Bad Combo?

[MadOgre]

I have an Edelbrock 1806 and a stock mechanical fuel pump. But I still run a fuel regulator($45) just for peace for mind and I keep it set to 5 psi. So IMO either way its nice to have the fuel regulator. A mechanical fuel pump is about the same cost as a lower priced fuel regulator. So in the end its probably cheaper to just purchase the fuel regulator and turn down the pressure. If you have a factory return line this will work very well. Also the TBI fuel pumps are in tank, and its not advisable to use a mechanical fuel pump and then draw through the in tank pumps.

 

[MadOgre]

So best to stay with electric for now. But why is there a plate covering it if it's just a casting?

Most don't even bother with the cover. But I have a few times I thought "Oh it has a cover it must have the provision" only to find out that it does not and for some reason it had a cover on.

 

[MadOgre]

Pictures of what you're talking about on where to hook the vacuum advance?

Front of the carburetor. Use the lowest 1/4" vacuum port. Connect directly to the vacuum can on the dizzy.

 

[RangRayy]

. If you have a factory return line this will work very well. Also the TBI fuel pumps are in tank, and its not advisable to use a mechanical fuel pump and then draw through the in tank pumps.

I left all the lines I have alone. So in theory all I would need is a regulator mounted to the firewall, a fitting with a hose attached ran to the regulator then another hose to the carb.

Front of the carburetor. Use the lowest 1/4" vacuum port. Connect directly to the vacuum can on the dizzy.

Oh simple enough. Well what about the speed demon 625 carb and the cam specs? Will the 12-300-4 be too much for it to handle?

 

[MadOgre]

It should be good I think. The stock 350 only flows like 550cfm so I think it should still be good with 625. I have Edelbrock's 1806 which is 650cfm and that's why I bought it rather then a 1406 600cfm. However I like the design of that 625 street demon way better then this Eddy carb.

When you order your cam phone Comp Cams and ask them what they figure it will require for cfm.

 

[RangRayy]

Called comp cams and the tech said on the 12-300-4 could defiantly get away with 500-550 cfm. Although the tech wasn't much help just said he could give me a ball park number but said oh yeah with that cam 625 would be more than plenty.

 

[MikeB]

If your going to go with the Street demon I would recommend the Edelbrock EPS intake its a killer intake. The only problem with a factory roller cam is it wont have a fuel pump lobe on it and if you use a factory roller cam or a GM cam like the ram jet cam you have to use a different distributor gear.

Doesn't a Street Demon carb block the 3/8" NPT vacuum port on the rear of a Performer EPS manifold? I prefer the Weiand Street Warrior (like the 8120) for that reason, plus it's a more modern design. However, the Edelbrock is a nicer-looking casting.

The GM HT383/RamJet 350 cam I recommended above has a fuel pump pushrod lobe, but many (or most?) GM roller cams do not.

Some aftermarket roller cams require a bronze-tipped pushrod, but GM roller cams do not. GM crate engines with roller cams specify GM pushrod P/N 3704817.

Yes, you will need a GM "melonized" (hardened) gear on the distributor. I used a new GMPP distributor, so I don't have the gear P/N, but it's easy to look up.

The problem is that no roller cam has a torque curve from off idle. All roller cams are from 1500 RPM up.

A roller cam with the same .050" duration as a flat tappet cam will have a wider powerband. So, if a flat tappet cam is designed to make good power from, let's say, 1500-4500 RPM, a roller will do it from 1250-4750. It's all about area under the curve. Do a search on "benefits of roller cams" and you'see why GM started using them in 1986 and has never looked back.

 

[MadOgre]

If you can find an EPS manifold for 87'-95' heads I would like to know? I cant find one in my catalogue. They make them for pre 86' and Vortec heads but not for TBI. They make a performer RPM intake for the TBI heads which is pretty close to the EPS but it is 1500-6500 RPM

 

[MadOgre]

Doesn't a Street Demon carb block the 3/8" NPT vacuum port on the rear of a Performer EPS manifold? I prefer the Weiand Street Warrior (like the 8120) for that reason, plus it's a more modern design. However, the Edelbrock is a nicer-looking casting.

The GM HT383/RamJet 350 cam I recommended above has a fuel pump pushrod lobe, but many (or most?) GM roller cams do not.

Some aftermarket roller cams require a bronze-tipped pushrod, but GM roller cams do not. GM crate engines with roller cams specify GM pushrod P/N 3704817.

Yes, you will need a GM "melonized" (hardened) gear on the distributor. I used a new GMPP distributor, so I don't have the gear P/N, but it's easy to look up.

A roller cam with the same .050" duration as a flat tappet cam will have a wider powerband. So, if a flat tappet cam is designed to make good power from, let's say, 1500-4500 RPM, a roller will do it from 1250-4750. It's all about area under the curve. Do a search on "benefits of roller cams" and you'see why GM started using them in 1986 and has never looked back.

All the roller cams I have looked at state that they are for 1500 + RPM. I can not find any that are for off idle.

And yes I agree roller cams are better for many reasons...but...they were also accompanied by a minimum 4 gears +. The cars now days are designed to stay in that sweet spot by shifting up or down a gear to keep you in the power curve.

When your dealing with 3 spd transmissions, off idle becomes a big deal.

It always annoyed me when those 90s vehicles would kinda lag until you picked up a bit of speed and then they would go. It was like riding a rocking chair.

Any who do you have a cam that you know of that would work well off idle?

 

[MadOgre]

And I do not believe they block that rear vacuum port any more then any other carb would???

 

[Joe383]

"All the roller cams I have looked at state that they are for 1500 + RPM. I can not find any that are for off idle."

I don't know were your looking but there are a lot of cams that are lower than 1,500RPM. The factory vortec cam for one. Look at small cams like the Comp cams Magnum 260HR it starts at 1,200 RPM. There Extreem energy 258 has a power band of 1,000-5,000 RPM. If your only looking in the Jegs and Summit catalog your not going to find every thing.

O dam they don't make a 87+ EPS intake that sucks. I have both the vortec EPS and the 86 and older EPS on motors. It is a better intake. I cant tell in the bottom compared to the regular performer but they have better mid and top for sure. The throttle response is better too. I would use the 2604 intake then. I had this intake new Well I had the 2601 which is for 86 and older heads but never put it on a motor. It is a performer Air gap spread bore intake. Its pretty much a tamed down version of the RPM air gap but for torque instead of HP. If they would have had this intake for the vortec I would have ran it instead and used a modified street trip Q-jet instead.

"A roller cam with the same .050" duration as a flat tappet cam will have a wider powerband. So, if a flat tappet cam is designed to make good power from, let's say, 1500-4500 RPM, a roller will do it from 1250-4750. It's all about area under the curve. Do a search on "benefits of roller cams" and you'see why GM started using them in 1986 and has never looked back."

Ya the roller cams usually have a wider power band. There is a lot of benefits to these things.

"Front of the carburetor. Use the lowest 1/4" vacuum port. Connect directly to the vacuum can on the dizzy."

According to my holley HP book and the instructions that came with my 670 street avenger, the metering block is the correct spot. You don't want vacuum at idle with the throttle blades closed. The Q-jet, edelbrock and street demon might be different but for the holley it is the metering block. If the Q jet, edelbrock and street demon have a low port for the vacuum advance than that port is gong to a source above the throttle blades when they are fully closed. Its just slightly lower than the sight plug on the Holley. The port is called the timed spark vacuum source. The lowest 1/4" port is full manifold vacuum at which point you might as well pull vacuum from the port on the intake it self.

 

[Joe383]

If you also are willing to spend the money you could just have a custom cam made like I did its about $280 though. If you wanted a roller cam with 800-4,000 RPM power band you could have a cam ground that will operate in that power band. Being a roller dose not mean it is confined to a specific power band. That is the grind of the cam it self just like a hydraulic flat tappet. There is a reason most new factory OHV motors and racers use these. Its like comparing carb to fuel injection. Roller cams usually have shorter seat timing in the same power band compared to a hydraulic flat tappet and usually will yield a wider power band, more torque, HP better fuel mileage and better throttle response. I guarantee if I swapped my roller cam out for flat tappet with a similar power bad in my Camaro I would loose drivability, HP and a little fuel mileage.

 

[MikeB]

All the roller cams I have looked at state that they are for 1500 + RPM. I can not find any that are for off idle.

1500 RPM is off-idle. And one manufacturer's 1000-5500 RPM cam may be another's 1500-4500 RPM cam, and a third's 1200-4800. A good example is the generic 204/214 flat tappet cam sold by Edelbrock, Summit, Jeg's, Sealed Power, Elgin, and more.

It always annoyed me when those 90s vehicles would kinda lag until you picked up a bit of speed and then they would go. It was like riding a rocking chair.

Not because of the roller cam, but gearing and emission controls.

Any who do you have a cam that you know of that would work well off idle?

A stock 96-00 Vortec 350 in a C1500 would smoke the tires from off-idle with a 700R4 and 3.42 axle. Oh yeah, it has a roller cam.

You may have used a roller cam that didn't make good torque or throttle response at low RPM, but that WAS NOT because it was a roller cam. It was due to cam profile, gearing, vehicle weight, tire diameter. etc.

If you wanted a roller cam with 800-4,000 RPM power band you could have a cam ground that will operate in that power band. Being a roller does not mean it is confined to a specific power band. That is the grind of the cam it self just like a hydraulic flat tappet.

Well said.

 

[Joe383]

I don't know what you have owed from the 90s but I have had some bad ass cars from the 90s. I have had about 25+ cars. Most form the 80s and 90s. Shoot I have probably had a lot more than that by now after just looking at the last 5 years hahaha. The 90s had some of he greatest cars and truck for performance. Ever drove an LS1 Camaro? The hesitation your feeling is not he cam its the factory tune. I have modified a lot of the cars I have owned. If your running an automatic your not going to need a cam that makes power at 1,000 RPM anyways. Your torque converter will flash around 1,500 RPM unless your running a diesel converter.

 

[RangRayy]

Which reminds me something I forgot about.... Torque converter. While upping the cam a bit will the stock(scratches head not sure if I have a stock converter still) converter be okay or is this something else I will need to replace.

I should be okay as long as the cam is idle-4500 instead of 2200-6400 right?