vibration and overheating at gm 350 (one piece rear seal carburated)

[Bronc Rider]

Re: vibration and overheating at gm 350 (one piece rear seal carburated)

Not too many chevy heads came with the center valve cover bolts that weren't vortec. Some did and weren't vortec but, I cant count the intake holes to be sure (crappy monitor I guess).

 

[sarantis]

Re: vibration and overheating at gm 350 (one piece rear seal carburated)

I'm sorry guys a mistake with the pictures.The photo where one can see the heads is not of my engine.This is indeed a vortec head engine but not mine.

 

[CharlieB]

Re: vibration and overheating at gm 350 (one piece rear seal carburated)

Looking at the pictures of the motor, I kept rubbing my eyes and wondering,

'What's wrong with these pictures?'

Til I finally determined that they are 2 different sets of heads.

One set is machined perfectly flat on the forward ends, while the other still has the casted indentations painted, that's NOT shadows.

Both are centerbolt valve covers.

Can you take any close pictures of your heads?

Maybe find any casting marks, #'s, and post them also.

 

[sarantis]

Re: vibration and overheating at gm 350 (one piece rear seal carburated)

Hello again,
yesterday i went to the boat to double check the compressions with another gauge.almost the same results.#5 has the lowest number 197 whereas the maximum is the 205.At idle in neutral pulling its cable makes no difference but in higher rpm 1500 i feel a slight change to the rpm.But putting all the plugs on again i found out something interesting.when cranked the engine without starting it i heard a psssssss from somewhere and this somewhere was the #5 exhaust port.Looking closer i realized that the gasket at that point looked damaged and burnt.So before other attempts i have to replace the exhaust gasket and since i ''ll take the manifold out i wonder if its a good idea to check the torque of the head at this side and if i find any bolts need tigthening then go to the other side.I remind you that this new or rebuilt engine had an overheating at the first hour and by now it has about 7-8 hours of operation.What do you suggest?

 

[tricone]

Re: vibration and overheating at gm 350 (one piece rear seal carburated)

i 'm have trouble getting by the 305 harmonic balancer on a 350..
seems to me when i did a swap in my truck i had to look for a different timing index tab..alot of this sounds so familiar with my swap 1 piece seal to two, different flywheel, eating some inspection cover...
any experts know if the balancer and index tabs are the same on the two engines

 

[dan t.]

Re: vibration and overheating at gm 350 (one piece rear seal carburated)

ballancer and timing marks should be exactly the same

 

[sarantis]

Re: vibration and overheating at gm 350 (one piece rear seal carburated)

I did some work and here are the results:
1)i retorqued the heads.i didn't notice anything strange.Each bolt took 1/8 turn about more tightening.
2)replaced the port side exhaust gasket
3)loosened a litle and then tigtened with a torque wrench this time the intake manifold
4)put again the carb and the distributor in place and adjusted the valves
I couldn't start the engine.When i played with the advance i realised to my surprise that the marks i had put didn't work.I turned the distributor a litle more and the engine started.Less vibration than before.I pulled again the cable of #5 and to my surprise the rpm difference was now clear.But now the #4 cable seems to make no difference to the rpm.
I suspect that old distributor (1978) although i 've changed rotor and cap.I 've decided to invest on a new electronic ignition.Don S had told me last year that it's a pity to swap from 305 to 350 and keep the points but that time i couldn't afford it.
So PLEASE TELL ME WHICH TYPE AND BRAND MARINE DISTRIBUTOR AND COIL I NEED.I don't want to convert the old distributor.I want a brand new one, efficient reliable and if possible in good price.
I post also two pictures of the heads in case someone can recognise them and explain why i have so high compression numbers.

 

[sarantis]

Re: vibration and overheating at gm 350 (one piece rear seal carburated)

continue

 

[Bondo]

Re: vibration and overheating at gm 350 (one piece rear seal carburated)

I post also two pictures of the heads in case someone can recognise them and explain why i have so high compression numbers.

Ayuh,.... Take the Casting #s,+ go Here....
Then come back,+ tell Us what you found...

 

[sarantis]

Re: vibration and overheating at gm 350 (one piece rear seal carburated)

Here is what i found about the heads
casting number year
14096217... 55-86...350..........Crate motor, 285hp/300hp, 64cc chambers, 72' or 90' center intake manifold bolt angles.
So my new block may have 55-86 year heads?
As about the block's casting number at the aft top "102637m109z00078" i can't find anywhere in the list any information but i don't like at all the last two digits "78".Anyway now i 'm sure i was cheated. The engine is remanufactured .What is left now is to find out if it runs beter than my old 305.May somebody now tell me which electronic ignition set suits my block?

 

[Bondo]

Re: vibration and overheating at gm 350 (one piece rear seal carburated)

May somebody now tell me which electronic ignition set suits my block?

Ayuh,... A used Merc. T-Bolt IV or the T-Bolt V would be Nice....
Late 80s to current production...

 

[sarantis]

Re: vibration and overheating at gm 350 (one piece rear seal carburated)

Ayuh,... A used Merc. T-Bolt IV or the T-Bolt V would be Nice....
Late 80s to current production...

so i have to buy exactly a mercruiser thunderbolt iv or any equivalent ?Any suggestions of brand or relative links ?

 

[dan t.]

Re: vibration and overheating at gm 350 (one piece rear seal carburated)

W ith your combustion chamber volume and a flat top piston you will have somewhere around 10.5 to 1 compression ratio, this would account for the high compression numbers. Be VERY carful you dont have pre-ignition or ping as it is commonly known. As for a distributor,I would recomend a merc thunderbolt IV or a Delco Voyager,both are very simple systems with all electronic advance

 

[Bondo]

Re: vibration and overheating at gm 350 (one piece rear seal carburated)

Any suggestions of brand or relative links ?

Ayuh,... Here's another alternative,..."The delco est is $300 at ebasicpower.com."

 

[CharlieB]

Re: vibration and overheating at gm 350 (one piece rear seal carburated)

A new distributor is the better way to go.

Your vibration may have been partially caused by inconsistant ignition timing. An older points distributor can have 'slop' in the shaft bushing as well as wear on the point lobes, the combination can cause variations in the point gap (dwell) and if the gap gets too small it will arc across and not fire that cyl.

I whole-heartedly agree that With your smaller combustion chambers and higher compression I would definitely be sure not to allow any detonation.

Possibly prop the boat to run at or near the top of the RPM range. I would NOT lug it down under 4800 WOT.

 

[sarantis]

Re: vibration and overheating at gm 350 (one piece rear seal carburated)

Searching the web i came up with Michigan Motorz and since i remember at the package of the engine was written "MICHIGAN" i sent them an email asking them about my engine.Finally i found they produced my engine but i can't say they were willing to give me details about its characteristics(kind of cranksaft,hp,etc.).The only thing they told me was "This is a brand new 5.7L (350ci) Base Marine engine from 1987-95. GM is the ONLY manufacturer of 5.7L marine (or truck) engines".
So what shall i assume? they buy the blocks and the heads from GM and they put them together with the other parts and they sell them?What does Base Marine engine mean?

 

[sarantis]

Re: vibration and overheating at gm 350 (one piece rear seal carburated)

Sorry for delaying to continue the thread but the Delco est kit came to me 4 weeks after ordering it and with a slight crack to the cap.They told me they 'll send me another one free and as i couldn't wait any more i set it up and started the engine.First impression: i had never experienced such a smooth idle.Now i want to set the basic timing and i want to ask the following :i know the advance angle for 350 is 8*.Does it stay the same even if i run hi octane gas (as described above the heads have smaller combustion chamber,so higher compression ratio and the experts here advised me i should run hi octane gas)?and may you give me a higher pair rpm-angle to confirm the advance curve after unlocking the distributor?

 

[Bondo]

Re: vibration and overheating at gm 350 (one piece rear seal carburated)

Ayuh,.... Start at 8? btc,...
If you get detonation, cut it back, a couple degrees at a time til the detonation goes away...

 

[sarantis]

Re: vibration and overheating at gm 350 (one piece rear seal carburated)

Ayuh,.... Start at 8? btc,...
If you get detonation, cut it back, a couple degrees at a time til the detonation goes away...

cut it back ? you mean to reduce to 6*? i thought that with the hi octane gas i could go to 10 degrees.Wrong impression?
and the 8* is at 650rpm?

 

[Don S]

Re: vibration and overheating at gm 350 (one piece rear seal carburated)

I haven't read all the replies except the last few. I see you now have an EST distributor, are you putting it into base timing mode before adjusting the timing" If not, you are wasting your time. It will keep moving.
You can also put the EST into and out of base timing at the wrong time. Here is some info on how to put it into and out of base timing.

http://forums.iboats.com/showthread.php?t=271407