Thumper cams
Thread Starter
Drifting
Joined: Sep 2017
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From: CT
Thumper cams
Who here has any experience with a Comp Cams Mother Thumper cam installed in a 454, it’s installed in a stock bottom end , with some pocket porting done to stock cast iron angle plug heads. I did not put this motor together so I can’t say with any confidence that the cam was installed straight up, to me it feel like it was installed retarded , I have to put a ton of Advance in just to get it to start and idle, it has no power, I have gone through the ignition and verified TDC, also verified the firing order is correct, he is running a billet tach drive MSD Distributor along with the Box. I know the thumper cams sound radical, and I nice lope is a great sound , but this is way too choppy, and 0 power, a lot of backfire through the exhaust if you try to back off on the advance, any advice would be greatly appreciated.
Le Mans Master
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From: "You may all go to Hell- and I will go to Texas- Davy Crockett
St. Jude Donor '12
Did the installer degree in the cam, and positively lined up the timing marks when timing it to the crank? It doesn't happen often, but I have seen cams that were ground one tooth off. I had a high dollar Crower that never ran like it should, and when I checked the cam timing, it was off a full tooth according the cam card.
Race Director
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I don't have any direct experience with them, but the marketing and various reports indicate that their primary objective is a rumpety-rump idle via very high overlap. Especially with manifolds excess overlap just kills low end torque, increases fuel consumption, and doesn't even give more top end power as a tradeoff.
No one with a genuine interest in performance and efficiency would install one of these seeping piles in an engine.
Duke
No one with a genuine interest in performance and efficiency would install one of these seeping piles in an engine.
Duke
Thread Starter
Drifting
Joined: Sep 2017
Posts: 1,951
Likes: 748
From: CT
Did the installer degree in the cam, and positively lined up the timing marks when timing it to the crank? It doesn't happen often, but I have seen cams that were ground one tooth off. I had a high dollar Crower that never ran like it should, and when I checked the cam timing, it was off a full tooth according the cam card.
Thread Starter
Drifting
Joined: Sep 2017
Posts: 1,951
Likes: 748
From: CT
I don't have any direct experience with them, but the marketing and various reports indicate that their primary objective is a rumpety-rump idle via very high overlap. Especially with manifolds excess overlap just kills low end torque, increases fuel consumption, and doesn't even give more top end power as a tradeoff.
No one with a genuine interest in performance and efficiency would install one of these seeping piles in an engine.
Duke
No one with a genuine interest in performance and efficiency would install one of these seeping piles in an engine.
Duke
Le Mans Master
Joined: Sep 2009
Posts: 9,151
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From: "You may all go to Hell- and I will go to Texas- Davy Crockett
St. Jude Donor '12
OP if you decide after checking the cam that you are dissatisfied with it, I have a brand new in the box Comp Cams flat tappet hydraulic that has the same specs as the L72 mechanical cam.A little Lumpy but with excellent power
I have nothing to put it in, pm if interested
I have nothing to put it in, pm if interested
Thread Starter
Drifting
Joined: Sep 2017
Posts: 1,951
Likes: 748
From: CT
OP if you decide after checking the cam that you are dissatisfied with it, I have a brand new in the box Comp Cams flat tappet hydraulic that has the same specs as the L72 mechanical cam.A little Lumpy but with excellent power
I have nothing to put it in, pm if interested
I have nothing to put it in, pm if interested
over this one more time with my friend and I will certainly PM you, that’s a nice cam.
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Race Director
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From: Central Arkansas
Or possibly not zero’d correctly when installing the timing chain and sprocket. There are some people out there trying to do their own mechanics that can’t tell 1/10 from 1/100 and a tooth off is good enough.
Tech Contributor
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From: At my Bar drinking and wrenching in Lafayette Colorado
Lars
Pro
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From: Morgan Hill, CA
Don't hold back Duke... tell us what you really feel about those cams! 
Le Mans Master
Joined: Feb 2008
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From: Folsom CA
They were designed to sound like you have a huge power engine under the hood when in fact you have a near stock engine that sounds great as you rumble into a car show. They are just bling for car shows. Useless for driving enjoyment. I do think being a 454 it should still have decent power off idle but not much or any more than a stock 454 so you may have two issues, wrong camshaft and installed wrong.
Thread Starter
Drifting
Joined: Sep 2017
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From: CT
I appreciate all the comments and I have convinced my friend to let me take it apart and replace the cam. Thanks to a fourm member I’m going to install the L72 cam the hydraulic version, once I take it apart I can almost guarantee I will find the the cam was installed wrong. You should never have to add so much advance that the vacuum canister is almost parallel to the carb.
Burning Brakes
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From: The Triangle, NC
Thread Starter
Drifting
Joined: Sep 2017
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From: CT
Safety Car
Joined: Mar 2009
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From: Corpus Christi, TX
I appreciate all the comments and I have convinced my friend to let me take it apart and replace the cam. Thanks to a fourm member I’m going to install the L72 cam the hydraulic version, once I take it apart I can almost guarantee I will find the the cam was installed wrong. You should never have to add so much advance that the vacuum canister is almost parallel to the carb.
Edit: if you go the NOS cam route, be sure you get a 67 and later L71 version with no groove cut on the back bearing journal. Will cause a nasty internal oil leak in a 67 and later block.
Le Mans Master
Joined: Jan 2007
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From: Prescott Arizona
Gavin - Any idea how many miles are on that 454 with the Thumper Cam? Any chance it wasn't broken in correct and maybe the cam is 'going away'? When I got my 65 NOM L78, it had a relatively fresh 454 +.060 and a warm hydraulic cam (228/238) but was a dog which turned out to be a flat cam. That engine is now gone and I'm assembling a hydraulic roller cam in a 427 for that Roadster.
Side note - do you have a Tremec Trans in your 65? I sent a PM and not sure if you got it, regarding stabbing in a Bigblock whlie leaving the trans in place. If you don't have a Tremec...uh, never mind.
Mike T - Prescott AZ
Side note - do you have a Tremec Trans in your 65? I sent a PM and not sure if you got it, regarding stabbing in a Bigblock whlie leaving the trans in place. If you don't have a Tremec...uh, never mind.
Mike T - Prescott AZ
Thread Starter
Drifting
Joined: Sep 2017
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From: CT
Don't use the hydraulic version. Get a blueprinted repop or NOS L72 cam. Comp's flat tappet hydraulic stick will drop dead in the mid 5000s rpm range, even with a good set of lifters correctly adjusted. Save yourself grief. Get a solid lifter cam.
Edit: if you go the NOS cam route, be sure you get a 67 and later L71 version with no groove cut on the back bearing journal. Will cause a nasty internal oil leak in a 67 and later block.
Edit: if you go the NOS cam route, be sure you get a 67 and later L71 version with no groove cut on the back bearing journal. Will cause a nasty internal oil leak in a 67 and later block.
Thread Starter
Drifting
Joined: Sep 2017
Posts: 1,951
Likes: 748
From: CT
Gavin - Any idea how many miles are on that 454 with the Thumper Cam? Any chance it wasn't broken in correct and maybe the cam is 'going away'? When I got my 65 NOM L78, it had a relatively fresh 454 +.060 and a warm hydraulic cam (228/238) but was a dog which turned out to be a flat cam. That engine is now gone and I'm assembling a hydraulic roller cam in a 427 for that Roadster.
Side note - do you have a Tremec Trans in your 65? I sent a PM and not sure if you got it, regarding stabbing in a Bigblock whlie leaving the trans in place. If you don't have a Tremec...uh, never mind.
Mike T - Prescott AZ
Side note - do you have a Tremec Trans in your 65? I sent a PM and not sure if you got it, regarding stabbing in a Bigblock whlie leaving the trans in place. If you don't have a Tremec...uh, never mind.
Mike T - Prescott AZ