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

Thanks that's really great info. The cost isn't the issue, timing (pun intended) for me gives me small increments of availability to do any work to the truck or the 50 shoebox ford. I'll have to clean the carb put it back on and roll the dice for some time until I have time to look into the timing chain. At which point I assume I should just change the cam as well? I may (just maybe) have a little bit of time in late August/September 2024. Post Holidays I'm in a real career grind/transition from Jan up to mid August and will drive the truck 10 miles maybe 5 or 6 times and probably not have time to do any work to it.

 

Honestly if the cam itself still has the lobes and power is enough for you no real reason to swap the cam unless you just want to. I'm still running the original peanut cam in said factory four barrel 76 350 lol. I fact aside from timing set, oil pan, and valve covers my long block is completely untouched. Even still has the original gm installed rear main seal installed in 1975(for 1976 model year) that doesn't leak a drop lol

 

What all accessories if any are on your engine? Or do you just have a waterpump and alternator?

 

Waterpump, alternator, and power steering pump in it.

Thanks, makes sense on the cam. I'll have to check compression when the cam is back on to see what that looks like. I'll plan to change the timing chain set.. probably a year from now during the next Holiday break.

 

I thought of something. My damper and its timing mark is 10 degrees off which I determined a while ago using a piston stop tool I made. It’s pretty much exactly 10 deg off. I had made a new mark and used timing tape to make sure I was setting timing correctly but I’m wondering if that gives any clue whether someone did any work to the timing chain. If the damper separated I would have thought it may be more random and kept moving? It’s not moved at all in the time I marked it. Maybe someone installed it 10 deg off after changing the timing set (I know I’m probably being too hopeful here). I’m still wondering why my timing mark is off an exact 10 deg.

 

Could be a damaged keyway. Or a bent timing tab. Also in the 70s and 80s gm wasn't exactly known for high production standards. Every hear of the g body shuffle people like the street outlaw goofballs blame on the four link suspension on g bodies despite being the same basic setup as 64-77 a bodies(that don't shuffle)? Most of it is because of the sloppy welds on the frames lol. I've messed with g bodies since around 2000 and came across frames with multiple sections where the weld completely missed the seam in lengths of 6" lol

 

This is the infamous nylon cam gear btw. Notice despite the gears being in good shape the chain it still sloppy

 

Thanks, timing chain set replacement is on the list now, however it may be a while before I can get to it!

 

An explanation of why gm (and I believe other manufacturers too) did the goofy nylon cam gears. In the late 60s the whole emissions thing was gaining momentum. They were also going after "noise pollution" on top of whiny people that didn't like to hear their engine at all. The nylon gear was an attempt to dampen normal top end noise. Gm used them in many engines from like 1968-the early 80s. They're why any time I buy a used engine I always replace the timing set first regardless on any engine (aside from series 2 and 3 gm 3800s) lol

 

That's a cool thing about this forum. You ask a question, get the answer to your question, and get a whole lotta other info like engine history. And I'm not even one of the "old guys" here lol

 

Makes sense! There's always the possibility the previous owner changed the timing set before putting this engine in the truck.. since it required some work to convert from inline 6 to sbc 350, perhaps that person had some insight on this issue and took care of it... then again if you saw all the things I came across you might think that person probably didn't have that insight.... given it has 8 degree slack my guess is that is more reminiscent of an original engine with wear? I have no clue on the history of the truck, when that engine was put in, etc.. I just know the engine code shows 1975 when I looked up the numbers. It had some distributor with electrical connectors cut off making me think maybe the previous owner dumped the motor in as is and didn't give a fuck.. I changed the distributor out for another HEI unit I had on my other SBC 350 (before I upgraded to streetfire HEI distributor).

I also read GM used nylon because back then they didn't expect the cars to have a very long life especially given how the bodies rusted much quicker than the timing gear would have worn out.

 

You'd also be surprised how many old guys that would insist on replacing the old nylon cam gear with a brand new nylon cam gear because "gm did it for a reason" and " engineers know what they're doing" lol.

 

It sounds like when you have the damper off to replace the timing chain set, you should also replace the damper and damper bolt. Then check TDC once again.
We'll get this thing sorted yet.

 

Yep thanks, was thinking I need to replace the damper while I'm at it!

 

do you think I could buy a decent timing chain set at NAPA? I’m working on my shoebox today and maybe carb some tomorrow. I plan to throw the carb back on when rebuilt and see how it runs but just maybe I’ll have an extra day free later next week and may be my chance to knock out the timing set especially if it’s something I can buy local. I rather look first before buying a new set although I suppose the 8 deg slack indicates I should do this even if it didn’t have the original nylon teeth gear.

 

thanks some of the choke parts were missing so I wired it shut for the time being and being in San Diego some told me choke isn’t needed here. The vac line for the choke was plugged. I was pulling 18 in Hg after replacing every single vacuum line with new.

I already changed plugs and wires.


If compression shows ok I think right now it’s likely a carb rebuild that will get it running great and then timing set replacement to avoid risk of catastrophic failure.

my last open question is on whether I might find a quality timing chain set locally once I take a look what’s in mine.

 

If you have 8° slack in the timing chain and sprockets, then the camshaft's timing events are also retarded by 8°. Just a new chain and sprocket set will advance cam timing back to where it belongs. The timing of the intake valve closing event specifically makes a noticeable change in whether your engine performs better at lower or higher RPMs.

Advancing the cam timing 6° or 8° can make a big improvement in idle and lower RPM driving. What you initially felt was a carb problem at idle and lower speeds may have been at least partially a result of the retarded cam timing.

 

Take into account that replacing the timing chain means removing the pan ( to do it correctly) how far down this rabbit hole are you willing to go ?

 

thanks. The irony is that I discovered later that the damper was off exactly 10 degrees and prior to that has timed it with the mark on the damper not knowing that. It worked in my favor I believe as I was giving it 10 more deg of advancement. Maybe that’s partially why it was struggling like you said after having done the valve seals, mechanical fuel pump, and resetting timing with the correct new zero mark I made.

I was wondering recently why it didn’t have pinging issues with 10 deg extra (giving it 24 deg idle) back then and now it makes more sense.

 

yep that’s why I was saying I may not get to it for a long time… dropping the pan at least right and changing pan gasket or using rtv? I haven’t observed how much room there is for the pan to drop the way the motor was put into this truck.


I think what I’m going to do is put the carb back on after rebuilding it then check compression and see if that gives any clues as to what else I need to do… perhaps the cam is no good and if I’m changing timing set better to do it at the same time.

 

TDC on the damper has nothing to do with the cam timing. Cam timing is a different part of a engine running.

 

Ah yes I reacted too quickly in my previous post!

 

There’s a difference between 10 degrees off, and 10 degrees of slack in the chain.
I may have missed it, but how did you determine it was 10 off?

 

I would have thought by now all the nylon geared small blocks would be dead...
I replaced my first one when I was 14 years old and 1993 in my auto shop class and it had a ton of play and had a crack then and it was only probably a 15 or 17 year old engine (at that time it seemed like an old car engine but the reality was it was just a used car).

I would definitely recommend replacing the GM fiber gear set with at least a cheap rock auto "engine tech" set because the fiber gear really is a ticking time bomb.

 

If the truck is bone stock and you're going to rebuild the two barrel carburetor there's no reason to put some wild cam in it or not even an RV cam.
Just get a standard pretty smog timing set it doesn't have any weird built-in retardation that all the American car manufacturers were doing in the mid-70s.
A cam gear swap on a mid-60s pickup I would imagine could be done in 3 or 4 hours taking your time there isn't a whole lot that has to be unbolted and the engine is pretty easy to get to.
You will have to loosen the fan belt and remove it, you will have to drain the radiator,
You will have to unbolt the four bolts for the water pump now you should have access to the timing cover remove the bolts to the timing cover and you are at the gear timing gears.
If you decide you're going to remove the camshaft and swap it then it's a much bigger project because you need to pull the valve covers off pull the intake manifold off remove all the push rods pull the lifters out that are probably stuck into place with varnish, then you need to pull the radiator out probably the grill out and then slide the camshaft out the front of the engine and replace it with a new one... It's a huge project for a little gain although the exhaust note will sound sweet if you give it an obnoxious grind camshaft but honestly it doesn't make sense if you're going to leave the two barrel on it and all that stuff just change the cam gear it's easy and you won't have to wait until late next summer to do it.

 

I M E , the one piece pan gaskets ,when installed properly , are far superior to the old 4 piece set , leave the silicone on the drawer ,( except for corners)

 

I had made a piston stop tool and verified it was off exactly 10 deg

 

thanks yeah that was my thought don’t change the cam unless it’s bad. What are some good ways to verify the cam is fine to leave alone?

 

You'd be surprised. In my junkyard sourcing I've come across so many of the nylon gears in the last couple years I always assume any engine from that era still has one till proven wrong lol. We're in a period where the vehicles from that era that are mainly hitting junkyards are limited use etc vehicles. Whether it be former government work vehicles(my 80k mile 76 350 came from a former military base truck turned fire dept service truck) or for some old person that babies it since new and either died or went to a nursing home resulting in their kids calling picknpull to pick up what they consider to be an old junker. In fact I worked at the junkyard where I got my engine for four years and EVERY 70s 350 or 305 we tore into had a nylon gear. Though all of them were in far worse shape than mine was.