Mods for pump gas

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!

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.

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?

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?

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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.

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.

TommyK nailed it, +1.

Chuck

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.

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!

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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.

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.

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Thanks for the tip Jay, I'll swing on over to 460ford.com and check it out.

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!

Click to expand...

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.

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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!

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.

As far as the hardened seats go, don't worry about it until you have the heads off for another reason. I was at college for automotive service when the change to unleaded gas was being made. Then Henny penny said to Cocky Locky the sky is falling... The best studies at the time showed "measurable" valve seat recession after 40-60k miles. It will take many years of regular use on a collector car to get to this point. If there is recession when the heads are off then go ahead and install the hardened seats. Generally it's not an issue. When I went through my heads I did install seats because I had access to the tools and could do it myself cheap (cause thats the way I roll).

on my 466 i have d1ve heads that were fully rebuilt with new valves and hardened valve seats. i have -26cc dome pistons which when you calculate everything together i have about 9.4CR not included the small decking they did on my heads when they rebuild the heads (they had to deck them to make them flag again) so i guess you could figure i got 9.5CR.

i wanted to be able to run 87 regular, but then no matter where i timed it it quite didn't run that GREAT. but when i put in 89 mid grade it runs alot better at about 14 degree. lately i've been playing with 91 premium fuel to see if it run any better. i quite didn't achieve the 87 regular fuel goal but at least i know i can run 89 fuel and it runs quite nice.

in the forum, i've heard a few guys say that the entire set up of the car depends on running pump gas. other things like manual or auto trans, rearend gears, weight of vehicle, etc etc etc.

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.

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Interesting, I never considered swapping out the heads. Since the engine isn't original to the car I wouldn't mind going that route. How would swapping to the D3 heads affect performance?

As far as the hardened seats go, don't worry about it until you have the heads off for another reason.

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Yeah, if erosion isn't as big of a problem as I thought (and I can avoid pinging by making some easy adjustments), then I probably won't worry about it. Unless I pick up some D3 heads like TommyK said, in which case I may rebuild those (depending on condition). Hmm...

in the forum, i've heard a few guys say that the entire set up of the car depends on running pump gas. other things like manual or auto trans, rearend gears, weight of vehicle, etc etc etc.

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Since it won't be a daily driver I'm not that concerned really, but I also don't want to cause any long-term damage.

So I think I'll research D3 heads, new cams, etc. etc...

Thanks guys, lots of good info!

do it myself cheap (cause thats the way I roll).

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BTW, you're not the only one. I'm cheap too!

Yeah Buddy! there ain't nothing wrong with using parts other people don't want anymore.

Jeff/Steve, count me in as a charter member to being cheap, however, I have learned to buy quality because buying cheap usually means means buying it again.

+1 with Don65stang. The cheapest way to do most things is correctly once. Chuck

I mean paying less than 1/2 price for good quality used parts when possible.

+1 on that, quality can be found at a good price.

I have a very similar engine in my Mustang, a 1971 429 with Dove heads, 10.5 to 1 compression, it was rebuilt at a local very reputable shop. They said the heads were in good condition with no erosion, and just did a valve job. We used a Comp cam XE 273, but the rest was a stock build. We did not install hardened seats, because the car sees few miles. I run the tune with 30 degrees total timing on the distributor, and have no pinging, on pump premium.

I bought a can of octane boost, but did not need it. I say keep your DOVE heads, check your timing and go with it. The forged pistons in these engines, are very strong, and the valves have a large contact area, and run at a relatively low rpm. The Dove heads are more efficient than the D3's, equals more power.