135 vs 155 HP

[Stage1]

1986 6.2L engine is rated at 135 horse power and noticed in 1993 the rating is 155 :eek: What changes were made to the engine for the increase?
Does the 93' feel like it has morepower.
thanks,
Les

[gmctd]

Power increase is from -
Revised air intake system
Revised injector location\angle in heads
Revised injector pipes to larger i.d.
Revised inj pump specs - timing, injected volume
Block is same

If you're thinking about doing something for more power, the 6.5 is direct drop-in - 16 cu in more.
If cost is main consideration, '93 heads, pipes and pump will bolt on your block.

[dieselhumvee]

There was also a 165 HP rating.... I know because my 1993 Hummer has one in it!!!

[grape]

My C truck is rated at 135 horsepower. I thought the J's were rated at 155 from 82 till the 6.5 came out.

[Stage1]

My 1986 manual(Military) says 135HP at 3600 RPMs,
print date is 7/86. What are the torque increases like for the updated engines?

Is the casting number available for the better 1993 head. Also does cylinder head air flow improvments( like bigger valves,etc) help torque and HP.
A 6.5 engine may be possible in the distant future.

thanks,
Les

[gmctd]

Don't know casting numbers, but earliest I've seen those heads is in '91 6.2L Subs, all original.

I've been wondering if that 165hp Hummer may be a 6.5L, rather than a 6.2L.
????

You can check the DP ad list, call Avant Salvage for specific casting numbers.

I never noticed the numbers, grape - I bought my 6.2L truck with a 6.5L goal in mind, so it seemed unimportant.
But, I do easily recognize the hardware.

[86burb]

My '86 J code is rated 155Hp. Standrd Abrasives has a great head porting kit (www.sa-motorsports.com),there are definite gains in power that can be found with properly ported cylinder heads regardless of the engine make. Larger valves can actually hurt low rpm air flow. A 3-angle valve job with ported heads is an excellent way to improve performance.

[Stage1]

Considering head mods along w/ additional fuel impovements. Which heads should I start with? Does the later 93' style heads provide a significant( 10-20hp) HP and torque increase over the early style heads when modifying heads?
thanks,
Les

[grape]

my C code 82 heads have .100" bigger exhaust valves than the brand new 6.5 castings I have ready for my engine. The intake valves are the same size. I had heard some of the old engines had big valves but I figured it was the J model stuff.

[G. Gearloose]

'82 had THE biggest valves period.

[62dog]

I use to have a 91 6.2 w/165hp sticker right on the air box. Sold it to my brother......regretably!

It was a 4WD 2500HD 3.73 with 4L80E, first year. I broke a valve spring($8) on the way home, drove it 10km. Obviously I didn't know it was a valve spring. Anyway, after taking the heads off not a mark on the piston. Since it was apart had the injectors reman. and port martched the head/intake ....wow what a difference.

sorry about the rambling

[gmctd]

Member #79 , with only 61 posts from Mar 2000?

And that was rambling??? Ha!
Read some of my posts!

Good info, rambling man - thanks.
;)

So we've got 165hp 6.2L from '91 - the new heads with revised injector angles must help.

[86burb]

A suggestion if you are going to port match the intake and heads, 1)Pick the largest port and match all the others to it, 2)Measure the roof thickness of the heads and depending on the thickness raise the roof .100' to .175'. Grind between 1" to 1 1/2" into the port. Clean up the floor and walls using 50 or 60 grit to leave a rough finish. Feel around the roof by the rocker studs for any depressions in the casting and fill with epoxy (JB-Weld is my favorite), This point is usually good for an extra 10 to 15 cfm. If possible raise the roof on the exhaust side .100" then finish with a 300 or 400 grit for a smooth surface.

[dieselhumvee]

I've been wondering if that 165hp Hummer may be a 6.5L, rather than a 6.2L.
????

Nope, it is a 6.2L 14022660 block to be exact, also has 62 cast into the block on the pass side front. I will try to get a pic of the valve cover sticker, may be a misprint on the sticker.... but it does in fact say 165!!

I just snapped a pic of it, I will have to get the film developed then scanned, and I will post it back to this thread.

[gmctd]

I'm certainly no authority on 6.2L numbers - I seem to remember a 145hp number in there, somewhere - but we've got one 165hp number from a '91 Sub, and one from a 6.2L Hummer pointing to head improvements.

My Hummer question was based on 'what you get is what you see' - vehicles past their prime are not always as oem equipped.

My truck is a good example of that concept.
Someone finding it in a car lot would be very puzzled, as I've tried to make it look factory in most details.
Passes State Inspection much easier when no thing appears out of the ordinary.

[ 03-07-2004, 03:12 PM: Message edited by: gmctd ]

[Stage1]

86' burb do you know the intake and exhaust port volumes? Just trying to get an idea of what the air flow pontential is? Any idea as to valve lift and cam timing. Also, I am interested in what the valves look like-lots of new technology in this area.

[Dezman125]

dieselhumvee,
my block has the same numbers,so does a parts engine i got,supposed to be a 91 goodwrench.
If you find out actall HP on yours,post it im curious as to what i have to start with.
thanks

[86burb]

Stage1, I do not know the port volumes as there are differant castings from differant years(lots of variation). That is why I recommend measuring for the largest port and matching the other to it,this will give you increased and balanced flow. The raised roof will increase velocity especially with flow @ .150" to .300" lift. Peak flow @ maximum lift is not very important as it only hits it once in its cycle, where as the valves cross the .150"-.300" range twice there cycle. The only cam specs I have are a Crane cams regrind (part#01112), 198*/202* @.050, .2934"/.3000" lobe lift (.440"/.450" valve lift), I.O.@6*, I.C.@24* Intake centerline 105*, E.O.@36*, E.C.@14* Exhaust centerline 115*, Lobe separation 110*.

[Ratau]

86burb

What should the reason be for the power shift I found.(141hp @ 3100rpm and the torque 410 nm @ 1300rpm) This is 500rpm lower than it suppose to be. Since the dyno test I replaced the timing chain with gears, didn't do another dyno but not any major change in power. Could it be the cam timing? The engine starts first time and runs fine.

[britannic]

Elevation is a factor, since the manufacturer usually adjusts the figures for sea-level. Other factors include relative humidity, barometric pressure, engine wear, drivetrain wear and drag etc., etc.

[Stage1]

86 Burb,
Agree totally on concentrating on mid lift flow numbers. On my race car heads I look at an integrated flow value from .100 to .500. Should I also consider the early 6.5 heads (w/mechanical FI) in choosing the best heads for my 6.2.

Sounds like I may need find a shop w/ the different heads, where I can inspected them, will also try different junk yards to see if I can purchase heads cheap. The junk yards heads will also let me find out where the coolent passages are!
thanks,
Les

[86burb]

Stage1, The heads you choose will depend on your goals and of course time and money(isn't that usually the way). Whichever heads you decide on have them magnafluxed and sonic tested before doing any serious modifying. The 6.2 heads should be cheaper and easier to get ahold of. If you decide not to modify then go with the 6.5 heads, but then where is the fun in that?

[86burb]

Stage1, The heads you choose will depend on your goals and of course time and money(isn't that usually the way). Whichever heads you decide on have them magnafluxed and sonic tested before doing any serious modifying. The 6.2 heads should be cheaper and easier to get ahold of. If you decide not to modify then go with the 6.5 heads, but then where is the fun in that?

Ratau, Was that an engine dyno or a chassis dyno that you used?

[Ratau]

86burb
Chassis dyno at altitude converted to sea level.