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Need cam help.

 
chesterd88
I love my Chevy Chevette!
Posts: 1
Joined: 02/13
Posted: 02/23/13 08:04 PM

I yanked my cam outta my chevy truck and i wanna put a thumpr cam in it but i have no idea what the cam code is. the stamping on my cam is shown in order like this. HO6, GMD4(i believe this is it), 363 and last CWC . there is a plus sign too but i don't think that matters. Someone please help.  

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pepsi1
Big Block power for the win
Posts: 940
Joined: 03/11
Posted: 02/24/13 05:31 PM

Chester88 welcome to Super Chevy:

Don't worry about the cam you removed for one second.

Now is it a roller cam or a flat tappet cam?

What is your truck going to be used for, towing, pulling, street/strip?

What is the trans your using. Automatic or Manual

Rear gear Ratio if you know?

Answer those questions and we can maybe help you.

Bob  

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Chester88
I love my Chevy Chevette!
Posts: 9
Joined: 02/13
Posted: 02/24/13 06:16 PM

Sorry. can't access the other account. i just want to upgrade it. street pretty much. give it some extra power and a nice lope. it has an auto transfer and i don't know what gears it has. Its a flat tappet. My truck is a 91 chevy c1500. short wheel standard cab.  

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pepsi1
Big Block power for the win
Posts: 940
Joined: 03/11
Posted: 02/24/13 08:30 PM

I have had trouble for over 2 months. I have been on Super Chevy for approx 1.5 years. The same with CHP. Don't know why. But it comes and goes....

Anyway I'll see what I can dig up for you. Hang in there. Grin  Cool

Bob  

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pepsi1
Big Block power for the win
Posts: 940
Joined: 03/11
Posted: 02/24/13 08:51 PM

Chester88
Make sure your engine is a flat tappet. Comp cams shows the 1991 engins as having a Hydraulic Roller Cam. If so let us know. Anyway some food for thought.

If you have a Hydraulic Flat Tappet Cam
Comp Cams P/N12-239-3 Grind# X426H (Cam Kit) K12-293-3
1300-5600 RPM .218/.226 duration @.050 .462/.480 Max lift with 1.5 rocker arms.
  Cam has a 111* lobe seperation with 107* intake valve center/line
Excellant throttle response, good mid range torque, and noticeable idle. Largest cam to be used with stock torque convertor. Needs a 3:23 to 3:73 Rear gears.
Any inprovement to exhaust flow helpfull....

Bob  

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pepsi1
Big Block power for the win
Posts: 940
Joined: 03/11
Posted: 02/24/13 08:59 PM

Chester88
This is if your engine has a Hydraulic Roller Cam.
There are many other cams so you don't have to be locked into any one cam...

If you have a Factory Hydraulic Roller cam
Comp Cams P/N08-411-8 Grind# X4260HR (Cam Kit) K08-411-8
1200to5200RPM .210/.214 duration @.050 .474/.474 Max Life with a 1.5 Rocker arms
  Cam has 111* Lobe seperation and 107* intake valve center/line
Needs 3:23 to 3:73 rear gears. Excellant mid range torque and HP. Largest cam to use with a stock torque convertor. Any improvement to exhaust flow helpfull....

Bob  

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Chester88
I love my Chevy Chevette!
Posts: 9
Joined: 02/13
Posted: 02/24/13 09:17 PM

Im positive its not a roller. It is a hydraulic lifter cam. According to comp cam I need the thumpr 279TH7. But I dont just wanna buy it and be wrong and have my truck down longer.  

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Chester88
I love my Chevy Chevette!
Posts: 9
Joined: 02/13
Posted: 02/24/13 09:20 PM

Failed to mention I already have headers and true duel so we're good on that. Also do u know anywhere to get a bowtie intake for tbi? I can only find them for carbed applications.  

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Chester88
I love my Chevy Chevette!
Posts: 9
Joined: 02/13
Posted: 02/24/13 09:26 PM

I also like the aggressive choppy idle the 279 has. So any cam that will give me that aggressive choppy idle im open to.  

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pepsi1
Big Block power for the win
Posts: 940
Joined: 03/11
Posted: 02/25/13 08:14 AM

If your going to change the torque convertor to a 2000 RPM plus then you can use the thumper 279th7. Now you need to watch the clearance between the valve stem retainer and the valve guide: Because the max lift on most of those heads was only .450.

The Comp Cam Thumper 279TH7 is a very agressive cam it needs rear gears like most cam changes. I know from experience with the 1500 the most Rear Gear was a 3:73 from the factory...With all that being said...

Bob  

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pepsi1
Big Block power for the win
Posts: 940
Joined: 03/11
Posted: 02/25/13 08:32 AM

Comp Cam Thumper 279TH7

P/N12-600-4 Grind #279TH7
1.Needs a 2000 RPM stall torque convertor

2.Headers always helps

3.Rear Gears depends on how tall your tires
are.

4.It has that Lopey Idle we all like....
True dual exhaust makes it sound very nice....

Specs for the thumper
P/N 12-600-4    Grind #279TH7
2000-5800RPM .222/.247 Duration @.050 .479/.465 Max Lift with a 1.5 rocker arm
107* Lobe seperation 102* Intake Valve center/line.

1.Use a Cloyes Double Roller timing chain and gear set.

2.Install this cam straight up and, check your piston to valve clearances. Steel rod engines require .080 intake .100 exhaust. .038 to .040 piston to head clearance. If you degree the cam watch your Exhaust/Valve to  piston clearance.


  As you can see the power starts coming in at 2,000RPM with the thumper 279th7.(With the correct gear) that maybe your cruise RPM. Then at 65MPH when you punch the throttle it should set you back in the seat. So you will need rear gears.
  Max RPM is always determined by how well the valve train is prepared. The wrong valve springs will drop the performance of any cam by 500 RPM to a 1000RPM. Valve float is a major problem also. It can also cause major engine damage.

Bob  

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Chester88
I love my Chevy Chevette!
Posts: 9
Joined: 02/13
Posted: 02/25/13 08:45 AM

I plan on getting the kit with the gear drive so I dont have to worry about chain slack. Im also going to buy the spring kit. I will purchase the converter and roller lifters on a later date. And where can I find different gear ratio that is also posi?  

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Chester88
I love my Chevy Chevette!
Posts: 9
Joined: 02/13
Posted: 02/25/13 08:47 AM

I also have bigger tires if that matters. 255/75/15  

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pepsi1
Big Block power for the win
Posts: 940
Joined: 03/11
Posted: 02/25/13 09:03 AM

You really need to be concerned about HOW TALL YOUR REAR TIRES are.
Tall Tires kill the Rear Gear Ratio.

Tires that are 26" tall with a 2004R O/D trans
a 3:42 to 3:73 rear gear ratio.

Tires  that are 28" tall with a 2004R O/D trans
a 3:73 to 3:90 rear gear ratio.

Tires taller then 30" need a 3:90 to 4:10
rear gear ratio at a minimum....

The taller the tire the more rear gear.
The lower the number. Grin  Cool

I.E. a 2:?? versus a 3:90. The 2:?? would be a
cruising gear NO POWER. The 3:90 rear gear is
a performance gear. Even if your engine does
not make a lot of power. By adding a lower
(Higher Number Gear) will make the engine feel
better to you and will it will not work as hard.

Bob  

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pepsi1
Big Block power for the win
Posts: 940
Joined: 03/11
Posted: 02/25/13 09:19 AM

Chester88 please disregard anything I mentioned
about a Hydraulic Roller Cam. I have listed some
Comp Cams, as that seems to be your preference.
Thats great. Just remember using too big a Cam
will hurt performance more then help it.... Tongue

Bob  

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