'61 348 Ignition and fueling upgrades

[Paddy399]

Hello everyone,

I'd like to start by saying I'm fairly green when it comes to this type of wrenching on cars. I've done tons of work to my motorcycle, and work on industrial mechanical equipment all the time, just never had the opportunity to do anything other than basic maintenance on a car. Until now...

I have a 3755011 E1361 348 block with Edlebrock Performer RPM heads, intake and dual 1404 carbs. I don't know much else as the car was bought at auction with little documentation from the previous owner. To me, the car feels like a slug, even when you get into it, I feel like it's lagging. Rather than dig into what is already on the vehicle, I'd like to start fresh by updating the ignition components and fuel delivery.

The car currently has a Delco HEI system in it. But again, I don't know where that came from and don't want to waste my time figuring that out. Instead, I've spent my time reading and searching this site, and think I've landed on the PerTronix Flame Thrower II distributor and coil. I'm pretty sure I have a new set of plugs and wires from last year that I never got around to putting on to go with it.

The car still has it's mechanical fuel pump with the sh*tty plumbing job from the PO. My thoughts here are to install an electric pump, regulator and new plumbing for more consistent fueling and to clean things up a bit.

My theory is, by replacing these systems, I can guarantee my fueling to the carbs is correct and I'm providing optimum spark. Overall, this should provide a better baseline in determining any other issues.

What do you all think, am I going down the right path? Is it a good place to start? What are some simple things I might be missing that'll give me more information about what the PO might have done?

Thanks, Pat

 

[Don Jacks]

I'd put a fuel pressure gauge and see what the fuel pressure is.You don't want more than 6 psi.While you have the plugs out do a compression test and let us know what it is.One of your problems just may be too big of a cylinder head for your engine size,and it could be too much cam,wrong cam[read Thumper,Bootlegger,and other noise type cams] causing a lack of low mid range power that you're having.Don't be so quick to discard that HEI as it may just need tuning.One of the best upgrades,and it's cheaper than a dist.replacement is to remove the dist module and use the dist.to triggeAttach filesr an MSD unit. While the plugs are out,take a boroscope, put the probe in a cylinder and see if the pistons have valve clearance notches.If not,then you've got low compression cast pistons there.

 

[rstreet]

I'd put a fuel pressure gauge and see what the fuel pressure is.You don't want more than 6 psi.While you have the plugs out do a compression test and let us know what it is.One of your problems just may be too big of a cylinder head for your engine size,and it could be too much cam,wrong cam[read Thumper,Bootlegger,and other noise type cams] causing a lack of low mid range power that you're having.Don't be so quick to discard that HEI as it may just need tuning.One of the best upgrades,and it's cheaper than a dist.replacement is to remove the dist module and use the dist.to triggeAttach filesr an MSD unit. While the plugs are out,take a boroscope, put the probe in a cylinder and see if the pistons have valve clearance notches.If not,then you've got low compression cast pistons there.

Great advice and I’ll bet cast pistons. Another item is I bet the carbs are out of the box and not A/F checked. I have had experience changing a 348 with automatic to two fours and was getting ready to go back to stock stuff! A friend on our site who is no longer with us was spot on with his procedure and I give credit to AFB for their jets and metering rods charting as I never touched them after changing to their recommendations. I really believe Don Jacks is a graduate or co instructor of the Ronnie Russell school of tuning
Robert

 

[Jim Sullivan]

Just an FYI on the Pertronix distributor, it's about 1 1/2" taller than a stock distributor. Which may interfere with the air cleaner. Also, what transmission and rear gears are in the car? A powerglide and tall gears can make the car feel like a slug.

 

[Paddy399]

I'd put a fuel pressure gauge and see what the fuel pressure is.You don't want more than 6 psi.While you have the plugs out do a compression test and let us know what it is.One of your problems just may be too big of a cylinder head for your engine size,and it could be too much cam,wrong cam[read Thumper,Bootlegger,and other noise type cams] causing a lack of low mid range power that you're having.Don't be so quick to discard that HEI as it may just need tuning.One of the best upgrades,and it's cheaper than a dist.replacement is to remove the dist module and use the dist.to triggeAttach filesr an MSD unit. While the plugs are out,take a boroscope, put the probe in a cylinder and see if the pistons have valve clearance notches.If not,then you've got low compression cast pistons there.

Thanks Don, you've answered one of my biggest questions here. I wasn't sure what to look for on the rotating assembly to see if any changes have been made without pulling the heads. Checking for notches has just made my to-do list. Based off sound alone, it doesn't sound like it has too much cam, but that still doesn't mean it's the right cam. I had compression check on that same to-do list last year but never made it around to it. In your opinion, why is using the dist. to trigger and ignition unit better than replacing the whole unit?

 

[1964SuperStocker]

The car is a 4spd according to the other thread. I'm thinking his best time and money spent would be a chassis dyno because no matter what you think about how good you have done, the dyno doesn't lie and will give you specific knowledge. Be sure your fuel gauge is up close to the Carbs after any pump or filter. There is nothing wrong with a fuel pump on the block, especially when you aren't running a drag car. Being sure you are getting enough fuel can be provided by your block fuel pump. I would guess your carbs need more help than anything. I also bolted on new 1404's and didn't do much to them either. One other point on carbs is what kind of linkage are you running. A progressive linkage between the carbs will bring in the second carb slower reaction time making the car feel sluggish but your driving style and how you intend to use the car will make a big difference there. My dual quad was set up as progressive but I switched to a direct link now. I also have a 2 speed powerglide for a transmission so sluggish is a given in my case but a 10inch converter and 3000 stall helps. What rear end are you running in the car? 17 spline factory or something else? Just wondering because I don't remember 3.73 being a gear option but there are a number of ways to get anything you want in this day and age. Also, which 4 speed do you have in the car?

 

[Don Jacks]

Thanks Don, you've answered one of my biggest questions here. I wasn't sure what to look for on the rotating assembly to see if any changes have been made without pulling the heads. Checking for notches has just made my to-do list. Based off sound alone, it doesn't sound like it has too much cam, but that still doesn't mean it's the right cam. I had compression check on that same to-do list last year but never made it around to it. In your opinion, why is using the dist. to trigger and ignition unit better than replacing the whole unit?

GM never made an HEI for the W engine,so unless someone used an adapter sleeve you've got an aftermarket unit.On most of them,the module is skechy at best.The pick up coils are good,so you replace the module with the small adapter cable and plug the MSD into that.This often makes a big difference.The carbs ,being out of the box may well need tuning,but one thing at a time here.Number one being determining what we actually have here so we can figure what we need.

 

[Don Jacks]

The car is a 4spd according to the other thread. I'm thinking his best time and money spent would be a chassis dyno because no matter what you think about how good you have done, the dyno doesn't lie and will give you specific knowledge. Be sure your fuel gauge is up close to the Carbs after any pump or filter. There is nothing wrong with a fuel pump on the block, especially when you aren't running a drag car. Being sure you are getting enough fuel can be provided by your block fuel pump. I would guess your carbs need more help than anything. I also bolted on new 1404's and didn't do much to them either. One other point on carbs is what kind of linkage are you running. A progressive linkage between the carbs will bring in the second carb slower reaction time making the car feel sluggish but your driving style and how you intend to use the car will make a big difference there. My dual quad was set up as progressive but I switched to a direct link now. I also have a 2 speed powerglide for a transmission so sluggish is a given in my case but a 10inch converter and 3000 stall helps. What rear end are you running in the car? 17 spline factory or something else? Just wondering because I don't remember 3.73 being a gear option but there are a number of ways to get anything you want in this day and age. Also, which 4 speed do you have in the car?

Randy's absolutly right,there was no factory 3.73 for these cars,but there was a 3.70.It's my understanding that some of the after market did make a 3.73,why I don't know.

 

[Paddy399]

The car is a 4spd according to the other thread. I'm thinking his best time and money spent would be a chassis dyno because no matter what you think about how good you have done, the dyno doesn't lie and will give you specific knowledge. Be sure your fuel gauge is up close to the Carbs after any pump or filter. There is nothing wrong with a fuel pump on the block, especially when you aren't running a drag car. Being sure you are getting enough fuel can be provided by your block fuel pump. I would guess your carbs need more help than anything. I also bolted on new 1404's and didn't do much to them either. One other point on carbs is what kind of linkage are you running. A progressive linkage between the carbs will bring in the second carb slower reaction time making the car feel sluggish but your driving style and how you intend to use the car will make a big difference there. My dual quad was set up as progressive but I switched to a direct link now. I also have a 2 speed powerglide for a transmission so sluggish is a given in my case but a 10inch converter and 3000 stall helps. What rear end are you running in the car? 17 spline factory or something else? Just wondering because I don't remember 3.73 being a gear option but there are a number of ways to get anything you want in this day and age. Also, which 4 speed do you have in the car?

The rear end was replaced last year and I now have confirmation that 3.73 gears with posi was installed. The trans is a T-10 from God knows what, and now might be a good time to mention nothing is original on this car.

 

[427John]

I guess my question would be is have you checked what the timing is set at currently and what does the advance curve look like?That would be the first thing I would verify,I don't know how many times someone has had me take a look at their car with complaints of poor power and I throw a timing light on it bump the initial up 4 or 5 degrees,they take it and test drive it and come back and think your some kind of mechanical genius.It is surprising how many cars I've checked that the initial was set at 6 or less,and you could tell right away because when they cranked it the starter motor would spin it at 100 mph effortlessly and it would spin 20 revolutions before the engine fired.

 

[427John]

As a side note builds such as the type you describe seldom see significant increases in power by upgrading to a high zoot race type ignition,if it does it just means that there was something malfunctioning in your old system,a properly functioning Delco HEI system is more than capable of supplying enough spark energy for your engine,now if you plan to race it and the shortblock is built to handle high rpm's then you can start to exceed the capabilities of the HEI,but most normally aspirated street cars will be quite happy with it.

 

[Tim]

I'd put a fuel pressure gauge and see what the fuel pressure is.You don't want more than 6 psi.While you have the plugs out do a compression test and let us know what it is.One of your problems just may be too big of a cylinder head for your engine size,and it could be too much cam,wrong cam[read Thumper,Bootlegger,and other noise type cams] causing a lack of low mid range power that you're having.Don't be so quick to discard that HEI as it may just need tuning.One of the best upgrades,and it's cheaper than a dist.replacement is to remove the dist module and use the dist.to triggeAttach filesr an MSD unit. While the plugs are out,take a boroscope, put the probe in a cylinder and see if the pistons have valve clearance notches.If not,then you've got low compression cast pistons there.

Don that block number is the same as mine and mine is a double notch truck block. Unless he has the goods inside the whole thing with those heads might be his problem??

 

[1964SuperStocker]

Don that block number is the same as mine and mine is a double notch truck block. Unless he has the goods inside the whole thing with those heads might be his problem??

I have 2 5011 blocks and neither is a double notch. As I mentioned before who would build such a top and end forget the bottom end. If someone was smart enough to pick up the phone/computer to order the Edelbrock parts, I highly doubt they would have left the motor hanging with 9.5:1 compression or worse.

 

[Tim]

I have 2 5011 blocks and neither is a double notch. As I mentioned before who would build such a top and end forget the bottom end. If someone was smart enough to pick up the phone/computer to order the Edelbrock parts, I highly doubt they would have left the motor hanging with 9.5:1 compression or worse.

I would certainly agree with that but there are some that would bastardize things without knowing the difference. Mine was such a case when I bought it. 2 different heads, Tri power intake(on a double notch which would never have to start with) and none of the carbs were right, had a truck distributor, had the update spin on filter and missing the bypass( filter was an ornament at that point) had pulleys welded together for no other reason than the holes didn’t line up and the list goes on... Having said all that anything is possible.....

 

[427John]

I also have 2 5011's 1 single 1 double,I agree with Tim every sin known to man has been committed on these cars over the years.Your right it makes no sense to do something like that,but it doesn't stop some people from doing it.

 

[427John]

But Don's right,to be able to determine what your best tune will be,you'll need to use a borescope and dial indicator and such to determine just what you have for cam and compression