1978 250 six

427carl · A Poncho Legend!

RE: 1978 250 six

72 luxo · Veteran Member

73SC wrote:
You got it. Lets put it this way, Sea Foam has been in business for about 70 years I think. Where did you buy it and how much, just curious. Parts Source has it where I live.

Hi there. I bought it at Carquest here in london, it was $11.96 plus tax. It did not really seem to work, there was no heavy smoking upon start up after letting it sit for the 10 min that they say to do!

73SC · A Poncho Legend!

Where did you pour it, crankcase or carb?

72 luxo · Veteran Member

I poured in the carb while holding the throttle slightly open to prevent stalling. I dumped in like half of the bottle and shut it off and let it sit for like 10 to 15 min. Upon restarting the engine there was like little to no smoke that the product claims there will be, so did it even work like it was supposed to?

72 luxo · Veteran Member

After I treated my engine to Sea Foam I went on a high speed run out in the country, TH350, 2.73 rear, 15 inch tires @ 140km/h=RPM so I deffinatly gave er a high speed blast. With factory base timming(10 degrees BTDC) there was still pinging upon acceleration from a stop, however I did notice a funky smell, maybe that was the carbon being blasted out.

73SC · A Poncho Legend!

Usually you get heavy exhaust but I have never shut off the car so I can't say.

Is there any difference in the engine? Why not bring the timing back to 8 degrees. That's where I am running my 454.

-- Edited by 73SC on Thursday 1st of December 2011 12:27:26 PM

72 luxo · Veteran Member

73SC wrote:
Usually you get heavy exhaust but I have never shut off the car so I can't say.
Is there any difference in the engine?

its tough to say for shure. I did set my timming back to 6 degrees BTDC and I have detected no pinging, but have lost some power, darn!

Hey 73SC, is there anywhere in london or area that I could take my carb to and have it mounted to a flow bench to see what the fuel metering would be at a cruise?

73SC · A Poncho Legend!

Don't know about London area shops.

If you want to run at 10 degrees put in 91 octane. Your power to weight ratio with that combination is never going to give you any level of performance so you shouldn't be expecting that from that engine. A friend had a 78 Nova with that 250 six and it rattled like heck under any load, like going up a hill, I'd almost want to get out and push. That was when the car was new too.

Canadian Poncho · A Poncho Legend!

Take it to Tiny's in Ingersoll. He doesn't have a flow meter but he is good with carbs.

72 luxo · Veteran Member

Canadian Poncho wrote:
Take it to Tiny's in Ingersoll. He doesn't have a flow meter but he is good with carbs.

Where abouts in Ingersoll might he be? Dose he have a shop or something, is this a business? thanks.

Canadian Poncho · A Poncho Legend!

Yes. Tiny (Jeff) is a member on here. Take the 401 to Ingersoll. Exit at Culloden Road (south). Turn left at the first dirt road. His shop is about 1/4 km on the right. (519) 425-0033. His shop is extremely busy but I'm sure he can fit you in.

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Jonno · Poncho Master!

Hey 72 Luxo, did you try the premium Esso or Shell?
Out of curiousity just to see if it helps get rid of the pinging.
C'mon, throw in a tankful just to humour us!

72 luxo · Veteran Member

Jonno wrote:
Hey 72 Luxo, did you try the premium Esso or Shell?
Out of curiousity just to see if it helps get rid of the pinging.
C'mon, throw in a tankful just to humour us!

I have not tried the 91 octane fuel yet, I dont want to rely on the good stuff to keep my 110hp engine alive! but will fill up next time with premium grade fuel and bump the timming back up to 10 degrees BTDC and see how it runs!

dualquadpete · Canadian Poncho Superstar!

Even with running the "good" stuff you may still have to retard the timing. My 389 is at 10:25 to 1 & even with Sunoco 94 I had to retard back 2 deg. lost a little power, but fuel mileage got better & not so hard to start when HOT!!!Lost the tire squeak into 3rd. but can live without that if I can get 17 MPG. hwy. with dualquads & a 454 lift camshaft!!!!!

the70judge · Guru

72 luxo wrote:
After I treated my engine to Sea Foam I went on a high speed run out in the country, TH350, 2.73 rear, 15 inch tires @ 140km/h=RPM so I deffinatly gave er a high speed blast. With factory base timming(10 degrees BTDC) there was still pinging upon acceleration from a stop, however I did notice a funky smell, maybe that was the carbon being blasted out.

Your going to have to retard the timing to 8 deg, and use the high octane gas maybe if the timing does not help.. Whats the compression ratio on that engine ?

timbuk · Canadian Poncho Superstar!

check distribitor advance system

72 luxo · Veteran Member

the70judge wrote:
72 luxo wrote:
After I treated my engine to Sea Foam I went on a high speed run out in the country, TH350, 2.73 rear, 15 inch tires @ 140km/h=RPM so I deffinatly gave er a high speed blast. With factory base timming(10 degrees BTDC) there was still pinging upon acceleration from a stop, however I did notice a funky smell, maybe that was the carbon being blasted out.
Your going to have to retard the timing to 8 deg, and use the high octane gas maybe if the timing does not help.. Whats the compression ratio on that engine ?

Well being a smog engine from the late 70's its low, I am shure it is 8.4:1 ratio so regular fuel should be no problem!

72 luxo · Veteran Member

timbuk wrote:
check distribitor advance system

When I first got the car it was all backyarded up with vacuum lines disconected, retarded timming ect. So I found a emissions diagram and replaced everything back to original. New TVS switch, delay valve and ignition moduel, inspected advance weights and springs and checked vacuum advance canister as well. Do you think that the mechanical advance flyweight springs are getting weak? It only pings bad when you accelerate from a stop or comming around a corner off the throttle and getting back on it!

427carl · A Poncho Legend!

72 luxo wrote:
timbuk wrote:
check distribitor advance system
When I first got the car it was all backyarded up with vacuum lines disconected, retarded timming ect. So I found a emissions diagram and replaced everything back to original. New TVS switch, delay valve and ignition moduel, inspected advance weights and springs and checked vacuum advance canister as well. Do you think that the mechanical advance flyweight springs are getting weak? It only pings bad when you accelerate from a stop or comming around a corner off the throttle and getting back on it!

You returned to stock, which was a 70's smogger motor.. They all pinged, and gave rotten fuel milage...

If yours runs well, try reducing the amount of pedal input, as you accelerate, from a stop or from turning That will stop the ping

timbuk · Canadian Poncho Superstar!

72 luxo wrote:
Do you think that the mechanical advance flyweight springs are getting weak?

id look and id try a curve kit

the70judge · Guru

timbuk wrote:
72 luxo wrote:
Do you think that the mechanical advance flyweight springs are getting weak?
id look and id try a curve kit

Thats a good idea!! :>) Never thought of that one

72 luxo · Veteran Member

A recurve kit consists of different springs and weights right? Dose it matter that I replaced my ignition moduel with an MSD rather than a O.E.M GM moduel, I am not talking about the 6AL or the red boxes just the under cap moduel.