Engine Engine rebuild suggestions
- Thread starter JulianR
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- 302 rebuild 5.0 rebuild
You can read up or watch videos on how to read spark plugs. Wide band O2 sensor is the other but they are not cheap relatively speaking.. I’m conservative by nature and have too much $$$ in my motor to want to lean it out. Kind of the attitude of if 24’s will work then 30’s get installed.
keel
Active Member
What were you running on that 306?
I seriously doubt a stock bottom end 302 with GT40 heads + intake + a mild cam is going to be making 300HP at the tire, at least not without some kind of power adder or a gnarly tune and a lot of luck. My best guess would put this combo at around 250RWHP on a good day.
Having said that, if you upgrade to basically any aftermarket aluminum head and/or aftermarket intake, you will probably run out of injector. So if you plan on going that route, you might as well upgrade now if you have to buy injectors anyway.
You can also increase fuel pressure to get your 19# injectors to flow more.
All the new Bosch stock fox body style injectors are China made now and crap shoot quality. We wouldn't even touch them at the dealer if they where that old. Need to update to newer pencil style or clean good old ones... Rust kills them so if you see rust don't even bother trying to get them flowed.
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You can make just over 300 rwhp with GT40 cast iron heads and Cobra intake manifold. You have to work over the heads and intake manifold a bit, but it can be done using stock valves. I built a few 93 Cobras doing that. Hand port the lower, Extrude hone the upper, good exhaust, (all Bassani) even using shorty headers. Good cam, (Steeda #19 if I remember right) still streetable, idle speed at 900 rpm and no surging. Did it without a chip or "tune" other than ignition timing. Stock short block never left the engine compartment. All stock 93 Cobra t-body/maf/injectors/ECU/rocker arms.
Don't under estimate what you can get out of GT40 stuff with attention to detail.
Just to continue with this, it's not just about getting bigger injectors, right? If you get bigger injectors, other parts need to be changed too? MAF, fuel pump (or at least fuel pressure regulator)
I cheaper workaround I hear is to get an adjustable fuel pressure regulator. However, if I recall, it's pretty buried in there on the lower intake. So, to adjust it, the upper needs to come off and such. So if that's the case, it should be ok to leave the stock regulator on. If it ever needs adjusting, it can then be replaced because the same parts need to be removed?
I cheaper workaround I hear is to get an adjustable fuel pressure regulator. However, if I recall, it's pretty buried in there on the lower intake. So, to adjust it, the upper needs to come off and such. So if that's the case, it should be ok to leave the stock regulator on. If it ever needs adjusting, it can then be replaced because the same parts need to be removed?
Lots of non-stock parts on the 306 and a custom cam. Went to 316 rwhp just by adding the 42 lb/hr injectors which indicated the 24's were maxed out. Drivability and idle we excellent with the 42's but the car had an SCT and a custom dyno tune. The tuner did not go for maximum hp just a really fat curve so it worked better through the rpm range.
Lots of GT40 head/ upper & lower stock bottom end motors making right at or over 300 rwhp but they are not stock heads or uppers and lowers like Bullitt347 stated. And I would be shocked if it was on a stock cam i.e. no way in hell naturally aspirated. There is a huge thread on this over on the Corral so you can get a lot of ideas on how to do it without making a lot of mistakes. It does take some planning and in the end if you would just buy a better set of aluminum heads you will spend about the same money or less and make more hp.
Key with building on a 93 Cobra is it already has 24 lb/hr injectors so it's got a lot more fuel available vs a LX or GT.
I keep coming back to why would you install just enough injector when moving up one size assures you will have enough injector for the motor. There is not a lot of cost difference. I will say that the stock fuel lines start posing problems when you are approaching the 450-500 fwhp area.
Also, raising the stock fuel pressure on the stock injectors with an ECU that does not have a chip and tuned can start to cause problems. The fuel tables in the ECU were developed with a base fuel pressure of 39 psi so altering the base fuel pressure will cause the ECU to try and trim those tables. The fuel pressure regulator works with the manifold pressure (the vacuum line that is attached to it) to keep a constant 39 psi on the fuel rails at all times.
You can get to an adjustable pressure regulator just fine to make adjustments without pulling the upper. I had a Kirban and currently have an Aeromotive unit and both were/are easy to get to.
Lots of GT40 head/ upper & lower stock bottom end motors making right at or over 300 rwhp but they are not stock heads or uppers and lowers like Bullitt347 stated. And I would be shocked if it was on a stock cam i.e. no way in hell naturally aspirated. There is a huge thread on this over on the Corral so you can get a lot of ideas on how to do it without making a lot of mistakes. It does take some planning and in the end if you would just buy a better set of aluminum heads you will spend about the same money or less and make more hp.
Key with building on a 93 Cobra is it already has 24 lb/hr injectors so it's got a lot more fuel available vs a LX or GT.
I keep coming back to why would you install just enough injector when moving up one size assures you will have enough injector for the motor. There is not a lot of cost difference. I will say that the stock fuel lines start posing problems when you are approaching the 450-500 fwhp area.
Also, raising the stock fuel pressure on the stock injectors with an ECU that does not have a chip and tuned can start to cause problems. The fuel tables in the ECU were developed with a base fuel pressure of 39 psi so altering the base fuel pressure will cause the ECU to try and trim those tables. The fuel pressure regulator works with the manifold pressure (the vacuum line that is attached to it) to keep a constant 39 psi on the fuel rails at all times.
You can get to an adjustable pressure regulator just fine to make adjustments without pulling the upper. I had a Kirban and currently have an Aeromotive unit and both were/are easy to get to.
keel
Active Member
For me personally, it was important to keep the stock MAF and stock MAF calibration by staying with 19# injectors. I know that for most people it works fine to upsize and get a calibrated MAF, but some people do encounter issues with calibrated MAFs and I wanted to avoid that possibility and just be confident that my car was going to work properly and was going to be easy to maintain.
A decent calibrated MAF is going to run you at least $200 and in my case I would have also had to buy another set of 8 injectors. Not a lot of savings but it's something.
It's either that or a tune, which I think is definitely the right way to do it but costs a lot more than just a MAF to set up.
I will say there are a lot of cars with heads, cam, intakes, bigger injectors with a calibrated MAF that are not tuned and making great power. You have to pick the parts very carefully so that they work really well together but it can be done. Bullett347, rednotch, FastDriver, TOOLOW91, and there are others on here can speak much better to this than I can. I have a guy that does all my motor work and guides me on parts.
350 posts later I kinda forget the original premise, your not gonna race it (yeah right) so I will guide you back to post #2, if you start wanting a lumpy idle and they sound sooo cool, it starts to get complicated because these computers are (basically) the second generation units, think speed density, then they figured out mass air. Still the cam overlap, which makes the cool exhaust sound, can cause the computer to work hard trying to keep up with the info the sensors are reading, it's not built to do it. It becomes hard to drive unless your in the upper RPM range. Other issues arise but it can be dealt with, tuning a chip can help but they are limited. All this through stock gears, and then people wonder why it a pooch.
Let's talk about a fun ride. Most butt dynos don't know the difference between 275 and 300 hp but forget all that, I am a believer in streetable torque, if planned right these stangs can hang with most modern day stop light euro trash. They can talk all day about their 350 hp, traction controlled, slush-o-matics in heavy tin boxes.
But you have to have a plan.
And you can have a fun ride on the cheap.
My junk was a stock headed, gt40 intake with a little bigger maf (same 19lb injectors and sensor) long tube headers (personal preference for low end torque) 2.5" mandrel bent pipes and a cheap muffler, oh, and the 355 rear gear. Oh, and inexpensive rubber on the rear (they tend not to last long with me)so I don't break sht. I've made fools out of many a kid with a headered up honda and a fart pipe. I can roll out onto the road in first gear, stab the go peddle, shift second ( not 'power shifting') and continue sideways for a fair distance, (yeah I've bounced off the rev limiter a few times) and shift third sometimes chirping the tires. All this with a 130k mile engine with 7 cylinders at 125 psi compression (or less) and one cylinder at 75lbs!
What I'm try'n to convey here is start out conservative, get the kid interested first, building a car that is difficult to deal with, lumpy cam, sticky go fast tires, jump'n, jerkin'n and breaking driveline parts try'n to schlep through the parking lot at school, work, or the local shake shop and you'll loose him to the honda crowd.
Just the opinion of an old guy that likes to have a fun car to drive without spending John Force money.
AND I AIN'T MAKE'N NO CAR PAYMENTS.
Let's talk about a fun ride. Most butt dynos don't know the difference between 275 and 300 hp but forget all that, I am a believer in streetable torque, if planned right these stangs can hang with most modern day stop light euro trash. They can talk all day about their 350 hp, traction controlled, slush-o-matics in heavy tin boxes.
But you have to have a plan.
And you can have a fun ride on the cheap.
My junk was a stock headed, gt40 intake with a little bigger maf (same 19lb injectors and sensor) long tube headers (personal preference for low end torque) 2.5" mandrel bent pipes and a cheap muffler, oh, and the 355 rear gear. Oh, and inexpensive rubber on the rear (they tend not to last long with me)so I don't break sht. I've made fools out of many a kid with a headered up honda and a fart pipe. I can roll out onto the road in first gear, stab the go peddle, shift second ( not 'power shifting') and continue sideways for a fair distance, (yeah I've bounced off the rev limiter a few times) and shift third sometimes chirping the tires. All this with a 130k mile engine with 7 cylinders at 125 psi compression (or less) and one cylinder at 75lbs!
What I'm try'n to convey here is start out conservative, get the kid interested first, building a car that is difficult to deal with, lumpy cam, sticky go fast tires, jump'n, jerkin'n and breaking driveline parts try'n to schlep through the parking lot at school, work, or the local shake shop and you'll loose him to the honda crowd.
Just the opinion of an old guy that likes to have a fun car to drive without spending John Force money.
AND I AIN'T MAKE'N NO CAR PAYMENTS.
General karthief I totally agree with you. When I said I don't plan to race it, I meant taking it to the track. I've had the mustang for 10 years now. Wanted to rebuild an engine since highschool when I took engines classes and others were building Chevelles and such, I didn't have the money to do that then, so I just watched. Anyway, with the rebuild, I just wanted a dependable engine and a little extra power than before to have fun on the streets. Also, wanted to own a built American Muscle car. I think what I ended up with now is according to my overall plan. You guys helped a lot. The cam is a TFS Stage 1. I've read even stage 2 is good on the roads, but stage 1 should give me that loopy exhaust and be great at low speeds as well. I just hope it starts in the end 
More progress being made. Received the rebuilt fuel injectors with the 4 nozzle spray from eBay. Looked good. Tested each one and the solenoid clicked. Installed in to lower intake.
One question I do have-- I decided to go the route of Black RTV on the China walls for the lower intake. I did a 1/4" bead on the block like I've seen online somewhere, placed the lower intake down and it seemed like there wasn't enough RTV. Lifted if off and in fact the bead didn't get crushed. Went over it again making the bead thicker-- maybe 1/2" from bottom to top. Put down the lower manifold, hand tightened bolts. Came back about an hour later and torqued the bolts in 2 steps. About 23ft/lbs on the 2nd round. The question is, the lower manifold is curved and hard to see the full bead. Does the black RTV expand? How do I verify it's sealed well before I install? I stuck a flashlight in the coolant elbow port and turned all the lights off-- didn't see the light, but I don't know if I trust it.
Another question: Just want to be double sure that the fuel system is all well sealed. Can I run like 35ft lbs of air in to it to check that all is well or is that a bad idea? Would hate to learn I have a leak when the actual fuel is running?
If you laid a 1/2" bead of RTV down it will have made contact all the way across. I usually use about a 3/8" bead and have zero issues. I good telescoping mirror works great for getting under the thermostat area of the lower intake to see if the bead squeezed out. And no, RTV does not expand.
Drop the motor in and turn the key to the run position. Fuel pump will prime for about 3 seconds. Do this a couple of times and check for leaks.
Drop the motor in and turn the key to the run position. Fuel pump will prime for about 3 seconds. Do this a couple of times and check for leaks.
keel
Active Member
Hahaha... Started with Julian saying prices are crazy and ends with a total top end and cam. Love hot rodding!
I read the first couple lines and thought explorer motor with a cam would be right up your alley. a
I think you'll be happywhen it's all back together, though.
I read the first couple lines and thought explorer motor with a cam would be right up your alley. a
I think you'll be happywhen it's all back together, though.
To be fair, I only spent $250 on GT40P heads, $50 on GT40 intake.
I didn't read all 18 pages. I just saw what everyone was recommending when you started with the premise that it was nuts to pay a couple grade on a, was it, $4,800 car. That's very affordable.
The days of $500 junkyard Explorer motors are gone, with exceptions. If someone has a running 5.0 on the FB pages, these days, they want a couple grand for it. Just for reference, I just got quotes from 3 machine shops for a rebuild and if it's a full decking, boring/honing, and hitting every surface kind of job, the prices ranged from $1k to $2.5. I'm going with the one that quoted in the middle $1.3-1.5k.
Of course, you could probably slap in new rings and bearings and go. Hell, with yours only at 100k miles, I wouldn't bother with any of it. Just slap on the heads/cam/intake, and roll out! I think my daily is likely in the 150k+ club. I just installed nitrous, and have been going to the races with it. I'm sure you'll be fine. The beauty in these cars is the reward for mods. The original H/C/I & exhaust were so anemic that anything you do can make a noticeable bump in power. P heads, explorer intake, & TFS1 cam will really wake things up.
The days of $500 junkyard Explorer motors are gone, with exceptions. If someone has a running 5.0 on the FB pages, these days, they want a couple grand for it. Just for reference, I just got quotes from 3 machine shops for a rebuild and if it's a full decking, boring/honing, and hitting every surface kind of job, the prices ranged from $1k to $2.5. I'm going with the one that quoted in the middle $1.3-1.5k.
Of course, you could probably slap in new rings and bearings and go. Hell, with yours only at 100k miles, I wouldn't bother with any of it. Just slap on the heads/cam/intake, and roll out! I think my daily is likely in the 150k+ club. I just installed nitrous, and have been going to the races with it. I'm sure you'll be fine. The beauty in these cars is the reward for mods. The original H/C/I & exhaust were so anemic that anything you do can make a noticeable bump in power. P heads, explorer intake, & TFS1 cam will really wake things up.
Now that I'm getting really close to the point of putting the engine in, I can't wait to test out and see if I did everything right.
Looking for advice-- do I need to hook everything up, once the engine is in, as though I'm going to drive it. Or, do I hook up just the minimum where I can turn the key and hear it start? Or, is there any other way to make sure it will run? I'd hate to hook up the radiator and add antifreeze and such if there's a chance I'll have to drain it all and pull the engine again. I'm pretty confident in my work, but it's also my first time rebuilding an engine. There could be mistakes.
Looking for advice-- do I need to hook everything up, once the engine is in, as though I'm going to drive it. Or, do I hook up just the minimum where I can turn the key and hear it start? Or, is there any other way to make sure it will run? I'd hate to hook up the radiator and add antifreeze and such if there's a chance I'll have to drain it all and pull the engine again. I'm pretty confident in my work, but it's also my first time rebuilding an engine. There could be mistakes.
