loss of power, increase in RPM

[Ciera2450]

Re: loss of power, increase in RPM

I'll give it a shot tail gunner. It'll only take a few minutes to check it out. I just don't get why all of the sudden it'd become an issue.
Thanks for your help! and that link, very informative.

 

[Tail_Gunner]

Re: loss of power, increase in RPM

That is an automotive HEI distributor, no HEI's were in that model year plus it has a vacuum advance can on it proving it's lineage. I do not know if it has anything to do with your problems, but you will not be able to order parts for it as an AQ225.

As far as timing, you just set the static timing as specified in the manual. However the automotive distributor may have more mechanical advance than the AQ225 is ready for and be over-advancing getting into the detonation range.

Try #17...You dealing with odd's and end's..

 

[Ciera2450]

Re: loss of power, increase in RPM

Thanks again... I am going to order the delco est dist. tomorrow and just replace the darn thing before I go disassembling my motor.
I'd be super happy if thats all it takes! lol



Edit: I plan to order this http://www.marine-ignition.com/imdist8v.htm

Anything else I will need to install this?

 

[bruceb58]

Re: loss of power, increase in RPM

Hooking up the vacuum advance is pretty much worthless on a boat. There will be no vacuum at WOT as you try to get the boat up on plane therefore you will have no spark advance due to the vacuum. That is why a marine distributor relys solely on centrifigul advance.

 

[captmello]

Re: loss of power, increase in RPM

Thanks again... I am going to order the delco est dist. tomorrow and just replace the darn thing before I go disassembling my motor.
I'd be super happy if thats all it takes! lol



Edit: I plan to order this http://www.marine-ignition.com/imdist8v.htm

Anything else I will need to install this?

If you're planning on keeping the boat, even knowing a valve job is most likely needed sooner or later, buying that distributor is also needed, so...

I did a valve job on my SBC about 5 years ago. It wasn't hard. the trickiest parts to me were installing/adjusting the distributor and adjusting the valves. But after having done it that one time, there really isn't anything to it. Just a little help from some trusted mechanics made it an easy diy job. Cost me around 700 to have my heads rebuilt, along with the gaskets and other misc. BTW, even if you pull the head, you may not be able to "see" the leaky valve, but clearly it's there.

I'm very interested in that est dist as well...I'd like to know how it is adjusted to a specific advance curve. According to the manual the Volvo/sbc of that vintage required a 30 deg BTDC total advance @ 4200 RPM. I'm not sure if that is a standard number or specific to some motors of that time. Sorry just wondering out loud...Always learning ya know.

 

[Ciera2450]

Re: loss of power, increase in RPM

I got ancy guys....the carb and intake manifold have been removed. Heads are next. I plan to get the heads rebuilt, new head gasket, valve job, replace distributor, replace carburetor.
#8 cylinder, this push rod looks like its not all the way "up", the rest are fully seated...

intake manifold removed:

I figured that i've gone this far, may as well go all the way and do it right.
Now to sweet talk the admiral! lol

 

[captmello]

Re: loss of power, increase in RPM

I don't know if you've seen them, but there have been a few good threads in the nonrepair I/O section regarding sbc rebuilds. You may want to start a thread there. Just an idea. I'll be following.

 

[Ciera2450]

Re: loss of power, increase in RPM

my block and head numbers match a 350 and not a 305. Someone has replaced the engine before and put the original 225D valve covers on. I guess i have a AQ260 now.

This morning I removed the manifolds and risers. Heads will be coming off later today. I'm trying to find a good instruction guide on removing the heads.... I've found a few and they are all different!!

 

[captmello]

Re: loss of power, increase in RPM

Keep track of where the pushrods go. You're supposed to put them back in the same hole upon completion. Unless you replace them.

Now that you have a 350, you could consider vortec heads for close to the same price as having yours rebuilt.
You would also need a vortec intake manifold, to go with your new carb.

You better be extra nice these next few weeks around the house...

Oh, btw, to remove the heads, you just remove all the rockers, then remove the head bolts. I can't think of any tricks.

My motor was originally an AQ225E. Someone swapped the block just like yours.

 

[Ciera2450]

Re: loss of power, increase in RPM

Heads are off! heres some pics....

If photobucket wasn't being dumbs, i'd post more pics.
I'm unsure of my next move..... get head rebuilt? get new heads? keep tearing down engine and rebuild completely????
Decisions....decisions....

 

[Ciera2450]

Re: loss of power, increase in RPM

Opinions greatly appreciated!

 

[captmello]

Re: loss of power, increase in RPM

Looks like you've got Merc exhaust manifolds.

(see post 67)

 

[captmello]

Re: loss of power, increase in RPM

What did the casting numbers say about the motor? Can you post the numbers? How do the cylinders look? Everything looks ok in the pics, what do you think?

Imo, doing the top of the motor does not lead into doing the lower end unless there are signs of low end trouble. However if the Admiral is up for the full rebuild...

 

[Ciera2450]

Re: loss of power, increase in RPM

the maniforld and risers are merc....i knew that when i purchased the boat. The PO replaced them (he said) shortly before i bought it. they are in good shape and do the job.

The casting numbers for the motor and head match a GM350.

I'm going to let a friend come over and look over the heads. I really don't know what i'm looking for...

 

[Ciera2450]

Re: loss of power, increase in RPM

It has been recommended that these heads are a "light casting" and have 72cc chambers. This is supposed to be too large for a marine application and the 64cc chamber heads are recommended for better compression.

What do you guys think? I'm trying to weigh all my options here before I spend all this money!

 

[captmello]

Re: loss of power, increase in RPM

The casting numbers for the motor and head match a GM350.

Ya, I got that. Usually the numbers also tell you if its 2 or 4 bolt mains, a year or range of years produced and sometimes it tells what vehicle it was used in.

I'm trying to get an idea of what type of cam may be in that motor. I realize you can't tell for sure without looking at the cam itself, but you might be able to narrow down the possibilities.

 

[Ciera2450]

Re: loss of power, increase in RPM

i'll see if I can find some other casting numbers....the block #3970010 is apparently one of the most common blocks used

 

[captmello]

Re: loss of power, increase in RPM

Ya, you're right. The website I looked at said it was used all through the 70s, which means it would have a two piece rear main seal and uses that era flywheel and starter. Besides that, it looks like they used that block in everything and may have 2 or 4 bolt mains...
That doesn't narrow down anything.

the "Light casting 72cc heads" however may be the info that could help narrow the field. those heads may have been used for specific auto models. That's the direction I would go in figuring out the motors original purpose.

 

[Ciera2450]

Re: loss of power, increase in RPM

Still researching all of this. I believe the heads are incorrect for a marine engine. Comparing the block and head numbers shows that most likely this engine was intended for a truck. It gave several different makes and year models but all trucks. So.....the cam should be appropriate.

i'm leaning toward leaving the short block alone (if all checks out) and getting different heads. Of course carb and distributor need replaced also.

 

[Ciera2450]

Re: loss of power, increase in RPM

new long block is ordered and paid for. Should arrive in two weeks. I just decided to replace the long block with the proper 64CC chamber heads. I hope to pull the old block out this weekend and begin rebulding the motor mounts. I'm pretty sure they are rotted out.