I am rebuilding a 460 boat motor. It has Dove A block and Dove heads. Heads have adjustable rocker pedestals and some kind of dual valve springs with unknown aftermarket cam, and rail rockers. I would like to install a 218/228 (at 0.05) cam with .503 total lift. Will the rail rockers be OK? Note that max rpm w/ jet drive is around 4600 rpm, with rev limiter set at 5200.
So you have a D0VE-A block and heads, and somebody upgraded the valve train but kept the OEM iron rocker arms? In order for the rockers to be adustable, the studs should be 7/16" from top to bottom, not like the OEM studs with are 7/16" at the base but "neck down" to 3/8" toward the top (<---these are non-adjustable positive stop valve train parts).
Looks like you want to install a Summit 3501 camshaft. The OEM rockers can easily handle this cam....but we don't know what you have for springs OR what you currently have for a camshaft in your engine.
Ahh. I see that I overlooked a detail. The rocker arms (railed) are not iron but cast aluminum. They are marked on top (on the flat zone above the push rod socket) G, and under the G the number 20 and the number 2. They are railed, and I had read that the Dove block was uniquely equipped with rail rockers, so just assumed they were original.
Other details about this engine are:
Windage tray and 12 qt. oil pan, maybe 1985 vintage
Crank appears to have been balanced
Double roller timing chain
One rod cap has been ground on, apparently to match weight with other rods? I will check weight
Cam unknown, but has mark on end "1058 M" (the cam and lifters look OK, so maybe this is a good cam. I would replace it just to be sure I have the right cam in the rebuild)
The entire engine appears to have maybe 100 hours or less. I tore it down because water entered cylinders 4 and 7 (improper winter storage). Everything inside is incredibly clean - except of course 2 rusty cylinders. BUT: the bigger problem is cylinder #1, which has a major beat-out area near the top of the cylinder. That piston had a broken ring - but no wear or marks on the piston or ring. I suspect that a previous build suffered the broken ring, and someone tried to fix without boring #1. Anyhow, all being bored now and we'll start over with a fresh motor!
Based on your most recent posts, now looks like you have a rebuilt engine that has a number of aftermarket parts in it.
Since you engine is completely apart, will be getting rebuilt, and will be seeing marine service, I think you shoudl look to forged pistons instead of the cast ones. With a proper bore clearance the cast pistons will likely be okay to your 5000 peak rpm, but 5000 sustained is a lot to them and you don't know their overall history and you are rebuilding anyway. I cannot tell you what brand rocker arms you have based on your description, but a picture could certainly help. It sounds as though the roataing assembly has been balanced, but with new pistons a re-balance is in order. And without knowing what your cam profile is, we cannot be certain whether the Summit 3501 cam is a performance upgrade or if you are stepping down to a smaller cam, in effect.
Also, maybe you can tell me what kind of boat you have and what you want for engine power and I can give you some suggests for a combination.
Its been a while, but we ended up doing a lot more to that motor than I had originally hoped. Replaced entire valve train, still based on the Summit cam, but new everything else: Comp Magnum (roller tip) rockers, guideplates, better guides, etc. 0.60 overbore necessary to remove cylinder wall damage (from previous broken ring), hypereutectic pistons, rebalance. The machine shop (Boise Cylinder Head - they are good) noted much evidence of detonation, and was concerned about putting it back together with the re******t 9:8 compression ratio. I promised to run premium and maximum 30 degrees advance.
I brought the long block home and began reassembly. Freshened all components. Starters were ugly as expected. But the big discovery was with the distributor. I think I found the "smoking gun" on the 460. That engine had clearly been detonating for a long time. The reason is that it was running total timing advance of 42 degrees. That happened because the initial setting was 6 degrees BTDC, and the centrifugal advance added 36 degrees. When I checked the centrifugal advance I noticed that it was set on the "18" slot instead of the "13" slot. The 13 slot would give centrifugal advance of 26 degrees, plus 6 initial making 32 degrees total advance – OK for a 460. But 42 would, and did, kill the engine. I will change to a 4 degree initial advance for a total of 30 degrees, and hope that makes for a more durable, happier engine.
Great observation on the distributor! DO NOT allow those hypereutectic pistons see any detonation, they really don;t like it. For the price, another $50 would have got you forged. Just keep spark advance where you noted and jet a little on the rich side...meaning do plug readings and make sure you are not lean, and you'll be fine.
A while back you asked about the boat. This engine goes into a 24' aluminum hulled jet boat, a river boat (guide boat actually) built in 1978 by Holaday in Meridian, ID. It is a mild V, about 8 degrees, and 6 feet wide at the bottom. The boat was originally built with a 350 Chev, but swapped to the 460 with a Hamilton pump. It planes at a low speed and lifts the bow beautifully for big river waves. I have taken it completely apart, replaced windshield and added hard top and windows. It sat in the boatyard 3 years during the windshield/top surgery - part of the problem. As I put it back together I will set it up as a camper (in the cabin) for two persons, with a large flat deck over the motor. I suspect this hull is very light in weight. Even with a motor that could not possibly have run very well (and a gigantic albatross of a zodiac strapped on top) it made 42 mph at 4300 rpm. Don't know how to insert a picture.
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Re: 460 Rocker Arms
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