888/302 camshaft selection

[racinrc14]

Hello,

Due to freeze cracked block, I am in the process of rebuilding my '77 888/302. Some of you may remember earlier posts.

Anyhow, can anyone suggest reasons why Mercury Marine selected 351W camshafts and heads for the 302 marine motor? I ask not because I want more HP, but simply because I want to choose the correct parts. The heads off the old cracked 302 checked out okay, so I had them re-conditioned for the 'new' short block. I want to install a new cam/lifters, but selecting the right one is proving to be confusing. Comp Cams suggested a 302 camshaft (High Energy 260H) for my marine application, but the factory cam was a 351w specific cam. Anybody have any input on this. I understand the differences in the firing orders. Also, I am sticking with the iron 2-barrel intake and carb.

 

[WizeOne]

Re: 888/302 camshaft selection

Your Merc 888 did use the 351 cam. I cannot say exactly why they did, but they did. You might want to call Scott at Delta Cams (253 383 4152) in Tacoma Wa and ask him. He can also tell you what acceptable upgrades would work for your motor but as I recall their marine grinds did not differ much from the stock 888 cam. Delta reground cams have an excellent reputation and are far cheaper than new.

As for the intake mani, I do not know why Bubba says no, he might be mixing it up with a 351 swap which you are not doing. Yes, there is no problem with re-using your intake. However, it is a bit of a shame 'cause a nice little 4bbl will really wake that 302 up. You just have to learn to keep your 'foot' out of the throttle and it will get the same mileage as the two bbl.

 

[WizeOne]

Re: 888/302 camshaft selection

Because his other post was about swapping in a 351.

You sure you are not mixing him up with BarryT's swap question?

http://forums.iboats.com/showthread.php?t=288400

 

[racinrc14]

Re: 888/302 camshaft selection

I had considered a 351 some time ago (a month or so), but I'm not interested in swapping a 351. I am reconditioning a 302 short block of the same year as the old one, and I will be re-using the intake manifold. And yeah, Mercury used the 351 cam in this engine as evidenced by the lack of firing order numbers on the intake (they ground them off at the factory because of the different firing order with the 351 cam).

My original question was about camshaft selection, not intake manifold information. I will contact delta cams.

 

[Surfdancer]

Re: 888/302 camshaft selection

I rebuilt a Mercruiser 888 (1974 model) in my John Allmand Ticonderoga (a 23' flybridge boat) many years ago and used a Truck / RV cam with no issues. II put over 1000 hours on that engine before I sold the boat. I would get about 3 mpg in smooth seas, fully loaded, turning a 17 pitch prop.

The firing order was not marine cam firing order - it was the firing order for standard 302 Windsor engines of that era. I provided the new owner all the paperwork, so I cannot provide the cam specs. It was a Ford Motorsports cam, and I believe it was around 0.484" lift and 214? duration.

A word of caution: I was told that 302's were notorious for damaged cam bearings, and after recently tearing down the 1976 model 888 engine on my project Starcraft boat, I believe it. Check the bearings carefully and install the cam gently. The cam bearings seem to be pretty fragile on the small block Ford V-8's. The forward edges tend to chip easily as the bearings are fairly thin.

 

[racinrc14]

Re: 888/302 camshaft selection

I had the machinist replace the cam bearings on my 'new' short block. I will be extra cautious with the install, thanks for the heads up.

I cannot get Delta Cams on the phone, so looking into the Comp Cams k31-218-2 camshaft kit. Comes with everything, cam, lifters, recommended springs, timing set, etc.. for around $350. Should be a nice little cam with a small increase in mid range power over the factory cam.

For what it's worth, the firing order at my distributor is 1-3-7-2-6-5-4-8. Looks like I'll have to revert to the non-HO 302 firing order with this cam kit.

 

[WizeOne]

Re: 888/302 camshaft selection

Did you bore your 'new' shortblock? If so, I hope you are going to flat top pistons. You'll pick up a point in compression over those dog bowl dished pistons. You'll still be able to run regular gas but will notice a significant difference in power.

If you are reasonably handy with a die grinder, air or electric, you should gasket match the intakes ports on your heads and grind down the thermactor bumps as well. It is very easy to do and will provide much better fuel/air flow into the combustion chambers.

 

[racinrc14]

Re: 888/302 camshaft selection

Wizeone,

Yes the new block has been bored .060. I will be installing new F.M. flat top pistons w/2 valve reliefs. This should give around 8.6:1 c.r. with the factory 69cc 351w heads I have. I was considering K. B. domed pistons, but since I am going the 2bbl route, figured was probably a waste of $300 for the set. The valves in these heads are relatively small compared to perf. heads, measuring 1.78 and 1.45, but with the cam I am installing, should run pretty good. Local engine guy estimates around 205HP w/ this setup. And I'll have all the reliability of the stocker.

I am familiar with port-matching and gasket-matching, but I am having trouble picturing these thermactor bumps you speak of. Can you decribe these in a little more detail? The heads are still at the shop, but I am picking them up after work, so I'll have them to look at this evening. Thanks.

 

[racinrc14]

Re: 888/302 camshaft selection

By the way, does anybody know how to get a hold of a tech rep at Mercury Marine that understands older engine/drive combos? Seems like anyone I speak to only knows about more current pp's.

 

[WizeOne]

Re: 888/302 camshaft selection

By the way, does anybody know how to get a hold of a tech rep at Mercury Marine that understands older engine/drive combos? Seems like anyone I speak to only knows about more current pp's.

What is it you need/want to know?

btw, I will post pictures of the thermactor bumps in the head exhaust port. I mis-stated their location in my above post.

 

[WizeOne]

Re: 888/302 camshaft selection

Using your .060 overbore, .015 for compressed head gasket, your 69 cc combustion chambers, .015 for below deck piston height and minus 5 cc for the piston's valve reliefs, I calculate your C/R to be at 8.91.

I could not find a picture of the thermactor bump but have included a picture where I removed the bump while gasket matching the exhaust ports as well. The bump rose directly above where the hole is in the floor of the port. Just grind it flat with the rest of the surrounding surfaces. You can also see the remnants of my gasket matching sharpie marks around the opening of the port. You can also check the openings of your exhaust mani ports and just fair back a bit if they stick out into the opening of your gasket. Little things like this can really make an engine hum.

 

[mkast]

Re: 888/302 camshaft selection

Take a look at the stock cam specs in the Mercruiser manual.
Match the new cam with the stock specs.
If you can't find something in a 302 cam, run a blueprint Crane cam for a 351.
If you're having problems with cam bearings, I'd look at the person installing cam/bearings, cam bearing failures in a SBF, after 47 years???

 

[racinrc14]

Re: 888/302 camshaft selection

I see the bumps now. Should be straight forward. Why are they there, anyway? Just to interrupt the flow? I'll check out the ex. mans. for matching after I check them for cracks.

Thanks Wizeone for the C.R. figure. I was estimating and was apparently a little too conservative.

Mkast, I'm not having any problems with the cam bearings, but I'll still be careful with the install. Actually, the machinist said the bearings that were in it (the rebuilder) were in really good shape, but the kit I ordered came with new ones, so I had him install them.

 

[WizeOne]

Re: 888/302 camshaft selection

Thanks Wizeone for the C.R. figure. I was estimating and was apparently a little too conservative..

ur welcome! Close to 9 is good!

I see the bumps now. Why are they there, anyway? Just to interrupt the flow? ..

They were there to deliver air, from the airpump, into the exhaust stream to further burn off the remaining elements of the combustion chamber. That system was the precurser to the catalytic converter. That system was not employed in marine engines as they were not subject to the emission requirement of the day. As such the passages were simply plugged on heads used on marine engines.

 

[racinrc14]

Re: 888/302 camshaft selection

That system was not employed in marine engines as they were not subject to the emission requirement of the day. As such the passages were simply plugged on heads used on marine engines.

Consider them gone. Any risk of un-covering any passages underneath them?

 

[WizeOne]

Re: 888/302 camshaft selection

Consider them gone. Any risk of un-covering any passages underneath them?

Just mark the throat of the exhaust port with your gasket, then cut inward, tapering the floor of the port from the opening back up into the rear of the port. Cut the floor flat, right thru the bump. Then clean the radius where the back of the port turns up into the valve pocket.

My pic above should be a good guide. If that is all you do you will not near cut thru anywhere. A full on 'porting' job would be considerably more radical.

 

[racinrc14]

Re: 888/302 camshaft selection

Excellent, thanks Wizeone.

 

[Faztbullet]

Re: 888/302 camshaft selection

Just my 2 cents, but all the suggestions are great but the thing that hurts you most is the restrictive log style exhaust manifolds. I would dump these and install the new center riser style (18-1998-1). You will have better cooling and free up exhaust and gain around 15hp.

 

[WizeOne]

Re: 888/302 camshaft selection

Just my 2 cents, but all the suggestions are great but the thing that hurts you most is the restrictive log style exhaust manifolds. I would dump these and install the new center riser style (18-1998-1). You will have better cooling and free up exhaust and gain around 15hp.

'twould be interesting, if all that were true, to know what you had to do to reconnect the risers to the "Y" pipe?

 

[Faztbullet]

Re: 888/302 camshaft selection

If doghouse has the room you would need 2 18-1998-1 manifolds,2-18-1939 and 2-18-1992-1 and 2 ft of 3" exhaust hose. I have changed a lot of these(log to center) and have seen better results all around. I have had two boats that actually gained enough to go up a prop size. As for cooling the engine runs 5-10 degrees cooler