"thumper cam"

[oldblue1968chevy]

I didnt pull the distributor out. Should I (put engine back @ TDC with my NEW mark) pull/check that my distributor is firing #1 plug?

Heck thats where im going now anyway..

[fleetsidelarry]

I'm afraid if I say anything more wwotr's rates are going to go up.

you shouldn't have to pull the dist. so your original damper/tab 0° marks WERE off? by 8-10 degrees?

[fleetsidelarry]

something like this:
http://www.summitracing.com/search/P...kr=timing+tape

[oldblue1968chevy]

Yes, I'll try to get a pic with the digital camera tomorow. Im going to double check myself tomorow, I didnt like the idea of turning the motor over with a bolt in the combustion chamber

I assume I need to measure the diameter and the depth of my balancer before I order tape..?

I can borrow a adj. snap on timing light if I need, but for less than $5 bucks I'll buy some timing tape lol

[gonnuts]

Originally Posted by fleetsidelarry

gonuts, what recurve kit were you using?

I believe it was a moroso.

[oldblue1968chevy]

With my new mark my initial timing is 6* btdc, the original mark is probably 40* btdc.

Im about to double check my work from yesterday. Turn motor until piston hits stop, turn motor opposite direction until piston hits stop. I have a pic of the mark on the balancer but cant find the cord.

The marks were within 4" of each other (I thought they would be alot further).

I had the initial set to around 12btdc* this AM but it was hard to start and idled sorta funny (didnt sound right) so I timed it by ear at the mall parking lot

[fleetsidelarry]

Originally Posted by oldblue1968chevy

With my new mark my initial timing is 6* btdc, the original mark is probably 40* btdc.

you mean the original damper groove is up around the 40° mark?

if I understand correctly, it sounds like you've got one of those dampers that requires a timing tab at the 12 o'clock position

Originally Posted by oldblue1968chevy

I had the initial set to around 12btdc* this AM but it was hard to start and idled sorta funny (didnt sound right) so I timed it by ear at the mall parking lot

been there, done that! beside the hiway at night, after a roadside distributor fix.

good job! Now you have a baseline from which to figure out your distributor's mechanical and vacuum advance.

[oldblue1968chevy]

So I need to buy a new timing cover? Im using the timnig cover that came with the motor, the machine shop said i need a new balancer I dunno whethere or not they ordered the right one, im double checking myself as I speak I came inside for a sharpie

[fleetsidelarry]

Originally Posted by oldblue1968chevy

So I need to buy a new timing cover? Im using the timnig cover that came with the motor, the machine shop said i need a new balancer I dunno whethere or not they ordered the right one, im double checking myself as I speak I came inside for a sharpie

no need to buy a new cover too, just need to get the damper that matches the cover you have now. can you get us a picture of how far off it was?

[oldblue1968chevy]

Ok, I must be a quack lol.

Re did everything again today. This time the 2 marks were about 8" apart, with the stock slot in the balancer in the center

Good bad, I dunno I went a lil slower this time too?

Uh.

Will have pix when the cord shows it self (its hiding right now)

[oldblue1968chevy]

You do have to have some marks on your damper, you can get a timing tape that goes around the damper or you can make your own marks. what I did was use a sharpie to make marks on the damper.

use the distance on the timing tab corresponding to 10° (for instance) as a reference as to how far apart to place the marks.
put a mark 10° clockwise of the 0° groove in the damper, another 10° past that and so on. 4 marks would get you 40°, also mark the 0° line on the tab

with the vacuum advance plugged off, as you slowly rev the engine
up, the marks start rotating counter-clockwise.

for example,then, at idle, if your initial timing was set a 10° advance the first mark you made (corresponding to 10°) on the damper will be at the tab 0° line. as you slowly bring the rpms up the next mark will approach the tab 0° line. at some point, 3000 rpm or so, the marks will stop moving, let's say at the 4th mark or 40°. the difference between your initial and the final is your total mechanical advance built into the distributor (in this example 30°)

likewise, the amount of vacuum advance is the number of degrees of change, at idle only, when you hook the vacuum advance back up. for instance let's say the damper jumped from the 10° sharpie mark to the 30° mark, you'd know that you have 20° of vacuum advance in the mechanism.

Makes one of those new timing lights look like a good idea

^
So could I turn the balancer from 0-10* and make a mark turn it another 10* make a mark so on and so forth?

I forgot to measure my balancer so I know what tape I need. What you just said helped alot im going to keep reading and re reading it I thik I understand it alot more, so now that Ive verified (i think lol) my exact tdc mark I need to see how much mech. timing im gettting and how much vacumm timing Im getting?

[fleetsidelarry]

when you made your marks on the balancer, were you making them in line with the 0° tab mark?

[oldblue1968chevy]

Yes DUHH

That is correct, isnt it hahaha

[CVA59]

Originally Posted by oldblue1968chevy

Im a poser

Don't feel bad oldblue........... I have been a drag racer and hot rod builder all my life and now i have relagated myself to the title of "poser" also, LMFAO. I am running the BMT in my 64.

[fleetsidelarry]

Originally Posted by CVA59

Don't feel bad oldblue........... I have been a drag racer and hot rod builder all my life and now i have relagated myself to the title of "poser" also, LMFAO. I am running the BMT in my 64.

I'm seriously considering it myself

Originally Posted by oldblue1968chevy

Yes DUHH

That is correct, isnt it hahaha

yessir. I was just double checking, 'cause I didn't specifically say that when I first tried to explain the method.

then, if your last try resulted in the original groove being exactly between your sharpie marks, that means both your damper and your tab are OK and you are showing TDC at 0° on the tab. you don't need a new damper. first try showed 40° off or did I misunderstand?

[oldblue1968chevy]

Yeah, I dunno what happned the first time. I still havent found the cable, sis and dad claim they havent touched it (BS) LOL

The marks were SUPER close together and WAY off.

So whats next (check mech. adv and vac. adv)?

[fleetsidelarry]

if you're satisfied that your 2nd check was done properly and the 1st was bogus, I'd say fire 'er up and see what you have in the distributor.

I was curious how you knew you had 18° initial before, the timing tab doesn't go that far does it?

[oldblue1968chevy]

Just an estimate, eyeballed guess. I think my tab goes to 16 on the before, and like 8 after?

I'll get back to you larry soon. May be a day or so (weekend comming other things to do). Thanks again!

[weircc]

i have the mutha thumpr roller in my big block and am having problems

wont idle in gear
always running rich
bout to give up

[LA72c10]

I own and installed the original Thumpr in my sbc...worst headache in my entire life...until!...I realized my timing was wayyyy off. I tried 8, 10, 12 initial time and ended up at 13 degrees running the best but i had to remove vacuum advance or else no power after 3000rpm, which was still horrible and caused my truck to jerk and buck from loading up at idle. Little did I know this cam or motor loves 4 - 6 degrees. After living with a horrible cam (during improper timing) for nearly a year and ready to give up I mentioned it to a guy from work and he tells me to crank it down to 6 initial. Well OMG everything fell into place and this cam is INCREDIBLE! Great sound and awsome driveability. I've got domed pistons and a 3 speed auto. at 92 octane, switched to a 670 avenger and wow this cam performs! As for torque converter i run stock and with proper timing it is tollorable but a 2000 stall which i am switching to in the future will make it that much better. Im glad i purchased this dual profile cam and i highly recommend it to anyone who doesn't care to be labled as a "poser".
Getting this problem all sorted out happened with in a matter of days ago so i'm still pumped about this cam. Booyah Thumpr! =)

[wwotr]

Originally Posted by LA72c10

I own and installed the original Thumpr in my sbc...worst headache in my entire life...until!...I realized my timing was wayyyy off. I tried 8, 10, 12 initial time and ended up at 13 degrees running the best but i had to remove vacuum advance or else no power after 3000rpm, which was still horrible and caused my truck to jerk and buck from loading up at idle. Little did I know this cam or motor loves 4 - 6 degrees. After living with a horrible cam (during improper timing) for nearly a year and ready to give up I mentioned it to a guy from work and he tells me to crank it down to 6 initial. Well OMG everything fell into place and this cam is INCREDIBLE! Great sound and awsome driveability. I've got domed pistons and a 3 speed auto. at 92 octane, switched to a 670 avenger and wow this cam performs! As for torque converter i run stock and with proper timing it is tollorable but a 2000 stall which i am switching to in the future will make it that much better. Im glad i purchased this dual profile cam and i highly recommend it to anyone who doesn't care to be labled as a "poser".
Getting this problem all sorted out happened with in a matter of days ago so i'm still pumped about this cam. Booyah Thumpr! =)

LA72c-10,
thanks for this post.
I'm sure your experience (that you posted here) will help many Member out!

[weircc]

Originally Posted by LA72c10

I own and installed the original Thumpr in my sbc...worst headache in my entire life...until!...I realized my timing was wayyyy off. I tried 8, 10, 12 initial time and ended up at 13 degrees running the best but i had to remove vacuum advance or else no power after 3000rpm, which was still horrible and caused my truck to jerk and buck from loading up at idle. Little did I know this cam or motor loves 4 - 6 degrees. After living with a horrible cam (during improper timing) for nearly a year and ready to give up I mentioned it to a guy from work and he tells me to crank it down to 6 initial. Well OMG everything fell into place and this cam is INCREDIBLE! Great sound and awsome driveability. I've got domed pistons and a 3 speed auto. at 92 octane, switched to a 670 avenger and wow this cam performs! As for torque converter i run stock and with proper timing it is tollorable but a 2000 stall which i am switching to in the future will make it that much better. Im glad i purchased this dual profile cam and i highly recommend it to anyone who doesn't care to be labled as a "poser".
Getting this problem all sorted out happened with in a matter of days ago so i'm still pumped about this cam. Booyah Thumpr! =)

im sure everyone will appreciate ur input i know i do and i will be trying asap thanks and sorry if this thread slowly got high jacked lol

[oldblue1968chevy]

Im going to adj. mine to 6* btdc and see what happens

[weircc]

well i tried but hell mine wont even run at 6 initial mine almost has to be at 30* initial or it starts back firing through exhaust

[oldblue1968chevy]

Did you check your tdc mark to make sure its spot on?