[1975sleekcraft]

all right i have posted earlier, i have been told what caused my engine to tulip four intake valves was too small of a carb(ran a holly 650 dp). so now i am in the process of trying to find a 750 or bigger. my machine shop told me it is better to go too big and jet down! he also said i cant use my 650 and jet up because i cant get the air flow through it!

i am running an olds 455 30 over with a comp cam .490 intake .490 exaust and just under 10-1 compression. also a 1975 mallory marine mechanical advance distributor.

my engine was rebuilt the summer of 03. it has been the most reliable boat i have ever had!! when i was rebuilding it i did alot of reseach on olds(thank god). i definatley built the bottom end right!

heres the deal, last winter i dumped a bunch of $ into my boat. i had my holly 650 dp rebuilt. it used to be hard starting and it wouldnt idle without loading up.

i also had the distributor rebuilt. the timing was jumping around a little with the timming light on it. i thought it was the chain getting sloppy so i replaced it(i could tell it didnt need one, but i was already there so i replaced it anyway).the only thing left to alow the timming to jump around(timming light)is the distributor. so i had that rebuilt. the guy told me that he made it a little more snappy for me and that i would like it. he also told me the most he could get out of it was 8 degrees. i set my timming at 34 @ 3000rpms, and went boating.

i have had my boat in four times since the carb, distributor rebuild.the thing ran and idled great. on the fourth day about half way through the day it started coughing every once in a while. nothing big(i thought) i just have a little water in my carb.it ran great all the way back to the launch, dropped of someone to go get the trailer, idled for 10 minuts perfectly then died. i didnt even try to start it because i knew there was water in my carb.

NOT, i tuliped 4 valves

so i have the heads back from the machine shop. he went through (machined) and replaced everything.

i dont want to do this again!

so i have been told to replace my carb with a bigger one. tony @ skagen marine told me i can jet my 650 dp to work just fine(keep my combustion chamber temp from spiking).

so just today i was told that my distributor may be the culprit. too much advance too quick???

i screwed something up, between my carb or dist rebuild, how do i make sure i dont melt my valves again?? i am not rich i am an unemployed carpenter!!!!!!!!!!!

 

[Futs]

Im no expert, but that doesnt sound right to me. I run my distributor locked @ 38* so all my timing is in it at the start.

 

[Malcolm]

I'd go for 36* degrees max. What jets are you running? I bought a 650 dp off craig's list and then picked up that Proform main body that makes it a 750 hp. It comes with 72/84 jets, but I think 74s might be better on the primaries.

 

[SS 201]

Sounds like a very lean condition, to hot of plug,water temp, lean fuel. The exhaust must show lean or hot temps. Something should be white, plugs?

 

[Moneypit]

Smells fishy

it ran great all the way back to the launch, dropped of someone to go get the trailer, idled for 10 minuts perfectly then died. i didnt even try to start it because i knew there was water in my carb.

NOT, i tuliped 4 valves

how do i make sure i dont melt my valves again?? i am not rich i am an unemployed carpenter!!!!!!!!!!!

If it ran fine back to the ramp, and the died after 10 minutes IDLING, I would suspect the cooling at IDLE. Jet pumps don't supply a lot of water at an idle, and idle speed doesn't supply much cool fuel to aide in intake valve cooling. I know my jet boat will heat up considerably in long "no wake" zones, and I have to neutral it and bring the Rs up to move some water through the engine. I would look for vacuum leaks on the 4 valves that got too hot, and I also agree that it isn't the 650 CFM causing your problem.....Something smells fishy..........Have you idled the engine that long before without problems?.........Ray

PS: Any weeds in the jet????

 

[1975sleekcraft]

long idle

before i rebuilt the carb(paid a professional), it didnt idle. i had to give it gas all the time to keep it from loading up. so i would say that this was the longest i have ever idled.

a little touch up on the last run. ran flawless for 1/2 a day. then at cruising speed it coughed. then again it coughed. i was really low on gas in that tank so i switched to the other one. that one had more gas in it, but really low too. it kept on coughing. i was camping on one of the dunes on potholes resevior. i turned around and headed back to the dune, coughing spuratickly as i am pumping the throttle every time it does till the coughing stops, and then repeating the process everytime it coughs. we made it back to the dune. camped out for hours, loaded the boat up with everything, and headed back to the launch at mardons. my boat wouldnt start. i tried pumping the throttle, nothing. so i held it wide open, it took a while, but finally started. i was about 5 miles from the launch. it ran flawless for over 2/3 of the way back. it then started the whole coughing rutine all over again. made it to the launch, dropped of someone to back the trailer in the water. continued to idle perfect for over five minuts-close to ten(felt like), then died. didnt even try to start it. i thought the hole coughing, hard starting, and dying at the launch was from water rolling around in my carb. since i was sucking the bottom of my tanks, NOT!!

 

[1975sleekcraft]

lean burn??

when i pulled the heads the plugs, top of the pistons, and combustion chamber looked fat(black).

is there anyway i was lean at wot and cruising speed(close to tulip) then shows fat from extended idle ????

 

[Infomaniac]

Dead or improper valve springs will do that.

Also loading and unloading the engine will do that.

There tons of causes for stretching valves

 

[1975sleekcraft]

I'd go for 36* degrees max. What jets are you running? I bought a 650 dp off craig's list and then picked up that Proform main body that makes it a 750 hp. It comes with 72/84 jets, but I think 74s might be better on the primaries.

i am not sure what jets. i was told the stock jets for a this holley
4776-4
9145

malcom where did you get that proform main body??

 

[Malcolm]

I got it from Summit, but Jegs and a bunch of other places sell 'em.

http://www.summitracing.com/parts/PRO-67100C/

To tell the whole story when I ruined 2 of my intakes, I was running my new rebuild with my old Q-jet on it. I found out that a stock style fuel pump and that carb will not run over 4500 on a 455 with a 280 cam. It wound right up to 5000 and then started running out of gas. I didn't figure out what was going till too late, and it was missing when I pulled back to the dock. It did run faster tho... for a minute!

I went thru the heads again, this time with all new stainless valves and started building an 800 Q-jet. Another BIG mistake! Q-jets just don't hold enough fuel. That's when I went Double pumper. I've been pretty happy since.

 

[1975sleekcraft]

I got it from Summit, but Jegs and a bunch of other places sell 'em.

http://www.summitracing.com/parts/PRO-67100C/

To tell the whole story when I ruined 2 of my intakes, I was running my new rebuild with my old Q-jet on it. I found out that a stock style fuel pump and that carb will not run over 4500 on a 455 with a 280 cam. It wound right up to 5000 and then started running out of gas. I didn't figure out what was going till too late, and it was missing when I pulled back to the dock. It did run faster tho... for a minute!

I went thru the heads again, this time with all new stainless valves and started building an 800 Q-jet. Another BIG mistake! Q-jets just don't hold enough fuel. That's when I went Double pumper. I've been pretty happy since.

when you pulled your heads were the valves white or black or???

are your able to run a stock type fuel pump now??