455 Olds

[Fournbr3]

I have a 455 Olds that I had previously inquired about. More problems. I now have a 800 CFM Double pumper on it. It cranks, idles and runs smooth up to about 4000 RPM, but thats it. No more RPM (I'm expecting 5500 or so). The ignition system has been checked but I still think it is suspect because I do detect some popping at the higher RPM and can see the little "puff"of backfire through the choke horn of the Carb. The valve springs are new, for that matter the whole engine is. It is almost as if I have a broken Valve spring but it only shows at 4000 RPM. What RPM is normal for this type of jet boat setup? I have a friend that had a 454 that turned 5600 all day long. HELP.


Gary

[blown 509]

depending on what size impellor u have it might not make enough power to rev any higher,also if this boat is set up with a loader scoop. if the loader was intended for a motor that will make 600hp and your motor only makes 500 hp it will bogg the motor because it is over loading the pump

[Stv Euro]

What parts do you have in your motor? Cam, any head work?

I have a 455 punched out to 468 w/ a custom ingle cam by Mondello w/ ported heads and 205lbs of compression on each cyc.

Now guess what mine turns? ONLY 4800 rpms!! So if you find the secret on how to turn these Olds please let me know.

Thanks Kevin

[sanger 455]

sounds like you mite have a bent valve to me .ihad the same thing too last year

[fijjity]

If the springs are installed taller than recommended, they will be weak and not allow the valve to seat properly. Are you runnin roller or stock hyd lifter. Stiffer springs will help upper rpms a little, but not gain ya more than 300 rpms. It may help the poppin unless you do indeed have a bent valve or a worn rocker arm saddle that isn't allowing full lift. A bent pushrod will pop, also. Hope this helps a bit.

[J Lamb]

Check the ignition system, is it hei or points. If points dump it for a good hei. Those motors are low rpm torque motors, no need to turn over 5300-5400. Won't live long like that. Mine I used to drag (1/8 mile) ran best shifting at 5300. I would also say the 800 double pumper is a bit overkill. 750 vacumm secondary at the most. I ran a 650. Definately check the valve train too. Oh do not compare a Olds BB to Chevy, no similarities at all.

[fijjity]

With points and 7800 with a mag-both points sytems. I would tend to think vtrain. check that spring pressures are set right. Check timing and advance. Drop to a 750 holley 3310 vac sec yellow spring in secondary no check ball. check your impeller i think a B/C impeller is right for it. Double check with the jetters. I ran a chevy afterwards and switched to an AB impeller.

[J Lamb]

I turned mine 6500 With points and 7800 with a mag-both points sytems.
Man you guys are livin on the edge turnin a BB Olds that hard :eek: . Long rod and long stoke=low rpm torque. I could turn mine to 6K with 4.10 gears but all that resulted in slower et's. The valvetrain may be the problem. There are 2 different seats, shallow and deep. The deep seats used valve rotators. Can't remember which castings used which. If the springs are wrong they won't have the correct pressure and "float" at a lower rpm than they should. Check the installed height and check the spring pressure at that height too. May have the wrong springs on it. Any adjustment for the valvetrain?? Need some type with an aftermarket cam.

[nitrousdog]

Keep twisting those grenades and they will pop. If you want to turn some serious RPM's you better get a BBC. Ive been turning 7000 for 4 years now. See if it turns the rpms out of the water. Just be too loaded.

Nitrousdog

[Stv Euro]

well the heads are brand new & ported! Looks like I may still have a problem!

[mrcrsr]

what are you using for a fuel system? what type and gph of the fuel pump? is gph noted at 7 psi? alot of manufacturers advertise there pump, for instance, to flow 100 gph, but if you really look at the info, it maybe at free flow(no backpressure), so it really isn't an accurate measure that way. the better pumps will tell you the fuel pressure(most often at 7 psi) and the gph at that pressure, t into the fuel line before the carb and hook up a pressure guage and pressure should not drop below 5 psi at wide open throttle- i had this happen w/ edelbrock hi perf mechanical fuel pump and the engine would lay down around 4200, so this could cause backfiring(leaness), if the fuel pressure is good run the boat at wot for 20-30 seconds and shut the motor off and do a plug reading- is your carb stock(untouched by the factory?) if not, what jets and powervalve(s), also, have you checked the float level while it was idling? what is your total timing? check it with timing tape, an advance timing lite, etc, what is your air inlet system like(filters, arrestor, etc)

[Stv Euro]

All good! I am running 84 front and 88 back jets on a holley 850 man secondary. Fuel pump is a red holley and fuel never drops below 7psi. I have no idea what to do next. The one thing I do want to do is get a true header and get rid of the logs. They are still over the back but they have to be holding the engine back somewhat? What do yall think?

[J Lamb]

I don't think you will see a lot of gain with a header setup but I don't know jet boats either :D . I do know how to get a BB Olds to run though. What cam are you running from Mondello? If you can borrow one I would try a 750 vac sec Holley.I kinda think anything over that is a little much on an Olds engine. I had good results with mine, had to use a 3.5 power valve though cause my motor didn't make much vacumm with the Engle cam I ran.

[DAVE BICKHAUS]

a 455 should make good power thur 5500 rpm , you will need 10qt oil pan, and oil cooler, if you need 7000 rpm find a 425 bbo,

[72Southwind]

I have a Holly 750 Manual second on my Olds and can turn 5500 easy. Well until I wrapped a ski rope around the flywheel but, thats a whole'nother thread ! :(

Chris

[Stv Euro]

c-johnson Are you a jet or a v-drive?

[72Southwind]

c-johnson Are you a jet or a v-drive?

I have a jet. A 5 blade Jacuzzi pump. When I bought the boat, I could do 65 mph and thats about as far as I wanted to push it. I was skeerd to go faster ! :eek: I had pedal left but all that iron turning 5500 plus.......made me go hmmmm...

I am doing a rebuild this spring. FYI - I need a new block if anyone knows of one sitting around. Plus I was wondering which blocks are the best to find for a marine application. Early 70's ? Everything else I own is Ford, so this GM/Olds stuff is new to me. I have been learning a lot and I am looking forward to learning more.

Chris

[The Big Al]

I think this will be your problem!!!!

"ingle cam by Mondello"


Also check total timing, and the cam could be retarded. This is a comon problem with non- reving.



A Mondello cam better be degree in to spec., old man is not a sharp as he once was!

Olds engine look for 4600-5000 rpm.

AL

[Stv Euro]

Yep try to find some "c" heads. I do have a Mondello "ingle" cam but something just not right. The heads are completely cut and relieved it has to be timing!? We are talking about a 200+ compression motor on 93 or 110 and it will not go. I do not think it would turn 5000 on the trailer!!!

[bad ass ta ws6]

Hmm, what is your ignition setup again? What are you running for a distributor?

What's it do when you free rev it?

Did you check you have the correct springs in the distributor, if so equipped?

[150aintenuff]

FIRST OF ALL YOU DONT NEED an 850 CFM carb.. that motor can only efectivly use 654 CFM at 6000 RPM... and that is at 100% efficency.. your can probably use a 650 double pumper and gain more power due to increased air speed in the manifold thus giving you better idle and Responce through 6000RPM.. also remember that a olds has oiling issues and will pump the pan dry at anything over 6000 unless drastic changes are done to the drain back and oil feed galleys to the heads...

[Stv Euro]

I took the jet out on the lake this weekend and again no rpm over 4200. Feels like I am pulling a log truck under the water. My throttle response is terrible. Maybe I do need a smaller carb. I always thought a bigger carb was better. You see people put 1050's on small blocks so i thought a 850 would be just fine on a 468 olds. Any thoughts?


Kevin

[J Lamb]

Definately try a smaller Holley. Something around a 650. I would check the cam timing also. i had mine dgreed in 2 degrees advanced due to it being a bit big for the street. It was a Mondello 25-28. People talk crap about Mondello but he knows what it takes to make an Olds run. The only problem I had was the hydraulic cams are hard on the valvetrain and noisey. Here's a good link for you. Lots of knowledgable Olds guys there. http://realoldspower.com/phpBB2/index.php