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305CID vs. 350CID Engine

R

rereaves

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Hi Folks, I currently have a 305 SBC in my 47 truck and having issues. The engine has exhaust smoke primarily at start up so I thought the valve seals were bad. I ran a compression check and had an average of 175lbs pressure +/- 10lbs. I changed the valve seals which has reduced the smoke at start up but the right bank still smokes when you jump on it. I do not know the history of the engine other than it is 1984 truck vintage. When I removed the valve covers it was very clean so might be a rebuilt engine, it has a mild cam.

1. What else should I check to resolve the RH bank exhaust smoke?

2. Is the 350CID engine the same block as the 305, can I use my existing manifold, distributor, motor mount, Is it an easy swap???

The truck does not need more HP, the 305 is fine however folks tell me the 305 was not a very good engine. Everone seems to suggest that I should switch to a 350 engine however I do not want to make a major investiment to go from the 305 to the 350 if possible.

Thanks
Ron
 
If you buy a 350 long block you shouold be able to use most of the parts from your 305. Depending on the carb you might need to install a bigger carb. A 650 or 700 cfm for a stock set-up should work fine. The manifold will swap over. All of the accesories will swap over.
 
Just a thought. Do you have an automatic trans? If the modulator valve is bad,it can suck transmission fluid into the carb causing smoke. Quick and easy fix. I have a 77 305 in my 53 and it has tons of power. I have no clue how many miles are on it and it runs great!
 
' Smokes When You Jump On It '

This tends to point to cylinder or ring problems , yank the heads and drop the pan , have a look at the bore's taper and the pistons , cylinder ridge etc. ~ often some minor freshening up will yeild a world of happy results .

Few piston rings are ever broken in properly .
 
Thanks for your reply's to my engine issue. Will a leak down test give me some clue before I pull the heads etc? I have also heard that 305 engine often have valve guide problems. When I changed the valve seals I pulled the plugs and they were all burning clean, in fact they looked like they were burning a little hot if anything. Each plug had a nice light brown color with no signs of oil. Maybe I will drive it until winter and then tear it down. I guess it will depend on the cost of rebuilding my 305 or buying a 350 long block and start swaping.

Thanks again;
Ron
 
Leak Down Testing

Yes ! this is the most accurate test you can do .

Some old tech info : when you have blue/white smoke off trailing throttle or initial startup , this means valve guides or seals as the vacuum in the intake plenums is highest then .

When you get blue or white smoke upon throttle application , this means it's coming up past the pistons & can be rings , pistons , excessive taper in the cylinders etc. , etc.

Clean spark plugs and no complaints of poor running is common in these instances .

In the old days , they'd ignore it and feed the oil habit .
 
Thank you !

brit 50 said:
I'd rip the old smoker out and put an original sixer back in if'n I was you:D
Click to expand...

Neil ;

That's what I wanted to write but I figured you'd all get upset if I began beating that drum again..... :rolleyes:

:p

:)
 
Thanks everyone for the feedback. Plan to do some more testing to determine problem. In the intrim I'm going to drive it until winter and then take a close look at the pocket book to determine if I rebuild or new.

This little truck is setting on a 1992 S-10 Chassis. It's a fun truck however still has some work but it's fun work. Again, thanks for all the feedback. I would like to post a couple pictures so you folks could see my junk but not sure how to do that on this site.

Ron
 
Hey , Ron :

If , you're really stuck upon V-ate madness , I know it is possible to mix 'n match various SBC parts and wind up with a " stoker " 383 C.I. SBC V-8.....

Some of the Mechanics I work with do it and it sounds interesting .

I'm an InLine kind guy so don't ask me how but I *do* know that many different big valve and high or low compression Chevy heads are out there super cheap that'll just bolt on and allow great flexibility it setup and tuning for your particular needs .

Pick-A-Part is your friend here , once you learn what P/N's to look for and what models .
 
If it is a S-10 then it is already been raped. Engine is not relevant although the new aluminum I6 really looks good. Especially in the older trucks
 
If it has 175#'s per cylinder and doesn't foul plugs I'd leave it alone. How often do you have to add oil? Is the puff of smoke causing you embarrassment? As far as an AD being on an S10 frame they can be a piece of crap or absolutely undetectable if done right. Of course being much more quiet due to having both the cab and bed mounted on modern rubber cushions and being able to steer with one finger at 70 mph may bother some. Here is how one that hasn't been "dropped here" or "lowered there" can sit when finished. The first three pics are under construction ones and last two are finished ones. Our "mule" for fitting the body to the frame has since had the bed welded to the cab so a one piece (would we dare call it a Unibody) can be lowered over the frame to gather measurements. Even the steering column and steering wheel are stock so unless you open the hood or crawl underneath no one knows.
 

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' that sound '

federale said:
Just sayin. The 305 runs and sounds great to me. Click on pic. :D
Click to expand...

Yes , it sounds very nice indeed .

No as good as a true Blue , BOWTIE 6 Banger of course.... :rolleyes: (I'm sorry , I can't help it , I'll die loving 6 Bangers) .

I see light blue puffs there , time for valve guide oil seals maybe ? .
 
Yeah , Yeah , Blah Blah

coilover said:
If it has 175#'s per cylinder and doesn't foul plugs I'd leave it alone. How often do you have to add oil? Is the puff of smoke causing you embarrassment? As far as an AD being on an S10 frame they can be a piece of crap or absolutely undetectable if done right. Of course being much more quiet due to having both the cab and bed mounted on modern rubber cushions and being able to steer with one finger at 70 mph may bother some. Here is how one that hasn't been "dropped here" or "lowered there" can sit when finished. The first three pics are under construction ones and last two are finished ones. Our "mule" for fitting the body to the frame has since had the bed welded to the cab so a one piece (would we dare call it a Unibody) can be lowered over the frame to gather measurements. Even the steering column and steering wheel are stock so unless you open the hood or crawl underneath no one knows.
Click to expand...

:p I hear you Evan but , I can easily steer my '49 with one finger @ 70 MPH , that has to do with the correct tires and properly lubricated suspension....

I understand , and that's a very nice job but not for the old Geezers here I shouldn't think .
 
Re:Blue Puffs

vwnate1 said:
Yes , it sounds very nice indeed .

No as good as a true Blue , BOWTIE 6 Banger of course.... :rolleyes: (I'm sorry , I can't help it , I'll die loving 6 Bangers) .

I see light blue puffs there , time for valve guide oil seals maybe ? .
Click to expand...
Nahhhhhhhh,just burning the moisture out of the exhaust system,been sitting for about a week. And Nate,I agree, a finely tuned 6 banger sounds goooood :)
 
305 Engine Issues

Great looking truck and thanks for the reply to my smoking issue. This engine has been setting for a long time and I think I have oil ring issues. Maybe stuck maybe bad so I'm going to run it for a while and see what happens. I changed the oil twice and added Rislon to see if it might free up a sticking ring issue. If not I will rebuild or swap over the winter.

Can anyone give me some feedback on correct plug gap spec is it 045 or 035? I'm running RJ 45 plugs.

Thanks
Ron
 
Proper Spark Plug Gaps

It all depends on the ignition system you're running ~ if a bone stock , breaker points ignition , it needs at least .035" , more if it'll take it without missing .

In general , you'll find any engine runs better with the widest gap it'll take . many shop manuials are written with .025" specs ans this is just plain wrong as it'll cause a poor idle at the very least .

As far as exhaust sounds , since I bumped the timing up on my 292 CI , it hums swweter than ever .

Not loud nor raspy in spite of the free flowing fancy-schmancy muffler it has .
 
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