I use the thumper cams in quite a few engines. They work VERY WELL. you will gain 20 horsepower EVERY WHERE. I am sure you will love it.

JOE SHERMAN RACING ENGINES

 

20 horsepower for $200 plus by the time you spend with labor, gaskets, and a retune? Spray a 100 hp shot and call it a day, only $500 bucks. Much more cost effective and your engine is already good to go. To recap, 20 hp for $200 or 100+ hp for $500. And the sound cares to who? Easy math. Go green baby!

 

You could gain a good 8-12hp with just some spark plug indexing too($13 at your part store). You might gain another 8-10hp with a 1" carb spacer. The Thumper cams look like a custom grind looking at the numbers. I know my XE284H cam is 240/246 @ .050 and is about 15hp more than the old magnum cam grinds. I found it pretty impressive to read about a 302 that had a custom cam with 225/252 @ .050 grind. Had stock unported GT 40 heads and ran 11.19 @ 121mph. Looking at the numbers, it appears the Thumper cams are a step up from the XE cams. Your gonna love that 5 speed.....I've got one too. That cam grind you picked out looks nice.

 

As far as spraying an engine to get HP...that's just not me. Not saying it's bad because it is a more "efficiant" way to get more "bang for your buck"!! Plus with my luck I'll hook it up and when it sprays i'll cook my engine!! Oh yeah...labor, gaskets and tune is all free....cuz it's me doing it!!! Finding Time..well that's another story!

I installed a 1" spacer last year and did notice a differance. I also went to electronic ignition and did the 10L switch on the timing advance for the ford distributor. So far very pleased with what I have the the 5 speed makes it feel like a whole different car. Although I did a compression check and I was getting 175 psi for all my cylinders but one, got 135, and now I have to find out where my leak is??!!

 

Just a quick note: on the cam specs you list Lobe Center on one and Lobe Separation on the other.....
They aren't the same thing!
The added duration will give a distinctive lope at an idle and the torque will come on about 500 - 1000 rpm later. It is not a big cam but it should provide you with a noticable boost in torque and HP.

 

The one in BOLD is the cam I'm currently running. I wanted a cam that was slightly bigger and wanted to try the first one...the one with 107 lobe seperation.

So far it sounds like a go...maybe next weekend I'll install it??

 

What is the lobe separation for the cam in bold?

 

Here's his cam specs.. Looks like he has a 107 lobe center.....which should be pretty healthy.

COMP Cams® - Cam Details

 

although it is the smallest of the Thumpr, it si a high rev cam.
Is your crank will be able to rotate at 6000-7000 without bursting??

 

The 289 is not very sensetive to high revs.
My stock 302 shortblock have seen several missed gears and the huge revs that follows when you plant that right foot thinking you are in gear...

 

Hi Rev Cam?? His cam makes it's best power from 2000-5800rpms. Where do you do see 7K rpms?? 6000rpms is probably the highest he will shift at.

 

Sorry, i forgot to say, the dyno2003 test was made with AFR 165 CP heads.
the results are higher in revs than with stock heads...

 

Try it with Dyno2003, you will see..

try to compare 264HR 270 HR and 283 THR...

 

With the 3:55 gears the car has seen 5800 numerous times. Not for an extended period of time but it has been there. If the cam is rated for 200- 5800 why woudl I have to spin it so high? Also what is dyno 2003?? desktop dyno?

 

Yes desktop dyno2003..

 

Your high revs caused by missed gears are very short in time (about 1 sec)
Can you compare it to a 10 or 30 sec WOT run between 5500 and 6500...?

 

I took my stock crank, stock block, stock rods (with ARP bolts) to 7,500 on the dyno where I plan to shift it at the drag strip when all is right. Several pulls done to 7,100. No big deal if all the little things are right.

I wouldn't take that desktop dyno program too seriously.

 

If I was going to spend the dollars on a new cam and lifters I would definitely not get a Thumper cam. No cam designer would grind you a cam with those spec's if you asked him to custom grind something (with max power in mind) for you.

JMO,

paulie

 

PLOVETT,
Can you please explain as to why the thumper cam specs are not that good. I'm always trying to learn something new and would like to know as to why...lift, duration, lobe seperation..???

 

PLOVETT,
Can you please explain as to why the thumper cam specs are not that good. I'm always trying to learn something new and would like to know as to why...lift, duration, lobe seperation..???

Sorry, not trying to dog on your cam. I'm sure a Thumper cam will sound awesome and make good power. My point was if you gave all your engine spec's to a good cam grinder and asked for max power I can guarantee you he wouldn't grind a Thumper cam. I'll stand by that.


The Thumper cams have a very tight lobe separation angle (LSA) to increase overlap to get the rumpity rump sound. A tight LSA may or may not be the hot ticket for your motor. It just depends on your combo. Then they have a super long exhaust duration, again to increase overlap and get that sound. I think they did that because you can increase the exhaust duration quite a bit without severely affecting low rpm power and drivability. Then they use a relatively short intake duration to make sure low end power and drivability are still okay. If you increase intake duration too much, again to get overlap, the consequences are much harsher. Low end power and drivability would drop significantly. You might need higher stall speed and/or lower rear gears, etc.


I think they did all these things to get the rowdiest sound they could without making the cam "doggy" at low rpm. You can't do the above and at the same time optimize the cam timing for best power. It's just two different goals.


It'd be interesting to call UDHarold up and get a cam recomendation for your motor and compare it to the Thumper.


As always JMO,


paulie

 

Thank you for the explination...didn't think you were dogging my cam choice. I can assure you that that cam isn't the best for my setup but for right now it's what I was looking for. Basicly I can't afford a super hot street motor SO I figured my engine runs good now but would like something that sounded a little hotter without sacraficing power and the thumper cam seemed to do the trick. Guess we'll see what happens!!

 

Sure thing. With those gears and a 5 spd it ought to run great. Let us know how it turns out.

paulie

 

The cam is a little on the large side for a stock headed 289. It might not be 'ideal', but won't be too far off, and will definitely 'thump'. Your heads will keep it from making much power above 5500 rpm, and the engine REALLY needs an upgrade in the head department, but I guess that can come later.

Whatever you do, be SURE to use the correct valve springs, and make sure they are installed at the proper height. You'll probably need the entire package of springs and retainers. If the required springs are doubles, the head will need machined. Else, you could use a beehive or possibly the 972 if it's enough, and the heights work out ok.

I believe the beehive you would need would be the 26918, and matching retainers.

COMP Cams 26918-16 - COMP Cams Valve Springs - summitracing.com

COMP Cams 774-16 - COMP Cams Steel Valve Spring Retainers - summitracing.com

Good Luck!

 

I never got a chance to install the cam and here I am almost a year later!! When you say height..can you explain a little further? Do you mean so I don't get coil bind?

 

The spring will be rated for lift and pressure at a specific installed hieght on the head..If the spring is compressed more than what it calls for the amount of lift required to put it into bind would be less and the seat pressure would be more as well..If the spring is installed too long the seat pressure will likely be too low...You can adjust the installed hieght by adding shims under the valve springs..It's more complicated if they are too short when installed..You can get special retainers to help with that one.