[Willshire]

Hello all,

I've revived my ambition to complete my 64 GP and was wondering if any folks had experience replacing the 345 heads with 62 heads on a 389?
389 - .030 over, ram air III cam (I believe)
Roller rockers (i'll have to swap the studs to the 62's)
65 tripower intake and carbs.

I am looking at using Felpro 8518PT gaskets

The 62 heads flow way better but are only 72cc. Still a few cc larger than the 345's.
Sealed power valve relief flat top pistons.

I don't really want to yank the engine. Just trying to get the CR under 9.9. I might have to use some boostane to drive it but that is still a long way off. I figured since the front clip is off i'd swap out those old inefficient 345's

Thank you in advance.
Adam

[John Milner]

If you are running stock style 389 pistons, you'll probably want to check your piston to valve clearance since the valve reliefs on a 389 piston are designed for a different valve angle than your 62 heads will have. You'll also want to run pushrods for a 400. Other than those things to look out for, it should run fine and run on pump gas.

[Willshire]

Originally Posted by John Milner

If you are running stock style 389 pistons, you'll probably want to check your piston to valve clearance since the valve reliefs on a 389 piston are designed for a different valve angle than your 62 heads will have. You'll also want to run pushrods for a 400. Other than those things to look out for, it should run fine and run on pump gas.

Thanks John.

Sealed power cast .030 pistons 4 valve reliefs (i think they are the 288P), 068 cam and 1.65 scorpion rockers. Custom measured pushrods on the 345's right now. would be around .470 lift with the 1.65 rockers.

[hurryinhoosier62]

Originally Posted by Willshire

Thanks John.

Sealed power cast .030 pistons 4 valve reliefs (i think they are the 288P), 068 cam and 1.65 scorpion rockers. Custom measured pushrods on the 345's right now. would be around .470 lift with the 1.65 rockers.

Plan on changing your intake manifold ( if memory serves me). I believe the #62 heads have the late bolt pattern. As far as the difference in the valve angles, do you know how far down in the hole your pistons are at TDC?

[Willshire]

Originally Posted by hurryinhoosier62

Plan on changing your intake manifold ( if memory serves me). I believe the #62 heads have the late bolt pattern. As far as the difference in the valve angles, do you know how far down in the hole your pistons are at TDC?

Stock deck height. I have a 65 tripower intake as well. I’d have to check the sealed power pistons 288p (silvolite 1516). 0.470 lift. Is valve interference often a problem on aftermarket stock 288p replacement pistons?


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[25stevem]

The 62 casting flows far better then the 345 heads , the problem is that your 389 intake ports in your manifold ( if it’s the same year as your 389 heads) will not match up with the 62 intake ports.

[Willshire]

Originally Posted by 25stevem

The 62 casting flows far better then the 345 heads , the problem is that your 389 intake ports in your manifold ( if it’s the same year as your 389 heads) will not match up with the 62 intake ports.

I have the 65 and up style tripower intake too. Bought it a million years ago just in case it was time to upgrade to better heads. Looks like it was a good purchase, in hindsight. Lol. Looks like valve angle may or may not be an issue.


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[b-man]

To stay on the safe side perhaps consider running 1.5:1 rockers to keep the lift low and have more clearance between the valves and incorrect pistons for the heads you’re using.

[Willshire]

Originally Posted by b-man

To stay on the safe side perhaps consider running 1.5:1 rockers to keep the lift low and have more clearance between the valves and incorrect pistons for the heads you’re using.

Just so happens I have a set of scorpion 1.5s as well. Not a bad idea. Thanks. I also may be able to mock something up on the bench since I have the original pistons too. The 345s just aren’t pump gas friendly. At all lol. I thought open chamber higher flowing heads might be a bit better.


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[25stevem]

With the lift of a factory ra3 cam you will have no clearance issues, you should be safe up to. .420” lift which that cam does not have, at least with 1.5 rockers,.
Non the less you should still check your piston to valve clearance, and it might save you some time at first to do that without the head gaskets in place.

In terms of compression with the 62 castings, they are more like 75 CCs unless they have been milled and if they have had a valve job done to them that will make them more then 75 CCs.

What pistons are in your 389?
If they have more then 4 valve notches then they are more likely the source of your knock issue since they have a huge deck clearance!

[Willshire]

Sealed power 288p 4 relief flat tops. It didn’t detonate often since I retarded the timing back to 6 degrees and disconnect the vacuum advance. 10.5:1 cr from factory and crappy high test gas didn’t help.


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[hurryinhoosier62]

Originally Posted by Willshire

Stock deck height. I have a 65 tripower intake as well. I’d have to check the sealed power pistons 288p (silvolite 1516). 0.470 lift. Is valve interference often a problem on aftermarket stock 288p replacement pistons?


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Sometimes there is when using later model heads to replace the earlier heads. If memory serves me the intake bolt pattern changed in 1968(?). As long as your engine hasn’t been “zero decked” or you are using a cam with hellish lift you should be OK. If in doubt, put a piece of modeling clay on a piston top. Install the head and valve train for that cylinder. Pull the engine through two complete rotations. Remove the head and installed valve train and measure the valve impressions in the clay. As long as you have .050 or more clearance you should be good. Good to see you posting again, Adam.

[Goatracer1]

I just put 1968 #62 heads on my 1962 389 with a 1965 TriPower intake . I opened the chambers up a little to drop the compression even more. The 389 pinged badl on 93 octane gas. I had all the parts necessary to do the swap so I figured it was an easy way to cure the problem. It had a "066" replacement cam so valve clearance was not a problem. It went from pinging on 93 octane to running well on a mix of 89 and 93 octane gas.

[b-man]

Intake interchange:

‘55-‘60

‘61-‘64

‘65 and up.

[Willshire]

They were rebuilt not long before I got them


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[bradleyc309]

I have a similar plan with a 1964 389 with 345 heads that I plan to install a 1965 Tri-Power with # 13 heads and a 068 cam, should I expect the same?

[25stevem]

Both of you converting over to the later heads for you 389s will also need to run the later 9.130” long push rods, as the ones from the 389 will be too short.

These will make for a drop in deal, but if your using a non factory cam you should check the geometry to pin down what length you might need to order.

If you cut one of your old 389 push rods in half and tap it out for a 6/32” stud you can make a adjustable one to make your checks with.

If your running longer then stock valves then for sure you will need longer then 9.130” push rods .

[Willshire]

I have a comp adjustable pushrod and have done the roller to valve stem contact check when I threaded studded the 345s. My 345s have custom pushrods already.


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[bradleyc309]

Thanks for the feedback, any other advise would be greatly appreciated.

[25stevem]

What pistons are in your 389 that you will put these number 13s on?

Is your 389 at .030” over also and is the short block already assembled?

These 13s unlike the 62 castings do have a 72 cc chamber .