Head Swap

SGS Welding · Guru

Head Swap

66 Beau · Poncho Master!

Aren't those the 300 HP 350 CID heads? 64 cc chambers, same as the double bump heads, but the 041 castings have the accessory holes?

If I remember correctly, depending on gaskets and with flat top pistons, those heads will give you about 10.25:1 compression. I seem to recall you could get down to 10:1 with a thick gasket. That's with an older block (60's) - I don't know the deck height of your block, nor the piston style.

From my experience, that'll still run on pump gas, though it will prefer mid-grade or premium. Cam selection, ignition timing and air-fuel mixture might need to be considered, but in stock form, I would bet most of the 69 Impalas that came with these ran their entire lives on regular (leaded). I know my uncles did. You will want to put in hardened seats though - those were leaded gas heads...

Depending on their condition, you might want to compare them against a new set of vortec heads. The vortecs are also 64 cc, 1.94" intakes, but they're already set up for unleaded, and from tests I've seen, they're one of the best flowing iron heads available. A few years ago, you could get a complete, brand new pair of vortec heads for under US$500. [EDIT - I see they're up to about US$300 per head]. So if your 041's need valves, seats and bunch of guides, it might be cheaper to go with the vortecs. Though, with the vortecs, you'll also need a new intake manifold and valve covers, and anyone can tell at a glance that the heads are not stock.

041's are nice heads though, good score!

-- Edited by 66 Beau on Saturday 18th of March 2017 03:23:15 PM

SGS Welding · Guru

I'm starting to wonder if I should freshen up the whole engine. The more I research I do the more I think this engine has been rebuilt And if I'm not mistaken the tops of the pistons I was looking at lead me to believe this engine had a little less compression built in in the rebuild.(flat top 4 eyebrows and another little triangular shape) Keep in mind this is the first engine I have "torn down" I am a greenhorn! Thanks everyone Greg

SGS Welding · Guru

Just to clarify The engine I'm talking about freshening is the "HN" suffix 350/300hp engine NOT the "CNN" engine Thanks

427carl · A Poncho Legend!

Vortec heads are a "free" 60 HP just saying

SGS Welding · Guru

I understand the vortec idea I have researched it a lot This is what I got Rather than buy vortecs and an intake I was thinking eddy performer heads But now that I see the pistons are right for the heads I have A freshening up will work for now

66 Beau · Poncho Master!

The 041's are pretty nice heads. If you're building "the one true engine" then I'd go with the vortec's. If you're just trying to get something that runs and has a little pep, the 041's could be perfect. But personally, I wouldn't spend much on them. New valve stem seals, maybe a manual hand-lapping of the valves. As long as you're not putting it in a truck for towing, and you're not putting them in a daily driver, they'll likely last for years. I'd run premium in that case, because any pinging would likely accelerate valve seat failure.

With the block, how much of a ring ridge is there? Can you catch it with your finger nails? If yes, you're likely over 0.015 inch taper in the bore, and the block should be bored. If you can't really catch your finger nail on the ring ridge, you might be able to run it as-is, or with a new set of rings (take the ring ridge off and hone the cylinders to give them a profile so the new rings will seat). Check the bottom end. Buy some plastigage and check the clearances and look at the journals. If the journals and bearing shells aren't scarred up and the clearances are within spec, you can probably run it as-is.

With a little luck, you could have a decent running 350 for a couple hundred bucks.

SGS Welding · Guru

Unless I stumble onto a good pair of vortecs and an intake for cheap, I think I will go with what I have. There is a pull your own part yard near me that has vortecs in it. The price is right but they are prone to cracking Just think if I'm going to drop some money likely just as far ahead to spend it on new eddy proformers. I have an eddy performer intake already that I found cheap at Hershey a few years back when the dollar was good.

-- Edited by SGS Welding on Sunday 19th of March 2017 06:56:39 PM

1980bigblockponcho · Addicted!

On another note the vortec heads are usually only good for .440 lift any bigger than that most ppl suggest bigger valve springs and machining the spring seat to accommodate , many arcticles on this job, just me mindful :)

-- Edited by 1980bigblockponcho on Thursday 23rd of March 2017 09:14:09 AM

dcneric · Poncho Master!

My 2 cents. I really like the 041 heads. A nice tight combustion chamber good port volume and easy to port if needed. With a mild cam and a dual plane aluminum intake with headers it is a decent motor.

Back in 95 through 97, the engine I had with a 700R4 in a 57 Pathfinder humiliated several 5.0 mustangs, 70 442, mid 90's Z28 to name a few. Plus I was able to drive it to work 45 minutes on the highway without any issues.

Plans are to build another 350 with a set of 041's in the near future.

SGS Welding · Guru

dcneric do you remember what pistons you used on that engine?

4 eyebrow flat tops?
What gasket? ( thin .018)
Did the valves in the head have flat faces? ( or recessed)

I think you can see where I'm headed here
Trying to build this engine to run on pump gas
91 octane or lower

My block has not been decked
Any insight is appreciated
Thanks Greg

66 Beau · Poncho Master!

Greg

I built a 350 using those heads about 25 years ago. It was set up for propane (which is 100 octane!) but when I sold it, the new owner switched it back to gasoline. I'd calculated the compression ration at 10.3:1 (up from 10.25:1 due to a 0.030" over-bore). That was with stock, flat top pistons (with the 4 eyebrow notches). I broke the engine in on gasoline (about 1000 miles) before switching to propane. I ran premium in it and had no problems with pinging, but I was pretty gentle on it (break-in).

I've sent an email to the guy I sold it to (it was in a '72 GMC Sierra) - asking for feedback on how the engine performed on gas. I'd given him all my calculations too. I'm hoping (long shot) that he might still have them and (even longer shot) he might be able to scan them to send to me. If I hear anything, I'll pass it along.

66 Beau · Poncho Master!

Heard back from the guy I sold the 350 to. The engine is now in a '57 Bel Air - still running strong on pump gas. I rebuilt it in about 1991. It ran on propane until about 2000 when it was converted back to gasoline. The guy I sold it to bought it for his teenage son. They still have the pick-up, but put something with a little more HP into it.

I think a 26 years is a pretty good testament to the engine. Nothing wrong with 041 heads on pump gas. (Yes, hardened seats were installed).

He has all my notes and calculations, but he's traveling. Promised to scan them for me when he returns home in a couple weeks.