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Mods for pump gas
#1
So I'd like to eventually run my car on straight pump gas, and it's got a reclaimed 1970 429 in it. I know that pump gas will eat up the valves/valve seats because the stock ones were designed for leaded gas. This begs a few questions:

1) Besides rebuilding the heads, do any other mods to the engine need to be done?

2) Would the heads require a full rebuild, or just replace the valves and valve seats? (supposedly the engine has less than 10,000 miles on a late '80's rebuild and it does run awesome).

3) For the time being, am I right to assume that I can run it on premium gas with an octane booster?

4) Anything else I'm missing?

Thanks experts!

Steve



[Image: 25yvyp3.jpg]
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#2
The factory 429 4V Thunderjet used a flat top piston with a 75cc +/- chamber which resulted in a compression ratio of about 10.5/1. With a carefully set up distributor and a well tuned carb you should be able to run 93 octane but you are on the edge. A cam which bleeds off some cylinder pressure may be the difference. You could also use a slightly thicker head gasket to lower compression but you are also increasing quench distance which can actually make the engine more detonation prone even with a lower static compression ratio. Polishing the combustion chambers can help as well.

Octane booster is not a cost effective solution for a car that sees any street miles. AV gas if available will certainly work.

The correct way to make the engine pump gas friendly would be to change the pistons/deck the block to achieve the desired compression ratio (9.5/1?) and optimal quench distance for the octane fuel you wish to run. Obviously this is essentially a full rebuild and there are not many piston choices available for the 429. The scenario spirals out of control from there to either a 460 rotating assembly or dare I say it a stroker kit.

Personally, I would get a properly set up distributor and carb with a custom cam and shoot the dice.

73 conv. 460, D0VE large valve heads, Performer RPM manifold, Voodoo 227/233 cam, Holley 950 HP carb, C6 trans, 3.25 trak-loc.
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#3
Hmmm...those scenarios are kinda shitty! LOL

Thanks TommyK. By AV gas I assume you mean aviation fuel?

What does everyone else do with your vintage engines? Full rebuild?

Steve



[Image: 25yvyp3.jpg]
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#4
sm3570;16576 Wrote:Hmmm...those scenarios are kinda shitty! LOL

Thanks TommyK. By AV gas I assume you mean aviation fuel?

What does everyone else do with your vintage engines? Full rebuild?

Yes aviation fuel, 100LL is what is sold around here. I notice you are in Colorado. What elevation are you at? Altitude helps the situation.

73 conv. 460, D0VE large valve heads, Performer RPM manifold, Voodoo 227/233 cam, Holley 950 HP carb, C6 trans, 3.25 trak-loc.
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#5
I live at ~7100 foot, Colorado Springs is at about 6500 ft. How does that affect detonation? They sell lower octane fuel around here, premium is 93 octane I believe.

Edit: premium here is 91 octane.

Steve



[Image: 25yvyp3.jpg]
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#6
TommyK nailed it, +1.

Chuck
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#7
The elevation will defiantly help but TommyK is right with his recommendations. You might go to 460ford.com there are a couple of sharp guys there that could help with distributor curving and custom cam along with other tips. Being a big block guy myself I scan through there alot and find it pretty helpful.

Jay
73 mach1
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#8
sm3570;16502 Wrote:So I'd like to eventually run my car on straight pump gas, and it's got a reclaimed 1970 429 in it. I know that pump gas will eat up the valves/valve seats because the stock ones were designed for leaded gas. This begs a few questions:

1) Besides rebuilding the heads, do any other mods to the engine need to be done?

2) Would the heads require a full rebuild, or just replace the valves and valve seats? (supposedly the engine has less than 10,000 miles on a late '80's rebuild and it does run awesome).

3) For the time being, am I right to assume that I can run it on premium gas with an octane booster?

4) Anything else I'm missing?

Thanks experts!
I am not a big block expert but if you say it runs awesome, I am assuming you are not hearing pinging or detonation.
You may already have a cam that helps bleed off some compression.
If I understand correctly you are worried about lack of lead in the fuel eating away your valve seats.
I have heard that on the small blocks, Ford started using hardened valve seats around 1970, So I would first try to find out if the big blocks of that era are prone to seat wear or if your "80's" rebuild already adressed that.
I run over 11 to 1 compression on 93 octane without any problems, a high stall converter and 4.10 gears help keep it happy as well as the right cam and advance curve. its not a big block but I dont think there is that much difference. I think 10 to 1 can be run on premium.
You may not have to do anything except some good tuning to make it last.

[Image: mustangnight010.jpg]
1972 Mustang Convertible 351C 4V
1966 Ford Galaxie 7 litre-4speed

Jorge
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#9
73mach1;16613 Wrote:The elevation will defiantly help but TommyK is right with his recommendations. You might go to 460ford.com there are a couple of sharp guys there that could help with distributor curving and custom cam along with other tips. Being a big block guy myself I scan through there alot and find it pretty helpful.

Thanks for the tip Jay, I'll swing on over to 460ford.com and check it out.
jorgem2;16618 Wrote:
sm3570;16502 Wrote:So I'd like to eventually run my car on straight pump gas, and it's got a reclaimed 1970 429 in it. I know that pump gas will eat up the valves/valve seats because the stock ones were designed for leaded gas. This begs a few questions:

1) Besides rebuilding the heads, do any other mods to the engine need to be done?

2) Would the heads require a full rebuild, or just replace the valves and valve seats? (supposedly the engine has less than 10,000 miles on a late '80's rebuild and it does run awesome).

3) For the time being, am I right to assume that I can run it on premium gas with an octane booster?

4) Anything else I'm missing?

Thanks experts!
I am not a big block expert but if you say it runs awesome, I am assuming you are not hearing pinging or detonation.
You may already have a cam that helps bleed off some compression.
If I understand correctly you are worried about lack of lead in the fuel eating away your valve seats.
I have heard that on the small blocks, Ford started using hardened valve seats around 1970, So I would first try to find out if the big blocks of that era are prone to seat wear or if your "80's" rebuild already adressed that.
I run over 11 to 1 compression on 93 octane without any problems, a high stall converter and 4.10 gears help keep it happy as well as the right cam and advance curve. its not a big block but I dont think there is that much difference. I think 10 to 1 can be run on premium.
You may not have to do anything except some good tuning to make it last.

AFAIK there is no pinging, I'll know more when I get the car in a few weeks. My dad has the car and I've heard it fired up and it sounds great, and that's at sea level. There may be no issues at all with the current build, but I want to get all the information I can. I'm kind of a research freak with stuff like this! I'll probably research the cams and figure out the tuning portion and with any luck I'll be in the zone!

Steve



[Image: 25yvyp3.jpg]
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#10
If originality isn't important and since you need to rebuild the heads you have (which I assume are DOVE heads), then the easiest solution is to swap to a pair of D3 heads which have 95CC chambers. This will get you back to a little under 9.5 to 1. They are cheap and very common. You coukd sell the DOVE's and make money on the deal.

73 conv. 460, D0VE large valve heads, Performer RPM manifold, Voodoo 227/233 cam, Holley 950 HP carb, C6 trans, 3.25 trak-loc.
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