# Should I replace engine?



## beer guy (Oct 22, 2014)

Folks
I am buying a pretty decent 66 GTO and it looks alright except....the original engine and tranny are long gone. Instead there is a 350 from a 74 Firebird with a leaking seal at the tranny. Not sure which tranny but I am guessing from the Firebird as well. So aside from fixing the leak with a new gasket should I keep or source a new engine???? Thx


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## ppurfield001 (Jan 21, 2008)

beer guy said:


> Folks
> I am buying a pretty decent 66 GTO and it looks alright except....the original engine and tranny are long gone. Instead there is a 350 from a 74 Firebird with a leaking seal at the tranny. Not sure which tranny but I am guessing from the Firebird as well. So aside from fixing the leak with a new gasket should I keep or source a new engine???? Thx


Depends on what you want. Since the car doesn't have a "numbers matching" engine and transmission, you may want to simply repair what's already in the car to make it a nice "driver quality" car. Or you might want to take it further as I did with a "date correct" engine, updated 5-speed manual transmission with overdrive, disc brakes, coil-over shocks, better sway bars, 2005 GTO bucket seats, or anything in between. Up to you. To me the most important thing is that the car is what you want so that you can enjoy it.


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## geeteeohguy (Feb 2, 2008)

X2. Me, I'd go for a 389 that was year-appropriate. No more expensive to rebuild than the 350, and way cooler sounding and more power, as well. Or, even easier, a 400 based engine. Up to you, though.


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## eeyore (Oct 23, 2014)

If drivable, I would evaluate the car for two weeks and list all that will be needed. Brakes, suspension, Interior, body, electrical, heater.. Then prioritize.


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## rickm (Feb 8, 2012)

not rankin on your car, but its gonna start buggin ya havin that motor. your gonna change it sometime in the future if you keep the car. good luck with it.


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## PontiacJim (Dec 29, 2012)

I have to mirror what has already been said. It really boils down to what you want to do. The 350CI is fine if your looking for a nice cruising engine. The 1974 350 is rated at either 155HP or 170HP and both with pump gas friendly 7.6 compression. Remember that HP ratings were changed in 1971 to reflect net HP versus the 1970 and earlier gross HP numbers. For comparison, the 1974 400CI was rated at 190HP to 225HP having 8.0 compression.

You can bump up the horsepower of the 350CI if you chose to do so. Bigger cubes with a Pontiac = more torque @ lower RPM's. The 350/389/400 all share the same 3.75" crank stroke, with the difference in larger cylinder bores. The 389/400CI would give you more HP & torque in stock form (as you can see above), but you could easily build up the 350CI to get the same numbers if you decided to.

The Pontiac engines are all the same dimensionally, so you could dress up the 350CI to look like the 389CI to include the 3x2 set-up if you wanted to build a higher HP 350CI engine and go that route.

The 400CI is probably your best route and bang for the buck if you're not into having a correct 389/year engine. Probably the most reasonable to rebuild as well.:thumbsup:


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## dan woodland (Jul 24, 2013)

I agree with eeyore and geeteeoh guy... I'd drive it for a bit and take note of all the things you see "wrong" then decide what to do with the car as a whole. 

Basically keep it long enough for the pedals to fall off the flower and evaluate it with regular glasses on... then you can decide to "do only what is needed" or go "all the way" etc. You should also keep in mind if you are a OE or resto-mod guy.



eeyore said:


> If drivable, I would evaluate the car for two weeks and list all that will be needed. Brakes, suspension, Interior, body, electrical, heater.. Then prioritize.


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## beer guy (Oct 22, 2014)

*I think I want more power*

Does a 389 have enough power to push me back in the seat? What about the 400? Also, are 389s hard to come by?
Thanks so much.
I have always had moderately powerful cars and while I don't want some drive shaft twister I do want something that will spin the rubber. At the same time I would like to hold true to the era of this car.
Am I nuts?


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## RunninLeMans (Apr 3, 2014)

I know these are not custom crate engines, but has anyone ever tried these guys:

Pontiac Remanufactured Engines


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## geeteeohguy (Feb 2, 2008)

A 389 will rip your head off. So will a 400. 'Big car' 389's are not hard to find, at least in my neck of the woods.


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## beer guy (Oct 22, 2014)

*I like the sound of that*

Having your head ripped off! I spoke to my engine guy today and he is going to start looking for a 389!
Thanks to all!


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## 666bbl (Apr 13, 2014)

Since it may never be a "numbers" car I'd go big. Dump a 455 in there and never look back. Like the 389s and 400s, the mundane version of a 455 will still yank those nasty feral trees out of your yard without a chain saw! Ok, maybe not but there's that golden rule: "No replacement for displacement." Just sayin...


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## geeteeohguy (Feb 2, 2008)

A 389 or 400 can be sourced more cheaply than a 455, and with the 3" main crank journals, is a stronger, more durable engine than the 455. The 455 will put out more power at lower rpm and makes a great street engine. Better than a stock 389 or 400. That said, better still, is a stroker crank in a 389 or 400, which will yield big inches, big power, and a more durable bottom end than the big-journal 455 engine. Stroker kits are not really expensive, and yield huge gains in usable power on the street in a very durable, street-friendly package. If I were building a new engine for one of mine, that's the route I'd go: stock/correct block with more displacement. Look at Bear's build for inspiration. 500 streetable HP with a born-with 400 block, now stroked to 461 CID.


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## beer guy (Oct 22, 2014)

*400 or 389*

I have been reading some conflicting articles. Some say the 66 had only the 389 but others say it had an optional 400. Which is accurate? Also, what type of tranny would be best with either engine? I believe the car originally had a 3 speed auto but as I said earlier that has been long gone. Thoughts?


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## geeteeohguy (Feb 2, 2008)

66 GTO: 389 only. The 400 didn't come out until the next year. 66 GTO: Two speed Super Turbine 300 transmission. Gear ratios: 1.76:1 low, 1:1 high. Strong, durable, and useless in a performance car. No '66 GTO's came with a three speed auto. That too, had to wait until 1967.


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## PontiacJim (Dec 29, 2012)

X2 with geeteeohguy on this one. It has been covered here many times. The 400 CI stoker kit (461 CI) is the best bang for your buck because you get a complete rotating assembly -balanced. New crank, rods, pistons, rings & bearings. You cannot beat the $1,498 price tag over at Butler Performance Butler Performance - Pontiac Engine & Rotating Assembly Combinations - Featuring Eagle Pontiac Kits

Other Pontiac builders and Pontiac suppliers also offer these kits at different prices. They also offer kits for the 389CI, but higher priced. 400 CI may be easier to find, but you want an earlier block as the later Pontiac blocks(as I recall 1975 & up) were made thinner and weaker. You get more torque and power out of bigger cubes and don't have to go wild on a camshaft to get something respectable in power, ie tire smoke. You can go big, but driveability may suffer, so bigger cubes with a moderate cam spec gives you the best of both worlds -my opinion. Do some searching through the threads and you should find more info on engine choices and builds. Put together a build and price list to see what you are getting into before buy anything, then you can adjust your plan as needed.

If you go automatic, the standard behind the 1967 HP Pontiacs & up is the TH-400 3 speed auto. Not to expensive to find and rebuild using good parts/shift kit/converter to work with your engine. You can buy it outright fairly reasonable or have your local shop build it. Better still is a modern OD automatic, but can become costly. Advantage is the gear ratios and the overdrive for highway cruising.


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## beer guy (Oct 22, 2014)

*tranny*

Currently, it has the 400 tranny as I found out today. I am going to check this Butler Performance out. Thanks one and all.


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## Goat Roper (Oct 28, 2014)

RunninLeMans said:


> I know these are not custom crate engines, but has anyone ever tried these guys:
> 
> Pontiac Remanufactured Engines


I am going to call them tomorrow.

My car is parts matching so I want the original motor rebuilt.
When I bought it the top end and timing chain was redone, I don't know about the cam, lifters etc.
When I start the car it runs great and even when it is warmed up it runs good and doesn't smoke.
The problem is when it is cold I get 55 lbs of oil pressure @ idle but once it hit operating temp that drops to 18-20.
It leaks at the rear main and I am sure the crank bearings are gone.

it is a 400 335 HP and I am going to have it bumped up to 360 HP.
I will pull the engine and deliver it to him in LV, the prima donna builder here quoted me 7K and told me he is booked up and to call him in Nov. so I called and he said call him again in Feb.
Screw that, the car runs good enough for around town but no way I would take it on a longer trip.
I can't seem to find a builder here in So Cal so I will see what he says.
I would rather get it done before it blows.
The only other guy I found was this builder, not really what I am looking for and I don't want to ship this engine.

pontiac crate engines


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## PontiacJim (Dec 29, 2012)

Goat Roper said:


> I am going to call them tomorrow.
> 
> The problem is when it is cold I get 55 lbs of oil pressure @ idle but once it hit operating temp that drops to 18-20.
> It leaks at the rear main and I am sure the crank bearings are gone.
> ...


FYI -I don't see a problem with your oil pressure, 55 cold idle and dropping to 18-20 hot idle seems Ok to me. Pontiac rates their maximum oil pressure around 2,500-2,600 RPM's hot. So if you are coming up with 55-60 PSI @ 2500-2600 RPM's, your pump should be good.

Leaking seal -need to pull the engine to fix that one. You are sure it is not the rear pan seal?


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## Goat Roper (Oct 28, 2014)

PontiacJim said:


> FYI -I don't see a problem with your oil pressure, 55 cold idle and dropping to 18-20 hot idle seems Ok to me. Pontiac rates their maximum oil pressure around 2,500-2,600 RPM's hot. So if you are coming up with 55-60 PSI @ 2500-2600 RPM's, your pump should be good.
> 
> Leaking seal -need to pull the engine to fix that one. You are sure it is not the rear pan seal?


I worked on the car today and found the noise the mechanic told me was the wrist pin knocking, one of the three nuts on the exhaust manifold was missing and the other two were loose.
I replaced the nut and tightened both sides and the noise went away.

I also talked to the motor builder and he said pretty much what Jim is saying about the oil pressure that this is normal for a Pontiac and it didn't sound to him like I need a motor so good guy he didn't try to sell me something he felt I didn't need yet.
He also told me to check the manifold nuts and sure enough he was right.
No noise at all from the valve train so it is getting plenty of oil.
My friend who is an ASE mechanic came up from LA today and bumped the idle up so now the V meter stays at 13.5 and the oil pressure is now 25 hot @ idle.
We took it around the lake and I opened it up he said there isn't a damn thing wrong with the engine and just to drive it.
I will go with Pontiac Jim and the two other opinions and disregard what the other mechanic told me.
I guess if it will break the tire loose upshifting into second the compression is just fine, I haven't punched it since I have had it worrying about the "knocking rod" and blowing it up. :/
If I get on it the oil pressure goes up to 55 and it stays at 35-40 just cruising and now with the idle bumped up it is at 23-27 hot.


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## 666bbl (Apr 13, 2014)

There's a replacement rubber seal for the rear main. You don't have to tear it down to do it but it's still a notably big job. If you do it you need to remember an old trick. "Clock" the seal about 1/4" so 1 side is below the parting line and the other above. Do the same on the cap, opposite of the block. What this does is remove the parting line in the seal away from the parting line of the rod cap, and the cap and block now "sees" a solid seal. It works like a charm. Just be sure to put the seal in the correct direction and forget about leaks for the next 20+ years.


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## Goat Roper (Oct 28, 2014)

The guy I bought the car from had 0-20 wt synthetic oil in it and I am now on my 3rd oil change to flush it out.
It now has 10-40 in it with ZDDP.
After going over the pan bolts and snugging them up I looked this morning after driving it and there was two drops of oil under it so for now I think I can live with it.
Pretty sure it was just the pan that and the oil line fitting going to the gauge had oil on it and I tightened that fitting as well.
I plan on going up to Big Bear today and putting some miles on it, part of the problem I think is it has been a garage queen since '08 and it needs to be driven.


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## PontiacJim (Dec 29, 2012)

Ya, buddy! Sometimes you just gotta crawl on the creeper and do some investigating hands on. I like to always get a few opinions before I do anything major, because it can at times prove to be something that was a simpler fix or repair -whether old car or new. 

My '97 Toyota was pushing oil into the radiator. No water in the oil at all. Strange. Car ran great. Radiator would literally fill very slowly over a month or so with oil until it came out the radiator overflow hose -that's how I caught it. Flushed the system, refilled with coolant, and about 1 month later, same thing. Being aluminum head on an iron block and me just firing the car up cold in winter and blasting down the road is not a good recipe for that combo -gotta let it warm up. Brought it to my mechanic and they said, hmmm, no water in the oil, cracked block. I never overheated it and always maintain it. So I didn't think so and my experiences with head gaskets told me different(and blocks just don't crack for no reason). They talked with "other" mechanics they knew and all said the same. It wasn't trans fluid, and the radiator was new. With high miles and old age, they said they didn't want to take my money and find a cracked block. I told them I'll pay them either way, pull the head. They did. No cracked block. What they found was a break in the head gasket around the oil pressure hole that goes to the head. That hole was about 1/16"-1/4" right next to the water passage in the block. The oil pressure was overcoming the water pressure in the system and bleeding right into the water without any water pressurizing into the small oil passage. Had the head milled, new head gasket, and am still driving it a year later. Got a lot of apologies from the mechanics and owner on that one. They said it was the first time they have ever seen anything like it in all the cars they do work on. If I had listened to them, I would have scrapped a perfectly good commuter car and had to $purchase another car to replace it. 

I don't know everything by a long shot and the more I learn, the more I realize the less I know. I have years of "tinkering" with cars namely due to never having the finances to send it to a shop and often I didn't really know what I was doing, but am pretty savvy mechanically and can tear something apart, study it, and figure it out. I also rely heavily upon shop & repair manuals, tech books, others experiences, some luck, a lot of cursing -and the occasional prayer while cursing.:lol: You also need the correct tools. But once you have been around cars for a while, the same principals can apply to other situations or cars. I can't say enough about the internet and Youtube as it too has bailed me out on working on these newer cars -when I do work on them. I've gotten a little better financially equipped so I can actually drop my car off at a shop instead of wrap myself up in long underwear, heavy coat, gloves, and use the heat from a drop light to thaw out my blue fingers!:smile2: When you haven't the money, you find a way to get 'er done and now that I do have the money, I've become cheap and still find a way to get it done.:lol: Go figure.


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## Goat Roper (Oct 28, 2014)

Yeah, I had listened to the first mechanic and he told me he wouldn't drive it until I had the motor rebuilt.
Better safe than sorry and I have been babying it until I got some more input.
I should have noticed the nut missing on the exhaust when I lifted the motor to replace the tranny lines it was right there in my face. :/

I put almost 100 miles on it today, this car sure loves it's fuel!
Now that the motor problem is solved and I have the suspension and brakes done all I have to do is drive it.
Well that and take it down next week to get the pinstriping done.
Since it has the black vinyl top I am going with black.


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