where ball end contacts the rocker cup or lifter cup. So technically a 7.375 should have a 7.363 gauge length. Why we're getting longer than gauge length makes no sense.
Yea I read up on that last night. So it's not an issue then. Personally I think thick oil 15w40 and too much preload could be contributing to my issue.
Interesting u got those measurements. I wish mine were... but it looks like I got a mix of 3 batches. The same batch was close but too much difference between the 2.
Here's a thought ...
I bet if you measure all 16 valves you get that much variation due to stacked tolerances. Mix and match the longer and shorter ones where they need to go and your preload might actually end up BETTER!
I know I did all 16 on mine and there was at least 016 variation total. I actually ordered four different lengths to accommodate because I was being ridiculously **** about it.
Well that might be the plan. Thinking I'm going to order some comp or another brand 7.350 to be safe. BTR doesn't sell 7.350 for some reason.
Started the car up. Running better no real vac increase but the exhaust sounds different. I did a new tune at the same time but still pulling 13.6" or 55kpa at idle.
when I say the exhaust changed.... like the tone completely and I wasn't getting the "tink" in the exhaust. I should do a compression test or some compressed air in the cylinder and check for the valves opening but lifter bleed down will keep them closed anyways.
Last edited by customblackbird; Apr 16, 2017 at 04:10 PM.
Dot to to dot is not really straight up. Straight up is the cam installed on the intake centerline, not advanced, not retarded. Dot to dot with a used chain could be off by plenty, you need to get a degree wheel, piston lock up tool and a pointer to find absolute tdc, your skipping a few steps. Getting your cam degreed and maybe advanced by a degree or two could get your missing vacuum @ idle. You might be chasing your tail with all the pushrod stuff. Just saying, maybe not.
Dot to to dot is not really straight up. Straight up is the cam installed on the intake centerline, not advanced, not retarded. Dot to dot with a used chain could be off by plenty, you need to get a degree wheel, piston lock up tool and a pointer to find absolute tdc, your skipping a few steps. Getting your cam degreed and maybe advanced by a degree or two could get your missing vacuum @ idle. You might be chasing your tail with all the pushrod stuff. Just saying, maybe not.
thanks for the post. I agree... decreeing the cam is important and has its reasons for being done. But given that cam motion checks every cam with cam doctor before it leaves I was assured it would be correct. I didn't splurge on an adjustable timing set so degreeing the cam would have been pointless as I couldn't adjust for it. I also did not use a used chain... the whole timing set was brand new and from cloyes which includes the chain and gears. I didn't feel that adjusting the cam would be necessary as factory motors are assembled without degreeing . I don't need every ounce of hp But I do want a nice idle. I also don't put the car in closed loop or even activate the STFT or LTFT as I find it runs better that way.
Pushrod stuff I should have done before. But I listened to cam motion and cospeed instead of measuring. I care more about vacuum and lifter noise at this point. But given today's logs even at idle and some throttle blips it seems to be running pretty well even given the 13.6-14" of vacuum.
Ok, another odd thought here after reading the last few posts. I have a friend I'm working with and his car is running rich. So the car keeps adding IAC counts and trimming fuel back at the same time. So it's actually running on more load until the AFR is right.
You might want to activate your fuel trims and then use your trims to dial in VE and MAF in idle regions. If you did need fueling adjustments your vacuum should improve when it's done
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