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1968 GT/CS Engine rebuild...go stock or mod?

daveS

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Joined
Jun 21, 2009
Messages
55
Hypotheically speaking, if one were to do a full engine rebuild on a '68 GT/CS, would you opt for a completely stock rebuild (standard head rockers, lifters, valves, cam, crank, pistons, etc)? Or, would you opt to upgrade the inside of the motor with a new rebuild kit, possibly a stroker kit?...roller technology upgrades to the heads?...all of this while keeping motor looking stock from the outside? Would upgrading the internals of the engine devalue the car or would the improved performance and reliability up the value? Any thoughts?
 

CougarCJ

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Jul 17, 2006
Messages
2,186
To me it depends.
If the car has been messed with, and has a common engine, have fun and make the mods. Nearly every modification can be undone.

If you are fortunate to have a low mile, rust free, original paint, garage kept survivor, I probably wouldn't.

I have a friend that installed a 302 crate engine, with 4V intake into a 1967. Most people could not tell that it wasn't stock. Even with an Edelbrock intake with the letters ground off. He used HiPo exhaust, with a stock air cleaner. He called it 'sneaky concours'. Would only pass in peoples choice type judging. LOL
 
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daveS

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Jun 21, 2009
Messages
55
The car is rust free, straight, repainted (color change to another Mustang factory color..not by me), has all the original stuff per the Marti report (except wire wheel covers replaced with GT wheels+caps), unknown mileage, new front suspension parts, new trans, original Selectaire AC...the block, heads, manifolds are all the right date codes and match the car. The carb was replaced with a Holley. There is an aftermarket steering wheel and front grille on the car, but I have the originals. It appears that this car has not been messed with much, if at all. It wasn't obvious that the low end of the motor had even been opened before. The heads have been worked on previously (I have no history of this). The motor was a tired so we're professionally rebuilding it. I want to keep it as stock as possible and definitely looking stock. The car is in great shape but it has been driven (not stored since it was made) and had a few little things done to it over the years. It will turn your head when you see it though. I don't plan on NOT driving the car and having it win concourse, etc. I want to take it out on a nice weekend, some shows and have this car to stay as true to its original form as possible (especially cosemtically), but have some modern technology in the motor that enhances the performance slightly, provides more efficiency, and increases reliability. I certainly don't want to go crazy and devalue the car though. I am on the fence about how far to take the rebuild in terms of rocker technology, stroker kits, etc.
 

Midnight Special

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Joined
Nov 5, 2005
Messages
3,713
Location
Grass Valley, California
...Always a good question, but in the end I hope suggestions help you to develop what you want. All I will say is when the day comes we're all pressured into making trailer queens, the hobby is over far as I'm concerned.

Updated power, handling & excitement to go with those beautiful looks will take you a lot farther in your circles than a handful of purists who usually seek to devalue your efforts over theirs, most often because you're having more fun than they are ;-)

The factory, in 1968 gave us all known options to create our own cars. That was 47 years ago and today, there exists many more to explore. 'That be my thoughts...
 

Mosesatm

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Jan 18, 2005
Messages
9,009
When I looked for California Specials to purchase I immediately disregarded all the cars with strokers, or 'big cams', because I was more interested in reliability than power that may be short lived.
Those items also made me wonder how hard the car had been driven.
 

mbsf1970

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Apr 10, 2013
Messages
795
Location
Calgary Alberta
+1 Midnight.

In my--personal opinion--- I prefer to see cars remain stock. I hold zero il will for anyone wishing to modify their car for personal enjoyment but when I looked for my current car, I moved on from any ad that show mods......its just me though cause mods cause me to wonder what else has been done to the car!!
I understand that almost 50 years is plenty of time to screw up a car and then put it back to stock many times over so seeing "stock" doesn't guarantee anything!! I like discussing my car at shows and relaying to people how stock it is....

In then end though, make it your car-- whatever that means to you.

Stephen
 

p51

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Joined
Aug 2, 2005
Messages
1,025
Location
NorCal
My personal preference is that "the car look 1968 but drive 2008"...

...meaning making mods to non-cosmetic things that improve safety and performance. Such things as: brakes (disc), headrests, metal backseat divider, suspension (for handling improvements), body (subframe connectors), transmission (T5 fun) and engine (some performance upgrades).

I especially think that the safety upgrades (including handling) are worth making if you're planning on driving it. Consider that a lot of the newer cars have faster acceleration, shorter stopping distance, and less road feel and you get a lot of drivers out there who, naturally, drive more aggressively - just because they can. And they have airbags in case they make a mistake.

The only versions I would consider keeping stock (for value/resale reasons) are the rarer big blocks, and then only if they have not already been modified. For the more common versions (eg C and J-code), well they have appreciated since 1968 at slightly above the rate of inflation (~4.5%/year on avg -> ~8x increase) meaning that they have retained their value but are not what I would consider a great investment. In fact if I were looking to buy another GT/CS I would likely pay a slight premium if the mods above were already done.

Bottom line: Given that you're going to rebuild the engine I would upgrade it for slightly more performance than stock (say, 300hp @flywheel). I would also strongly consider making safety mods as well.
 
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daveS

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Jun 21, 2009
Messages
55
Thanks guys...keep those opinions rolling in!

Right now we are leaning towards a mild stroke kit for the engine which includes pistons, rods, crank, cam ,etc. The desire is that we would chose a stroker kit that would not require any mods to the block (if this exists). If we do not go with a stroker kit, we will go with standard low end rebuild and keep it stock. With either of these options, I plan on keeping any and all original parts that I do not reuse.

As for the heads, at the very least as a tier 1 enhancement, I would like to replace the press in studs with tapped/threaded studs. I feel this just makes good sense and is a better way to engineer these stud mounts...the press in fit is mostly a cost saver for production but the thread in studs should be more reliable.

As a 2nd tier mod to the heads, we may do some porting an polishing of the heads.

If we take the heads further, as a tier 3 enhancement, we will go with roller rockers and lifters.

One other thing we have discussed is doing some porting and polishing work on the stock exhaust manifolds in conjunction with the head polishing/porting.

I like the idea of upping the ante on the safety features. The car already has factory disc brakes that work really well. I could perhaps make it handle better but right now I am just focusing on the motor. I know that the shock towers on these cars are inherently weak and often need repair or enhancement. Mine look pretty good but there was a weld done on the drivers side at some point.

The C4 Transmission was replaced in 2009, operates excellent and has hardly any miles on it...maybe 150 miles tops.

I'm also considering doing just some of these mods...or even none of them at all and leaving it stock. I think some of this would be very beneficial to the motor life and performance, help it run better on modern fuel and would not be visible from the outside.

As for those who would want to buy the car in the future and wonder what else has been done to it...I plan on documenting everything with specs and pictures, just as I have with everything else on this car since I began ownership of it.

All of these responses are great and I appreciate the responses!!
 

franklinair

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Joined
Mar 1, 2007
Messages
4,740
I prefer basically stock configuration: These models are primarily fair weather/weekend drivers. No need for extensive mods IMHO. I just finished a 289 O/H. The only performance upgrades I did= 4BBL intake & carb, Pertronix ignition.

Neil
 

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dalorzo_f

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Jan 7, 2006
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Location
Brisbane Australia
... and on the shock tower issue can't say I have seen it. Have 3 big blocks and the C code GTCS, all accepted a Export brace as almost a "drop in" add. Abuse and rust seem to be the main players here in my view. Many of these cars have lasted 50-ish years with no issues.

And on a mild build porting and polishing can be detrimental so assess carefully. Sounds wonderful but is not a one-size-fits-all solution. As an example I bought a pair of 428CJ heads. Was going to use them on a 390 stroker (445). The engine builders I talked to, who listened to my goals (a good street-er) said not to use them and just apply larger valves to the 390 heads I had. Too much porting meant lower velocities at low rpm, which can hurt performance in that range. Which is where you drive 97.8% of the time on the street.

No one rule fits everyone, just do your homework and assess if you are talking to a "bigger/faster" type or actually looking at your wants/needs...
 

CougarCJ

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Jul 17, 2006
Messages
2,186
Dave, you haven't indicated if you have a 289 or 302 engine. A 289 is not something that you want to stroke. I would definitely start with a 302 block.
 
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daveS

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Jun 21, 2009
Messages
55
This is a J code, 1968 302 4V with 8C5 & 8C7 heads, with numbers matching block. The heads, block and body all map together. The Marti report indicates the car was built March 25, 1968 and indeed was a J code. If we stroke the motor, the furthest we would go is 347 or 331...I certainly don't want to run into any issues with having to remove any material from the block skirts or mod the block in any way or create too much hp for the rest of components in the car.
 

p51

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Aug 2, 2005
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Location
NorCal
Dave, you haven't indicated if you have a 289 or 302 engine. A 289 is not something that you want to stroke. I would definitely start with a 302 block.

I was under the impression that the 289 and 302 used the same block. Was I wrong? Or is there some other reason why a 289 should not be stroked?
 

robert campbell

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Apr 10, 2007
Messages
4,321
Dave,
The 289 and 302 block both have the same deck height and are virtually the same to answer the last question. Does your engine block have the VIN # stamped in it? I did not see you say that.

I can do some research, but to stroke to 347 on the 8.2 deck height of the 289 and 302 may require some minor notching to the bottom of the piston liner to clear the rod end caps. Not sure for the 331. This notching is minor and not a problem for longevity. The new 347 stroker kits have improved the piston pin location to allow for better oil ring sealing. The first 347 strokers had oil ring issues.

There are no longevity issues with strokers. And most kits come with premium upgrades that will last even longer. Based on equal driving habits. But with me , "mo power means mo abuse"!!!!

Your primary concern is to build a package. Your main consideration on a 289/302 is the exhaust valve size, exhaust porting, and your choice of exhaust manifolds.

You can port a stock set of 302 exhaust manifolds all you want, but they are the weak link. If you plan on these manifolds forget about stroking and forget about much of a cam or carb increase. The manifolds are too restrictive. Build a stock engine with minor upgrades such as roller rockers. Leave the heads stock.

So the next step up would be the HIPO 289 reproduction exhaust manifold. The can be ported on and will be a significant upgrade, but only so much. They will support some mild porting on the exhaust side of your head and again I would not waste any money on stroking, unless you plan exhaust flow upgrades in the future.

Next step is a shorty header.

http://www.cjponyparts.com/jba-289-...ign=shopping&gclid=CNbZ986578YCFZFgfgodUy4FdQ

These fit great and work with stock power steering hoses and no ram drop. Now you can get some exhaust flow and could build a "torque" 331 stroker. and get some value out of a roller cam and such. Larger valves and more exhaust port hogging on the heads. Roller rocker arms from Comp Cams are a smart choice for any build and cost about the same as fresh stamp steel rockers. And at this time I would opt for the screw in studs, guide plates, and short tip valve stems like the early 289 heads.

Next step is of course long tube headers.

http://www.fordpowertrain.com/347step.htm

Now you can go to the 347 stroker kit, more cam/carb and huge power. These headers tuck up very tight and do not require the PS ram to be dropped. I have them on both my cars. They will support all the HP you can develop in your basic 302 block.

The secret to 302 HP is the exhaust valve size and the exhaust porting. The intake side needs very little other than cleaning and a larger valve. Port pocketing where you remove much of the valve guide into the combustion chamber is very important. The 347 will respond well to stock "ported" iron heads with 1.6 diameter exhaust valves and either 2.02 or 1.94 valve sizes common to Chevy heads.

Do not drop below 10.0 to one compression. It will run just fine on 92 octane if properly tuned. Also remember that the 302 J Code head has the small 53 CC combustion chambers when selecting pistons.

Again, your biggest decision is the end state of you exhaust manifold or header choice. It will drive your entire build. I help people with mild to wild packages every day. You need to make the above choice and I can recommend the rest of the parts.

An (automatic overdrive (AOD) with a drop to 3.5 or 3.7 ratio rear gears is you best bang for the buck for a quick seat of the pants feel. Even with a stock motor. And way better cruising mileage. A see you have a new C4, but it needs 3.00 gears for freeway use. Huge acceleration robber!

Below is a link to an MRE book on head porting. Great info to get you up to speed. If you want to talk about this I talk way faster than I type. (360) 377-5164 9:00 a.m. to 5:00 p.m. pacific time. I have build dozens of similar motors.

Rob

http://www.mre-books.com/ford/engines/cylinder_heads.html
 

CougarCJ

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Jul 17, 2006
Messages
2,186
I was under the impression that the 289 and 302 used the same block. Was I wrong? Or is there some other reason why a 289 should not be stroked?

Though 302 blocks looked virtually identical to the 289 block, the cylinder bores had extended skirts to handle the 302’s .019-inch longer stroke. This extended cylinder skirt reduced piston slap and improved stability for quieter operation.
 

dalorzo_f

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Jan 7, 2006
Messages
1,886
Location
Brisbane Australia
Think the lower ends of the bores are machined/cast to clear the 302 crank ( a minor "stroker")

So think you would need to machine a 289 block to stroke it to clear the crank/rods. Which "could" be done??? Just extra cost.
 

p51

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Aug 2, 2005
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1,025
Location
NorCal
Though 302 blocks looked virtually identical to the 289 block, the cylinder bores had extended skirts to handle the 302’s .019-inch longer stroke. This extended cylinder skirt reduced piston slap and improved stability for quieter operation.

Thanks. I didn't know that. I had read that some late 289s used 302 blocks and assumed they were the same. Seems like the 289 could use the 302 but not the other way around - or at least it wasn't as good.

For anyone interested here is a good reference noting the 289/302 differences...
http://www.mre-books.com/interchange/interchange2.html

But this brings up another general question...
... if you stroke even a 302 (to say a 347) wouldn't you get a similar problem? I mean 0.019in is only ~2/100 of an inch. In going from a 302 -> 347 you add much more than that to the stroke (> 0.25in+ ~= 10x+)... there must be a ton of slap in a 347 even if it was made from a 302...
 
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