NEWS PARTS JEEP & 4x4 ATV & UTV

earley 304 vs late 304

736 Views 19 Replies 3 Participants Last post by **DONOTDELETE**, Oct 30, 1999

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Discussion Starter · Oct 28, 1999

I know that the early 304's performed better than the later 304's because of emmisions controls but what exactly was changed. Where the pistons or heads changed or modified or was it all changes in the equipment mounted on the motor like the carb, exhaust, etc. I have a new short block of unknown year that I am gathering info on for building up and would like to a better idea of what changes I could make.
Thanks for your help
David

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CJDave

· #2 · Oct 28, 1999

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/wwwthreads_images/icons/tongue.gif Most of the total-smog era engines were ruined by the smog cam, the smog spark timing, and the low compression. I had a small block Chevy which was the worst dog you could ever imagine (1978), and when I got tired of getting 8 miles to the gallon I knocked it in the head and gave it pop-up pistons for more compression and an RV cam. It was like day and night difference. The fuel mileage popped up to 14-15, and it had tons of power./wwwthreads_images/icons/wink.gif The other thing was that it continued to pass smog with NO PROBLEM!/wwwthreads_images/icons/crazy.gif

CJDave

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G

Discussion Starter · #3 · Oct 28, 1999

So maybe I should change out the stock pistons or something for better compression? I'm already planning on intalling a non-stock cam and ingition system.

CJDave

· #4 · Oct 28, 1999

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/wwwthreads_images/icons/smile.gif Yep, that will be a must-do. RV (or other) cam, HEI, and pop-up pistons should do the trick. You may also want to get adjustable push rods, since some guys have problems setting the hydraulic lifters so that they run quiet. Check the book, but didn't the 304 HAVE adjustable stands at one time? Oh well, anyhow, you need to be able to set the hydraulics so get some adjustable rods. JCW had them in a little supplement catalog. If need be I could find it for you. /wwwthreads_images/icons/wink.gif

CJDave

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G

Discussion Starter · #5 · Oct 28, 1999

I agree that the compression will give you nothing but smiles, but I'm not so sure about the cam. Now, maybe mine was an "early", but my stock '74 304 was a torque monster on trails. In fact, that motor made me believe that the I-6 superiority was purely a myth. With equal gearing & tires, I could idle up stuff that my friends needed to hit at speed with their 232's & 258's. I think the most desirable feature of the 6 was that you could get a 4-speed instead of the 3-speed. But, all of my friends had 3-speeds in their 6-cylinder CJ's & they couldn't go where I could without taking a run at it. I think the main reason a lot of 304's are just so-so on trails is because of hot cams swapped in. Depending on what you plan to do with that Jeep, I'd be careful about going much hotter than stock with that cam, unless you can find some specific examples of cams that you KNOW work well 'cause you know someone who HAS that.

Just my $.02.

TEX

/wwwthreads_images/icons/wink.gif Got Mud?
G.U.M.B.O. Mud Racing

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116

· #6 · Oct 28, 1999

Don't forget if your looking at the difference in Horsepower between the 73 and later years. HP was calculated differently for 74 and up . Thats why the HP for 73 is great and in 74 the rating drastically decreased.
It's Bhp vs. SAE HP. Don't know the specifics.

G

Discussion Starter · #7 · Oct 28, 1999

I'm looking at only mild cams, nothing outrageous. Where do I get these pop-up pistons? What do you think about Roller rockers?

CJDave

· #8 · Oct 29, 1999

2

/wwwthreads_images/icons/tongue.gif The engine rebuilder has a piston catalog which will help you find something. Roller rockers are nice. $$$$$ But nice./wwwthreads_images/icons/crazy.gif

CJDave

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Discussion Starter · #9 · Oct 29, 1999

So stock lifters and adjustable push rods would make a significant improvement on performance over stock lifters and stock push rods?

CJDave

· #10 · Oct 29, 1999

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/wwwthreads_images/icons/smile.gif Not necessarily an IMPROVEMENT IN POWER, you would just be able to get better, more precise adjustment of the hydraulic lifters and avoid the headaches that Swissjeeper has in his 360 wih the incessant 'ticking'. The cam should be changed if that is a total smog engine, and then use the adjustable rods. THAT will give you the right setup./wwwthreads_images/icons/crazy.gif

CJDave

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Discussion Starter · #11 · Oct 29, 1999

I'll be putting all the necessary smog equipment so it will pass inspection. I'm think I may go with a Competition Cam along with stock lifters and roller rockers. Sounds like I might as well get adjustable rods too. Will I need to make frequent adjustments?

CJDave

· #12 · Oct 29, 1999

3

/wwwthreads_images/icons/smile.gif Of course not.....the hydraulic lifters don't need it. The problem is on initial setup, getting the proper preload on the lifters. Without adjustable pushrods, you are gambling that everyone did a perfect job and the lifters will be set exactly where they need to be I DON'T THINK SO!/wwwthreads_images/icons/wink.gif That's why you need adjustable pushrods. See my post on the HEI source./wwwthreads_images/icons/smile.gif

CJDave

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Discussion Starter · #13 · Oct 29, 1999

Since I don't have the engine building savy I wish I had, and I do get non-stock pistons, should I use moly rings or some material other than stock to help increase the longevity of the engine(or at least that part of the engine)?

CJDave

· #14 · Oct 29, 1999

2

/wwwthreads_images/icons/tongue.gif Get with the guys from FLA who build AMCs.....there is usually a particular ring that seems to work best with some engines. Find out what they have been using./wwwthreads_images/icons/smile.gif

CJDave

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Discussion Starter · #15 · Oct 29, 1999

FLA is American Performance in Florida?

CJDave

· #16 · Oct 29, 1999

2

/wwwthreads_images/icons/smile.gif Yep, the address is in the 304 booklet./wwwthreads_images/icons/crazy.gif

CJDave

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Discussion Starter · #17 · Oct 30, 1999

Where can I get the engine rebuilder piston catalog?

CJDave

· #18 · Oct 30, 1999

2

/wwwthreads_images/icons/smile.gif You would be probable be way ahead to order a complete rebuild kit from American Performance which would then have the correct piston upgrade, the rings that they normally use in those blocks, and a cam that they have some success with. That way, you get the advantage of their experience. You have to get the parts SOMEWHERE, and that way you would get all the right stuff. They can send you the oiling upgrade for the block as well./wwwthreads_images/icons/smile.gif

CJDave

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130

· #19 · Oct 30, 1999

While we're on the subject of camshafts for the 304 I'd like to put my $.02 worth in. A stock cam IS better, but not the stock cam from a 304.... A camshaft out of a 401 will drop right in and turn the 304 into a gutless wonder. Thats almost an exact quote from the Jeep 4x4: Performance Guide by Jim Allen- the best Jeep book I've ever found.

G

Discussion Starter · #20 · Oct 30, 1999

so is any one running a 401 cam in their 304? I've still looking for a cam was originally thinking of getting the edelbrock cam to go with the new intake manifold, but I really haven't heard anything about it from anyone

-MarkyMark
80 CJ-7 Laredo 304v8 TF999 3.73's BFG M/T's

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