intergrated heads, options and modification

[jake wells]

this thread covers the rare engine that is not seen that much anymore in these trucks called a straight 6 or inline. Covered on all years and engines including the dreadful cast integrated head used on the 1975-1984 models. C10-C30/K5-K30 trucks including the C15-C35/K15-K35 covered on gmc trucks.
--NOTE-- INTEGRATED HEADS WERE ONLY USED ON 75-84 MODELS SOME WITH OR WITH OUT THIS. Hotrodpc or anyone else is free to change this if you have more info on this or need to correct errors pertaining only to this thread or related content.

********** SPECS FOR 6CYL CHEVY/GMC ENGINES****************

250 Chevy inline six
The stroked 250 version produced 155 hp (116 kW) for Chevrolet and GMC. Between 1975 - 1984, an integrated cylinder head was produced, with one-barrel intakes for passenger cars, and two-barrel intakes for trucks after 1978.
Passenger car use of the 250-cubic-inch (4.1 L) engine was discontinued after the 1979
This engine was used on the following vehicles:
1966-1984 Chevrolet (passenger cars to 1979, trucks/vans to 1984)
1968-1976 Pontiac Firebird
1968-1970 Pontiac Tempest
1968-1976 Pontiac LeMans
1968-1969 Buick Special
1968-1972 Oldsmobile F-85
1975-1976 Oldsmobile Cutlass
1971-1975 Pontiac Ventura
1968-1971 Buick Skylark
1968-1979 Chevrolet Camaro
1969-1979 Checker Marathon
1968-1992 Chevrolet Opala (Brazil)

L22 6 cylinder Chevy
The L22 was a 250-cubic-inch (4.1 L) I6 engine produced from 1967 to 1979. The '78 Camaro had 105 horsepower (78 kW) and 190 ft·lbf (260 N·m) of torque with the 250.

LD4 Chevrolet 6 cylinder
The LD4 was a 250-cubic-inch (4.1 L) I6 engine produced strictly in 1978.

LE3 6 cylinder Chevrolet
The LE3 was a 250-cubic-inch (4.1 L) I6 engine produced from 1979 to 1984.

292 C.I Chevrolet 6 cylinder
The 292 was only used in Chevrolet and GMC trucks; the block deck is taller, along with a relocated passenger-side engine mount. These were produced between 1963 to 1990; production of the engine shifted to Mexico after 1984.

L25 Chevrolet 6 cylinder
The L25 was GM's "last" push rod straight-6 engine, produced from 1977 to 1988. It was used in Chevrolet trucks, displaced 292 cubic inches (4.8 L) and produced 115 hp (86 kW) and 215 ft·lbf (292 N·m).
The Chevrolet straight six has been used from the early days in sedans & trucks, It became popular with many hot rodders & racers. Over the years there have been many brands of headers, aluminum cylinder heads, hotter grind camshafts, 2 & 4 barrel manifolds + a huge range of multi carb intakes from speed equipment companies both large & small. Many back yard & home work shop creations have also been invented.

Pictures below show the Chevy Blue flame straight six inlet & exhaust manifold compared to the later Chevy straight six engine. Note the blue flame manifold has round exhaust ports. The later L6 has rectangular ports.
*********************************************************
Chevy Straight six engine specs bore and stroke sizes

194: 3.563x3.25
215: 3.750x3.25
230: 3.875x3.25
250: 3.875x3.53
292: 3.875x4.125

firing order
1-5-3-6-2-4
*********************************************************

Chevy straight six crankshaft strokes.

Straight six Chevrolet crankshafts from these engines will interchange. There are 3 basic crank types.

194/230 (3.25" stroke)

250 (3.53" stroke)

292 (4.125" stroke)

The 292 cubic inch straight six engine has a different con rod journal diameter. When swapping cranks it is recommended both crank & rods be swapped as an assembly.

Some parts that will & wont interchange between Chevy engines
starter motors,

Most Chevy sixes run a through bell housing starter motor

harmonic balancers,

Do not interchange with small block or v6 Chevy's as the pulley on the balancer is integrated with the balancer, bolt on pulleys are used to run air con,power steering & air pumps.
Push rods,

The push rod length on the Chevy's six is a length of its own & will not interchange with small or big block Chevrolet's
Con rods & rod bearings,

Due to rod length & big end sizes they do not interchange with v8 engines.
rocker arms & roller rockers,

Despite having a ratio very similar the rocker length is not the same
camshafts and timing gear sets,

The 292 Chevy six does not interchange with the smaller cube engines.
Fuel pumps,

292 Chevrolet straight six engines had the fuel pump switched to the other side of the engine block, The lobe on the camshaft that operates the fuel pump lever is not in the same location as the smaller cubic inch engines.
Distributors
from v6 Chevrolet, small or big blocks do not swap either
Information that can also be useful.
crankshaft tunnel alignment is very important when changing rotating assemblies .
Crankshaft weights on casting # 407/407N are 10 lbs lighter than crankshaft casting # 802 the con rod,piston,flywheel & harmonic balancer weights will also need to be matched if swapping cranks.
Cylinder heads can be shaved .060 to .080 without affecting the head face.
Head bolt bosses that run through the intake ports can provide more airflow if reduced and reshaped or removed & replaced with crush tubes
It is a known problem that the blocks can get cracks from the head bolt on the front drivers side to the water pump. This can be prevented by installing head studs when rebuilding,
Any straight six Chevy engine made before 1975 was not designed to run unleaded fuel. It is advised to fit hardened valve seats & higher grade exhaust valves to over come future problems
Fiber camshaft timing gears run a lot quieter than steel or aluminum cam sprockets. The down side is they can strip at any time & is more prone in older engines. It is advised if you are changing your camshaft or hotting up your Chevy inliner that both cam & crank gears be replaced as they are designed to be run as a matched set.

 

[HotRodPC]

Great Info for those I6 users. The integral head motors can be converter to NON integrated head since the blocks are the same. Just find you an older head, intake and exhaust manifold and away you go. You'd have an engine then that you can't kill and will tolerate some overheating too. The integral head don't even have to overheat to get cracked.

 

[oneluckypops]

AWWWWW yes the famouse I6 250.

Gutless wonder but one tough ******* motor.

I had 1 that we ran the dog **** out of for 2 years, average RPM of that motor when we had it was 4000 we drove that truck for 2 years and NEVER once changed the oil in it, we tried like hell to blow it up and failed.

 

[Gigom47]

Looking to delete integral head in my truck. Any words of advice before I get too far in? It's a good truck but has seen a lot of life, they don't die till about 350k I'm sure. But my 250 is at 190k, so is it worth it. I love the mileage and the torque it puts out so should I stay where I am and mod it like no tomorrow, or upgrade?

 

[ruddog]

intergrated head

hello im rebuilding a 250 it had a cracked integrated head, im looking to purchase a new integrated head for about 500. bucks is it worth going through all that trouble just to keep it original or is it just going to crack I have heard so many bad things about integrated heads. the other option I have is to purchase a standard head, intake and manifold and would have to install a smog pump to pass. it is a 1981 chevy 250 in line 6. how is yours running, please give me some info anybody.

 

[HotRodPC]

IMO, do away with the very crack prone integrated head. You'd probably spend the same to swap to the non integral head by the time you bought the manifolds and added the smog pump, but it'll be a rock solid dependable vehicle after that. If you can find a 230 head, that would be even better yet. I doubt the head ports have the NOX smog bump in them and probably a smaller combustion chamber that will bring the compression ratio up .5-1 point and get a bit more torque out of it. Otherwise, just an older 250 head will get the job done too.

I did a motor rebuild for a customer once on that integral head. Of course his head was cracked. It took me to the 5th head out of the wrecking yard to finally get one that was not cracked.

 

[Rule_So_Hard]

Glad this thread pooped up. I love the straight 6s! Hopefully one day I'll run across a deal on one.

 

[84scottsdale]

integrated head

does someone have more specific info on swap for non integrated head on GM 250?? needing some help truck is down!!

 

[84scottsdale]

Do you have specifics on what to get exactly to swap out the integrated head??

 

[HotRodPC]

The head, intake and exhaust manifolds, throttle linkage bracketry to the best of my I can recall. The best thing to do is find a complete engine and take everything with the head.

 

[MikeB]

The head, intake and exhaust manifolds, throttle linkage bracketry to the best of my I can recall. The best thing to do is find a complete engine and take everything with the head.

Don't forget the carb. I think the 2bbl is unique to the integrated head/manifold engines. Not only that, but it's a nightmarish, emissions-laden POS to work on.

Best place for 250 six with integrated head and PAIR system.

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[HotRodPC]

Yes, the smog riddled 2bbl carb too. The non integral heads run single bbl carbs, though an Offy or Clifford intake you can run a 2 or 4bbl.

 

[vkh]

Did the 292 ever have an integral head? I've been scrounging the internet and can't find a definite answer. Seems like the 292 is on its own in a lot of ways.

 

[Jumbagumba44]

So I need some help! I have a 1970 Chevy c-10 with a 4.1L 250 IL6, I’ve done a lot of work on it but it’s come down to the fact that the timing covers on the side, and the head gasket is leaking coolant! What’s the procedure to replace the head gasket? I’ve taken valve cover off before so would I have to take out the rods and springs and all that too?

when I do get all the parts off is there anything in particular I should look for (known crack locations or anything common like that?) or any tricks to help with making sure the new gasket(s) don’t leak or tear? And what about the bolt torque specs? Will I need all new bolts or can I reused the ones in there right now?

any information would be greatly appreciated! Also I’m going to get a boss bolt lump kit for increased air flow!

 

[WamboJambo]

So I need some help! I have a 1970 Chevy c-10 with a 4.1L 250 IL6, I’ve done a lot of work on it but it’s come down to the fact that the timing covers on the side, and the head gasket is leaking coolant! What’s the procedure to replace the head gasket? I’ve taken valve cover off before so would I have to take out the rods and springs and all that too?

when I do get all the parts off is there anything in particular I should look for (known crack locations or anything common like that?) or any tricks to help with making sure the new gasket(s) don’t leak or tear? And what about the bolt torque specs? Will I need all new bolts or can I reused the ones in there right now?

any information would be greatly appreciated! Also I’m going to get a boss bolt lump kit for increased air flow!

I've yet to pull the head off of my own 250, so I'm afraid I can't help with a lot of personal experience there. Referring to my Haynes manual, it says you will need to remove rocker arms and pushrods in addition to the valve cover. Obviously since they're attached to the heads, you'll be removing the intake and exhaust manifold assembly as well.

As far as head bolts, specs seem to indicate 95 ft-lbs, though again I'm looking at a book for 73-87 so I can't be positive that's correct for your (presumably 1970) inline 6, you may want to do some independent verification of that. I personally would just re-use the bolts after a thorough cleaning, but that may be a terrible idea because (again) I've never done this before. Also here's a (poor) picture of the torque sequence, it seems to jive with some other diagrams I've found online.

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The Haynes manual also suggests adding a coat sealant if you're using a steel gasket.

Not sure if any of that helps at all, but good luck I suppose. Also, you may want to start a new thread with your question since this one's kinda old.