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69 chevy truck comp cam 287t " thumper"

  
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69 chevy truck comp cam 287t " thumper"

 
dale49 dale49
I love my Chevy Chevette! | Posts: 16 | Joined: 07/13
Posted: 07/29/13
10:01 PM

my kid put the mutha thumper cam in 350 , stock valve train, aluminum intake,neww lifters, he never finished putting it together Confused i put the carb on it, and cranked it up, fiddled with the timing until it stayed running, it ran like crap, but the gas was 1.5 years old, will this cam run with stock springs, i really dont want to do a bunch of work to it, and it probably wont get run to hard, just looking for some opinions thx  

68scott385 68scott385
I have an SS396 tatoo | Posts: 325 | Joined: 07/09
Posted: 07/30/13
09:23 AM

It is advisable to always use the springs recommended by the cam manufacturer. Most cam manufacturers will not warranty a cam if you do not use the springs they recommend.

Since you did not say what size the cam is, or what year the motor is, we have no way of knowing how close in compatibility the stock springs may be, which is probably not close due to the pedestrian nature of factory cams and the low spring pressures they require to control the valve actions.  
68scott385 68scott385 68scott385

dale49 dale49
I love my Chevy Chevette! | Posts: 16 | Joined: 07/13
Posted: 07/30/13
07:55 PM

RPM Range: 2,200 to 6,100 rpm
Duration @ .050" lift: 235/249 (int/exh)
Valve lift: .489/.476 (int/exh)
my kid put it in the motor, then quit with it, i just want to get it driveable , so i can move it out of my way, until i decide what to do with it, it sounds very angry, i was more worried about it bending something in the valve train, than valve float at high rpm, i was thinking that spring strength would be more of an issue than spring height, its been 25 years since i built or worked on a high performance motor and im a little rusty  

68scott385 68scott385
I have an SS396 tatoo | Posts: 325 | Joined: 07/09
Posted: 07/30/13
08:40 PM

Valve float occurs when the springs can no longer control the valve movement and the valves either never completely close or the bounce off the seat, neither is good and the rpm doesn't have to be all that high for float to occur if the springs aren't of the right strength to begin with. That cam is much larger than a stock cam and stock springs won't keep up for long. At minimum I think you should get the right valve springs for that cam unless you plan on pulling it out and selling it to someone else before putting much more runtime on it. JMO  
68scott385 68scott385 68scott385

Ravoll Ravoll
V-6 Camaros rule! | Posts: 85 | Joined: 02/12
Posted: 07/31/13
02:30 AM

Is this a new cam/lifter set or a used one that may be toasted?

You need proper springs and the exhaust springs will need to be shimmed,if you do away with the rotators that is.Plain old over the counter Z/28 style springs would probably be enough.It will run to an extent with the stock units until you start getting up in the RPM's,where valve float occurs.

Low compression engines don't respond well to high lift cams.The valve overlap will cause a serious drop in the Dynamic CR,causing a rough ,stumbling idle,along with lower vacuum.Been there done that.How is it at off idle conditions?

Things to check:

This procedure works best if a new timing chain set was installed.If the old ,worn set is used it will have some slack,and put you off a ***

Make sure the cam was installed with the correct timing to start with.
Pull the driver side valve cover,turn the engine clockwise (looking at it from the front,not the drivers seat) by hand until both the intake and exhaust valves on the #1 cylinder are closed.Pull the #1 spark plug,insert a length of coat hanger wire ,or similar, into the hole to find the piston.Use a long piece and make a big loop on the end so you don't lose it in the cylinder.With the wire in the hole turn the engine a little more until you feel the piston coming up to top dead center.If you go past TDC just turn the engine back a little till TDC is achieved.Once your confident that the #1 is TDC,have a look at where the timing mark on the crank balancer is lined up.Should be close to zero degrees.

If all is well then check the valve lash adjustments.Valves to tight will stay open, and the engine will run like crap,if at all.
You didn't say if this is a solid or hydraulic lifter cam ,but here goes for hydraulic.For this I always loosen the 5/8 nut holding the rocker arm till there is slack between the rocker/valve stem contact area,tighten it back up until I can just barely feel vertical movement at the push rod,and then give it a quarter crank after that.This will put you in the ball park.

Engine off.
Pull both Valve covers.
With the engine still at #1 TDC ,both valves closed,from the previous check,you will be adjusting.

#1 exhaust valve
#1 intake valve
#3 exhaust valve
#5 intake valve
#7 intake valve
#2 intake valve
#4 exhaust valve
#8 exhaust valve

Now rotate the engine clockwise by hand 360 degrees. The mark on the balancer should be back at the TDC mark. Keep in mind that this is not the TDC where #1 would be firing! It's where #6 would fire.Then adjust:

#3 intake valve
#5 exhaust valve
#7 exhaust valve
#2 exhaust valve
#4 intake valve
#6 exhaust valve
#6 intake valve
#8 intake valve

And your done.Let us know how it goes.  
The older I get,the faster I was.

68scott385 68scott385
I have an SS396 tatoo | Posts: 325 | Joined: 07/09
Posted: 07/31/13
08:06 AM

The Chilton's manual way of setting hydraulic lifter preload may not work on a performance cam. Better to do it the way Comp Cams suggests on their website.

http://www.cpgnation.com/forum/how-set-valve-lash-5810.html  
68scott385 68scott385 68scott385

Ravoll Ravoll
V-6 Camaros rule! | Posts: 85 | Joined: 02/12
Posted: 08/01/13
01:21 AM

Comp does it that way also.They just have you turning the engine by hand for each and every valve.For example they say turn the engine until the intake is open on #1 and then adjust the #1 exhaust.Then turn the engine till the #1 exhaust is open to adjust the #1 intake.IMO this has you wiping all the pre lube off the lifter bottoms by spinning the engine 16 times for lifter adjustments.

But they recommend only 1/8th turn after zero lash.That cost me 3 keepers on my first set of comp lifters. Tongue

But by all means ,if you have the comp instructions ,do it the way they say.  
The older I get,the faster I was.

dale49 dale49
I love my Chevy Chevette! | Posts: 16 | Joined: 07/13
Posted: 08/03/13
10:51 AM

i haven't had time to mess with it any more since the other day. talked to my kid and he set the lifters according to the instructions, i was more worried about actual vale lifter damage than valve float, it will mostly just haul trash to the dump and pull my boat to the landing neither of witch is race conditions, it still has the stock torque converter to, i might put all the " right " parts in it this winter when i have time to mess with it, i'm going to go see if i can get it to run correctly today or tomorrow, and ill check back in  

dale49 dale49
I love my Chevy Chevette! | Posts: 16 | Joined: 07/13
Posted: 08/03/13
11:21 AM

i set the timing by "ear" and got it to start,,,,,,,,,,,,,,,,  http://s1273.photobucket.com/user/saltlife49/media/VIDEO0013_zps1e3ea4e9.mp4.html  

dale49 dale49
I love my Chevy Chevette! | Posts: 16 | Joined: 07/13
Posted: 08/03/13
11:21 AM

i set the timing by "ear" and got it to start,,,,,,,,,,,,,,,,  http://s1273.photobucket.com/user/saltlife49/media/VIDEO0013_zps1e3ea4e9.mp4.html  

dale49 dale49
I love my Chevy Chevette! | Posts: 16 | Joined: 07/13
Posted: 08/17/13
07:58 AM

ok here we go, i set the timing at 13 deg. comp cam guy said to start between 12 and 14, took it for a spin, it is the weakest ,slowest thing i have ever seen, didnt go out on the highway, was on the dirt road by my house, this thing has the stock torque converter, is it not getting enough rpm to "use" the cam? or could it be not enough compression, i think i would like to see it in a crusher, yep im tired of it allresdy!!  

dale49 dale49
I love my Chevy Chevette! | Posts: 16 | Joined: 07/13
Posted: 08/17/13
08:03 AM

i set the timing at 13 deg. took it for a spin it is horrible slow week embarrassing, it has absolutely no power, could the stock torque converter be not letting the motor get enough rpm or should i crush it and get my 200 bucks  

68scott385 68scott385
I have an SS396 tatoo | Posts: 325 | Joined: 07/09
Posted: 08/17/13
08:23 AM

Icon Quotedale49:
RPM Range: 2,200 to 6,100 rpm
Duration @ .050" lift: 235/249 (int/exh)
Valve lift: .489/.476 (int/exh)
my kid put it in the motor, then quit with it, i just want to get it driveable , so i can move it out of my way, until i decide what to do with it, it sounds very angry, i was more worried about it bending something in the valve train, than valve float at high rpm, i was thinking that spring strength would be more of an issue than spring height, its been 25 years since i built or worked on a high performance motor and im a little rusty


Look at the specs you posted for that cam. When they say 2200-6100 operating range, they mean it. Now that you have made the same rookie mistake that everyone else has made, either change the rest of the drivetrain to accommodate that cam or change the cam to something that will work with the rest of the vehicle. SERIOUSLY. I say it because I did the same thing, big cam stock converter & gears...not so happily married.

For the cam specs listed the torque convertor should have about 2000 stall rating and the rear gears should be in the 3.73 neighborhood. If you were to take it out and matt the gas and wait for it to go you'd probably feel it start to make power right at 2300-2400rpm. It'll lug along until the rpm comes up to the cam's operating range and you'll feel it start to make good power. Without the correct t/c & rear gears it will be a slug from idle until it gets to the cams sweet spot.

IMO change the cam. It is cheaper to buy a new cam than to buy a t/c or a set of gears. Get a cam with duration numbers @.050 in the 205-215 range for low end torque. If you get much higher than 220* duration you get into torque converter and gear changes.  
68scott385 68scott385 68scott385

dale49 dale49
I love my Chevy Chevette! | Posts: 16 | Joined: 07/13
Posted: 08/17/13
09:21 AM

ive got 373 gears, the trucks just gonna be used for pulling a boat and stuff like that, even with the right torque converter it will probably suck for boat pulling i think, whats your opinion,
i found this cam comp cam part #12-105-3
the lifters have maybe thirty minutes of run time do u think  i could reuse them?  

dale49 dale49
I love my Chevy Chevette! | Posts: 16 | Joined: 07/13
Posted: 08/17/13
11:36 AM

iwas looking on comp cams website and found these two cams 12-670-4, 12-105-3, but they dont say anything about compression and i have no idea whats in this motor, does anyone have a suggestion as to which would be a better choice  

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