Technical Upgrade from Rochester 2G to Edelbrock 1406 worth it?

I bet!

I'm going to just buy what I need now before I lose my chance until maybe summer or possibly 2024 Holiday season. If I wait to rebuild the carb, fire it up and check compression, and then tear into it and take the timing cover off to look, by the time I do all that and order something and wait for it to arrive I will have lost my chance to take care of it now. Since it has 8 deg slack indications are to just change the timing set now regardless if it was changed from nylon by previous owner.

Here's my list:
1. Timing chain set
2. Timing cover gasket
3. Damper/harmonic balancer
4. One piece oil pan gasket

Is that all I likely need? Is my best bet to look for all that stuff on Summit Racing? I'm guessing going to NAPA or Oreilly will result in not as good options?

Regarding the cam, I'm thinking and hoping its fine for now (I'm ok with stock for the time being if it works) although it would be so much easier to take care of that now vs later.

 

You kind of threw me for a curve there for a moment, but I think I understand what you're saying.

Slack in the timing chain is only relative between the positions of the crank and the camshaft. Being 10° off from TDC is only relative to the position of the crank and the timing mark on the balancer/dampener.

 

You might grab a balancer keyway to be safe. While it's more likely the ring slipped on the balancer it's also possible the keyway sheared

 

Sorry I spoke too quick. I determined the timing mark on the damper was off 10 deg using a piston tool. I determined slack in the timing chain by spinning the harmonic balancer clockwise and lining up the damper to tdc and watching for the rotor to turn when going counter clockwise.

 

thanks! I’m guessing summit racing is my best source for all this vs struggling to find stuff at local parts stores?

 

I'd also replace the damper bolt while it's apart.

 

That’s what I was getting at, sorta failed to mention it.
But I know Ford had some timing sets in the ‘70’s when the dots were one to one, cam was 4-6 degrees retarded. I don’t know if GM did the same thing.
10 degrees is a funny number (to me). Aren’t teeth being off one way or the other like 20-something degrees? I used to know the number, but my how the years have gone by

 

I get ya now. So you are starting “behind” in timing.
I thought you were referring to cam timing.

 

Would really depend on local part stores. I had no trouble getting timing parts at my O'Reilly. And theres a kid that works at O'Reilly that I'm helping update the 327 in his 67 c10 that's needs most of the list we gave you and we found everything in the O'Reilly computer. Just order the parts for a 75 c10

 

One tooth off would be 10° at the camshaft. But that would be 20° at the crank, wouldn't it?

 

I can’t recall. I’d have to go look at a timing set and count the teeth.
But with the cam gear larger than the crank gear, I think it would be opposite.
Two turns of the crank is one turn on the cam.
In my thoughts, 10 off at the crank would be 5 off on the cam.
Just thinking of the teeth, not a slipped balancer.

Edit: I think we said the same thing

 

@SDrocker , how much slop was in the timing change?

 

The "keyway" is where the " woodruff key " sits . The key is what shears , not the keyway .
In 76 years , I have seen ONE damper hub move out of position & no damper keys sheared , FWIW .

 

I buy pretty much everything at Rock Auto. Much better prices than local stores and you have more choices when it comes to each part.

 

@SDrocker I'm going to correct a little engine math error that "The Chevy Pope" made.

2200 RPM is just what it says, 2200 crankshaft revolutions per minute.
1 mile at 60 MPH also takes one minute.
In one minute, 2200 revolutions of the crankshaft means the cam gear makes 1100 revolutions, NOT 6000 revolutions.

A "Chevy Pope" should know better, but maybe he read the wrong Bible?

I'm considered a jackass by some for doing it, but I'm a stickler for accuracy, and will make corrections when I read information that is not accurate.

 

I measured 8 deg or so... by turning the harmonic balancer clockwise to a zero tdc mark and watching the rotor for movement as I went counter-clockwise on the harmonic balancer.

 

I'm going to get everything from summit. I want a 6.75 inch diameter harmonic balancer and rockauto only has 8 inch when I look up 1975 C20 chevy.

The summit brand is 6.75 but read reviews the timing marks are hard to see.. although I have timing tape maybe I'm better off with this one that has a nice solid groove for the zero mark (can see when you look at 360 deg view).

https://www.summitracing.com/parts/pro-66510


I'm not sure if I need the woodruff keys for the crankshaft gear? Would I need an additional one for the harmonic balancer? I've seen some 3/16 wide short/long ones but not sure what I need.

Also I'm going to get this timing set below.. im not sure if I need to get a new cover that has more width to accomodate the chain width... hmmmmm

https://www.summitracing.com/parts/clo-9-1100

 

I honestly can't remember if the keys are separate. I'd just want one for the balancer in any event. Never actually seen a crank gear on sbc slip from a key issue.and like I said it's highly possible the original balancer key is fine. Just something nice to have on hand before just in case

 

Are you going to change the timing set as well? If so id plan ahead and get two keys, one for the balancer and one for the crank gear.
AZ may rent the crank gear puller installer if you don’t have one and don’t want to buy one.

 

Thanks, I just can't find what I need (or even know what the correct size is)... im guessing 3/16 width, 3/4 inch length and height of 0.300 inches ?

 

Yep, thanks going to change the timing set. I don't know what key size I need, or at least can't seem to find the keys on summit.



I was thinking to borrow the tool from Oreilly or AZ

 

One of the keys(maybe both) are like 1/2 moon shaped if memory serves.

 

thanks I saw some that look like half moon. Wasn’t sure if you use two separate or one long one? Ive seen both types on jegs

 

Well, pull the balancer off, you’ll then know.
That way you can just make one order.

 

i want to finish rebuilding the Rochester carb and fire it up without any other changes so I don’t want to take it off right now…. I was just trying to get ahead and have all the timing set parts in case I have the opportunity to take care of it perhaps next week before I lose my chance for a while.

Maybe I can deal with the keys later and buy the rest now.

 

Last time I lost/misplaced keys, NAPA had them in stock. They used to also carry 1 foot lengths of key stock as well.

 

I ordered the following (though from RockAuto):
1. Timing set
https://www.summitracing.com/parts/clo-9-1100

2. Timing cover gasket
https://www.summitracing.com/parts/fel-tcs45121

3. 1 piece oil pan gasket
https://www.summitracing.com/parts/fel-os34510t

4. harmonic balancer
https://www.summitracing.com/parts/rnb-594-012

5. harmonic balancer bolt
https://www.summitracing.com/parts/arp-134-2501

6. woodruff keys
https://www.summitracing.com/parts/pio-839009

Once I rebuild the rochester carb i will fire the truck up to see if the carb is behaving and possibly check compression. If time permits I'll get on the timing chain set before 2nd week of Jan when I'll start getting busy at work.

 

Here's a progress update on the rochester carb. Looks like someone has rebuilt this in the past.

1. the check ball below the venturi cluster and one below accelerator pump were swapped.. smaller one should go under accelerator pump but was the other way around and was kind of stuck and had to tap hard to get it out. See photo with red arrows.

2. Nitrile float weighs 9.5 grams and I didn't see flakes in the float bowl.

3. Idle mixture screws have some ridges from someone tightening them hard (wasn't me).

4. It looks like the metal sleeve or bushings that go below the venturi cluster are not there or the previous person who rebuilt this left them out.. not sure if they are critical. hmmm. (see photo with green arrows).

5. Accelerator pump seemed to be working fine but not sure if I should replace it with whatever the Walker rebuild kit comes with hmmm?


I'm not sure if I should order anything before rebuilding it, for instance new idle mixture screws, float? I wouldn't mind having this thing back together very soon though.

In the mean time I'm going to start cleaning this up and hope my siamese cat doesn't go on my counter and start playing with all the little pieces like they are toys.

 

It would be nice to have new idle mixture screws, but I don't know if they are available.
Good catch on red arrow balls.
I'd just go with what you have on the green arrows. Probably the only choice.
I'd use the new accelerator pump.

Hope this helps.

 

Thanks! What about the nitrile float? It measure 9.5 grams and I found online the spec is 9 grams... I sort of want to not rebuild this for a bit of time and wonder if the ethanol content in the fuel will make an issue or not too much.

I can always buy new idle mixture screws and install them later but at least get what I have now rebuilt, fire up the truck to see how it idles/runs and take for a short drive before I tear down for timing chain set.