980 hours on engines - compression test

[Scott Danforth]

Scott Danforth - I have done some Craigslist searches in the area. It looks like there are some steel gantries for about $1K, which would be a little pricey, but worth a continued look over the winter. :thumb:

they are only $700 at harbor freight


maybe rent a mini excavator. I believe its $250 per day

 

[Scott Danforth]

my last gantry I made was 3 2x10's standing on edge, on top of 5 2x6's with 2x6 bracing and 2x6 base

I may have over-built, however it didnt even budge

 

[harringtondav]

tpenfield After I hit 'post reply' I remembered you are pulling twin engines. So the chain will be off center, with less max. bending moment and close to, or over your angle braces You will know right away if the 2x8 beam starts objecting. If you have an extra 10' 2x on standby, you could screw sister it onto the main beam. If you don't need it, return it.

I was also thinking about accessing the rear mount bolts on big twin engines. I'm a small guy, 5'6", <160#, and I had to do a semi-headstand to access those bolts on single engines. I don't know the space between you engines, but getting at the two center bolts, plus muscling off the inside rubber exhaust tube may require a yoga session or two before.

 

[tpenfield]

Good point about the engine spacing. They are 35” apart on center and only have about 2” between the exhaust manifolds. So, as long I have about 5’ of clear space between the cross braces, then I can move the chain hoist appropriately, while the gantry straddles the boat.

My twin engines are very tight side-to-side and at the transom, but I have gotten used to the contortions of working on them.

 

[Mischief Managed]

When you have your gantry built, feel free to borrow my chain fall and engine leveler. You may want to use them (and the gantry) for the ESP too.I found that mine was much easier to install when it was suspended form above with infinitely variable height and angle.

 

[Scott Danforth]

Ted, you could simply buy these:

https://www.offshoreonly.com/classi...ce-509-cu-in-550-hp-engine-motors-o73494.html

 

[alldodge]

Don't forget the height of the leveler and such

I like using two 1 inch lifting straps, one under each exhaust manifold to a central hook. The straps make it easier to tilt just a hair if needed, and also allow small adjustment to center prior to lifting

 

[tpenfield]

Thanks for the offer and comments guys. Having the gantry for the Extended Swim Platform project would probably be good.

Seems like I have too many projects lined up.

 

[Scott Danforth]

Seems like I have too many projects lined up.

you are not alone

 

[tpenfield]

Quick Update . . .

I have been reading up on engine rebuilding in preparation for next year.

I would think the cylinder heads will need a valve job and I plan on inspecting the lower end ( crank, cylinders and cam ) for wear, then decide next steps. I have the engine production and service specs for the crank and cylinder bore in Manual #16, starting on page 3A-10.

Just doing a little research on the camshaft . . .
It looks like the Mercruiser # is 431-840453T (850453), which cross matches to a GM 12551622 camshaft ? :noidea:

Lobe heights are: IN 0.282" EX 0.284" (valve lift would be about 0.48")
Durations are: IN 204 Degrees, EX 209 Degrees
Lobe Separation Angle is 118 Degrees

So a pretty mild cam, it seems. I wonder is 118 LSA is typical for a marine engine, whereas I see some high performance street rod cams at 230 degrees duration and LSA of 104.

My understanding is that the engine (Gen 6) has roller lifters (Mercruiser 850467) not sure what the GM part # is for those. I'm assuming roller lifter result in less cam wear :noidea: I wonder if I will even need to worry about the cam shaft, but just do some measurements to check it.

Any comments about a slightly better cam, yet still avoid reversion?

 

[Scott Danforth]

Ted,

Comp Cams has a better roller lifter than stock GM. that comes from Scotty at Innovation Marine.

most marine EFI grinds are 114 degree or more.

the best BBC marine cam guru is Bob Madara. he grinds most of the BBC cams on OSO.

http://www.marinekineticsonline.com/contact.html

here are some of the cam specs that I have. they may be a bit much for a stock bottom, stock head BBC

for stock bottom end, Maybe a stock Comp Cam grind http://www.compperformancegroupstor...=CTGY&Store_Code=CC&Category_Code=GVICAMHYDXM
like the XM284HR http://www.compcams.com/Company/CC/cam-specs/Details.aspx?csid=596&sb=2
Here is an article on that cam in a rock-stock L29 gen 6 http://www.superchevy.com/how-to/en...power-on-a-junkyard-454-with-simple-cam-swap/


or a custom Hardin Marine / Comp cam grind
https://www.cpperformance.com/c-362-comp-cams.aspx

I have a custom Comp Cam grind in my 468 BBC that was obtained thru Arizona Speed Marine. its supposed to be an HP500 clone.

Here are the old crane specs for the HP500 EFI.

292*/298* @ .004"
230*/236* @ .050"
.352"/.359" lobe
.598"/.610" valve
114* LSA
109* ICL
119* ECL

Here are the HP500 carb’d cam specs

284*/292* @ .004"
222*/230* @ .050"
.576"/.598" valve
110* LSA
105* ICL
115* ECL

The comp-Cams custom grind version thru AZSM

277*/287* @ .004”
228*/232* @ .050”
.588”/.596” valve lift
114* LSA
110* ICL
VOI 4
VOE 54
VCI 44
VCE -2

here is a link to my page https://forums.iboats.com/forum/eng...01672-bbc-build-don-t-tell-the-admiral/page18

I had to drop my base timing back for reversion issues at idle with my build, however the new exhaust should solve that problem so I can push more base.

 

[alldodge]

Good to look into replacement cam but more then likely going back stock you may not need another one. Will need to measure it, and may need to turn cam journals .010

 

[tpenfield]

Good to look into replacement cam but more then likely going back stock you may not need another one. Will need to measure it, and may need to turn cam journals .010

Yes, I think it depends on what I measure when the engines are apart. I'm thinking the camshaft will be fine, even at 1,000 hours. I have been trying to equate 1,000 engine hours to miles traveled in a car . . . seems like it would be about 40,000 miles, which is nothing. But . . . I know marine engines operate at the higher end of their HP range, and typically are going 3,000 RPM, vs a car is going maybe 2,000 RPM.

Maybe 1,000 hours on a marine engine would equate to about 80,000 - 100,000 miles on a car engine. :noidea:

 

[tpenfield]

If I could get a slightly more aggressive camshaft as part of the rebuild, that might be OK. Here is what the cam profile looks like for the standard cam . . . No real possibility for reversion based on this cam . . .

 

[Scott Danforth]

Ted.... look at the graph....this is a family site....

 

[tpenfield]

Ted.... look at the graph....this is a family site....

They all look like that . . . some bigger, some smaller . . .

 

[achris]

Ted.... look at the graph....this is a family site....

 

[Scott Danforth]

Chris, shouldnt you be in bed yet....

 

[achris]

Chris, shouldnt you be in bed yet....

Just woke up....

(It's 0804hours here)

 

[JASinIL2006]

Ted.... look at the graph....this is a family site....

:laugh::laugh::laugh::laugh: