Yet another winter 5.7 engine build, oil pump, camshaft choices

[christoner2002]

I have a 1997 Larson 206 SEI, with a Mercruiser 5.7, Alpha one Gen 2, with a 1.62 ratio drive. Engine has the older style, non vortec centerbolt heads, and was originally a 2bbl and was rated at 210hp. I swapped to a 4bbl intake and a Edelbrock 1409 600cfm carb. This engine will be finding a nice spot in my garage to stay safe, in case it ever needs to go back in.

I am building another engine for the boat this winter. The new engine is a 10243880 2 bolt main 350 block, std bore, with a 14088532 forged steel crankshaft, Speed-Pro +6cc dish pistons, and a set of fresh vortec heads with a valve spring kit from alex's parts, giving the heads ability to take up to a .550 lift. The boat has only thru Prop exhaust, and I am not really wanting to change that.

The cam I am looking at is the Comp Cams Xm270hr, with lift of .495 intake/.503 exhaust, 112 lobe separation, and 270 intake/276 exhaust duration. Thinking of matching that up wit a Edelbrock RPM Air gap manifold. Does this seem reasonable for a thru prop exhaust?

Next will be the Oil Pump. Should I run a Standard oil pump? I thought I remember hearing that a high volume will pump to much oil to the top end under higher rpm for a extended stretch, like a boat does. What do you think is my best option?

I have read the warnings of not giving a Alpha wide open throttle starts, and not getting the prop out of the water. And will be adding a drive shower, and running synthetic Mercury gear lube, like I always have. Any insights will be a great help. Thanks for looking

 

[Scott Danforth]

The XM270 cam is too large for wet exhaust. Even comp cams stated that on their website

Run a mehling high volume oil pump and pump drive shaft

 

[alldodge]

You have a 1995 to 2000 350 that has a virgin bore? Reason asking is your stating your going with a standard bore.

Agree with cam

Don't agree with high volume pump.

 

[Bondo]

Ayuh,.... No reason for a hi-volume oil pump,...

What sorta piston dish are +6cc dish pistons,..??

 

[christoner2002]

The XM270 cam is too large for wet exhaust. Even comp cams stated that on their website

Run a mehling high volume oil pump and pump drive shaft

The page I was looking at on comp cams page, I did not see anything stating that. Looks like I will be back to the drawing board on cam choices. http://www.compperformancegroupstore...Category_Code=

Would this be a better choice? Or still to much cam?http://www.compperformancegroupstor..._Code=CC&Product_Code=08-416-8&Category_Code=

And yes, it is a STD bore block. The Machine Shop I have used for years for all my Engine work in cars, etc, had it. Bores were checked, and are in excellent condition. The Forged Crank is also going to be std on the rods, and mains.

And for the Pistons, I am using a Speed-Pro h345dcp, Which after reading the other 5.7 build near the top of the page here, I understand will not be the best piston for the application. But I already have them installed on the rods.
http://www.summitracing.com/parts/slp-h345dcp

 

[Bt Doctur]

No Hi-Vol pump unless you can fit a 12 Qt pan

 

[Scott Danforth]

Guys, I have been running hi volume pumps for years. Run them in everything, boats, trucks, cars, hotrods, drag cars. My buddy runs them in all his race cars as well. And yes, I have gone as much as 60 miles at a crack in the boat at 4800 rpm. 20% more volume. Being pumped does not need 60% more oil capacity

I stand corrected, the XM270HR is the largest roller cam recommended by comp. The 268 is largest flat tappet cam

 

[christoner2002]

But the XM 270hr would still be to much cam for thru prop exhaust? What are your thought on the xm264hr? http://www.compperformancegroupstor..._Code=CC&Product_Code=08-416-8&Category_Code=

 

[flipbro]

If you go with the HV pump screw off the oil filter change the part were it screws on over to one that doesnt have a bypass or you run the risk of running onfiltered oil through your block at high rpm.

 

[Scott Danforth]

I ran the XM268 flat tappet in my 350

 

[flipbro]

With those piston pins at 1.548 and already .025 below deck and .040 head gasket puts you at .073 quench TO MUCH mabe you could run a .015 steal shim gasket and get the quench down to .048 not perfect but acceptable. If not you run the chance of your new motor sounding like a can of marbles. Have you looked at the ram jet 350 cam?

 

[alldodge]

And yes, it is a STD bore block. The Machine Shop I have used for years for all my Engine work in cars, etc, had it. Bores were checked, and are in excellent condition. The Forged Crank is also going to be std on the rods, and mains.

Just a comment: Wanting to build a motor and have more hp but looking at doing it as inexpensive as possible, and I'm ok with that. The issue that gets me mixed is the things which do not cost much but ensure you start with a sound foundation. Buying new pistons but not going the extra step for the crank and block.

I wouldn't rebuild a used motor with original bores and crank journals. Just to many slight variations which could cause some issues later, also knowing that very surface is spec. Pistons and bearings will cost the same if they are bored (with torque plate 0.030) and ground (0.010).

 

[christoner2002]

With those piston pins at 1.548 and already .025 below deck and .040 head gasket puts you at .073 quench TO MUCH mabe you could run a .015 steal shim gasket and get the quench down to .048 not perfect but acceptable. If not you run the chance of your new motor sounding like a can of marbles. Have you looked at the ram jet 350 cam?

So, If I choose to switch pistons, I would want something with a higher compression height, if I am understanding his correct? I will want a piston with more compression height to get it closer to the top of the cylinder. What is the optimal number for quench with vortec heads? And I plan on using a Fel-Pro 17030 Marine head gasket, that is .039 thick, and has a 4.125 diameter.
I had not looked at the ht383/Ramjet cam. I believe I read on offshore only that is a similar grind to what Merc is using on it's 350 mag Mpi, etc.

Thank you for everyones advice. I appreciate any help I can get.

 

[flipbro]

Your best quench is .040. If you don't deck the block it makes it tricky. Unless your deck and heads are strait enough to run a steal shim gasket. Take it to machine shop tell them what pistons you have. They will zero deck then just buy a good .040 gasket. Likely cheaper in the long run..

 

[christoner2002]

I will look into getting the block decked to get my quench closer in line. And will research the Ramjet cam more. Was reading a lot of guys saying the Lt4 hot cam works well also, but I am just a little worried with it being a wet exhaust

 

[Scott Danforth]

No way you are going to bore your block to 0.125 over (4.125). That is the bore of a 400 (siamese bore block)

 

[Bondo]

Just a comment: Wanting to build a motor and have more hp but looking at doing it as inexpensive as possible, and I'm ok with that. The issue that gets me mixed is the things which do not cost much but ensure you start with a sound foundation. Buying new pistons but not going the extra step for the crank and block.

I wouldn't rebuild a used motor with original bores and crank journals. Just to many slight variations which could cause some issues later, also knowing that very surface is spec. Pistons and bearings will cost the same if they are bored (with torque plate 0.030) and ground (0.010).

Ayuh,.... I just noticed in this thread, as well as the other SBC build thread,...

Nobody has mentioned, what I consider the most necessary step in buildin' a motor,...
Balancin' the rotatin' assembly,....

While I have bought virgin blocks from a machine shop that spec'ed out Perfect,...

Buildin' a solid long lived lower end starts with align-borin' the block, 'n Balancin' the rotatin' assembly,....

It's not a place to pinch pennies in a reliable build,...

 

[christoner2002]

Looking at a different set of Pistons. If I am doing my math right, here is my new plan. Pistons are a Keith Black silv-o-lite, with a flat top, +6.00cc dish taken into account for the valve reliefs. They have a 1.56 compression height http://www.summitracing.com/parts/ue...-std/overview/
If I use a .016 Fel-Pro head Gasket, http://www.summitracing.com/parts/fe...et?prefilter=1
That should put me right into a .41 quench. But if my math is right, will also get me really close to 10.01 to 10.03 compression. Will I be limiting myself to running 91 octane or better with this setup?
Or would I still be better just to have my block decked?

 

[flipbro]

When you get a good tight quench it's what we call free octane.You get a much better burn and flame travel in the chamber. And with the vortec heart shaped chambers helps a lot. You would be fine at 10-1 on premium providing it's tuned properly. And yes 100% balance the rotating assembly. Bondo I did post about this in 1979s Build..I wouldn't use a 4.125 head gasket. When your only boring .030 over. As Scott mentioned I believe that gasket is suited for a 400 sbc. Remember to use a steal shim gasket your block and heads need to be perfect flat. They are not very forgiving. Spray both sides with copper coat spray gasket let tak up then install

 

[christoner2002]

No way you are going to bore your block to 0.125 over (4.125). That is the bore of a 400 (siamese bore block)

I was not looking to bore the engine that big. That is what size the opening bores are on the Fel-Pro 17030 marine head gaskets that I had found. I understand now they are not the right ones for this engine. Sorry for the confusion there.

I will look for a thinner, 4.00 bore head gasket set up for the 350.Maybe something like this, http://www.summitracing.com/parts/nal-10105117
And will look into getting the rotating assembly balanced. You guys have all been a big help. I have learned more in one day then I ever thought I would have. Thank you

I am kind of leaning towards the RamJet350/ht383 cam that Flip mentioned, and or the xm262hr Comp cams marine cam I linked earlier. Thinking the xm270 will be to much cam for a wet exhaust.