Aftermarket EFI installation - Questions

[Rembrant]

In the end I bought that carb cause it came highly recommended and everyone loved it.

Ya, it seems to get pretty good reviews when installed on the small V8's. I specifically wanted a 500CFM, and the smaller Holley carbs (465, 390, etc) are really expensive...like almost double the cost of this one. A couple people have told me that the 500CFM will work better on a 302 than a 600CFM. After all, a 302's max requirements are barely 400CFM, so a 500CFM carb might actually be a better fit.

I had my 302 (actually, 304 I think) broken in and tuned on a dyno, but the down side of that is that they basically only tune the engine between 2800-5500RPM. That is all well and good, and it is also where most people's brains are when discussing HP and TQ, etc.

My interest is in street and highway drivability, mainly between 1500-2500 RPM, and this is where the 500CFM and annular boosters is supposed to shine the very best.

Something I've noticed about the Holley 4160 I have installed now is that it doesn't like the cold, and it takes a long time to warm up. I have to clarify that, because when I say "cold", I just mean a fresh start, even on a warm day, and when I say takes a long time to warm up, I'm not referring to coolant/engine temps, I just mean that it seems to take a long time to really smooth out. The climate I live in is quite a bit different than what some of you experience down south. This summer in particular has been cold and damp, and a "hot" day this year has only been about 70F.

It seems like the hotter the ambient temps, and the hotter the truck gets, the better it works, and the smoother it runs. Last year when we had some hotter days (maybe 80-85F), and I was driving for a while, and even stuck in traffic, the engine would run the smoothest.

Maybe one of you guys can tell me what all that means, but I've had it in my head that it is the carb that is working better when it is hot.

Anyway, after reading up on the Summit carb, I found a few people reporting that they run great in the cold (even in winter temps), so that drove my decision...at least partly.

We will see. I'll start a new thread on the Summit carb when I get it, and try to come up with a comparison between the two. It was on back order for a couple weeks, so it will likely be September before I can get to it. I also have to deal with relocating my IGN coil, so that will throw a small wrench into this swap as well.

I have an AFR gauge installed, so that will help with any jetting changes, if required. I might grab a jet kit myself, just so I have it on hand and can get this carb tuned quickly if required.

 

[Gary Lewis]

In the end I bought that carb cause it came highly recommended and everyone loved it.

Ya, it seems to get pretty good reviews when installed on the small V8's. I specifically wanted a 500CFM, and the smaller Holley carbs (465, 390, etc) are really expensive...like almost double the cost of this one. A couple people have told me that the 500CFM will work better on a 302 than a 600CFM. After all, a 302's max requirements are barely 400CFM, so a 500CFM carb might actually be a better fit.

I had my 302 (actually, 304 I think) broken in and tuned on a dyno, but the down side of that is that they basically only tune the engine between 2800-5500RPM. That is all well and good, and it is also where most people's brains are when discussing HP and TQ, etc.

My interest is in street and highway drivability, mainly between 1500-2500 RPM, and this is where the 500CFM and annular boosters is supposed to shine the very best.

Something I've noticed about the Holley 4160 I have installed now is that it doesn't like the cold, and it takes a long time to warm up. I have to clarify that, because when I say "cold", I just mean a fresh start, even on a warm day, and when I say takes a long time to warm up, I'm not referring to coolant/engine temps, I just mean that it seems to take a long time to really smooth out. The climate I live in is quite a bit different than what some of you experience down south. This summer in particular has been cold and damp, and a "hot" day this year has only been about 70F.

It seems like the hotter the ambient temps, and the hotter the truck gets, the better it works, and the smoother it runs. Last year when we had some hotter days (maybe 80-85F), and I was driving for a while, and even stuck in traffic, the engine would run the smoothest.

Maybe one of you guys can tell me what all that means, but I've had it in my head that it is the carb that is working better when it is hot.

Anyway, after reading up on the Summit carb, I found a few people reporting that they run great in the cold (even in winter temps), so that drove my decision...at least partly.

We will see. I'll start a new thread on the Summit carb when I get it, and try to come up with a comparison between the two. It was on back order for a couple weeks, so it will likely be September before I can get to it. I also have to deal with relocating my IGN coil, so that will throw a small wrench into this swap as well.

I have an AFR gauge installed, so that will help with any jetting changes, if required. I might grab a jet kit myself, just so I have it on hand and can get this carb tuned quickly if required.

I know you have the AFR gauge on, but I'd guess that the reason it runs better in warm ambient temps is that the mix is a bit lean. As the inlet air temp goes up the AFR gets richer.

[grumpin]

In the end I bought that carb cause it came highly recommended and everyone loved it.

Ya, it seems to get pretty good reviews when installed on the small V8's. I specifically wanted a 500CFM, and the smaller Holley carbs (465, 390, etc) are really expensive...like almost double the cost of this one. A couple people have told me that the 500CFM will work better on a 302 than a 600CFM. After all, a 302's max requirements are barely 400CFM, so a 500CFM carb might actually be a better fit.

I had my 302 (actually, 304 I think) broken in and tuned on a dyno, but the down side of that is that they basically only tune the engine between 2800-5500RPM. That is all well and good, and it is also where most people's brains are when discussing HP and TQ, etc.

My interest is in street and highway drivability, mainly between 1500-2500 RPM, and this is where the 500CFM and annular boosters is supposed to shine the very best.

Something I've noticed about the Holley 4160 I have installed now is that it doesn't like the cold, and it takes a long time to warm up. I have to clarify that, because when I say "cold", I just mean a fresh start, even on a warm day, and when I say takes a long time to warm up, I'm not referring to coolant/engine temps, I just mean that it seems to take a long time to really smooth out. The climate I live in is quite a bit different than what some of you experience down south. This summer in particular has been cold and damp, and a "hot" day this year has only been about 70F.

It seems like the hotter the ambient temps, and the hotter the truck gets, the better it works, and the smoother it runs. Last year when we had some hotter days (maybe 80-85F), and I was driving for a while, and even stuck in traffic, the engine would run the smoothest.

Maybe one of you guys can tell me what all that means, but I've had it in my head that it is the carb that is working better when it is hot.

Anyway, after reading up on the Summit carb, I found a few people reporting that they run great in the cold (even in winter temps), so that drove my decision...at least partly.

We will see. I'll start a new thread on the Summit carb when I get it, and try to come up with a comparison between the two. It was on back order for a couple weeks, so it will likely be September before I can get to it. I also have to deal with relocating my IGN coil, so that will throw a small wrench into this swap as well.

I have an AFR gauge installed, so that will help with any jetting changes, if required. I might grab a jet kit myself, just so I have it on hand and can get this carb tuned quickly if required.

When I got my new Holley 4160 I jetted down for the altitude I live at, 4100 feet.

I have since jetted up, it came with number 66’s, went with 64’s, back to 66’s and now 68’s. I also richened the idle mixture.

Could be the 460’s drinking problem or the carb, but this truck likes it richer. Runs better when “cold” as you described, I will find out this winter but so far no or very little hesitation or stumble (pumping the pedal to keep it running) when accelerating when freshly stated for the day.

I was going to add choke, but it’s better so I didn’t.

[Rusty_S85]

In the end I bought that carb cause it came highly recommended and everyone loved it.

Ya, it seems to get pretty good reviews when installed on the small V8's. I specifically wanted a 500CFM, and the smaller Holley carbs (465, 390, etc) are really expensive...like almost double the cost of this one. A couple people have told me that the 500CFM will work better on a 302 than a 600CFM. After all, a 302's max requirements are barely 400CFM, so a 500CFM carb might actually be a better fit.

http://forum.garysgaragemahal.com/file/n102355/CFM.jpg

I had my 302 (actually, 304 I think) broken in and tuned on a dyno, but the down side of that is that they basically only tune the engine between 2800-5500RPM. That is all well and good, and it is also where most people's brains are when discussing HP and TQ, etc.

My interest is in street and highway drivability, mainly between 1500-2500 RPM, and this is where the 500CFM and annular boosters is supposed to shine the very best.

Something I've noticed about the Holley 4160 I have installed now is that it doesn't like the cold, and it takes a long time to warm up. I have to clarify that, because when I say "cold", I just mean a fresh start, even on a warm day, and when I say takes a long time to warm up, I'm not referring to coolant/engine temps, I just mean that it seems to take a long time to really smooth out. The climate I live in is quite a bit different than what some of you experience down south. This summer in particular has been cold and damp, and a "hot" day this year has only been about 70F.

It seems like the hotter the ambient temps, and the hotter the truck gets, the better it works, and the smoother it runs. Last year when we had some hotter days (maybe 80-85F), and I was driving for a while, and even stuck in traffic, the engine would run the smoothest.

Maybe one of you guys can tell me what all that means, but I've had it in my head that it is the carb that is working better when it is hot.

Anyway, after reading up on the Summit carb, I found a few people reporting that they run great in the cold (even in winter temps), so that drove my decision...at least partly.

We will see. I'll start a new thread on the Summit carb when I get it, and try to come up with a comparison between the two. It was on back order for a couple weeks, so it will likely be September before I can get to it. I also have to deal with relocating my IGN coil, so that will throw a small wrench into this swap as well.

I have an AFR gauge installed, so that will help with any jetting changes, if required. I might grab a jet kit myself, just so I have it on hand and can get this carb tuned quickly if required.

I think it really depends on the build of your 302. If you are running OE heads with a fairly stock cam then the 500 cfm would probably be better. In my case running AFR heads pushing 255 CFM flow on the intake side with a aftermarket roller cam the 600 cfm would have been more correct for me due to the ability for higher flow.

I dont remember where I read it but I read that a intake valve opening sooner creates a supercharger effect where the scavaging of the exhaust pulls the air intake charge in as if you had a supercharger forcing more air and fuel in. This also helped me decide on 600 cfm for my 302 build as well. The sniper how ever is 800 cfm but it doesnt matter on the air velocity as you are not dependent on air velocity to meter the fuel as you are in a carburetor. So over sizing the air flow is not a hinderance as the fuel injectors will inject the proper amount of fuel for how ever much air your engine is able to injest.

On my setup using the cfm calculator on summits site putting in 6000 rpm max rpm (cam redlines at 6,000) and 307 displacement (engine is bored 0.040" over calculates to 306.8 cid) it gives me 453 cfm for a street carb and 586 cfm for a racing carb. The street carb cfm is based on 85% VE as that is where your stock street engine will operate at around 85% VE. the racing size is for 110% VE which is where performance engines are based.

Summit also has a article on VE (found below) that states a modern stock engine is 85% VE, a slightly modified engine* is 100% VE, and a Highly Modified Engine** is 115% VE.

It states for * to be performance cam, performance intake manifold, headers, ignition upgrade. It states for ** to be aggressive cam, performance intake manifold, headers, ignition upgrade, aluminum or ported iron cylinder heads, 11:1+ compression.

https://help.summitracing.com/app/answers/detail/a_id/4741/~/volumetric-efficiency-%28ve%29

I fall some wheres between the two which is where I consider my engine to be around 100% to 110% VE with the roller aftermarket cam, the performer intake, the shorty headers, the 255 cfm intake flow AFR Renegade heads, and the 9.5:1 compression ratio I am almost at. I how ever am still running the stock ignition system cause I dont agree with summit, the ignition system only needs to be upgraded for two reasons, higher than stock RPM which I will not be turning over 5,500 rpm and I believe the DSII is good to 6,000 rpm with no performance issues, or super high compression which 9.5:1 is not super high, the Explorer 302`s came with GT40 heads and 9.5:1 compression and I doubt their OE ignition system was hotter than the DSII system.

I agree with you on the tuning for where you spend most of your time. Its why I selected the parts I did even though I had many people on performance forums tell me I am hindering my performance with the Performer intake over the Performer RPM intake. The Performer RPM intake doesnt come into its power range till 1,500 rpm and goes to 6,500 rpm. The Performer intake comes into its power range at idle and goes to 5,500 rpm. For me the Performer covers more of my rpm range than the RPM does. For me my engine will spend majority of its time between 1,500 and 3,000 rpm. I doubt I would turn more than 3,000 rpm cause I am setting up my C6 and 9" rear axle to give me a 75 mph speed of around 2,750 rpm like I currently have. That would put 65 mph to 75 mph with in the 2,400 - 3,000 rpm cruise range that crane lists for my cam. In your case with you running down around 1,500 - 2,500 rpm you need the power tailored to that rpm range more than you need it at 4,500 rpm. Its why I am willing to give up some top end power to move it more to the bottom and mid end range.

I dont think you could go wrong with going with the 500cfm on a 302. Like you noticed with the sniper and any EFI system that is offered to fit a wide range of engines they shoot for high CFM which confuses people cause they are thinking in the terms of carbs that too much CFM will make your engine sluggish and a pig at low rpm. I find myself even at work having to remind customers that the reason the sluggish nature shows up is with a carb you are relying on air speed to create a low pressure point to pull fuel in and too big slows the velocity down and makes it harder to pull the required fuel in and you dont have that issue with EFI. In fact every one Ive installed has a super crisp throttle response crisper than the carbs that were installed on the car that came in. I even seen major improvements on OE stock spec restoration jobs switching from the OE carb to aftermarket EFI.

But I know EFI is not for everyone. Part of me hates the idea of going EFI cause you are relying more on computers and electronics than with a carb. But at the same time I know it can do so much more and give me more than a carb would. I can now with this setup install a remote start system on my truck to actually warm the engine up and get the cab nice and warm before I go outside to go to work. Something like that you really cant do with a carb cause there is no way to prime the system and set the choke for a cold start since its all mechanical. Another positive is you can link so much between the sniper to the Dakota Digital cluster if you run one.

[Rembrant]

I think it really depends on the build of your 302. If you are running OE heads with a fairly stock cam then the 500 cfm would probably be better. In my case running AFR heads pushing 255 CFM flow on the intake side with a aftermarket roller cam the 600 cfm would have been more correct for me due to the ability for higher flow.

Right, understood. I will never be anywhere near 4500+ RPM, so I wouldn't need the extra capacity of a 600CFM. The 500CFM is supposed to be a little more responsive in the lower RPM range where I'll be, so it should do me just fine. My 302 is bored 0.020" over, with factory style flat top pistons, GT40 Explorer heads, and a full Comp Cams kit (XE-256H). My compression is right around 9:1. My truck is just a cruiser, and once in a while highway traveler. In hindsight, I probably should have built it a little milder than I did.

Fingers are crossed that the Summit carb works nicely. I'll report back when I get it all installed and set up.

 

[ArdWrknTrk]

I think it really depends on the build of your 302. If you are running OE heads with a fairly stock cam then the 500 cfm would probably be better. In my case running AFR heads pushing 255 CFM flow on the intake side with a aftermarket roller cam the 600 cfm would have been more correct for me due to the ability for higher flow.

Right, understood. I will never be anywhere near 4500+ RPM, so I wouldn't need the extra capacity of a 600CFM. The 500CFM is supposed to be a little more responsive in the lower RPM range where I'll be, so it should do me just fine. My 302 is bored 0.020" over, with factory style flat top pistons, GT40 Explorer heads, and a full Comp Cams kit (XE-256H). My compression is right around 9:1. My truck is just a cruiser, and once in a while highway traveler. In hindsight, I probably should have built it a little milder than I did.

Fingers are crossed that the Summit carb works nicely. I'll report back when I get it all installed and set up.

Smaller primaries and annular boosters should help quite a bit with response at low flow rates.

[Rembrant]

Smaller primaries and annular boosters should help quite a bit with response at low flow rates.

Thanks Jim, that's what I'm aiming for.

Any thoughts on carb spacers? I am running a dual plane Edelbrock intake, and currently have a 1" four hole spacer under the carb. Should I try an open spacer, or leave the four hole that's in there now?

[LARIAT 85]

Smaller primaries and annular boosters should help quite a bit with response at low flow rates.

Thanks Jim, that's what I'm aiming for.

Any thoughts on carb spacers? I am running a dual plane Edelbrock intake, and currently have a 1" four hole spacer under the carb. Should I try an open spacer, or leave the four hole that's in there now?

Keep the 4-hole spacer. These work better at lower RPM street use.

I think you made the right decision going with a smaller 500 cfm Summit carburetor. It is a better size for your 302 engine, and the annular boosters will atomize fuel almost as well as fuel injection. The Summit carburetor is very similar to a Ford Autolite 4100, which is what I have on Lucille. And honestly, I can't tell the difference between driving it and my other two vehicles that have fuel injection. Other than pushing the gas pedal down [once] to set the choke on a cold engine, of course. But that is what makes driving it unique!

The Bullnose trucks are the very last generation of trucks to use a carburetor, and I personally think having a carburetor is actually part of the personality and charm of these old trucks.

 

[ArdWrknTrk]

Smaller primaries and annular boosters should help quite a bit with response at low flow rates.

Thanks Jim, that's what I'm aiming for.

Any thoughts on carb spacers? I am running a dual plane Edelbrock intake, and currently have a 1" four hole spacer under the carb. Should I try an open spacer, or leave the four hole that's in there now?

Keep the 4-hole spacer. These work better at lower RPM street use.

I think you made the right decision going with a smaller 500 cfm Summit carburetor. It is a better size for your 302 engine, and the annular boosters will atomize fuel almost as well as fuel injection. The Summit carburetor is very similar to a Ford Autolite 4100, which is what I have on Lucille. And honestly, I can't tell the difference between driving it and my other two vehicles that have fuel injection. Other than pushing the gas pedal down [once] to set the choke on a cold engine, of course. But that is what makes driving it unique!

The Bullnose trucks are the very last generation of trucks to use a carburetor, and I personally think having a carburetor is actually part of the personality and charm of these old trucks.

I agree that the four hole spacer is probably best for this application.

But I have to point out, Rick, that my '87 came with a carb even though the fuel injected heads that arrived on the '88 model year are designated E7TE because they technically started production then.

Some of the medium duty 429's and the 460's in F53's were carbureted up to 1990 or '91!

[Rusty_S85]

I think it really depends on the build of your 302. If you are running OE heads with a fairly stock cam then the 500 cfm would probably be better. In my case running AFR heads pushing 255 CFM flow on the intake side with a aftermarket roller cam the 600 cfm would have been more correct for me due to the ability for higher flow.

Right, understood. I will never be anywhere near 4500+ RPM, so I wouldn't need the extra capacity of a 600CFM. The 500CFM is supposed to be a little more responsive in the lower RPM range where I'll be, so it should do me just fine. My 302 is bored 0.020" over, with factory style flat top pistons, GT40 Explorer heads, and a full Comp Cams kit (XE-256H). My compression is right around 9:1. My truck is just a cruiser, and once in a while highway traveler. In hindsight, I probably should have built it a little milder than I did.

Fingers are crossed that the Summit carb works nicely. I'll report back when I get it all installed and set up.

You should be fine either way. It sounds like yours is pretty mild build I dont know how much milder you could go without it be a stock engine. I think my build is a bit higher up on the mild scale, yours sounds like its basically a stock 302 just with a Comp Cam thrown in.