Inliners International Forums General Discussion Truck Talk 270 Engine Info

Hi Guys!

1st Post after lots of reading..Good stuff!

Anyhow, I have a 57'GMC truck 3/4 ton with a stock 270 in it. The engine area is where my knowledge is weak and its time to get into it

Here is what I know (please correct if wrong)
-270s are moderately rare, and I would like to keep it rather than dropping a V into it
-302s and 270s have some interchangeable parts (have basic interchange manual)

So here are my plans:
-I've found, through here, where I can get a 2-up intake or a single 4 barrel (Preference for 1 v 2?)
-2pc exhaust manifold (Never have seen single like stock)

But here are my problems
-Would like to put an IFS in..hence need a new oil pan for 270 along with a rear oil pickup. Know where I can get one at?
-Motor Mounts?...Have seen Classic Pickup do a very 1-off v-type engine mounts for a 6...anyone have experience or suggestions they can shed? Basically 1st step in the IFS install is to cut off the old cross member and throw it out.

Any help or guidance would be greatly appreciated. I'm really trying to go the distance to keep the I6 rather than a junky V.

Thanks!
Ben

Oil pans are pretty limited in the configurations offered for the GMC 6 . . . the 270 and 302 share nearly everything in common except piston diameter and head. 270 heads don't flow as well but flow well enough to make decent power.

Motor mounts will require some fabrication - and once you figure out the cross member for an IFS - the oil pan will also likely require sectioning / better brush up on your sheet metal fab / welding skills.

I've found that many more people can weld sheet metal than can design oil pans. I can't weld, but pan design is not as bad as it looks until you get into G forces and dry sumps.
Try to get the best dimensions for what interferes (X-member, tie rod, etc.), and at least 1/2" for engine movement in the mount (an another 1/2" minimum for error).
Next, rather than try to explain to the welder "I need this wall moved back to here, and a dent like this", I try to visualize what geometric shape (especially a cylinder, half-cylinder, and "dome") would correct the problem if it were inserted. Avoid using any shapes with corners or angles if possible
I cut it to slightly oversize, and identify with a china marker etc. both inside and out including "#1", "bottom", "UP" arrows, clean and de-burr. Then, mark the pan both inside and out with "#1" etc. for location.
A tie rod sometimes looks like a big problem, but can be passed right through the pan (assuming it's safe inside) by adding a hollow tube welded at both sides. The tie rod is installed in the tube before the pan goes up.
An X-member underneath is sometimes fixed with a really big tube cut in half lengthwise, and sunk into the pan bottom with the open end down. Pick a tube with 2-4" larger OD than the X-member width (front to back).
If your oil capacity goes down, move the sump area down by adding a sump cut off another pan (need not be the same type).
Remember to re-calibrate the dipstick. What's important isn't how much oil there is, but where the oil is when it safely covers the pickup by the same amount as original.

One problem with the GMC pan is the oil pickup is in the middle of the pan. On my dragster 302 I fabricated a new pickup and placed it at the back of the pan. It took some fabrication but I used common sense and some head scratching and it wasn't difficult at all.

The military pans have a much deeper sump if the extra capacity is needed. I have a friend with one of these pans if you need it.

I eventually went to an external oil pump (BB Chrysler) driven off the front of the engine with a Gilmer belt. Works great and confuses people when they look at it.

Ron

I've heard about the military pans, but have never seen one. The most common IFS 6 pan I see has a half moon shape cutout just where the cross member clears.

Are the military pans more like a traditional one? ie low clearance and then a deep well in the rear. From what I have gathered fabricating a new tube to relocate the pickup to the rear isn't too terribly difficult.

Does anyone have a picture of the military style pans?

Thanks!

Moving the pick-up is what it looks like:
1. new tube enters the pump body straight on (no bend right at the entry)
2. same tube ID or larger as original
3. clears counterweights, rod path etc.
4. positive attachment for the pick-up head to the block, main cap, pan wall, etc. if possible (don't "hang" it on the pump unless you have to)
5. use the original pick-up head and screen, or larger
6. pick-up bottom is 1/4" to 3/8" above the pan floor

Keep the straight axle and you don't have to mess with any of it. There is nothing wrong with a straight axle that new king pins won't fix.

Well, it's no worse than other beam axles, but a 1-wheel bump still disturbs camber on both wheels (IFS geometry attempts to improve camber on bump, and leave the opposite wheel unaffected). It also has considerably higher unsprung weight, so the ride quality for the same degree of control is worse, and it needs somewhat stiffer shocks.

Cletis has a point - I have logged 12,000+ miles on my truck over the last two years - one jaunt across the US and back all on a semi-stock straight axle. I put needle bearing king pins in along with radial tires. With the warmed up 270 it kept up with traffic and had no problems running all day long at 65 - 70 mph on the interstate.

I have designed and built a disk brake kit that bolts to the stock spindles and allows you to run stock rims - add an after market sway bar and you have a great handling truck that looks stock to the uninitiated.

Here is a photo of the mock up in the shop vise.



I have done IFS conversions on trucks with repowering with a V8 - it is a relatively easy deal.

Putting an IFS into a truck and then wanting a 270 - you are going to have to be a good fabricator and know what you are doing - it will be doable, but the level of difficulty goes way up.

Personally - I am happy with the stock straight axle with a couple of minor modifications - drives nice, steering is light and tight and looks stock.

If all driving is on a well-paved, flat road the front suspension type almost doesn't matter. You don't need any suspension at all to drive on a pool table.
Unfortunately, most of that good feeling is gone after 5 minutes on a washboard.

what was I thinking . . . I guess trucks can't handle washboard roads.



Hills are out, cobble stones too . . .



Pool tables only!




Drop a V8 in it - you'll get cheaper, faster, easier results.

Since you want to pursue this, compared to IFS a beam axle has hundreds of lbs. less weight on the front tires after each rebound, and hundreds more after each bump on a rippled surface.
What do you think that does to steering and braking?
Try touching the shock body after 30 minutes of that road, and see if the paint is burned off yet.

If they work so well, why don't passenger cars use them for the last 70 years?

I looked at going with a dropped front axle (~3") but I ran into several problems there too. My truck is a 150 series..(ie 3/4 ton). I can find the axle easy enough but then finding new 1/2 ton spindles and then custom forging the steering links appeared a little daunting as well.

In any event, if your shocks are getting that hot to burn off paint I would say that you need heavier coil or leaf springs.

Keeping the 270 in and dropping in the IFS is what would set this tuck apart, in my opinion at least. How many shows have you seen this combo: 57' GMC 150 series, original rebuilt 270, and an IFS with all around disc. Odds are you rare you have seen a 55-59 pickup with an IFS and the 270..let alone it being a 57'gmc (arguably one of the rarer tucks to find now from that time period)

I have decent welding skills and can fab some sheet metal, but to do the job right I think I would need a true fabricator to modify the oil pan.

Memphis Equipment Company ( http://www.memphisequipment.com/ ) can probably provide a NOS military 302 oil pan and pickup. They used to publish a printed parts book that illustrated these pieces. You can find used pans and pickups available. i have one and so do others in this forum. The rear sump is deeeeep, but if the front of the pan clears your suspension, then the sump could be modified relatively easily in a truck.

i never encountered a problem with a beam axle at speed until about 40 years ago when i owned a 1937 Chevrolet pickup that wanted a GMC but had a 348 big-block. We had a lot of labor to overcome "shimmy" at 55-60 mph in that truck, no matter how smooth the road. Cranking in the caster would stop it, but then the truck would not pass state inspection. On the other hand, many people over many years have driven beam axles at high speed on rough surfaces at the dry lakes. i am generally suspicious of most IFS conversions, especially when they replace an older IFS in a 1950s Chevrolet, which is the same as an early Corvette. i do not doubt that a beam axle under a truck can be made to handle relatively well and safely. i'll have an opportunity to test that theory when the new engine and overdrive are installed in my 1949 Studebaker 2R10.

God's Peace to you.

d
Inliner #1450

Shawley, what IFS are you considering?

It might help to know that for more accurate suggestions.

One of the strongest arguments in favor of the beam is that GM already did all the work - can't be too bad, and whatever it's doing is easy to diagnose. To improve: lightest wheels and tires you can find, and the lightest spring that never bottoms (or crashes the bumpers). If this lower the front too much, use a longer but smaller diameter spring.

An IFS can be installed wrong many different ways.
1. if the wheelbases don't match, or the IFS is not installed with the axle center in the same position, the Ackerman is wrong (an inch or 2 is harmless, a foot affects long speed turning and inside tire scrub)
2. the chances of weight distribution being the same between the donor and the Chevy are not great, which means the donor sway bar is not the optimum rate
3. chances of inheriting some bump steer is fair to good, and should be fixed (typically by moving something up/down)
4. for best alignment and tire life, use the donor wheel offset and tire OD to remove some variables

If the shock gets too hot (the paint shouldn't really burn off - but does happen to race bikes), stiffening the spring will reduce this by reducing travel - at the expense of ride quality and making the chattering worse. The cure is to reduce the unsprung weight, or increase the shock capacity (typically larger diameter).

Most older beam-axle pickups -- like my Studebaker and the '37 Chevy i once had -- mount the axle on two stout leaf springs. Does this increase the likelihood of "shimmy" at speed?

My Studebaker came with 6.50 x 16 bias-ply tires mounted on split rims. i'd like to mount radials if i could find some modern wheels (infinitely lighter!) that match up with my six-lug, 14-inch drums. That in itself should be a huge improvement in handling.

God's Peace to you.

d
Inliner #1450

Shimmy means something is loose, zero toe, or both.

I'm thinking of going with Fatmans IFS. I think they are just about the highest price, but from what I can tell they'll really work with you to help make sure that they design it correctly for your install, rather than buying a more popular mass produced one.

Anyone have any better recommendations?

I've used a Fatman kit in my 45 for 7 years with no problems and a whole bunch of miles, if you want to drop your 3/4 ton axle give Sid a call or visit his web site http://www.droppedaxles.com/ , I;ve got a 4" drop he did for me on my '46 flatmotored Ford PU.

Don, I have been thinking about drilling the rivets out of the 16's that came on my '50 Jimmy and having the centers from my wheels installed in some new rims (hoops).

That would ensure the new wheels would fit, and take whatever 16" tubeless tiere I could want.

But I want to convert to discs so I have to find out if those centers will clear the calipers (later model 1/2 ton Chevy van IIRC).

Some of the wheel shops do that kind of work, likely more now with the economy the way it is.

Hope that's usefull.

Thank you, Erik, for that suggestion. It's certainly a question to ask, and it's a compromise that might work to mount radials.

Some years ago, when i wanted to widen the stock rims on my '52 Chevrolet two-door, no wheel shop in Indianapolis wanted the job. Finally a race car fabricator referred me to a former employee who did the work, and it has turned out well.

i have a small fortune in the 16-inch bias plies on my pickup, and i'd still like to mount those wheels to "show" the truck, which is still almost "original," at least in outward appearance. Yet i should hope to find a lighter, modern wheel that would mount on those 14-inch drums with radial tires for driving the truck.

God's Peace to you.

d
Inliner #1450

I am running stock 16 inch rims on my GMC - with tubeless BF Goodrich Commercial T/A's from Costco (no tubes).

I had the rims sandblasted and powder coated and they sealed up fine.

I also came up with a late model GM 4x4 rotor and made my own caliper brackets and with a little time on the rotors in the lathe, I was able to get brakes that perform very well.

see photo above . . .

The tires now have 12,000 miles on them and I have rotated them a few times but have only had to top the pressure up once in 2 years.

The brake rotors were turned down 1/4" on the radius and then standard GM Truck calipers worked just fine.



You can click on the photo for the whole story . . .

I also put a dual chamber master cylinder on my truck and the rear axle has Bendix style brakes . . .

WOW Ken those Pics of all the work you've done is really nice! I just wish I had access to the lathe and water jet to play with!

Yes Ken, Nice job!
As far as using newer GM 16" outers with old GM 16" centers. They don't fit. The centers are too small. I ended up cutting the outsides off the old 16s leaving the riveted section on the center. Then we turned it down to fit the new outer. They came out fine but I really didn't like the look so I gave them away. Here' a picture. The fronts are 15s. The rears are the ones I made. Also Cokers don't loke dirt roads. Beater

Beater, I was thinking of using aftermarket hoops.

There is a shop that frequents the HAMB (guy goes by Wheelkid IIRC) that does that sort of work.

Theres a tech article over there too that shows what lengths they go to, so you get a striaght and true wheel.

I don't recall where it is though. (the HAMB is kind of a big place to search)

If you can find an AMC Pacer front end, they are easy to install and will clear the stock pan. Joe

Speaking of front ends, I once had a'56 Chevy half ton pickup with a .060 over "Corvetteed" 261 and a stock front end. It drove terrible, if you stepped on the brake at an intersection, you would never know in which lane it would land! I adjusted the brakes, put in new kingpins,shackle bushings, caster shims, tightened the tierods, had the toe adjusted, even found a new drag link at the local Chevy house-nothing helped much. Finally when I went to sell it, I swapped my offset chrome wheels for my bro-in-law's '57 half ton stockers, and it drove like a Caddy! (WTH?) The chrome wheels had an offset that altered the Kingpin/Wheel Centerline Intersection Point. That is when viewed from the front, if you draw a line thru the kingpin, and another thru the centerline of the wheel you find that they will intersect some where, either above the road surface or below it.
What you want is for this point to be AT, or close the road surface. Mine was way below, this allowed any road bump or ridge to have a mechanical advantage and allow the wheel to be pushed back (thus pivoting backward about the kingpin) changing the"aim" of that wheel, (and with the tierod dutifully doing its job by making the other wheel do the same) it would cause the truck to take off in a new (and usually not desired) direction. Looking back, I could have had the desired good looking chrome wheel look and good driving manners if I had less offset OR a less diameter tire. The biggest part of wanting to get rid of the truck was its evil wandering ways (and a short wide '67 chevy I had my eye on). Just something to watchout for.

very nice work ken! while I won't argue about whether straight axles or independent front ends are best, I will go so far as to say a straight axle will handle much better than most people realize with the addition of a sway bar. I was really surprised at the difference it made on my truck. was even more surprised when I put one on the back too. I'm guessing further improvement will come when shocks are added to the back. I live on a twisty, curvy, crooked mountain road & it's amazing to me the cuves I can take at 60 & 65 now & my truck is a 1 ton sitting rather high in the air.