Pump gas 440 advice

[Dusty997]

I'm picking up a bone stock all original 1969 Chrysler 440 motor tomorrow that is advertised as a 10:1 compression.

My plans are to run it in my duster on the street and id like to get it as pump gas friendly as possible without having to change pistons. Ive heard that certain camshaft profiles can lower dynamic compression, but im also not sure what compression translates to needing what type of fuel ext, ive always run stock 360 magnums that are 9:1

Open to all tips and suggestions, this will be my first big block ever.

 

[davek]

if its bone stock just add octane boost and you will be fine. Thats all I do to my Bee 440

 

[PROSTOCKTOM]

I run my 440 at 10 to 1 on 93 pump without issue.

What cam you have in them really makes the difference.

Tom

 

[RemCharger]

If it's all stock even with a cam, it's a good premium gas motor. I don't see anything to sweat about.

 

[Dusty997]

Great! A lot of what i was reading online was saying 10:1 was too much for pump. This is good news

 

[OMTWF-72SE]

I've found it depends on the gas. Out here where commifornia influences our gas products the blends just don't work. I went the piston route after fighting it for years.

 

[Dusty997]

I've found it depends on the gas. Out here where commifornia influences our gas products the blends just don't work. I went the piston route after fighting it for years.

I was thinking just throw the thickest head gasket i can find on it, and maybe a camshaft that will lower dynamic compression some.

 

[Jerry Hall]

An all stock 69 440 should perform good on premium pump gas. If you get any detonation you can bump the octane up a little with an octane booster or lower your timing by a degree or two. I choose to keep stock timing and eliminate any thoughts of detonation with an octane booster, or mixing some 100 octane AV gas in. The only octane booster I have found that really works is a product called Boostane. The 90 octane non ethanol that I can get around here isn't quite enough so 2 1/2 Oz. of Boostane takes it to 96 octane and problem gone.

 

[Curiousyellow71]

Most engines have less compression then what the factory rated them. You won't know exactly unless you measure. If it still has the factory piston it will be in the mid 9's give or take using a typical .039 thick head gasket. Factory used a thinner steel head gasket and will be a little more if its still running them. A Cam with a wider LSA lowers the dynamic compression and is more friendly to pump gas when you compare cams of the same size.

 

[33 IMP]

As stated above, the rated comp ratios were often a 1/2-1 point higher than actual. 9-9.5 should run okay on 91, 93 would be better.
Since stock 69 heads have no quench anyway, a thicker head gasket is an easy solution if you do have detonation problems.

 

[PROSTOCKTOM]

I was thinking just throw the thickest head gasket i can find on it, and maybe a camshaft that will lower dynamic compression some.

Putting a thicker head gasket on is a bad idea in my opinion. Adding a little more cam will help, but I see no issue with using the stock cam.

Using less cam is a waste of time.

Tom

 

[Dave6T4]

I had the heads off my '68 440 a couple of years ago. At that time, I replaced the factory steel shim head gaskets with thicker Felpro's. I could feel no difference in performance: my car is mainly a highway cruiser, and I don't race it. I can run 91 octane in it, with no detonation.

 

[Jerry Hall]

Putting a thicker head gasket on is a bad idea in my opinion. Adding a little more cam will help, but I see no issue with using the stock cam.

Using less cam is a waste of time.

Tom

I agree keep it running as good as it was when new, anything less takes the thrill out of it, and as @PROSTOCKTOM says, is a waste of time.

 

[RR Fan Dan]

I concur that 91 pump gas is fine. 93 is better if you have it which my state does, but 91 isn’t a problem . Never had any issues with 10.5:1 on pump gas at 91 or higher.

 

[lewtot184]

actual compression ratio from the factory is around 9.7. Thicker head gaskeys don't work. They just make the quench distance worse. The real problem is the crummy combustion chamber with the 88cc heads. I got tired of fighting the problem and changed pistons to fix the quench area problem. It works! Octane boosters only work on lower octane fuels and that can be marginal at times. Some octane boosters contain metallics that set you up for another problem. For a true fix that works there's no cheap easy way.

 

[gtxrt]

the stock cam has a wide LSA from the factory so if you change cams you would need more duration. keep the stock cam with the stock motor.

 

[gtxrt]

the stock piston is about .051 in the hole plus .020 steel head gasket = .071. adding a .039 head gasket plus .051=.090 in the hole. does it really matter for quench if it's .071 or .090 ? I am thinking if it's more than .055 in the hole does .071 or .090 really matter ? what I heard more than .055 hole it does not matter there is no quench.

 

[WileE]

Sunoco 94.

 

[33 IMP]

the stock piston is about .051 in the hole plus .020 steel head gasket = .071. adding a .039 head gasket plus .051=.090 in the hole. does it really matter for quench if it's .071 or .090 ? I am thinking if it's more than .055 in the hole does .071 or .090 really matter ? what I heard more than .055 hole it does not matter there is no quench.

With a 516 or 915 closed chamber head, quench is possible.
With a stock 69 906, with its completely open chamber, the is NO QUENCH, NONE, unless aftermarket quench reverse dome pistons are installed (or the heads milled about .125!)
I believe the o.p. is anticipating problems. He might not have any. It kinda depends on the quality of fuel available in his area. If he had to run California Cat cat piss 15% he might have problems. 93 available where he is? Probably not a problem.

 

[68BabyBlue]

If it's all stock even with a cam, it's a good premium gas motor. I don't see anything to sweat about.

My fifth GTX was a stock rebuild, with the exception of a Hemi grind purple shaft cam. I bought the car in Iowa in 2016, flew out, and drove it back to Pennsylvania, 1400 miles. Good test of octane results. In Iowa, the best I could get was 91, and the car ran, but slight problem of run on after shut off. When I reached Indiana, I was able to get 92, and the problem lessened. From Ohio east, I used 93, and had no further problems. Like @Jerry Hall, I'm able to get 90 octane ethanol free locally, and have used that in my last four GTXS, three 440s, and a Hemi, all with stock engines. I've followed Jerry's recommendation for octane booster.

When I drive the current car to Carlisle every summer, I run on 93 octane pump gas with no detonation issues. However, in my car, the ethanol gas boils off after sitting for a day on the show field, or overnight at the hotel. A nuisance deal, remedied by priming the the carb.