4.8L Motor ideas

Performance modifications, tips & tricks

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stroker97k1500
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4.8L Motor ideas

Post by stroker97k1500 »

I have been working on 4-5 different projects and still haven't had time to work on my truck to finish swapping the trans out yet... It's still 1/2 way out
I have been reading up at night on the LR4 4.8L and was thinking of putting 6.0L lq4 heads on it (same 71cc chamber but the 6.0's have larger intake valves and D shaped exhaust) on it with a different cam and the M112 Instead of just using the 4.8 in stock form.
These are just thoughts of making more flow for a small cube higher compression motor. Has anyone else other than car craft tried to get best of both worlds with this small entry level v8?
Any thoughts

Speeder
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Post by Speeder »

I did, and while I came out with more power than a 5.3L, I didn't get the mileage I expected. My ultimate goal was to build a high mileage, high speed cruiser even if it meant giving up a bit of acceleration. I think my main problem, aside from literally not having time to do a proper tune even though I have EFI Live and a wideband O2 sensor, is I am running 3.42 gears with 31.7 inch diameter tires. Shoulda gone with 3.73s or 4.10s, and if I ever need to redo the gears again (or if I ever come up with enough money to waste) I'd go 4.10s. The truck does need new tires so I'll be going with 30 inch tall tires, which will give me an effective 3.60 rear gears in relation to what I have now. If I could tune, and do the tires, I might get better mileage. But overall, I am dissatisfied with the results.

By the way, Hunt Engines out of Fort Smith AR is who did my engine. I strongly recommend that if anyone here wants a really good engine that you run FAR FAR AWAY from this shop. They screwed the engine up on the first build, and I think they half-assed it when they fixed it the second time. I'd have been money ahead had I bought a crate 4.8L and just swapped heads to boost compression and I probably would have liked it better. After I deal with my housing situation I will probably revisit the whole thing but I'm just running with it right now.

stroker97k1500
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Post by stroker97k1500 »

It's sad but seems that a shop is only as good as its worst employee. I have tried many
Many machine shops and its hard to find a good one anymore. I will be doing this one as a stock bore/stroke build
Just to see what happens.
I would guess yours is as close to mine as it could get with the same tranny but mine is a 2500 with 3.73:1 ratio
What cam did you use again?

Hog
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Post by Hog »

I keep hearing stories like Speeders when ordering GEN 3/4 engines to specifc specs. Not so bad when bought from reputable shops that have a certain performance line, but no-one has a 4.8 liter fuel economy line of engines.

I have a 220hp@4800rpm/300lb/ft@3000rpm SUper Turbo Fire (aka PowerPack) 283 that has the higher c/r heads-9.5:1, slightly larger cam, single 4bbl cab and dual exhaust. The step down Turbo Fire-non-Power Pack 283 has the smaller cam, 8.5c/r, 2 bbl carb, single exhausr rated at 185hp@4600rpm/275lb/ft@2400rpm
Step down the rpo list of available engines and we get the 1957 Turbo Fire 265, a rareity with 2 bbl carb 8.0:1 c/r 162hp@4400rpm/257 lb/ft@2400rpm.
Then the old Blue Flame V6 235 cubes 8.0:1 cr 140hp@4200rpm/210lb/ft@2400rpm.

Above the Super turbo Fire 283 on the rpo list are the High Performance "Corvette" engines, all these engines were available in the Vette and the other passenger cars in 1957.

283 Dual 4bbl carbs 9.5:1 c/r 245hp@5000rpm/300lb/ft@3800rpm
283 Fuel Injection 9.5:1 c/r 250hp@5000rpm/305lb/ft@3800rpm

Then these were replaced with the engines that contained the "Competition Camshaft"
283 Dual 4bbl carbs 9.5:1 c/r 270hp@6000rpm/285lb/ft@4200rpm
283 Fuel Injection 10.5:1 c/r 283hp@6200rpm/290lb/ft@4400rpm

On the actual dyno these competition cammed "fuelies" actually outputted 290hp and the later Ramjet 283's are the same exact engines as the 57 ramjet, just with the different 290hp rating.

The guy that rebuilt the 283 PP in the car right now has since passed away, and the other shop that builds engines is closing. So when it comes to rebuild the 283 that actually in the car, or to rebuild the 283 that I have wrapped up on a pallet, its going to be like placing a certain important part of my anatomy on a chopping block and letting a stranger hold the knife. TBoth engines are proper numbers matching Power Pack 283's for the car. The engine currently in service already has an overbore of 0.040" so its rebuild potential may be limited. The other 283 I have no idea on its rebuild history.

I so wish I could pay the $2000 it costs to buy a brand new Vortec 350 longblock from GM and pass it off as a 283. That engine would work awesome with a carb in that car.

Mom left with the car on Wednesday to a show in Nashau New Hampshire and the odometer was about to hit 80,000 in short order. I need to do a compression test when she gets back. The car is running great though, but man is the lubrication service list for every 1000 miles ever long. All these little oilers where you squirt some engine oil into to lube the distributer, generator p/s etc etc.


The 317 heads that came on the LQ4 and LQ9 will have the 210cc LS6 like ports. Should be great for forced induction. I always though that using these heads would drop c/r though, that's why lots of people use them on forced induction apps. But I just checked and yes the 27 LQ4/9 heads have the same 71cc chambers at least according to this.
http://www.enginebuildermag.com/Article ... block.aspx

peace
Hog

Speeder
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Post by Speeder »

I used a Comp XR259HR. It's got excellent pull over 3000RPM. I could really use more stall to make it really take off because while it pulls well below 3000RPM you can feel it struggling a bit. I think if I had smaller tires and a lower (higher numerically) rear gear to get the cruise RPM closer to the torque band it would also get a lot better mileage as it would be easier for the engine to maintain speed. Right now, my cruise RPM at 80MPH is something like 1900RPM. Just bumping that to 2200RPM would likely net me a 3MPG improvement at 80. Smaller tires come before winter, may look at lower gears next spring. I'm really glad that you can't get 3.23s for a 4WD front diff now, because that is what I was originally going to get.

stroker97k1500
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Post by stroker97k1500 »

Speeder wrote:I used a Comp XR259HR. It's got excellent pull over 3000RPM. .
Wow that is the exact same cam i was looking at.I guess we were going along the exact thought process at different times... Haha just me later than you. The 80e gear set and now this road.
My main thoughts were improving mileage at cruising speed in overdrive with a smaller cubic inch motor and the trans to take it up to speed easier... And the blower whenever it needs more ass.
This may be a mistake but I may still try it.

What was your final compression ratio?

Speeder
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Post by Speeder »

I don't know and don't know how to check without pulling the head, but I'll be willing to bet based off the rest of the "work" done that I have about a 9:1 compression. Was debating perhaps swapping the stock 4.8 heads with a set of L92 heads to boost it closer to 10:1. Also, was thinking about doing a TrailBlazer SS intake as it is supposed to have all of the low end of the truck intake with the top end of the intakes found on the Camaros.

The 80E low gearset has been the one bright point of the whole thing. I almost have the same takeoff as the weak sister, but it feels like it can be flogged all day and all night whereas the 60 feels like you're trying to walk across a bridge made of wet tissue like it's not if but when it's going to puke all over the road.

Another couple of parts to stay away from are the Pacesetter headers, at least if you are 4x4, because they don't fit right. I would look at Doug's Tri-Ys instead as they look like they will fit between the frame rail and the front driveshaft without a 5 pound sledge massage. Money wasted there, since I will most likely have to swap headers now. And, the Hughes 25-30L torque converter, which is supposed to stall at 3000RPM, apparently has no torque multiplication at all. My truck was sluggish and weak when I installed one. I went back to the TC sent to me by FLT, and got my acceleration back. The Hughes TC is now in the trash, because I wouldn't inflict that on anyone else. I'd have returned it but due to the other problems I had I had it in the truck too long to do so before I decided it was time to go. More money wasted.

Don't get me wrong, the truck is fun to drive as it is, it just isn't living up to my expectations.

stroker97k1500
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Post by stroker97k1500 »

pauly
thats the information in the link You posted that i was going by but now reading more..... there are conflicting issues with the 5.3/4.8 combustion chamber sizes.....
another link that says different is HERE
I am going to try to make sure of whats what before making my movo on my current 6.0lq4 or playing with anoither setup.

Hog
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Post by Hog »

stroker97k1500 wrote:pauly
thats the information in the link You posted that i was going by but now reading more..... there are conflicting issues with the 5.3/4.8 combustion chamber sizes.....
another link that says different is HERE
I am going to try to make sure of whats what before making my movo on my current 6.0lq4 or playing with anoither setup.
That makes more sense, I always remember people saying that the 317's are good on the 4.8/5.3 for forced iunduction as they lower the c/r. That lnk you posted makes more sense.

peace
Hog

Speeder
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Post by Speeder »

Never mind on mine then. I thought the 4.8 had 71cc chambers, if they have 61cc chambers then there's nothing for me to do there. Bummer.

SikSilverado
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Post by SikSilverado »


s10mods
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Post by s10mods »

I am running a stock 4.8 with that 259 cam and in my 4x4 jimmy the best i got was 20 mpg and that was driving it like a grandma with LC enabled. 235/75R15 tires and 3.42 gears. after i put a 3k stall in the best i can get now is 17 mpg same driving with LC. if i drive normal i get ~15 ish only change was converter. I hate how that 4.8 drives with that 259 cam. i only put down 259 to the wheels which means its better than the stock 4.8, but not by much. i also hate the way that cam idles with its 112 lsa too rough . i have an lq9 on a stand and someday thats getting L92 heads and a cam with a better idle (im getting old and like smooth) and getting swapped out.

stroker97k1500
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Post by stroker97k1500 »

s10mods wrote:I am running a stock 4.8 with that 259 cam and in my 4x4 jimmy the best i got was 20 mpg and that was driving it like a grandma with LC enabled. 235/75R15 tires and 3.42 gears. after i put a 3k stall in the best i can get now is 17 mpg same driving with LC. if i drive normal i get ~15 ish only change was converter. I hate how that 4.8 drives with that 259 cam. i only put down 259 to the wheels which means its better than the stock 4.8, but not by much. i also hate the way that cam idles with its 112 lsa too rough . i have an lq9 on a stand and someday thats getting L92 heads and a cam with a better idle (im getting old and like smooth) and getting swapped out.
I will buy that cam from you if you want to sell it

s10mods
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Post by s10mods »

It probably wont be till next summer some time before i pull the 4.8 and swap it for the 6.0. but when i do pull the 4.8 i can pull the cam, when it goes up for sale you have first dibs.

stroker97k1500
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Post by stroker97k1500 »

Sounds good

s10mods
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Post by s10mods »

You may end up with option to buy that cam earlier than I thought. I'm doing the swap now rather than waiting. The 4.8 is out on the stand and the 6.0 is getting prepped to go in. As soon as it's in and I see how it is I'll let you know about the cam.

stroker97k1500
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Post by stroker97k1500 »

whenever you are ready.Pm me with a price to zip 31210.
Robby

stroker97k1500
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Post by stroker97k1500 »

s10mods wrote:You may end up with option to buy that cam earlier than I thought. I'm doing the swap now rather than waiting. The 4.8 is out on the stand and the 6.0 is getting prepped to go in. As soon as it's in and I see how it is I'll let you know about the cam.
out of curiousity, I have never put a cam in to a LS motor before. I have only been familiar with 350's and bbc's.
are the stock LQ4 valve springs ok with that cam or are they not sufficient for the lift? I can call compcams but wanted to see what you did for the valve geometry on the 4.8L first.

s10mods
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Post by s10mods »

I used the ls6 springs with that cam and it was fine. The stock lq4 springs are not sufficient for that cam.

s10mods
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Post by s10mods »

stroker97k1500 wrote:whenever you are ready.Pm me with a price to zip 31210.
Robby
I live near grand Rapids and am getting ready for the metro cruise. After that's over I'll pull the cam and make sure it's in good shape. Should be the oil pan was very clean and it only has about 15k miles on it.

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