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

robert campbell said:

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....

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Rob, great information. Thanks. Roughly, where along that spectrum of changes could you get an additional 60hp from a stock J-code engine w/10:1 compression (240BHP -> 300BHP)? A swag is fine... I'm just curious...

Where in the rev range do you want the power? Many hp upgrades don't show up until you're over 3500rpm. If you want it to come on at lower rpms you need more torque.

p51 said:

Rob, great information. Thanks. Roughly, where along that spectrum of changes could you get an additional 60hp from a stock J-code engine w/10:1 compression (240BHP -> 300BHP)? A swag is fine... I'm just curious...

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I think you could get that 60 hp with a cam, carb, and hipo exhaust manifold upgrade. An Edelbrock performer manifold would be a good add and I would still change to a 500 CFM Edelbrock carb to keep the intake air speed up and create more torque. But I bet you could get it through a stock J code 4 barrel and keep a stealthy look.

Cam selection will be critical. I would use a mild Comp Cam grind. The cam choice would be coupled to the rear end gears you are using.

Give me all the info and I will recommend a complete package. It could all be under the air cleaner and no one would see other than the exhaust manifold change. Again the exhaust is the critical upgrade.

Rob

Rob

Mosesatm said:

Where in the rev range do you want the power? Many hp upgrades don't show up until you're over 3500rpm. If you want it to come on at lower rpms you need more torque.

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Arlie,
You could create monster power out of a 302 all below 4,000 rpm. Open up the exhaust and torque just happens. when combined with the right cam and head upgrades. A mild 347 or 331 creates way more torque at lower RPM's. And a 302 could do the same, just not as much. The newer cam grinds have much quicker "ramps" allowing for more lift and longer valve events without the overlap of the older cams that pushed hp up in the RPM band.

Rob

I've heard that 351 exhaust manifolds are as good as, or better than, the hi-po manifolds. Is that true?

Mosesatm said:

Where in the rev range do you want the power? Many hp upgrades don't show up until you're over 3500rpm. If you want it to come on at lower rpms you need more torque.

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What I would look for would be more torque than hp... It would be for quick-n-agile street car. So, that would mean moving it down on the RPM curve...

robert campbell said:

I think you could get that 60 hp with a cam, carb, and hipo exhaust manifold upgrade. An Edelbrock performer manifold would be a good add and I would still change to a 500 CFM Edelbrock carb to keep the intake air speed up and create more torque. But I bet you could get it through a stock J code 4 barrel and keep a stealthy look.

Cam selection will be critical. I would use a mild Comp Cam grind. The cam choice would be coupled to the rear end gears you are using.

Give me all the info and I will recommend a complete package. It could all be under the air cleaner and no one would see other than the exhaust manifold change. Again the exhaust is the critical upgrade.

Rob

Rob

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Thanks. That info is sufficient. Not really planning to do this, I was just sorta wondering how much had to be done for this type of ~25% performance increase. Also, actually looking for more torque than hp... but have less of a feel for torque as a qualitative metric...
... very interesting comment on the Hipo manifolds. Seems like they should've been a standard feature... I mean, what's the downside vs stock (except cost)?

p51 said:

Thanks. That info is sufficient. Not really planning to do this, I was just sorta wondering how much had to be done for this type of ~25% performance increase. Also, actually looking for more torque than hp... but have less of a feel for torque as a qualitative metric...
... very interesting comment on the Hipo manifolds. Seems like they should've been a standard feature... I mean, what's the downside vs stock (except cost)?

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I totally agree. The one downside might have been cold weather performance. The stock 302 creates a lot more backpressure to force the exhaust through the passage in the intake under the carb to prevent carb icing. But the also had the sheet metal on the manifold that fed hot air in the snorkel of the air cleaner.

Kinda a balance between street ability and high performance made some of the decisions.

Rob

Mosesatm said:

I've heard that 351 exhaust manifolds are as good as, or better than, the hi-po manifolds. Is that true?

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Side by side they are very similar. I have 351W exhaust manifolds on my 1968 Cougar with 302-4V.

Poor mans HiPo exhaust manifolds. :grin:

CougarCJ said:

Side by side they are very similar. I have 351W exhaust manifolds on my 1968 Cougar with 302-4V.

Poor mans HiPo exhaust manifolds. :grin:

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But those 351 Windsor manifolds are sure hard to find these days!!!!

It's your car

I kept the stock short block, added a Comp Cam, and the rest is modified. It's a lot more fun to drive with an estimated 385 hp than the stock 197. I agree with an earlier response. If it's all original, keep it that way. Like yours, mine was repainted, pollution controls were long gone and the engine was tired, so I went with fun. Rest assure, all original parts are in storage. Nothing wrenches can't put back. Make it driveable and Have fun!

More power = more fun!!!! In my mind!! I refuse to grow up!!!

Rob

Late getting to the party, but here's my take. From earlier research I did, the 331 kit doesn't require skirt notching, with a 302 block. The 347 kit does.
I built my engine with a comp cams 268 xtreme energy cam, 9.3-1 Hyper-eutectic pistons, Alum intake, Holley 600 and Thorley Tri-Y headers. Everything else stock, including the crank. My engine builder had previously dyno'd the same build at 275 hp, although I never got around to checking my engine. It was a great engine and fun to drive, but easy to convert back to stock if I chose. I saved all the factory stuff, which is now in Georgia with the car.

Steve

Wow this is awesome stuff guys...lots of great feedback!!

So since we got the engine apart, we determined that the block and heads match the car for sure.

The engine looks like it was rebuilt at least once before. It was an "average" rebuild and the block was bored slightly. The pistons and cam do not appear to be original (no markings on either of these), however the piston rods look original...still haven't fully verified the crank. We are going to magnaflux the block (and possibly heads) to look for cracks, etc.

Now we are trying to verify the carb authenticity. We've been doing some detective work on the carb...there's no tag or clear markings, but it appears to be a 4300 carb, 600cfm that appears to be from '68...perhaps could have been on a 428 T-bird or full size Ford of that era with 600cfm and appears to be visually the same as a GT/CS 302 4V carb. Anyone know what to look for on the original GT/CS 302 4V carbs? Know where I could find an original one? :grin:

We're still contemplating the stroker kit..331 or 347. Maybe I should consider HiPo exhaust manifolds or some kind of header? I've heard that the HiPo exhaust manifolds interfere with the steering box..true/false? I'm shying away from headers because I really want to keep the car looking stock under the hood.

Also we would like to switch the head studs to thread in versions instead of press in versions.

Lastly, the car has factory Selectaire AC (on the Marti). One of the mounting holes on the compressor casing has a crack around it, rendering this tapped hole useless. The compressor either needs to be replaced or repaired. Any thoughts on this? I've got a picture I could probably post. The AC was functional before pulling the motor. I'm guessing an accurate replacement compressor could do the trick too if they are available.

More updates to come...maybe I should start posting some pictures :grin:

Thanks everyone for chiming in!

Hipo exhaust manifolds will not interfere with the steering box. Again, without these on your cars engine, do not bother stroking it. Stock 302 manifolds will be the limiting factor in you build.

Screw in studs and guide plates are high RPM pieces. Sounds cool but not necessary for a stock motor.

If you want to stroke this engine then you must consider a shorty header or Hipo exhaust manifold. If you go Hipo you may want to consider the factory H-pipe for a 1967 Mustang with the Hipo engine. Nice fit and comes with the cross over pipe. If you go with Shorty headers, then you will get even more power and more than likely will require a custom built H-pipe. I would go with a minimum of 2 and 1/4 diameter exhaust.

The carb is under the air cleaner and not easily seen. I would go with an Edelbrock 500 cfm on a stock 302. If you stroke it to 331, do port work on the exhaust side of the heads and go to Hipo or shorty headers, than upgrade to the Edelbrock 600cfm or Holley 600.

Go long tube headers and increase valve sizes and port the exhaust side you can then go 347 and a 670 Holley Street Avenger.

Dump that C4 in the corner of your garage. Install 3.50 rear end gears and get an AOD. Best bang for your buck!

Rob