1995 GMC 350 swap to a 1968 327

Hi All, Could anyone tell me what I should know about taking a 350 engine from a 1995 GMC Sierra 4x4 and install a 327 in its place? What I would like to do is still run all systems connected to the computer and install them on the 327. Is this possible? And will it bolt up to the 4L60E transmission that is in the truck? I guess I just need alot of guidance through this. I have restored many autos and rebuilt many engines so I know all the basics involved. The reason for the swap is that the 350 is pumping coolant into the block. Thank You To All That reply, Desperate and on a Tight budget,


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The cam needs to be computer compatible. If the 327 is high compression, the knock sensor will retard hell out of the engine and performance can suffer from not enough ignition advance.

The intakes have different mounting holes. If it's a TBI, there are aftermarket intakes that'll work, or use an adapter to put the TBI onto an older-style 4-bbl. intake.

To have any chance of using the 327 heads, they need to have accessory bolt holes.

If you have no accessory holes in the heads, you could either get later heads, like Vortec's (would need an intake manifold) or use the 350 engine's heads on the 327. This would take care of any issues with CR, and then some.

If you have EFI that isn't TBI, you will need the 350 heads and entire EFI system to keep the computer happy. Then there may also be issues if the crank position sensor is taken off of the crank at the timing cover- then things can get interesting.

You may run into sensors located in the block and/or heads that might have a different tap size.

Ok, Thank you for that info (gives me alot to check) With all that in mind then will it bolt up to the 4L60E transmission?

Sure will.

Ok, I'll check everything and see what I come up with. If you want I will keep you informed about my progress and if it would be OK I probably will have more questions to ask would it be Ok to ask you again?. Thank You Again

If you're on a tight budget, it would be better to use the 350 from 87 to 95.
You're headed for 3 problems 1 easy, 1 medium, and 1 fairly pricey.

1.a.) easy; changing from the one piece rear seal 350 to the 2 piece rear seal 327 will require the 327's flexplate to match the balance and bolt pattern requirements of the 327's crankshaft.

1.b.) The 327 v-belt water pump a nd fan turns opposite to the 350's serpentine belt pump pump and fan. Which ever system you put on the 327 has to have water pump and fan that is compatible with the belt system used.

2.) medium; the 327 heads will not easily bolt to the TBI intake. The center 4 bolts are at a different angle than those of the 327 heads. This can be cobbled together by egging the holes to force an angle change which then requires the mating surface between the manifold and bolt head be spot faced to provide a flat and parallel mating surface. Easy solution would be to use the 350 heads.

3,) pricey; TBI doesn't take kindly to changes that affect mass flow and vacuum settings against throttle position. At best it can adjust for a +/-5% change using the O2 sensor to adjust the fuel mixture. But assuming the cam timing and compression of the 327 are very close to those of the 350 you've already got a 7% change in displacement which is a 7% change in mass flow. thru the engine. This quickly gets into a new chip with a new program that understands the changes, these are about 3 to 4 hundred dollars and requires you to find and open the computer to replace the chip which is easily damaged in the R&R process if your not familiar with clomping around inside computers. (TBI and some TPI systems compute Mass Flow rather than measure it as some TPI systems do. To do this the computer is expecting sensor data of Manifold Absolute Pressure, RPMs, and throttle position to be in a very tight zone with respect to each other. It takes this data to compute a number that represents a position on a fuel and timing map. The computer goes to that site gets the data and tells the injectors how long to be on and the distributor what advance to use. When the sensor data relations get changed by much, the computed look-up value is different from the characteristics of that point on the maps vis-a vis how the engine is actually operating. So the computer delivers an incorrect signal for fuel delivery and ignition timing. A new chip is needed that corrects the sensor relationships to the fuel and ignition maps.)

If I were you I take the KISS approach and either hunt down an 87-95 350 new or rebuilt short block and rebuild your heads. Or find an 87-95 new or rebuilt long block and swap out the existing motor. Many places will take your old block and or heads for rebuild cores which will put some change back in your pocket.

Bogie

OK, WoW, Is there a way of using the computer with the transmission and not the engine? Or doesn't the transmission depend on the computer?

transmission has a few functions that are controlled by the ECM or PCM yes. it is a 4L60E, E is for Electronic

howcome you want to put such an old engine in a 95 ?

going to be so much $ and modifications and so much more.

interesting.


good luck

Transmission needs the computer and engine sensor data for shift points and the speedometer needs the computer to resolve electronic data from the transmission back to the electronic speedometer which looks mechanical but isn't. These functions can be separated, but again it's costly. You've either got to buy the stand alone electronics or tear everything out including the transmission and dash and go back to mechanical systems.

Which is why, if your on budget and the TBI works, then just go get a freshened TBI 350, it's so much simpler and less expensive than even trying to get a free 327 to run properly without a custom chip.

We see a lot of people on this forum inquiring about why these kind of swaps have problems, they of course communicate after they've made and executed decisions that now are having problems. By asking first, you're on the way to head off these problems before they exist.

Anything is doable in swapping things around but these more modern vehicles with lots of computer systems can become very expensive when you try to back date them. The later OBD I systems, say starting in 91-92, are heading in complexity toward the mandated OBD II systems of 1996 to the present. The 95 GM trucks in particular are a foot and half into that pool and are tough to back date without lots of experience and cash.

Bogie

I personally put a 229 in place of a 4.3L in a '94 TBI GMC 1/2 ton pick up.

In that swap, I encountered zero problems with the PCM/engine management systems. The tranny is an optional TH400- it was a fleet vehicle from the local electrical co-op.

That swap amounts to a 14-ish % difference in displacement. Idle, response and cruise are as they were, pre-swap. I used all the exact same sensors that were OE to the 4.3L engine- I changed absolutely nothing in that regard.

I still own and drive the truck- have about 15K miles on it since the engines were changed. Used it 2 weeks after the swap to trailer my '81 Camaro to Atlanta from Orlando. Ran great, mileage was another story.

Now I'm not saying this will be the OP's experience- too much apples to oranges? Or maybe not.

But this is my experience.

I am asking questions before it really creates more problems than it would be worth. The 327 is not a free motor, it is one that I personally rebuilt a while back but is still as fresh as the day I completed it. I will never be too proud not to ask questions before I jump into unknown territory. That is why I first ask questions before I leap. Thanks To All that have replied, Definitely opened my eyes to how bad Detroit has crippled Small Guys and their ability to possibly make a motor run a little better or unleash a lot of unused horsepower without breaking the bank. Again, Thank You All For Your insight and expertise, it has been greatly appreciated

*Might make that Washington...

That makes it what we'd call a "sunk cost" motor, you have it and it's been paid for but it isn't paying its way yet.

Actually all Detroit did is respond to government mandates for both pollution reduction and mileage improvements. You get both with these modern systems but at a cost not only financially but in orders of difficulty. The modern vehicle has moved from an assemblage of distinct parts to an integrated system. And this is a world wide thing, all the industrial nations have, or are going to, adapt a close form of California and U.S. standards with some twists of their own. Our rules are nothing compared to Japan where you must replace the power plant and it's systems every 50,000 miles or scrap the vehicle. This is where the huge supply of low mileage Japanese replacement engines comes from here in the U.S. In Europe controls include how far you must go between oil changes, and trust me it ain't 3000 miles. They also mandate how many miles you must get on a set of tires without paying a fine, needless to say no-one except the rich do burn-outs. All this is coming here, its just a question of "when" not "if". Welcome to the new crowded world where fewer resources will be stretched over larger populations. Nations and cities around the world are preparing for the demise of the automobile and suburbia along with it. I figure it was estimated as a 50 year proposition that started in the 1970s so were over halfway through to where it was planned that most everybody would be living as they do in Manhattan. However, in a democracy it takes longer to achieve goals if you can't get the population to buy in. For example, here in Washington state the government was making up their own values for cars (much higher than Blue Book) and taxing accordingly. Before Tim Eyman came along with his initiative to force 30 dollar a year tags, new cars such as my wife's previous Mazda 6 was costing 900 dollars a year to license. You don't think for one minute that the government was using its taxing authority to force people out of their cars as much as they're using it today to force an end to tobacco smoking. The problem governments have, especially here in Populist states is that pesking voter initiative process slows their objectives down. So our legislature and governor are trying to find a way around it, which takes two forms one is to ignore voter mandates and the other to strip voters of the initiative process or at least limit it to non-financial matters. What ever that means?

OK off the soap box and back to engines.

Bogie