COCHEV
1/2 ton status
speakin of that, do you still want my performer? im kinda interested in a performer rpm model
I think that could work out just fine
CK5
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how much performance without hurting mpgs or emissions?
- Thread starter COCHEV
- Start date
I think that could work out just fine
1BEATK5
1/2 ton status
I think that could work out just fine
coo coo. mine is ready to remove whenever. i dont have my replacement engine yet. its still in its old truck so speed is not a issue.
CGT80
1/2 ton status
I can feel the truck start to pull nicely at about 2000 rpm. At 2500 it runs very strong. In OD I cruise at 65 at 2200-2300 rpm. At 70 mph and 2500 the engine gets real quiet and the truck moves along almost effortlessly. It feels like the torque peaks somewhere in the area of 3500-4k rpm but it will still push you back into the seat all of the way to 5500. I can roll down the city streets at 1300 rpm in OD (th400 and Gearvendors overdrive) doing 40mph, lay into the gas a bit and the truck will gain speed quite quickly. My trans was not working properly for a little while. It would start off in second gear from a stop but I often times didn't notice it until I was up to speed without feeling it shift twice as usual.
My head/intake guy wanted a bit bigger cam, but the next size up would have failed smog in his opinion and the price for a custom ground cam to meet his specs was too high to keep a reasonable budget on this engine. I also opted for a hydraulic flat tappet cam but am running roller tipped rockers. I learned that a roller cam has some advantage for power but it is more noticeable when you step up to a bigger cam. There were some small benefits to a flat tappet cam but I don't remember what they were other than saving another handful of hundred dollar bills.
Advancing the cam is supposed to increase cylinder pressure and help with the low end torque. I don't have much knowledge about this but a close gear head friend of mine and the engine builder (bottom end and complete assembly of the engine) agreed. If this wasn't a smog engine we would have run a bigger cam and at least pushed the HP numbers higher.
My friend's mustang (428fe) made 525 HP at something like 6500 rpm but made 400 ft pounds of torque at 2000 rpm. It had a pretty lopey cam in it. It was from the same head guy and was dynoed. It made it onto the cover of carcraft because it "Looks Stock and Hauls Ass" as they put it.
I only run 91 octane gas. Running a heavy truck with a decent amount of timing advance in the southern california heat at 10:1 compression pretty much dictates at least 91 be used, so I'm told. Running a higher compression engine gives more power per cubic inch, but you have to deal with causes of detonation.
The thermal coatings on the intake, valves, heads, and headers was all to help keep under hood temps down as well as the temp of the incoming air and fuel to the carb. The idea was to keep the heat from the oil hitting the bottom of the intake and the coolant in the intake from transferring to the plenum and runners that should contain "cold" air and fuel. Coating the valves reduces the the amount of heat transferred to the air/fuel mixture.The driver's side exhaust cross over was also plugged so that exhaust doesn't flow from one side of the intake to the other, but there is still exhaust pressure to the EGR so that it will work when needed.
If this engine was in a lighter car it would handle quite a bit more compression without detonating. I am still playing with my timing curve. I think I need to run a stock set of weights in my MSD distributor (8365). It is kind of a bastard distributor because it is just like a GM HEI distributor and requires stock style parts where all of the other msd dizzy's seem to all use the same msd parts. I bought the part number that the msd tech told me to use for weights, but in the directions it says for all msd distributors except 8365. I set it up for a curve that should have been "all in" at 2800 rpm and it came in at 1800 rpm. The engine ran much cooler when I got it to actually max out at 2800. I might push it up to 3200 or so.
Sorry for the long post.
To rap it up. My goal was to get as much torque as possible out of a SBC while also making it very well mannered and at the same time sticking to a budget. For my power and RPM (5500 max working rpm) requirements a forged crank rods, and pistons were not required, and running trw hyperutetic pistons and scat 9000 series cast crank and rods actually had some benefits. Thermal coatings may not help make power, but they allow the engine to stay at peak power longer in less than ideal conditions.
We tried to carefully build an efficient engine in regards to torque vs. cu inches, and the same attention to detail is probably helpful when building a fuel efficient engine.
COCHEV
1/2 ton status
update
so, after a solid week of commuting with the q-jet, i'm happy i did it. it starts well and is smoother off the line. also seemed to pick up some mid to upper rpm power. it pulls better up the hills now.
economy wise, its a wash tho. mileage last week = 140+ miles, average speed= 38 mph, MPGs = 10.6
i wasn't expecting any miricles tho. I will mess with the timing next. then it will be what it is... a full size truck with a V8
so, after a solid week of commuting with the q-jet, i'm happy i did it. it starts well and is smoother off the line. also seemed to pick up some mid to upper rpm power. it pulls better up the hills now.
economy wise, its a wash tho. mileage last week = 140+ miles, average speed= 38 mph, MPGs = 10.6
i wasn't expecting any miricles tho. I will mess with the timing next. then it will be what it is... a full size truck with a V8
COCHEV
1/2 ton status
Thank you for all the detail. Seems like a pretty impressive motor! And it passes California emmisions???
1BEATK5
1/2 ton status
so, after a solid week of commuting with the q-jet, i'm happy i did it. it starts well and is smoother off the line. also seemed to pick up some mid to upper rpm power. it pulls better up the hills now.
economy wise, its a wash tho. mileage last week = 140+ miles, average speed= 38 mph, MPGs = 10.6
i wasn't expecting any miricles tho. I will mess with the timing next. then it will be what it is... a full size truck with a V8
atleast it drives better. thats always a plus. im dd-ing my brothers 1500 dodge with a 5.2 auto 3.92s and 33s. last tank=11 mpg. which is also the same as the cherokee gets. so i think you are doin pretty good.
CGT80
1/2 ton status
I am pretty happy with it. The guy that did the head work said it would pass with no problem. I hope he is right. I will have to smog it next month. My friend said he built a similar engine for a camaro once, and that the high performance rebuild actually burned cleaner than the factory engine.
COCHEV
1/2 ton status
That makes sense. Please post up on this thread when you pass your emissions
CGT80
1/2 ton status
I thought I was going to have to smog my truck again this year. It seems like I have had to do test only for the last 5 years if I remember right. To my surprise, California only wants my money. Looks like I will have to wait a year to find out how clean it burns.
How early can I have my truck smoged for registration renewal? If there are issues I want to leave myself some time to get them sorted out.
How early can I have my truck smoged for registration renewal? If there are issues I want to leave myself some time to get them sorted out.
you can go in for a test any time you want. Just be sure and tell the tech that you want a pretest. If they do the regular one and it fails the state goons may force you to fix it immediately.
