Neutering My Engine??

horseballz

10 Year Member
Sep 30, 2009
824
20
49
Las Vegas, NV
Hey All,
I've discovered that I "over-built" my 5.0 for my needs. Here was the originally executed plan:
>Brand new from Ford 99ish Explorer long block
>GT-40"P" heads
>Hypereutectic pistons
>B303 roller cam
>1.7 to 1 ratio roller rocker arms
>Performer RPM intake
>Autolite 4100-1.12" venturi
>Mallory magnetic breakerless distributor
>Tri-Y headers
>T5 transmission
Well, heres the story, the engine is a ball when my foot is in it all the time but that was NOT my intention for the car. It doesn't even start to wake up until 1500-1600 RPM (intake) and then REALLY comes alive at 3000 (cam/rocker combo) and above and is a true screamer. Part of my problem is that this car is intended to be my daily driver/cross country highway cruiser but still have enough poop to be fun. The way it is simply encourages me to drive WAY more aggressively than is prudent and is not practical. Not to mention fuel mileage (especially with my foot in it) is horrible. Best, gentle driving 11mpg in town and 15mpg highway, foot in it, welll....:shrug: WORSE! I want to give the car a little bit more low end/rpm grunt (more fun for my application) and don't mind sacrificing a bit in the higher RPMs. In other words, drop my power RPM range a bit. I have already swapped out the 1.7 rockers for some 1.6 to 1 rollers and that certainly took some balls out of the cam and made it a bit more docile, but still the intake kinda limits things a bit. I guess the main purpose of this post is to get some opinions on what intake to swap to, given all of the other details. I don't really want to start from scratch with a new cam, etc. I'm even thinking that an intake that actually has the coolant crossover at the rear might be a good thing, as I plan to spend some serious highway time including air conditioning and likely pulling a fairly light back half of a Mustang trailer.:D Maybe Edelbrock Performer 302 (3721) or something similar. All thoughts, comments, opinions and suggestions are appreciated.
Thanx,
Gene
 
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Hey All,
I've discovered that I "over-built" my 5.0 for my needs. Here was the originally executed plan:
>Brand new from Ford 99ish Explorer long block
>GT-40"P" heads
>Hypereutectic pistons
>B303 roller cam
>1.7 to 1 ratio roller rocker arms
>Performer RPM intake
>Autolite 4100-1.12" venturi
>Mallory magnetic breakerless distributor
>Tri-Y headers
>T5 transmission
Well, heres the story, the engine is a ball when my foot is in it all the time but that was NOT my intention for the car. It doesn't even start to wake up until 1500-1600 RPM (intake) and then REALLY comes alive at 3000 (cam/rocker combo) and above and is a true screamer. Part of my problem is that this car is intended to be my daily driver/cross country highway cruiser but still have enough poop to be fun. The way it is simply encourages me to drive WAY more aggressively than is prudent and is not practical. Not to mention fuel mileage (especially with my foot in it) is horrible. Best, gentle driving 11mpg in town and 15mpg highway, foot in it, welll....:shrug: WORSE! I want to give the car a little bit more low end/rpm grunt (more fun for my application) and don't mind sacrificing a bit in the higher RPMs. In other words, drop my power RPM range a bit. I have already swapped out the 1.7 rockers for some 1.6 to 1 rollers and that certainly took some balls out of the cam and made it a bit more docile, but still the intake kinda limits things a bit. I guess the main purpose of this post is to get some opinions on what intake to swap to, given all of the other details. I don't really want to start from scratch with a new cam, etc. I'm even thinking that an intake that actually has the coolant crossover at the rear might be a good thing, as I plan to spend some serious highway time including air conditioning and likely pulling a fairly light back half of a Mustang trailer.:D Maybe Edelbrock Performer 302 (3721) or something similar. All thoughts, comments, opinions and suggestions are appreciated.
Thanx,
Gene

Hi! I dont think the intake would make a big difference, you can try advancing you cam timing if you timming chain allow, it would increase low end torque a little and reduce top end power. or put in a smaller cam
 
I think what's killing you is the duration...you helped the lift with the rockers, but those valves are still holding open. The only way to fix that is a new bumpstick. I did that EXACT same thing with my 69 camaro when I built the motor for it, car was a dud below 3000 rpm. I didn't drive it around for a week before I just pulled the cam out and replaced it with a milder one and man oh man...what a difference. Anyway, not what you wanted to hear, but I think you will be money ahead swapping the cam. By all means tho, try the timing, and any other freebies first!
 
I retract most of what i JUST wrote, wasn't familiar with the cam....the cam isn't that agressive, when you said roller I assumed high lift, and assumed the duration to be 303...my bad, but that cam is only 284 dur 4.80 lift....great street cam....if I am reading right info. Play with your timing and see what you can do.
 
Have you had the engine tuned? Any idea what your A/F ratio is?

MPG seems wayyy low with that setup. I built a 331 for my '88 GT with a Trickflow Stage 1 cam (.499/.510 lift, 221 intake/225 exhaust), GT-40 heads (not P), T5 and I never got below 20 MPG even in city driving with plenty of "lead foot" driving. I could get up to 26 mpg on the freeway. Of course I ran fuel injection and Stock 3.08 gears, but the '88 'vert is also way heavier than your '68.

A "B" cam with P heads is pretty mild combo...I'd guess you should be close to 20 or maybe a little above on the highway. Maybe a good dyno tune could solve your problem?
 
I think what's killing you is the duration...you helped the lift with the rockers, but those valves are still holding open. The only way to fix that is a new bumpstick. I did that EXACT same thing with my 69 camaro when I built the motor for it, car was a dud below 3000 rpm. I didn't drive it around for a week before I just pulled the cam out and replaced it with a milder one and man oh man...what a difference. Anyway, not what you wanted to hear, but I think you will be money ahead swapping the cam. By all means tho, try the timing, and any other freebies first!

Seriously, replacing the cam is not necessary, simply swap to the lifters I suggest, and bingo! instantly he'll have a milder cam, at low rpm.
 
The Rhodes lifters is a good idea, and the Performer 302 intake will help also. I am running a Weiand Action Plus with a 600 cfm Edelbrock and a mild cam in my 72' Grande and get close to 20 highway with no overdrive.
 
I think some tuning will make the motor way more streetable. I agree the mpg seems very low! My 408w with a T5 behind it pulls 18mpg on the highway and thats running a 3.70 gear. Good luck!
 
The cam isn't very dramatic now with the 1.6 ratio rockers, but when the 1.7s were in it it gave a little more than 6% more lift and a little more duration at .050. Lift was like .518 with the 1.7 as opposed to the standard .488 with the 1.6. Changing the rockers bumped my vacuum (measured at the same RPM) from about 14.5 up to about 16. I checked out those lifters that 2+2GT mentioned and they are pretty cool, but require swapping from pedestal mount rockers to studs and guide plates. All said and done about $350-$375, just not in my budget at this time, as I'm out of work on Workmens Comp. But I really appreciate the thoughts., please keep them coming. By the way, one of the reasons for the crappy mileage is the T5 with 2.79 gears and 26" tall tires. All the gearing is kinda working against itself.
Thanks,
Gene
 
11 - 18 MPG doesn't seem wrong to me. I used to get about 10 mpg with my EFI 302 when I lived 2 miles from work. Now that I live 25 miles from work I get about 18. I don't have EGR on it and I have a somewhat big cam for a streeter. I also don't drive like a grandma. With a carb I think it would be difficult to drive aggressively and get the kind of mileage some people say they get.

To the original poster, all the obvious things that people do to increase performance you can do in reverse if you want to. Restrictive intake and exhaust will slow you down. However, those changes won't improve your gas mileage. A cam with less overlap will increase fuel economy, but you'll have to drive a lot of miles to make back the money you spent on the cam. You could add EGR. EGR doesn't hurt performance but it will help a lot with highway mileage. The other thing would be to get a wide band AF sensor and optimize your carb tune. I'm not much for Rhoads lifters but I can't say I've used them. I just heard that they are noisy and don't really work as well at high RPMs as Rhoads claims.

Probably gears would be one of the better things you can do. Go to at least a 3.23 - 3.55 would probably be better. You're probably wasting a lot of gas just being out of the engine's powerband when cruising on the highway.
 
I checked out those lifters that 2+2GT mentioned and they are pretty cool, but require swapping from pedestal mount rockers to studs and guide plates.

I would consider it more of a recommendation than requirement, but I have always considered non-adjustable rockers something that doesn't belong on my car. Nothing performs as well as carefully adjusted rockers. I'm surprised it wasn't done when the other modifications on your engine were done. Sounds like a good summer project if your situation changes.

You can get guide plates for under $25, nuts for under $15, and studs for about $25. The machine work for this is dead easy, you could do it on a drill press at home if you had to. The most expensive part of that project would be the gasket set, and of course the lifters.

Your future should include a change to better gears, though, the 2.79 was fine with a 289 2V and C4, but with a T5 5th gear must be pretty much useless, and your engine probably rarely runs in its best rpm range, which would be 2500-3500, unless you drop down a gear. You'd be a lot happier with 3.25-3.55. Heck, my 5.0 Explorer has 3.73 gears.
 
What Hack said is right in line with what I was thinking. My tires are actually 25.6" and at 75 mph (average highway speed around here) RPM is 1868. Since swapping the rockers, it starts to come alive at about 2300 instead of 2800-3000. 3.40 gears would put me at 2276 and 3.55 at 2376. I'm waiting on a friend bringing me a new rear as, mine is whooped, bearings, gears, housing and all. Ignition timing with the 1.7 rockers liked to be at initial 18 BTDC with 24 deg mechanical for all in timing of 42 BTDC at 3000 RPM and only about 4-5 deg of vacuum advance on top of that. After the rocker swap, it seems to like 14 BTDC initial + 24 for 38 deg all in and 13-14 of vacuum advance. Understand that I have a Professional Products damper that popular rumor says the scale on it for the driver side bolt on pointer is 2-4 degrees off, :shrug: so these specs are relative as opposed to being exact. Kinda hard to check EXACT TDC without pulling a head or the timing cover, but it appears (checking with a small screwdriver the the spark plug hole) to be at least within a couple of degrees. I'm pretty OK at this point (minus the right gears, of course) and if I could just bring my "sweet spot" down 100-200 RPM I'd be really happy. From my research and opinions from some trusted racer friends, changing to the Performer (or similar) intake should net me a little more velocity at the carb in the 800-2000 RPM range and give me a bit better "touch of the toe" response in that range. I don't know if it will necessarily drop my "sweet spot", but we'll see. Intake swap will be fairly cheap, as the intake I have is virtually new and I should be able to sell it for at least 1/2-2/3 the price of new, same with the rockers. I'm just wondering if there is a better intake for what I'm trying to do? If I can afford it, I'd like to keep it all, so that if I ever get a bug up my butt to go to the strip, all I have to do is swap the intake, rockers and give it a proper tune.:D According to just the fuel gauge vs miles driven, fuel milage, in varied (highway and around town) driving seems to have improved quite a bit. Tomorrow or the next day, I'll give it a fill up and do a 250 mile round trip on the highway and let you all know the results so far. I really do appreciate all of the good opinions and comments. I'm fairly certain, as Hack and pabear89 mentioned, that my rear and gear swap/upgrade will help bring me just about to where I want to be.:flag:
Thanks Again To All,
Gene
 
I'd put 3.50 gears in it and look into a custom grind cam built to your specifications. All of the FRPP alphabet cams are absolute dinousaurs and while they were solid performers back in the day, cam technology has advanced pretty radically in the last 10-12 years. Custom cams aren't expensive at around $300 and can really make that car into a pleasure to drive. Thats a very mild build you've got, all things considered. Taming it down any more could cause it to be a total turd and still not pick up any mileage.
 
Reading what you posted and approaching this as if it where mine i would do the following

1. Put the 1.7's back on as more lift will help make more power everywhere in the rpm range.
2. Dump the junk B cam. Don't put Rhodes lifters on it. Just sell it to someone else.
3. Have a pro like Buddy Rawls either spec a ots cam or grind you a custom. I can tell you from experience that you would be happier with the stock roller cam 4 deg advanced over that b cam.
4. 3.50/3.73 gears
5. dyno tune the car


I know that you can find more power in your combo and increase the mpg but as far as you keeping your foot out of it well good luck.