Harry's 345 Rebuild

harrywt

harrywt

Member
The tapping coming from my 304 comes and goes. Since it has now been 2 years I am pretty sure it is not a rod bearing. In any event I recently purchased a running 345 and was told by the seller that I could just throw it into my Scout. This kind of goes against my grain as it is a lot of work to change an engine, I would much rather rebuild it.

It has been suggested to me that there has been a parts shortage lately and maybe I will get stuck waiting for parts. Any opinions?

I read through the post with the discussion of head and deck milling, squish, CR etc and I think that this is a bit too much finesse for me. I am open to suggestions to this effect though.

I am going to a 345 from my 304 since I have trouble maintaining highway speed on climbs. I think I mostly picked the wrong ratio for my new differentials. They are 3.73's and the speedometer is now correct but I don't feel that I hit the power curve quite right. I would sacrifice 80 mph for being able to maintain 60-65 on climbs.

The tear down will start soon and I will post pictures as I go. I am open to suggestions such as an after market camshaft. BTW, it has a spreadbore intake manifold.
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3.73 to 1 is a great gear ratio. It is definitely not a long legged "highway" gear, like for instance the 3.07 to 1. Unless you're running 40 inch tires, I would think a healthy 304 that is able to achieve full throttle should do fine up grades with this axle gear. Maybe not 65 per se, but not dogging along at 40 or 45 either.
 
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Compression test it, Pre oil it and run it. Pull valve covers, check rods and lifters/ cam lobes.

Its a 1 or 2 day job to swap an engine, it's a 6 month to 1 year project to rebuild that engine. And yes a lot of the rebuild parts are getting hard to come by, especially valves for the heads.

What size tires are you running with 3.73's. I had them with 35s. Great highway gear for 35's could do 75-80 mph no prob however I dont live in the mountains. Id want 4.56s / 4.10s second for an all around rig on 35's. I did go to 4.88s with the 35s and could no longer maintain 75 mph without excessive RPM and blow by on my 345. It was a worn out engine, had mega ring ridge etc. But guess what still had decent compression so I had the heads rebuilt/ milled to maintain compression with new head gaskets and put the engine back together and ran it another 2 years and now another guy is running it in his truck as I did the dreaded 5.3L swap. (regret it to be honest)

Only place I could find exhaust valves 5 years ago was Ebay, as an NOS set.

Good luck in what ever you decide.
 
Winchested said:
Compression test it, Pre oil it and run it. Pull valve covers, check rods and lifters/ cam lobes.

Its a 1 or 2 day job to swap an engine, it's a 6 month to 1 year project to rebuild that engine. And yes a lot of the rebuild parts are getting hard to come by, especially valves for the heads.

What size tires are you running with 3.73's. I had them with 35s. Great highway gear for 35's could do 75-80 mph no prob however I dont live in the mountains. Id want 4.56s / 4.10s second for an all around rig on 35's. I did go to 4.88s with the 35s and could no longer maintain 75 mph without excessive RPM and blow by on my 345. It was a worn out engine, had mega ring ridge etc. But guess what still had decent compression so I had the heads rebuilt/ milled to maintain compression with new head gaskets and put the engine back together and ran it another 2 years and now another guy is running it in his truck as I did the dreaded 5.3L swap. (regret it to be honest)

Only place I could find exhaust valves 5 years ago was Ebay, as an NOS set.

Good luck in what ever you decide.
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Why do you regret the 5.3 swap?
 
FDChappie said:
Why do you regret the 5.3 swap?
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On paper #s the LS HP/TQ seem just as good. From seat of the Pants I call 100% BS. The 345 had way more bottom end torque. And my 345 was worn right out. I get the pretty well the same fuel mileage within +1 MPG with the LS. 12.5 MPG has been my best when towing my little 2000 lb pop up camper. Mind you I'm on 40s (150 lb wheel/ tire combo) with one tons, a doubler and NP205. So all pretty heavy gear combos 5.38s in the diffs. The NV4500 gear splits suck with the 5.3L powerband.

I was getting 11.5 to 12 MPG with that worn out 345 on the same 40s and 1 tons with Hamilton fuel injection. But I could not cruise over 65 mph. (T19 wide ratio) Atleast now I can do 70-75 mph and maintain it unless there is a medium to large hill and I'll lose 5-15 mph because the shifts drop me right out of the powerband.

I think With an Automtic it would be better. I do have a 4L80E sitting here, but if I put it in I wanted to do a reverse manual valve body. I can prob buy that/ the shifter set up etc and still sell my NV4500 for what I have into it. (These GM NV's wornout are selling for $2k-3k CDN now, I only have $2k into this one rebuilt)

Or I just buy/ build a toruey 6L or hit the lottery and put in an LSX.
 
Scoutboy74 said:
3.73 to 1 is a great gear ratio. It is definitely not a long legged "highway" gear, like for instance the 3.07 to 1. Unless you're running 40 inch tires, I would think a healthy 304 that is able to achieve full throttle should do fine up grades with this axle gear. Maybe not 65 per se, but not dogging along at 40 or 45 either.
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I have 33" tires with my 3.73's and T19 wide ration. When I go to Frazier Park I can climb all the hills (on the 5) at speed if I am close to 3000 rpm or close to 75mph. If I start a climb at <65 then I slowly lose speed. I can cruise on the flat at 80+ if I want to. I would rather be at 65mph at 3000 rpm and sacrifice going 70+ so that I can maintain speed better. That's why I'm thinking 3.92 would have been better, especially since the necessary carrier change to go from 3.73 to 3.92. This kind of precludes the possibility of going to 35's

I know it's a bit counterintuitive since 3000 rpm should be past the power peak but my 304 seems to have a good amount of pep left there. I run 91 octane and have advanced the spark about 5 degrees.

When I go up Frazier Park road there's places where I have to go down to 3rd to maintain 45-50 mph and this without towing anything. If this is the way it is then so be it, I am hoping that a 345 will help enough to make the swap worth it
 
FDChappie said:
The 345 with the additional HP and bottom end torque may work fine with your current gear set.
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should I consider anything fancy like decking the bores to get a higher CR? What what about a different than stock camshaft? I don't want to deal with vacuum loss or too rough of an idle.
 
Probably not necessary to achieve your goals. That said I bored .020 over, decked the block and put a mild comp cam in my build. The build thread is on this board.
 
FDChappie said:
Probably not necessary to achieve your goals. That said I bored .020 over, decked the block and put a mild comp cam in my build. The build thread is on this board.
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what is the title of the thread. I can't seem to get a list of only threads for a user, just individual posts
 
Wow it's been 10 years since this thread was started.

Building a fresh 345 for the Scout

I haven't pulled the old engine apart yet, but I believe it's spun a cam bearing and damaged a tooth on the timing gear. This happened when I changed the oil and started it after having not run for a couple of weeks. I guess it just took to long for the oil pressure to come up...
forums.ihpartsamerica.com
 
My suggestion for a mild build would be bore engine as necessary, balance rotating assembly including clutch, deck block to where pistons are recessed to .005, mild port job on exhaust, and Isky cam 190156. Will have a good idle and make good power.
 
ihpartsjeff said:
My suggestion for a mild build would be bore engine as necessary, balance rotating assembly including clutch, deck block to where pistons are recessed to .005, mild port job on exhaust, and Isky cam 190156. Will have a good idle and make good power.
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Could you please the porting in more detail?
You sell this cam, correct?
Do you know of Bill Hamilton grinding the drain holes in the heads to allow oil to return to pan faster? What do you think of this?
 
harrywt said:
Could you please the porting in more detail?
You sell this cam, correct?
Do you know of Bill Hamilton grinding the drain holes in the heads to allow oil to return to pan faster? What do you think of this?
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If I'm understanding you correctly, you're wanting more details on the port work? I match port the intake and open up the exhaust portswhere the emissions hump is. Also match port the exhaust to manifold or header.

Yes we sell the camshaft on our webstore - https://www.ihpartsamerica.com/store/isky-190156.html

Any smoothing of the oil return feed holes is going to help with drain back.
 
ihpartsjeff said:
If I'm understanding you correctly, you're wanting more details on the port work? I match port the intake and open up the exhaust portswhere the emissions hump is. Also match port the exhaust to manifold or header.

Yes we sell the camshaft on our webstore - https://www.ihpartsamerica.com/store/isky-190156.html

Any smoothing of the oil return feed holes is going to help with drain back.
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syntax error. I know what porting is in a general way, when I looked it up, especially exhaust porting, the article mentioned different ways depending on the geometry of the head.

my understanding of porting is to match openings and gaskets as you say. If I understand correctly, I will see a hump in the exhaust port and this can be grinded down some?
 
Adding to Jeff's porting recommendations, the valve bowls are very important both intake and exhaust.
1) Looking into the port from the valve head direction, any overhang or machining termination below the seat must be removed and blended into the main port before it turns the corner. Use care not to undercut the seat area, only remove material perpendicular to the valve head.
2) The guide boss's needs to be profiled to minimize/reduce it's projected area. Thin at the opening not to cut into the guide press fit OD.
3) The short side radius (port floor) needs to be blended into the valve bowl.

These take many hours to accomplish and can't be rushed, but the reward is significant. If you are not experienced in port flow dynamics, I recommend taking them to a reputable performance shop.
I'll look through my head pictures and see if I can find some before and after port photos that will be relevant to the IH port style.
 
ihpartsjeff said:
Yes, if you have the humps in there, grind them out.

Also, if humps are machined for air injection, install the proper plugs before porting, otherwise you will get a chirp noise from your engine that will drive you nuts. These are the proper plugs - https://www.ihpartsamerica.com/store/iheng-air-inj-plugset.html
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I was wondering if once the steel air injection tubes are removed during the porting process, do those plugs reach all the way down to the new roof, and you blend them in? I've been wondering what to do about those holes, and have been considering trying to weld them closed, then blend the weld into the roof, but having a plug screwed in all the way from the outside is probably the better way to go as there would be zero chance of warping anything or a bad weld falling out into your moving parts (because that WOULD be my luck).
 
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