383 dyno success!

[JHuck]

After dealing with TB V ignition issues in another post, we were able to run the 383 with a new MSD distributor and box today. We ended up with 466 ft/lbs at 4400 rpm and 433 hp at 5500 rpm. The lowest torque reading was 423 ft/lbs at 2900 rpm. Needless to say I am happy with the results. Once again, I want to thank Chris Straub for the custom grind. I will be able to use my GLM manifolds with this cam. I also want to thank forum members who chimed in on everything from gear lube to carb CFMs.

Now I need to calculate the new prop pitch. Should I base target RPMs on peak tq or peak hp? At peak hp, tq drops to 412 ft/lbs. Using a 21p 3 blade with 1.5 ratio right now (Alpha).

 

[straubtech]

Re: 383 dyno success!

Congrats Jeremey, thats a stump puller with that kind of torque. You will need to baby that Alpha. You need to prop for 1000 to 1200 rpm over peak torque. Running the drive propped for peak torque will put the drive in constant torque load and that Alpha will not be happy.

How was throttle response of the engine?

 

[mylesm260]

Re: 383 dyno success!

You should prop it for peak hp, but you should never spend too much time there.


You're 383 is making peak hp nearly 1000 rpms higher than factory marine engines. Your engine is going to wear much much faster at 5500+ rpms.


If you prop it for below your peak HP (4800) than you will never be able to use all the HP you have available to you, and you would have been better off going with a colder cam.

Can you tell us more about your build?

What are you using for heads? Aftermarket "Fastburn" aluminum?

Did you buy a stoker kit (pre balanced, with crank, rods, pistons)?

What are your cam specs? lift/duration?

What about compression ratio and fuel?

Obviously you're using 4 bolt mains, what are you using for rings and bearings?

Also, any chance you could scan and post your dyno graph? I wouldn't mind seeing the full torque curve of that setup.


Thanks,

 

[JHuck]

Re: 383 dyno success!

I should have the engine in the boat this weekend so I'll know how responsive it is then.

 

[HT32BSX115]

Re: 383 dyno success!

Now I need to calculate the new prop pitch. Should I base target RPMs on peak tq or peak hp? At peak hp, tq drops to 412 ft/lbs. Using a 21p 3 blade with 1.5 ratio right now (Alpha).

Those are awesome HP numbers!

You can use this Prop slip Calculator to get yourself in the ballpark.

Use about 12-15% slip for a single prop drive.

If you're using an Alpha, I'm sure you have heard all the warnings about it. If you "straight-arm" the throttle, you'll probably break it in short order.

I didn't follow your build info. Could you post it again?

I would love to put a 383 in my Liberator with the Bravo III. A 383 with aluminum heads, manifolds and risers would probably shave 300lbs off the back of my boat!!

I would probably limit the RPM to 5000 or less though just to put less stress on the drive. I could probably run 70 mph with 30p props! More than fast enough for a 4300lb boat!!


Cheers,


Rick

 

[mylesm260]

Re: 383 dyno success!

Bump.
I would like very much to see the dyno graph and hear more about this build.

My 4.3 powered boat is beggin' for more mmmmpphh.

 

[Bob_VT]

Re: 383 dyno success!

Isn't 300 hp the max for an alpha one? Great numbers but I pity the outdrive

 

[mkast]

Re: 383 dyno success!

Weight of the boat dry?

 

[JHuck]

Re: 383 dyno success!

Not sure of the dry weight. Tried to find specs online but no luck. It's a 21' open bow. To get an idea of size, scroll down to "Boat of the Month".

http://www.indycovers.com/

I had the cover made in May...back when I thought the boat would be done by Memorial Weekend, Ha.

My set up involves AFR 195 heads, RPM Air Gap intake, Eagle 383 rotating assembly with cast crank, stock two bolt mains with ARP studs, full roller rockers, short valve covers (barely clear rocker retainers with thicker cork gaskets), Holley 750 with vac. secondaries, and custom ground roller cam 214/218. There is nothing trick to this set-up just components that work well together. My goal was to keep this affordable compared to performance marine engines I've seen on the net. Even after buying the aftermarket ignition, I think I am getting great bang for the buck (minus future outdrive).

I think one thing that helped the low end is that I really paid attention to valvetrain geometry. Based on what I've seen online, I would guess that I measured my pushrods different than how most people would have done it (based on true lift vs. being overly concerned about the roller being in the middle of the valve stem). If I would have centered the roller on the stem, I would have gotten .3" of actual lift. I adjusted it until I got .53" of max lift which is exactly what the cam and rocker combination was set up to provide.

The Holley was spot on for A/F ratio right out of the box. All we did was adjust the idle. The MSD billet distributor was head and shoulders better than the TB V as it allowed us to go to valve float 5800-5900 rpm. I don't plan on taking it that high (neat to hear it do it on the dyno though).

I need to input the dyno data from the hard copy I have into Excel. I can then chart out the curves. I've got some video that I will try to download tomorrow.

 

[Mkos1980]

Re: 383 dyno success!

So what size pushrods did you end up with? Did you verify the lift of the cam before you installed it to make sure it was exactly what it should have been? If its a hyd roller I know alot of people just measure using a stock lifter when infact they should have made it a solid roller lifter. I took apart an old roller lifter and filled it making it a solid for mock up purposes.

 

[ringmaster72]

Re: 383 dyno success!

You will be fine with the Alpha. I am pushing close to 400 HP on mine with no problem. I have seen people rate the Alpha up to between 350hp and 400hp. I would worry more about the torque than the HP for the Alpha.

 

[n2ostroker]

Re: 383 dyno success!

You will be fine with the Alpha. I am pushing close to 400 HP on mine with no problem. I have seen people rate the Alpha up to between 350hp and 400hp. I would worry more about the torque than the HP for the Alpha.

Come on now...
We all know as soon as he drops the motor in the boat the Alpha will quiver and instantaneously explode when he throttles past the 300hp mark!!

Nice numbers BTW. You'll have fun with that one. I was looking at almost an identical setup when I build another motor this winter. Maybe a little hotter cam though.

 

[JHuck]

Re: 383 dyno success!

I will say the pushrods were longer than 7.700. This put the roller toward the outer (exhaust side). I used my stock lifters that were still pumped up but I substituted my intake and exhaust valve springs for lighter ones so the lifters wouldn't collapse.

Yes, the cam specs showed .53" lift using 1.6 rockers.

I used a Comp Cams adjustable pushrod to measure length. I started it short and then kept increasing the length until the lift peaked and started to come back down on my dial indicator. I then went back to that length and quadruple checked the lift. My intake and exhaust lengths differed by .05 so I split the difference so I could buy 16 equal length chromoly pushrods. I then added a little extra length to account for the pre-load of the pushrod into the lifter once everything was buttoned down. I went 3/4 of a turn pre-load on the rocker retainers.

If I was using stamped rockers, I might be more concerned about the lifter not being centered on the stem but the rollers have such little friction that, IMHO, I think they allow a bit more leeway of placement.

I filled the Alpha with Quicksilver synthetic and splashed it with holy water. It may take an act of God to keep that thing together.

 

[Mkos1980]

Re: 383 dyno success!

I'd still put some blue dye on top of the valve stem , run it and double check to make sure the mark is centered. It doesnt matter if you have stamped or roller lifters, if its anywhere but the center, your putting a strain on the sides of the valve guides.

 

[CharlieB]

Re: 383 dyno success!

Changing OD gear ratio may be another option rather than increasing prop pitch by large #'s. Talk to your prop shop about it.

Pushing that much power through an Alpha you may elect to install one of the shower type coolers to help keep the drive temp within reason.

 

[JHuck]

Re: 383 dyno success!

Charlie-thanks for the gear suggestion.

Mkos-I don't doubt there is probably some additional stress on the guides but I haven't been able to find what the increased amount would be or even if that amount would be a cause for concern. I communicated back and forth with K-star (moderator in another forum and performance engine builder) on this very topic. He has gone round and round with others regarding push rod length. He informed me that on the last 40 or so SBC performance engines he's built, he hasn't had any issues from having the roller off center because of the longer pushrods he used. I'm not saying this means a guy could use this set up in a car and run it for 150,000 miles but in my boat that will see less than 100 hrs of use a year, I won't lose sleep over it. My main goal was to make sure I was getting the lift my cam and lifters were designed to provide. Regardless, I still appreciate your input, thanks.

As of last night, the engine is on the stand with everything installed except for the harness. My only frustration with the rebuild involved installing the manifold drains into the GLMs without cross-threading them. Anyone else have this issue? Seemed like the threads were a little off.

Hopefully I'll get the engine in the boat tomorrow morning and we'll be on the water by the afternoon.

 

[straubtech]

Re: 383 dyno success!

I worked for a rocker arm mfg m13 or 14 years ago and one word of advice he gave me was to concentrate on width of pattern on the valve tip. He didn't really worry about if the pattern was centered but narrow. He said a pattern width of .060" is perfect and it could be justified towards the exhaust or to the intake side of the valve as long as it was that width or narrower. Any wider on pattern you then have the tendency to rock the valve back and forth in the guide and where the valve guide out.

 

[HT32BSX115]

Re: 383 dyno success!

I'm not saying this means a guy could use this set up in a car and run it for 150,000 miles but in my boat that will see less than 100 hrs of use a year, I won't lose sleep over it......................

My only frustration with the rebuild involved installing the manifold drains into the GLMs without cross-threading them. Anyone else have this issue? Seemed like the threads were a little off.

I think that we sometimes expect our marine engines last long enough to actually wear out!

Unless you're doing 100 mile endurance racing at or near WOT for hours on end, It's unlikely you're ever going to wear out a marine engine before something else goes wrong with it! (this is probably why oil doesn't really matter)


On the cross-thread thing, It seems like I read in a thread that someone that installs those cheap GLM manifolds frequently just runs a pipe tap in ALL the threaded holes to ENSURE that they're clean and straight!


A GLM manifold I put on a 3.0L engine last summer did have some holes that needed a little re-threading up with a good NPT tap.


Cheers,


Rick

 

[JHuck]

Re: 383 dyno success!

Chris-That's what I did for this build and the width of the line was very close to what was recommended to you. I have read that peak lift will naturally make the narrowest line. Thanks.

 

[wca_tim]

Re: 383 dyno success!

Changing OD gear ratio may be another option rather than increasing prop pitch by large #'s. Talk to your prop shop about it.

Pushing that much power through an Alpha you may elect to install one of the shower type coolers to help keep the drive temp within reason.

Great result! Have been following your posts with interest.

I haven't seen any temp problems with my alpha even running cose to flat out for significant time periods.

On prop pitch, I'm running a 1.81 gear behind my 383 (different build but at least on par power-wise) to put pitch about 2x diameter - faster than lower pitch props onc eyou get over 50 or 60 mph according to everything i've read. And my set-up runs a good bit faster on the top end with a 1.81 gear upper outdrive than it does with a 1.47 (both propped accordingly)

There are some GREAT props available in the 24-32" pitch ranges. You'll probalby see the best performance in the long run with a hydromotive quad 4, a bravo or a mirage... or at least based on my experience. you can find most of those available on ebay on occassion as people upgrade boats and go to higher pitches.