403 olds is just slow?

« **on:** July 24, 2021, 04:57:09 PM »

Hey everyone. I recently picked up this 83 charger bubble deck with a 403 olds and berkeley 12JE pump. I rebuilt the carb, replaced the fuel pump, and took it to Silverwood Lake to test it out. The boat overall ran pretty good but it would only get to 4000 RPMs and my gps speedo clocked it 42 MPH top speed. is that normal? I feel like I should be getting more RPMs and the guy I got it from said it would do somewhere around 60 MPH so I'm a little disappointed to see 40. Should I expect more out of this setup? If so how do I get it? Any help is appreciated

just a little more info: the carb is a holley 600cfm double pumper on a edlebrock performer intake. hardin marine thru the transom exhaust. And the engine has some 3A heads I think are from a 350 olds

« **Reply #1 on:** July 24, 2021, 10:24:37 PM »

A quick Google search showed the 403 olds made a whopping 185 hp. But that's net hp. If the gross hp was 100 hp more, you're working with 285 hp.

Per Jet Boat Performance impeller dyno, and assuming an "A" impeller, it's producing 228 hp. At least it's above net hp levels.

I ran a mild 350 Chevy, to 45-4600 rpm, "A" impeller. Chart shows 326 hp, and summit and jegs list it as a 330 hp engine. (Very similar combo).

Also at Silverwood, you're probably down 2-300 rpm due to elevation.

Couple of things to check-
Accurate tach?
Pump condition?
Proper timing?
Tired engine?
Pitot speedo or gps? (Pitot speedos are notoriously inaccurate)

I can't see 285 hp (or 228 @ the impeller) breaking 50. 40 does seem low.

Just my $0.02

Dan'l

« **Reply #2 on:** July 25, 2021, 11:03:02 AM »

I appreciate your $0.02! But I just made a pretty big discovery. I was checking the casting numbers on the block and it’s actually a 350 olds. That explains the heads. I have a suburban with 454 at my dads maybe I’ll look into swapping that into the boat later down the road because I wanna go fast haha

« **Reply #3 on:** July 25, 2021, 11:40:06 AM »

That makes more sense.
Run of the mill olds 350s were rated at 160 to 185 hp, net.
So turning 4K at Silverwood lake at 3500' elevation (228 hp absorbed, theoretically) is pretty respectful, considering. Assuming an "A" impeller.

A mild cammed 454 and headers can easily hit 400 hp. 500 isn't that difficult either.

The draw back is the e pump, not the greatest for performance potential. The shape of the intake/hull hinders water delivery to the impeller. But for a mild hot rod, it'll be fine and fun.

Dan'l

« **Reply #4 on:** October 14, 2021, 04:34:33 PM »

Quote from: BeefSupreme on July 25, 2021, 11:03:02 AM

I appreciate your $0.02! But I just made a pretty big discovery. I was checking the casting numbers on the block and it’s actually a 350 olds. That explains the heads. I have a suburban with 454 at my dads maybe I’ll look into swapping that into the boat later down the road because I wanna go fast haha

Hey there! Dont count the olds out yet! haha. brother in law has an 88 commander with a 350 that i think is only rated for 265 hp and it turns i think he said 4300 or 4400 with a berkeley A impeller at the colorado river (lower elevation but hot crappy air)

You shouldnt have too much trouble getting the olds up to 55 mph if you were so inclined before attempting a BBC swap.

« **Reply #5 on:** November 17, 2021, 09:41:48 PM »

I typically only run the river too. I just go to silverwood for annual pre season shakedown. Since I have some other projects going already, I’m just going to pull the 350 this winter and clean it up and go through some things and drop it back in. I wouldn’t mind doing a few budget friendly upgrades while I have it out. If you have any suggestions I’m all ears.

« **Reply #6 on:** December 16, 2021, 01:38:51 PM »

Quote from: BeefSupreme on November 17, 2021, 09:41:48 PM

I typically only run the river too. I just go to silverwood for annual pre season shakedown. Since I have some other projects going already, I’m just going to pull the 350 this winter and clean it up and go through some things and drop it back in. I wouldn’t mind doing a few budget friendly upgrades while I have it out. If you have any suggestions I’m all ears.

If it were me....

Before pulling engine do a hot compression check. Once apart verify compression, deck height etc and optimize on rebuild.

Mild port work on the heads and fill the center crossover ports. -since you are going to have it apart? -

Verify cam and valvetrain, optimize for your boat if needed.

check and optimize all oil drain back locations in the block. ( how apart do you plan to go to cleaning it up? )

Check and optimize exhaust system.

« **Reply #7 on:** December 16, 2021, 01:42:25 PM »

Oh, and verify timing and that the carb is getting full throttle. 4000 still seems a bit low.

« **Reply #8 on:** February 19, 2022, 06:52:45 PM »

I went ahead and pulled it and now I have the engine on a stand. I haven?t cracked it open yet so im not sure what previous works been done to it, if any. I hit up a local machinist about working the heads a little bit but he?s dragging his feet so I?ll probably need to find another guy. Im no engine builder so bear with me I don?t know crap about how to make power I just know how to pull a motor

I just want to get more speed maybe, 55 to 60 mph and still be reliable as possible. I?ll probably tear into it this weekend or next and try to identify what the internals parts are looking like and see what I?m really working with and post a better update then.

« **Reply #9 on:** February 24, 2022, 10:03:23 AM »

I like Berkeley 12JE pumps . Had a 1978 20.5 FT. Kona mini day cruiser .Harman Ford 460 stock except 428 timing chain assembly, JE pump ,ride plate, JP marine intake grate,massaged hull to intake area, saddle tanks . That style pump brings the engine farther back towards the transom . Kona with no hook in the hull ,saddle tanks and no place diverter ran 55+ and got loose on Havasu mild chop pretty easy above 50.

« **Reply #10 on:** June 17, 2022, 03:32:13 PM »

Quote from: BeefSupreme on February 19, 2022, 06:52:45 PM

I went ahead and pulled it and now I have the engine on a stand. I haven?t cracked it open yet so im not sure what previous works been done to it, if any. I hit up a local machinist about working the heads a little bit but he?s dragging his feet so I?ll probably need to find another guy. Im no engine builder so bear with me I don?t know crap about how to make power I just know how to pull a motor I just want to get more speed maybe, 55 to 60 mph and still be reliable as possible. I?ll probably tear into it this weekend or next and try to identify what the internals parts are looking like and see what I?m really working with and post a better update then.

Sorry, forgot about this site for a bit. What did you find out?

« **Reply #11 on:** June 20, 2022, 11:49:23 PM »

Well the good news is the olds is back in the boat and just about ready to fire up for the first time this season. Unfortunately the machinist I talked to flaked on me. And after some research and shopping around i found out there isn?t a lot of parts available for the ?77-?80 olds 350?s I couldn?t even find a complete set of gaskets for a rebuild so since it seemed to run healthy before I pulled it and it looked clean inside the valve covers I decided to just clean it up and paint the block, heads, and valve covers. Put in a new valley pan resealed the intake, change the oil, spark plugs, cleaned the carb. Regular tune up stuff. Now I just have to add oil, fuel it up, do a nut an bolt check and buy a new battery or two because I?m an idiot and left :Dignition on for weeks in before I started this projects. If my work schedule permits I?ll take the Morning Wood to silverwood lake for a test run and check timing and replace my trailer bunks while I?m at it. Once I clean it up and all back together I?ll try to get a couple of good pics to post.

Hope every one else is on the water already

« **Reply #12 on:** June 30, 2022, 11:21:29 AM »

Dont feel bad. I just took the boat out for the first trip last weekend at havasu!

Good luck, let us know how it goes.

« **Reply #13 on:** July 03, 2022, 04:20:58 PM »

Good news and bad news. I was going to put my new plug wires on so I checked the firing order on the distributor for the first time and found out cyclinder 1 and 5 were swapped

so that may explain a lot. Wish I had checked that sooner. I ran new fuel lines and filter. Installed a new battery had some wiring issues. Got those taken care of and finally it was ready for a quick test fire. She fired up and ran pretty good sounded better than before with no audible misfires. Here?s where the bad news starts. I hooked up the garden hose ran in for a few minutes she was idling a little high about 1,000 to 1,100. I assume the timing is off. Both valve covers have a small leak probably just need to be tightened down a little. Exhaust leaks on both sides. Whatever. But the main issue is water immediately got into the oil noticed it seep out of the the valve cover pulled the dip stick and confirmed milkshake.

not sure why or how. Im hoping its something easy to fix. I really wish I pulled the whole thing apart while I had it out but I guess I know next time.

« **Reply #14 on:** July 04, 2022, 01:42:53 PM »

Happy 4th to you and everyone else on here. Sorry to hear your troubles with the boat. Sneaky plug wires & carb issues can sound the same. When you run it on the hose do you start the engine first then turn the water on? Then while running, do you turn water off before engine is turned off? Depending on what exhaust system you have & waterline routing, higher water pressure from house hose can make oil milky too. Hope to hear you get it figured out.

« **Reply #15 on:** July 13, 2022, 06:55:11 PM »

It?s been a headache. I start the engine then turn on the water. I have Hardin logs and snails plumbed pretty basic, water in from pump to logs to block out thermostat housing back to logs and out. I installed a water pressure gauge on my intake manifold but the gauge read zero even after even with the gate valve wide open. My suspicion is the head gasket or worse case a possible cracked block maybe? Any suggestions on tests to track this down or any ideas before I tear it apart again. I?m also having a hard time tracking down gaskets that will fit the engine is somewhere between 1977 and 1980 and I think only those years will fit. Correct me if I?m wrong please. Thanks every one!

« **Reply #16 on:** July 15, 2022, 07:02:03 AM »

Always subtract 20mph from seller top speed claims unless they can prove it via gps or your water test.

« **Reply #17 on:** July 15, 2022, 07:44:32 AM »

Ain?t that the truth, I?m ready to just sell this boat and get a clean full stringer hull

« **Reply #18 on:** February 08, 2023, 01:07:57 PM »

BUMMER!

ive milkshaked a few times on the 455, most common area was the timing cover where the water enters the block. second most common seemed to be the water crossovers from the intake to the heads.

« **Reply #19 on:** February 08, 2023, 05:16:44 PM »

Junkyard digs did a show on a 455 Olds powered jet boat. They do a pretty good job of highlighting the usual areas on an Olds where water intrusion occurs. Also show what the fix is. I attached a YouTube link to that episode. Hope that helps.

Sent from my iPhone using SoCal Jet Boats

« **Reply #20 on:** July 11, 2023, 01:27:26 PM »

Little update

I finally tracked down and ordered the proper head gaskets, better intake gaskets and sealant. The plan now is pull it apart inspect everything and rebuild for as cheap as possible and get it to run properly since I?ll most likely ditch this motor later on.
Hopefully the rest of the internals aren?t hammered I really don?t want to put more money into this poor little olds

« **Reply #21 on:** July 11, 2023, 05:02:14 PM »

Good to hear, do you have any suspicions as where the water is leaking from? What did you take apart over winter?

Let me know if you have any engine questions, i have an old mondellos book that might have some useful info for you

« **Reply #22 on:** July 11, 2023, 07:23:00 PM »

I got busy with other projects and moved into our new house so unfortunately I hardly touched the boat.
I did pull the intake off again but no sign of leaks there I?m going to put a pressure relief valve in the system too before I try to run it again

Sent from my iPhone using Tapatalk

« **Reply #23 on:** July 13, 2023, 11:32:26 AM »

The front timing cover is a big culprit especially with fresh water cooling as the thin 1/8" plate starts pitting pretty bad.

« **Reply #24 on:** July 31, 2023, 07:59:15 PM »

Update time with some good news? so far

I pulled the heads. Inspected everything to the best of my ability. Everything looked okay for the most part. Cleaned up the surfaces replaced the head gaskets, intake gaskets and water pump cover gasket. Now it?s all back together and I have my fingers crossed.

I bought cheap oil and filter from oreilly and filled it up cranked it over to get the oil pressure up, I hooked it the hose started it, turned on the water, ran it just long enough for water to come out the exhaust, shut it down and checked the dip stick ?..milkshake.. Defeated once again I went inside to cool off and think of the next move.

When I removed the filter there was still plenty of milky oil left in it from last time I tried to fix it and since I didn?t check the dipstick prior to running water thru I figured it could be residual water mixing with the new oil. So I flushed it 3 times with cheap oil until it started to look like clean oil before I hooked it to the hose again. This time I started it, ran it with water til it came through the exhaust and checked again and it appears to look like oil again!! Great success. Still need to flush it to get %100 clean oil but I think the head gasket fixed the problem! Any tips on flushing and getting all the water out faster? I want to take it for a proper test run. Im not big fan of running in the drive way since I can?t disconnect my drive line.

Thanks again for all your help and the dudes on the Facebook groups!

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