weak 304....need help(long)

[jfoster]

So I recently purchased a '80 Scout II with a 304 and 727, neither are original. Got a good deal on it, the 304 runs but not well. The 727 is good to go. So I am wanting to replace the 304. Wanting to do this myself as I need to save the money and gain the experience. I have a friend that is willing to help, he is in an auto tech class and so he has rebuilt (in class) a couple 350s. I myself am fairly mechanical but this will be the first time I have pulled a motor. I have the manuals to the scout for reference.

In wanting to make this as simple and cost effective as possible I have been debating whether I should buy someones "strong" 304 they are selling out of thier scout or to rebuild the 304 out of mine (but that gets kind of pricey). This is a trail machine and not a daily driver, but it needs to be reliable because it needs to drive to and from the trails and some are quite a ways away.

I have a pair of rebuilt 345 heads and a bare 345 block available to me for next to nothin so will those heads work on a 304 just the same? The scout also came with a four barrel 345 intake(extra), and uses a four barrel carb with adapter plate. So would building the 345 block be a good idea? Then would the 345 short block and heads swap in with the rest of my 304 stuff? From the looks of the interchange guide http://www.binderplanet.com/faq/7.htm#8 it would but like I said I don't know first hand. Maybe I should just build my 304 block.

I just don't know what to do, and it is due to my lack of experience, so anyone who has some please give me your opinion. Thanks, James

[Whyle]

You will get more hp and Tq with the 345 , I would run the 304 till it dies it will run a long time I't IH. in the mean time you could build up the 345, I hada 196 in my 78 Terra when I bought it it had weak rings I knew they would let go it lasted a year and that was driven it every day, It now has 345 in it's place a lot more power then my friends 76 Terra with a 304 and both have 3:54 gears
But I get only about 15mpg if I keep my foot out of it , but that's hard to do .I only run a 2 barrel Carb,

[Bill Bennett]

Need to determine 'why' the 304 feels short on power. Have you checked the timeing or maybe could just use a tuneup? Plugs, points, condenser, plug wires, dist vacuum advance, rotor and cap. Is the air filter clean or is the exhaust restricted? Check the flapper valve, it may be stuck in the closed position - blocks the exhaust outlet. How about a carb rebuild? Follow the included instruction with the kit. Do a compression check with the plugs out - so the engine spins easier. Crank the engine so each cyl hits compression 4-5 times, but same on all cyls. Pressure should be within 10% of each other. Blow the dirt away from the sparkplug holes before removing the plugs. Don't want to suck anything into the cyls.
The IH engines 'time' off the #8 cyl. That's 'rear on passenger side'. The fireing order# is cast on the intake manifold and the cyl# is cast on the intake manifold runners near the head. Mark the plug wires so you get them back on the correct cyl.
Thats providing the previous owner has them correct now!
Base timing - with vacuum advance plugged, try 4deg BTDC to start. Then reconnect the vacuum from the carb to dist.
Bill Bennett 68 Travelall 304

[jfoster]

Thanks for the replies. The carb is fairly new and works well. The 304 has alot of problems. I won't know until I pull it apart. It has noises like lifters and/or valves. It does not have enough power to pull a high gears with out shifting up and down constantly. I would not trust it to take me to town and back.It leaks oil from multiple places. Definatley time to replace/rebuild.I want to make it stong and healthy.So would the heads from a 345 work on a 304 too? If so I will most likely get the heads since they've been redone already. And then would a 345 short block swap in just the same (as easily and straight forward) as a 304 short block?Thanks again, I value the advice.

[Joe D.]

345 heads will not work with a 304. The intake manifold will not line up, and the runners are the wrong shape. For the same reason, the 345 intake manifold will not work with the 304.

The 345 block will bolt to your engine mounts and transmission just fine, making it a good swap. If you can really get heads, block and intake from a 345 for cheap, then that's what I'd suggest. You'll save money on the machine work on the heads, because you're just rebuilding the bottom end. It's a good was to gain experience. And, the 304 is a good motor, but the 345 has a lot more pull to it.

Your 4-barrel carb will also work a lot better with a 4-barrel intake than with an adapter to a 2-barrel intake.

[mlhscout]

I was gona say maybe the carb is too much for the 304, besides the valve noise. Also what kind of carb is it?.........mlhscout

[Tom Mandera]

4bbl is over-carbing the 304. I imagine it's running quite rich, robbing you of a LOT of power.

You need to do a compression test on the warm engine.

You need to check the oil - is it filthy black like someone never bothered to change it?

Borrow a 350cfm 2bbl Holley in good condition and try that out, dump that carb adapter.

I bet it runs stronger after that.

you may still have lifter oiling issues, probably stemming from shot cam bearings, but make it run well first, and get a few oil changes through it - might just be some dirt in the lifters, and some "frequent" oil changes may clean it right up.

It's worked for me on several occasions.

Then check the timing, and advance it until it pings, then back off. I run 10-15deg BTDC on most of mine.

That said, if it still needs replaced...

You "can't" use the 345 heads on the 304.

If you can get the 345 core cheap/free, then why not rebuild it?

You'll still need a 345/392 crank and connecting rods, along with pushrods.

You can use the 304 pistons (assuming the 345 doesn't need bored, and the 304 pistons are not shot.. in which case, 345 and 304 pistons are the same anyhow, so no extra cost to buy "345" pistons over "304" slugs).

Use the 304 rocker shafts and arms, assuming they're not shot ("mic" the arms and shafts to make sure they're not the cause of your "valve noise").

You just need a 345/392 crank, 345/392 rods, and 345/392 pushrods (for the same type of rocker arms the 304 uses, either the welded or the boat)

The rest all swaps. Well, you'll need a 345/392 valley pan/tappet cover, too.

You'll "want" to spend $2k-$2500 on anything but the most basic re-ring job (which I doubt the 345 would be).

On the low end of cost, you could pull the 304 out, tear it down, have it cleaned, replace the cam bearings, hope the bores and pistons are OK, and just re-ring it, throw in a new cam, and spend under $1000.

But give your 304 a chance, first.

I run a ~375+hp 304 with 10.25:1 compression with ported heads. I ran a 350cfm Holley 2bbl and it was good to 4300rpm (beyond the factory 3900rpm redline).. I put on a 500cfm 2bbl and I'm hovering around 5300rpm before it just won't go any more.

I put on a 4-2 adapter and a Holley 600cfm vac. secondary square-bore 4bbl.. and still got 5300rpm, and it was a LOT more temperamental.

Maybe I need more cam.. but you're not going to want to run too far past the stock redline anyhow, unless you upgrade the valve springs, upgrade the cam, port the heads, balance things, etc.

Point is.. a stock 304 has no need for more than 350cfm.

[rlireland]

Originally posted by Tom Mandera

Then check the timing, and advance it until it pings, then back off. I run 10-15deg BTDC on most of mine.

Point is.. a stock 304 has no need for more than 350cfm.

Really basic question here. My 304 is missing the pointer to be able to index the timing marks on the harmonic balancer so I've set the timing "by ear". I'm going to reset it using Tom's method. Turning the distributor counter-clockwise will A) Retard the timing or B) Advance the timing?
And... Advanced = BTDC or ATDC?

Thanks,

Roy

[Tom Mandera]

The "pointer" is just a slot cut in the center of the balance weight..

Or do you mean you don't have the "scale" on the front cover?

I always have to think about which way I need to rotate it.. and I've also been known to wire it backwards on occasion (plug wire orientation)..

Note that it's "advance it until it ping *while driving*" and then back it off.

So go hit a few WOT passes around the neighborhood between adjustments.

[rlireland]

Originally posted by Tom Mandera
The "pointer" is just a slot cut in the center of the balance weight..

I guess I need to scrape off a little more grease to see the slot.

AFA the advance/retard question... I think ADVANCE means to rotate the distributor the OPPOSITE direction that the rotor normally turns. Hence, turning the dist counterclockwise on a distributor that rotates clockwise would ADVANCE the timing.

Roy