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fudggj
07-11-2006, 02:14 PM
Greetings to all...
I am building an 84 Chevy C10 short bed to drive yearly from Ohio to Florida. Not going to haul much other than a few suitcases, hand tools, and fishing poles - no heavy towing. Looking to get reliability and decent gas mileage. Considering engine swap. Have excellent, strong, low mi, 305 from '86 Pontiac Grand Prix (GP). The '84 C10 came with 305, automatic 3 speed, and 2.73 gears - but now has early 350 of unknown quality. Question is: "Will the '86 GP 305 bolt up to the '84 C10's stock transmission, motor mounts, and exhaust manifolds?" Has anyone made this or a similar swap? ('88 Hollander manual does not show this as a "complete engine" interchange.)
Thanks for interest and replies.
fudggj

85-bowtie
07-11-2006, 02:20 PM
I think that Chevy has a different bolt pattern for the transmission than Pontiac, but I don't know about the motor mounts.

twinturboc10
07-11-2006, 04:08 PM
Everything should bolt right up to the 305 from the 350. The 1986 305 should be a corporate chevy engine, not Pontiac.

nic
07-11-2006, 05:19 PM
It's true, the Pontiac GP 305 for 1986 had the same 3.75 bore and 3.48 stroke as the other 305's...

It's personal preference, but I wouldn't waste my time with the Pontiac 305... At best it was 165 hp (new) in a car that weighed only 3,200-3,300 lbs., and they were slow.

If you're going for fuel economy and reliability I'd go with a 4.3 V6 engine. Fairly new Vortec 4.3's go for almost nothing and can be setup with a carb-friendly intake. The V6 would have more power and torque than the 305, while getting better mileage.

RSBAD454
07-11-2006, 05:33 PM
Do not put a 4.3 V6 in a full size truck, you will not net any better MPG and the 4.3 will have to work that much harder. 305 will be fine and add a TBI set up with Megasquirt to make a great traveling combo. Dropping the tailgate down while on the freeway doesn't help fuel mileage either.

hescop
07-12-2006, 12:44 AM
The 305 should be a direct drop-in. Make sure you use the distributor that is currently on your truck. Don't over-carb it either. 600 CFM will be more than adequate.

fudggj
07-12-2006, 01:58 PM
Thanks for all replies thus far - all replies were appreciated. I wonder "Will I have to drill and tap the bosses on the Grand Prix 305 block to accomodate the C-10 truck motor mounts?" (Or are the corporate Chevy 305 blocks predrilled with extra holes at the motor plant to accomodate multiple motor mount applications?)

RSBAD454
07-12-2006, 07:06 PM
Thanks for all replies thus far - all replies were appreciated. I wonder "Will I have to drill and tap the bosses on the Grand Prix 305 block to accomodate the C-10 truck motor mounts?" (Or are the corporate Chevy 305 blocks predrilled with extra holes at the motor plant to accomodate multiple motor mount applications?)


305 should have the standard chevrolet holes on either side of block to mount on various frames.

Euzoa
07-14-2006, 12:36 PM
correct me if i am wrong, but wont it be more work than it is worth to switch from a chevy motor to a ponti? the mounts will be different for one. i would go with a straight 6, plent of power, better fuel economy

Old88
07-14-2006, 08:15 PM
pontiacs of that era used chevy engines

Pete-FWA
07-14-2006, 09:50 PM
Many GM 5.0L engines in the 80s and early 90s were not Chevrolet 305 CID; rather, they were Oldsmobile 5.0L 307 CID.

The easiest way to tell if it's an Oldsmobile engine is to look for the oil fill lid. Is it on a valve cover or in the front of the engine in a stand-alone filler tube sort of setup?

fudggj
07-15-2006, 08:35 AM
For the "305" motor I have, the oil fill is in the valve / rocker arm cover.
Thanks for replies...

vcrazy8
07-15-2006, 05:10 PM
It has the chevy 305

BlackC10
07-15-2006, 07:54 PM
305 - 165HP
262 - 150HP <--- that is the 4.3L V6. My '86 came with that.

The fullsize 4.3L w/ 2.73 gears yielded a max of 19mpg. My truck did very well with that, considering a TH400 was behind it. Pulled that all out in 2000 b/c I ran it hot with a blown head gasket. A direct replacement went in, and I put 49,900 on it before it sat for a year. Those weren't high HP motors, but TQ was a different story.

Personally, 350s are a dime-a-dozen here in La. Not to mention aftermarket is enormous. Good luck with whatever you decide to do.

RSBAD454
07-16-2006, 02:22 PM
For the "305" motor I have, the oil fill is in the valve / rocker arm cover.
Thanks for replies...

by all means, use the 305 then....you'll be happier with the extra 2 cylinders in the heavier truck. Also look into the Holley 2 barrel fuel injection either with the Holley fuel controller or the Megasquirt controller and tune for maximum MPG. My mom's 91 camaro came with a 305 and TBI, engine ran great and netted about 25MPG.

fudggj
07-23-2006, 11:25 AM
Thanks for all replies...found all interesting and were appreciated.
Any thoughts about using the computer (with carb and distributor) system from the 86 Grand Prix (GP)? This is what is currently on engine and was working fine and giving good mileage when the GP donor car was wrecked. Is trying to use these original components with the 305 from the GP going to be more trouble than they're worth if transplanted with the GP's 305 into my 84 Chev C-10?

Troyc20
07-23-2006, 12:04 PM
I know your probably not lookin for loads of power but have you thought of a tuned port? Great low end and mine got great mpg on the highway if i stayed out of the throttle.

82Blaze
07-23-2006, 09:38 PM
I have an 82 2wd Blazer that had a 350/700R4 from a 92 Suburban that I liked. I just finished swaping an LS-1 with all the accessories and a 4L60E auto. I REALLY like this combo much better. It has a ton more horsepower and gets better gas mileage.

hescop
07-25-2006, 12:55 AM
Is trying to use these original components with the 305 from the GP going to be more trouble than they're worth if transplanted with the GP's 305 into my 84 Chev C-10?

Probably.

the silvrod
08-06-2006, 11:32 AM
can i use parts for a 86 305 to a 84 305

VEGAS84
09-01-2006, 02:46 PM
The Chevy 305 and 350 are exactly the same on the outside. Bellhousing pattern, engine mounts, exhaust manifolds, distributor, and accessories all interchange. Intake manifolds are different between centerbolt heads and perimeter bolt heads (valve cover bolts), but they interchange on the same style engine (centerbolt to centerbolt or perimeter to perimeter) reguardless of displacement.