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compression test HELP

4K views 25 replies 7 participants last post by  350chevyrob 
#1 ·
ok heres the story on my truck i had a stock 5.7 tbi in my truck and did a cam ,head,intake,and crab swap the heads are

world sportsman II heads 200cc runners 2.02 1.64/64cc

comp cam 4x4 X4270H 270/274 480/498 @111

intake with 4160 750 holley

now after getting it to run right i took it out to test drive it and there's no power .motor rev's up and sounds good but it's worse than the tbi setup i had on it before .so i noticed a ticking sound coming from the valve cover.i think i have a collapsed lifter or didn't set the rockers arm right.so i was going to do a compression test to see if i'm losing compression in any cylinders.
so i question is about what psi should i be in when i do the test??

thank you rob
 
#6 ·
350chevyrob said:
also when i first put the lifters in and set the rocker i didn't prime the lifter's i just soaked then in oil for a hour.so maybe i wasn't getting the right per load on the lifters
I hope you used a break in lube on the lifters and lobes, as well as an oil supplement for the cam break in, and you also broke the cam/lifters in correctly. :sweat: :pain:
 
#7 ·
ok i just got done pulling the intake and check all the lifter .i pulled each one out and look to see if it collapsed or wore down the cam. all of where good for one was collapsed .so what do i do now??can i just buy one lifter.


and i put the lube that was supplied with the cam.all on everything
 
#8 ·
350chevyrob said:
ok i just got done pulling the intake and check all the lifter .i pulled each one out and look to see if it collapsed or wore down the cam. all of where good for one was collapsed .so what do i do now??can i just buy one lifter.


and i put the lube that was supplied with the cam.all on everything
If one of the lifters is worn concave on the lifter face, the only way forwards is to replace the cam and all the lifters. The lifters are wear-matched to the cam during break-in... if you try to change replace the lifters without replacing the cam (or vice versa), you'll be almost guaranteed to wipe all the cam lobes very quickly.

PS. Comp Cams provide red lube with their cams which doesn't have a great reputation. Can't go wrong with moly lube on the lobes and the face of each lifter.
 
#9 ·
v8hed said:
If one of the lifters is worn concave on the lifter face, the only way forwards is to replace the cam and all the lifters. The lifters are wear-matched to the cam during break-in... if you try to change replace the lifters without replacing the cam (or vice versa), you'll be almost guaranteed to wipe all the cam lobes very quickly.

PS. Comp Cams provide red lube with their cams which doesn't have a great reputation. Can't go wrong with moly lube on the lobes and the face of each lifter.

the one lifter was just collapsed .the lifters face looked like the rest of them.

so is there a way to fix the lifter ?
 
#10 ·
350chevyrob said:
the one lifter was just collapsed .the lifters face looked like the rest of them.

so is there a way to fix the lifter ?
Oh, well that's not so bad then... you could strip that lifter down, clean it out and reassemble. Not sure what would cause it to collapse though. I'm sure someone else will be along to advise on that.
 
#12 ·
richard stewart 3rd said:
Hi
Just buy one lifter & put it in. Use some break-in lube, it will be fine.
Rich

yea i call the mechanist at napa at he said the same thing.

also when i took the lifter apart it only had the top plunger.there was no spring in it .so i must of got a defeted lifter

i just put the cam in two weeks ago and only drove maybe 20 miles to get it home from my buddys house where i worked on it at
 
#14 ·
350chevyrob said:
the one lifter was just collapsed .the lifters face looked like the rest of them.

so is there a way to fix the lifter ?
This can usually be fixed.

You'll see a C-clip at the top of the lifter body. Carefully remove it, the pushrod seat and metering disc. Now tap the lifter upside down on a cloth covered piece of wood so as to not harm the lifter and see if the piston will come out.

If not, you will need to see if you can free it up w/compressed air and/or carb spray. If you still cannot get it to budge, as a LAST resort, carefully heat the lifter up from the bottom. I would say to try a hot air gun but I have had lifters that I had to wrap in a rag to catch the piston and heat the damn thing up w/a pencil butane torch. Should you have to resort to this- BE CAREFUL!!! There will be hot oil, hot steel, and it can be ejected at high speed- any or all of it will hurt/burn/maim you or bystanders. Wear gloves. Wear safety glasses. Wear a shirt w/sleeves. Work outside or in a well ventilated shop- not in the kitchen.

Once you have the piston out, remove the clipped-on retainer on the bottom of the piston. Careful not to lose the tiny check ball and tiny spring that are both under the retainer.

Clean everything spotless and check the piston and the lifter bore for any signs of burrs or irregularities that might cause them to bind.

Apply a very light amount of oil (WD40 or 3 in 1 oil works well for this) and see if the piston will easily slide in and out of the bore. Work w/it until it does.

Reassemble the lifter and relube the lifter bottom and the lobe, reinstall the lifter and pushrod, set the lash and that's it.

The photo is of a roller hydraulic lifter. It has the same components as most lifters. The arrow is pointing at the clipped-on retainer that contains the check ball and spring.

 
#16 ·
350chevyrob said:
ok heres the story on my truck i had a stock 5.7 tbi in my truck and did a cam ,head,intake,and crab swap the heads are

world sportsman II heads 200cc runners 2.02 1.64/64cc

comp cam 4x4 X4270H 270/274 480/498 @111

intake with 4160 750 holley

now after getting it to run right i took it out to test drive it and there's no power .motor rev's up and sounds good but it's worse than the tbi setup i had on it before .so i noticed a ticking sound coming from the valve cover.i think i have a collapsed lifter or didn't set the rockers arm right.so i was going to do a compression test to see if i'm losing compression in any cylinders.
so i question is about what psi should i be in when i do the test??

thank you rob
This will not make any bottom end power, the heads are huge for a 350 the cam fairly long and the valves large not to mention the 750 Holley, you're going to have to wind this up. If you're running an automatic with a stock stall converter the engine is going to bog out of the hole as it's held to the lower rev range this cam needs more stall.

Lots of good parts but it's going to take some sorting to get this up to its potential.

Lifters are an increasing problem, seems nobody can make a good set any more. ID the ticker then R&R it and start over.

Bogie
 
#19 ·
before i built this motor i had a 388 stoker in and pretty much did the same thing with how i set it up with the dizzy and it ran great .i have a 4l60e in my truck and i made a TPS bracket to mount on the side of the carb to run the tranny .i never had a problem with the dizzy not firing right .it made great power with the 388 in .just having trouble with this bish LOL
 
#21 ·
350chevyrob said:
so your saying that it won't make any power ?
I'm saying two things:

1) The power band will be at pretty high RPMs, this is because the flow capacity of the carb, the ports and the valves is quite large so at lower RPMs the velocity in the induction system will be low such that the late closing intake valve of this cam will blow much of the mixture out of the cylinder as the piston rises until it gets enough RPMs to where the incoming mixture velocity can overcome the reverse pumping forces of the piston. This pushes the torque peak toward the RPMs of the horsepower peak and softens lower RPM power. Also an associated problem with this if you're running an automatic is the need for a higher stall converter. This works like a slipper clutch allowing the engine to rev up into its power band before loading it.

2) You have a lot of good parts, but some of the selections like the 200cc ports and big valves are overkill on a 350 that doesn' turn 7000 RPM. They can be tamed but it takes a lot of time and testing to get there.

There is a point where it's hard to tell if the engine's power issues are the result of tuning or of large capacity components working too far from their best solutions in terms of displacement and RPM. There is a lot of work after putting the parts on an engine, the further the part selection gets toward high performance the more the work is involved in getting them settled down.

You've hit into one of the reasons the Vortec head is so popular for hot street and certainly off road 350s, because they offer a significant power boost without resorting to large cams, big ports and valves. So they are much happier when mated to an engine that runs from idle to 6000 or so RPM. Your big port and valve choice of heads will take some extra work to get them working their best.

I would ask if you know the static and the dynamic compression ratios of this engine. The both compression ratios against the cam timing is very important to getting all the power you paid for, again because of the big ports, valves and cam timing the compression is used to restore power lost to the reverse pumping effects. So knowing the deck height, thickness of the head gasket, and the volume of the piston's dish is important to computing the compression ratio. For the dynamic CR you need the point where the intake valve closes as well and the rod length. you can play with the numbers at this URL. http://www.kb-silvolite.com/calc.php


So I don;t know if this is a tuning issue or whether the power band is just higher than you realize. But first you need to understand what you've got for compression ratios, that will lead into what the timing needs to be both in terms of how much but also when it comes in. You need to figure out the mixture ratios, it's unlikely the Holley is correct out of the box.

Bogie
 
#22 ·
Hi
Here's an accurate way to adjust the valves. The lifter must be on the heal of the lobe to get an accurate adjustment. To accomplish this you split the firing order, 1843 6572 now with #1 Int. at full lift, #6 Int. lifter is on the heal of the lobe ready for adjustment etc. etc.
Rich

#1 cylinder Intake Valve at full valve lift .... Adjust #6 Intake Valve
#8 cylinder Intake Valve at full valve lift .... Adjust #5 Intake Valve
#4 cylinder Intake Valve at full valve lift .... Adjust #7 Intake Valve
#3 cylinder Intake Valve at full valve lift .... Adjust #2 Intake Valve
#6 cylinder Intake Valve at full valve lift .... Adjust #1 Intake Valve
#5 cylinder Intake Valve at full valve lift .... Adjust #8 Intake Valve
#7 cylinder Intake Valve at full valve lift .... Adjust #4 Intake Valve
#2 cylinder Intake Valve at full valve lift .... Adjust #3 Intake Valve
Now The Exhaust
#1 cylinder Exhaust Valve at full valve lift .... Adjust #6 Exhaust Valve
#8 cylinder Exhaust Valve at full valve lift .... Adjust #5 Exhaust Valve
#4 cylinder Exhaust Valve at full valve lift .... Adjust #7 Exhaust Valve
#3 cylinder Exhaust Valve at full valve lift .... Adjust #2 Exhaust Valve
#6 cylinder Exhaust Valve at full valve lift .... Adjust #1 Exhaust Valve
#5 cylinder Exhaust Valve at full valve lift .... Adjust #8 Exhaust Valve
#7 cylinder Exhaust Valve at full valve lift .... Adjust #4 Exhaust Valve
#2 cylinder Exhaust Valve at full valve lift .... Adjust #3 Exhaust Valve
 
#23 ·
richard stewart 3rd said:
Hi
Just buy one lifter & put it in. Use some break-in lube, it will be fine.
Rich
350chevyrob said:
yea i call the mechanist at napa at he said the same thing.
This goes against everything I've ever read regarding flat tappet (assuming you're not running rollers) cams/lifters. You should never swap out a flat tappet lifter once it's been run.
 
#24 ·
H
Remember when Rhoads V D L came out?
Many people have put Rhoads variable duration lifters‎ in without changing the camshaft without problems. I've don it myself. I put a whole new set of lifters in 2 different SBCs that sounded like machine guns when they came down the street. Why
Because that is what I was being payed to do. (Of course that was before this crap oil there passing off now) neither car had a problem.
Rich
 
#25 ·
350chevyrob said:
before i built this motor i had a 388 stoker in and pretty much did the same thing with how i set it up with the dizzy and it ran great
Not using an advance curve on the street gives away power and economy. That looks like an HEI w/o any type of advance. If that's the case, you really ought to be using an earlier large coil-in-cap type HEI (w/o computer control required for an advance curve) like used in the '74-'80 cars and some trucks through '86. You don't have to use the in cap coil, there are caps to adapt it for an external coil like you now have.

Good luck w/using a new lifter on your cam- you may need it. :mwink:
 
#26 ·
oldbogie said:
I'm saying two things:

1) The power band will be at pretty high RPMs, this is because the flow capacity of the carb, the ports and the valves is quite large so at lower RPMs the velocity in the induction system will be low such that the late closing intake valve of this cam will blow much of the mixture out of the cylinder as the piston rises until it gets enough RPMs to where the incoming mixture velocity can overcome the reverse pumping forces of the piston. This pushes the torque peak toward the RPMs of the horsepower peak and softens lower RPM power. Also an associated problem with this if you're running an automatic is the need for a higher stall converter. This works like a slipper clutch allowing the engine to rev up into its power band before loading it.

2) You have a lot of good parts, but some of the selections like the 200cc ports and big valves are overkill on a 350 that doesn' turn 7000 RPM. They can be tamed but it takes a lot of time and testing to get there.

There is a point where it's hard to tell if the engine's power issues are the result of tuning or of large capacity components working too far from their best solutions in terms of displacement and RPM. There is a lot of work after putting the parts on an engine, the further the part selection gets toward high performance the more the work is involved in getting them settled down.

You've hit into one of the reasons the Vortec head is so popular for hot street and certainly off road 350s, because they offer a significant power boost without resorting to large cams, big ports and valves. So they are much happier when mated to an engine that runs from idle to 6000 or so RPM. Your big port and valve choice of heads will take some extra work to get them working their best.

I would ask if you know the static and the dynamic compression ratios of this engine. The both compression ratios against the cam timing is very important to getting all the power you paid for, again because of the big ports, valves and cam timing the compression is used to restore power lost to the reverse pumping effects. So knowing the deck height, thickness of the head gasket, and the volume of the piston's dish is important to computing the compression ratio. For the dynamic CR you need the point where the intake valve closes as well and the rod length. you can play with the numbers at this URL. http://www.kb-silvolite.com/calc.php


So I don;t know if this is a tuning issue or whether the power band is just higher than you realize. But first you need to understand what you've got for compression ratios, that will lead into what the timing needs to be both in terms of how much but also when it comes in. You need to figure out the mixture ratios, it's unlikely the Holley is correct out of the box.

Bogie
i agree with your post.its like saying bigger is not always better.

when i was looking for heads i keeped in mind that i still have the 388 i want to rebuild and put some good heads on.and i kind figered that the heads where going to be a lil over kill on the 350 i'm try to put it on.

but your right!! on alot of aspects of your post.it will take alot of tuning before it is going to at it's best and some detuning lol

i'm just a guy how love's to wench and make something my own .even if it's not right .this is how i learn :thumbup:


well didn't get it all back together last night so i'm going to start working on at the crack of dawn.just a few odds and ends i need to button up
 
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