Engine mods

Engine mods
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snapper7024

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Atlanta Georgia
Vehicle(s)
1973 CJ5 304 STOCK, EVERYTHING FAR AS TRANSMISSION AND TRANSFER CASE IS STOCK AS WELL.
Looking to do some engine mods on a 73 CJ5 with a AMC 304 . Thought of starting possibly with a cam, intake, and headers. Motor is stock but was wanting to get feedback on what people are using on these motors.
 
Generally speaking from my racing days. The key to mods of this type is to keep things in balance. A bad example is more easy to explain: Putting a "huge" cam but leaving the rest of the engine stock. You'd probably come out with much worse than stock performance.

However some things can help alone. Better breathing is a good start and easy to do. Headers and exhaust can be done without worry of degrading performance.

I wouldn't suggest a cam alone. When you get ready for cam then do the a carb, intake, cam (and likely fuel supply) at the same time and of similar performance specs.

You could also do any number of things to increase reliability. Radiator, electric fan, oil pump, new hoses/belts, etc...
 
As Dave said, we need more info on what your plans for the jeep are.
for example mud would need different engine mods than rocks.
 
Swap out your 2 barrel AMC 304 for a 4 barrel 360 with dual exhaust. You would gain 70hp and 100ft of torque. Straight swap, and you can sell the AMC 304 to cut your costs on the 360 or save it for another project. Just a thought.
 
My grandfather came me this jeep a few years ago as a gift, he has owned it for the last 35 yrs or so. He drove it to work occassionaly then it ending uip on there farm to drive and was stored in a barn and was only used by me or my family. The motor was rebuilt stock a little while back and runs strong.I have mainly used it for off-roading, but would like to drive it on the road as well. I would like to beef it up a little, nothing extreme. No rock crawler. I will definitely look in to the ignition for sure. I would like to keep the AMC 304
 
I'd leave the cam alone or, at most, a very mild, e.g. RV cam. As BusaDave9 eluded, low-end torque is key off-road. But, so too is drivability. A lopey motor (big cam) really sucks on the trail. Unless you're spending your time in the mud, you'll be in the 600-1,200 RPM range. Ya don't want a motor that wakes up at 1,500 RPM.

Ignition would be my first thought - lots of opportunity to improve the AMC :dung:. Next would be fuel (better/bigger carb - set up for off-road) and exhaust.
 
Yeah when i was given the jeep i replaced the coil, plugs, wires, etc., but i replaced it with stock replacements just to give it better juice. Didn't really invest the money better at the time. If i was to upgrade the igniton and go with the edelbrock performer intake, hedman long tube headers and exhaust with a mild cam, what size carburator would i need. I saw two different series through edelbrock the thunder series and performer series. Didn't know if the performer was more suitable considering the intake. What cam would be good with this setup as well. thanks
 
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snapper7024 said:
What would be a good size carb?
Click to expand...
Anything from 400 to 600 CFM
I have a 600 CFM Edelbrock 1406 Performer Four Barrel Carburetor. Although it may be a little bigger than necessary, I love it.
Or a Holley Truck avenger is a great carb made for off road use.
I installed an off-road kit in my Edelbrock. That consists of a spring for the float valve. If you do much off-roading is is also good to adjust the float level a little low to prevent flooding on rough terrain.

I like Holley and Edelbrock carbs because they are made for aftermarket. For that reason they are made to be very easy to adjust and calibrate. Both companies have great tech support. I didn't buy my carb. It came with my CJ from the PO but I still called up Edelbrock. They told me what needle and jet to use at my altitude and they gave me advice for calibrating it.
 
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As was already touched upon, you will want to change out the ignition for a more up to date Duraspark system. This will include changing out the dizzy and replacing it with a Motorcraft dizzy, installing a post-'78 ignition control module, coil, and wires.
A great upgrade as you are doing this.....Once you upgrade to a Motorcraft dizzy, source a cap, rotor, and adapter from a Ford 460cid. With this, use the coil that goes with that system, 8mm plug wires, and a plug re-gap. This is commonly called a TFI ignition (Thick Film Integration) and provides loads of spark over the stock Duraspark ignition....

As far as headers, dont bother. The stock cast iron dog-leg manifolds provide ample flow. My 401 pushes a healthy 430 horsepower and I have no issue using the stock manifolds. Upwards of 500hp and I would start thinking headers. The AMC 304 , 360, 390, 401 can all use the same exhaust manifolds. The one you want is the one you have. ;)

I strongly recommend ditching the cast iron intake manifold for an Edelbrock aluminum one. You save a bunch of weight, heat exchange is more efficient, as well as fuel delivery.

I've ran Edelbrock carbs and absolutely love them for crisp response. Where I didnt care for them....in stock form...was anything with a hill. :D The best carb I have ever ran (as far as carbs go) was a Quadrajet. I used it for several years on my 401 before I went full propane and it was a dream...seriously. The small primaries are great for lowend ideling and the huge secondaries will give you the punch you need when you open it up. Offroad, I have never seen a better carb. I could run this thing sideways and straight up and down without a hiccup.
A quick note on Q-jets....a good functioning Qjet is worth its weight in gold. One that needs rebuilt (worn throttle shaft) is nothing more then a flashy doorstop as far as reliability and performance.

I've seen guys build the AMC 304 up to a monster. Cam, high compression pistons, headwork....the AMC 304 is capable of a lot. The drawback is unlike its 401 brother (sister?) the connecting rods, crank, and pistons are cast vs. forged. This is a weak point when looking to increase power. The AMC 304 and 360 also have lower nickel content in the blocks then the 401...this is just an issue of block longevity.
 
Yeah i just want to get sounding and looking good, and use it for a weekend toy and occasionally drive it during the week. Its needs some tlc for sure, body is good, paint is decent but the gauges, lights, and seats need to be replaced. jeep really only has around 76,000 original miles on it.
 
Razorfish said:
Generally speaking from my racing days. The key to mods of this type is to keep things in balance. A bad example is more easy to explain: Putting a "huge" cam but leaving the rest of the engine stock. You'd probably come out with much worse than stock performance.

However some things can help alone. Better breathing is a good start and easy to do. Headers and exhaust can be done without worry of degrading performance.

I wouldn't suggest a cam alone. When you get ready for cam then do the a carb, intake, cam (and likely fuel supply) at the same time and of similar performance specs.

You could also do any number of things to increase reliability. Radiator, electric fan, oil pump, new hoses/belts, etc...
Click to expand...

I am interested to your explanation and was hoping perhaps you can share some lights with me:

I own a 1981 CJ7 with AMC 258 i6 / 4.2l I6 engine ... I have installed a Holley Truck Avenger 470 and Crane Cams 753941 cam .. it was a 272in/284ex advertised duration.

So far, the engine was running smooth on idle and this makes me wonder if the cam was installed correctly as its supposed to have some rough idle.

My installer comment that the smooth idle is caused by the Holley as this is a big 4 bbl carb, the fact is during idle only 2 bbl are working .. just like the stock carter ... in fact the venturi size of the Holley TA is a bit smaller than the Carter.

Appreciate your comment/thoughts... thank you.

regards,
Jaya
 
The AMC 304 v8 is thirsty to begin with, run her stock, get rid of the points and go with an HEI. CRT performance has what you need. Keep the MC 2100 carb, it's excellent Offroad at all angles. Clean it up, rebuild if necessary, throw on a K&N...done. The money you save will buy more gas to feed that thirsty v8.
 
With junkyards online its a lot easier than it was just 10 years ago. Retailers make it as simple as it can be. The only problem you'll encounter is sourcing parts for the intermediates 1972-75. With a credit card, and an Internet connection you're halfway there.
 
I will consider that, thanks for the input ... will keep my eye on local junkyard 1st ... those importer mainly are on japanese jeeps i.e.: Suzuki & Toyota, half cut cherokee is also popular here while local enthusiast were more on chevy v8 engines ... hope I can get a good deal someday ...

Meanwhile ... is there anybody have used this Crane Cams 272/284 before ? any good or bad experience with it ? ....
 
Jaya said:
Meanwhile ... is there anybody have used this Crane Cams 272/284 before ? any good or bad experience with it ? ....
Click to expand...
No I don't have experience with that specific cam.
Maybe someone else will chime in.

That cam is for higher RPM than what I would prefer in a jeep.


Brand: Crane Cams
Manufacturer's Part Number: 863941
Product Line: Crane Hydraulic Flat Tappet Camshafts
Basic Operating RPM Range: 2,200-5,800
Intake Duration at 050 inch Lift: 216
Exhaust Duration at 050 inch Lift: 228
Lobe Separation (degrees): 112
Computer-Controlled Compatible: No
 
This is the one I have actually ...

Part Number: 753941 Grind Number: H-272-2 (REPLACES HMV-272-2)
Engine Identification:
Start Yr. End Yr. Make Cyl Description
1964 2005 AMERICAN MOTORS 6 Good low and midrange torque, good idle, daily usage and off road, towing, performance and fuel efficiency, 2600- 3000 cruise RPM, 8.75 to 10.5 compression ratio advised.
Engine Size Configuration
199-AMC 258 i6 / 4.2l C.I. I

It's idling smooth as if were stock ... So I just want to find out comment from other jeepers that own the same .... I might missing some setup or need redialing ... who knows ? ... Everybody is using Isky 282/282 so no local comparison here .... Thanks
 
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