[leeklm]

Hey everyone, I am helping a buddy with his 66 GTO, and think we found the issue with 2 cylinders with 80% leakage!

Knowing the engine needs a rebuild, my thought for him was to keep it relatively basic, but a couple of upgrades with out of the box eheads and a hyd roller cam. Here are my initial thoughts, and could use some suggestions on a cam for this combo...

-stock flow edelbrock heads
-RPM rods/stock crank
-factory tri power (not original on car)
-factory exhaust manifolds
-355 gears
-T10 4 spd
-pwr brakes and steering
- rockers??? Could go roller but maybe stamped steel sufficient here?

Definitely not a race car, just street cruising. Heads are overkill, but figure they are a good value vs spending 1k on old Iron heads. Same with roller cam, but i do not want him to have to worry about oil, etc.

Thoughts on a cam for this? I assume 400hp would be pretty easy with the eheads and not too radical cam?

Thank you for the suggestions!

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[77 TRASHCAN]

The ports on stock "D" ports or stock Kauffman "D" port heads are too much for a 389ish engine.
Lotsa bad reports on roller cams (here...) about roller cams these days.
Port velocity is an important thing, especially with a smaller engine. A 389 is NOT small but could mostly benefit from higher flowing aluminum heads at higher RPM's. Not much in a Hot Rod Cruiser, my opinion.
I would not use a roller cam. depending on the end comp ratio, there's many flat tappet cams that will be awesome!

I'd send the stock heads to SD Performance. Dave isn't taking in any new iron head work at the moment, but I'd email him just to see what's up, beware that could take a while. The wait is worth it, to me!!!

OK, experts, carry on!!!

[firechicken]

Which 2 cylinders are leaking and where are they leaking from?

[leeklm]

Originally Posted by firechicken

Which 2 cylinders are leaking and where are they leaking from?

#7 was at 80% leakage into the oil pan. #5 was 65% leaking through intake valve. Couple others were around 40% with no obvious leak path. Four of them were good at 20%. This motor is very low on power- tired.

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[leeklm]

"The ports on stock "D" ports or stock Kauffman "D" port heads are too much for a 389ish engine."

I did not consider that. The ideal behind alum heads was simplicity and power potential. Don't really NEED the power, but was thinking why dump 1k or so into old iron.

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[b-man]

I’d rebuild it using the original 093 heads. Just upgrade all the components to allow it to run well on today’s questionable fuels. Hardened exhaust seats, good quality stainless valves and screw-in studs would be wise. Forged dished pistons to adjust the compression ratio to where you feel safe for driving under all conditions it might see along with a good set of aftermarket forged connecting rods bushed for floating pins.

If it’s just a cruiser why upgrade to aluminum heads at all? I’d keep it looking as ‘original 389’ as possible under the hood for that classic Tri-Power 389 GTO look. Those neat factory chrome valve covers with the pentroof pressing at one end look so cool, topping off the special high-compression 093 heads that were standard equipment on all ‘66 GTOs. Be a shame not to run the 093 heads.

Keep it looking factory correct, those ‘66 Metallic Blue 389s have a factory hot rod look that’s hard to match. I’d even run the old school 068 cam in it, plenty of punch and more than fine for a cruiser. Easy to tune and maintain, great all around performance.

[i82much]

I would build a roots-blown 535 with Tiger heads and an 041 cam. And get some fuzzy dice too.

[389]

I would use the 091 or 092 heads. Forged rods and pistons. Keep the compression at 9 to 9.25.. So you can run 87 octane and the motor will have more snap.. Keep everything nice and clean smooth all the edges. Use a nice solid cam from Crower like the 60310... A set of trips with three Holleys or Dual quads with two AFBs. Actually the stock four barrel with a nice AFB works well on them. Grind off all the exhaust heat and choke provisions and run a cable... Use the stock single points to trigger a CD box..

[Jerry H.]

I would definitely upgrade to Ram Air exhaust manifolds over the stock ones. Keep it simple. Good 3 angle valve job on the 093's and dish the pistons to get the compression ratio down. Agree on the 068 cam. Use the money saved on other upgrades.

Keep us updated.

[tom s]

I'm with Bart,just rebuild it stock with some up grades.I just did a 421 HO with a 068.Tom

[Cardo]

This worked out well for me. https://forums.maxperformanceinc.com...d.php?t=836191

[1_Wild_Cat]

Cardo's engine is super impressive - call it 400 hp at 4900 RPM. If I were building a 389 I would follow a very similar recipe.

[leeklm]

Thanks for the suggestions. On a side note, this engine has the 93 heads

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[max 93]

Why are the aluminum d ports a bad choice for a 389?

[firechicken]

I think an out of the box aluminum d port head would be a nice upgrade for a relatively mild street build and probably skip the roller cam just for cost purposes.

[77 TRASHCAN]

Originally Posted by leeklm

"The ports on stock "D" ports or stock Kauffman "D" port heads are too much for a 389ish engine."

I did not consider that. The ideal behind alum heads was simplicity and power potential. Don't really NEED the power, but was thinking why dump 1k or so into old iron.

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Max 93, here ya go!!!

Wow, I should read what I write...
Meant ports on Edelbrock or Kauffman heads are too large to start with. Port velocity is important (Jim Hand, thank you!!!).
A stock, well thought out tri power 389 with the proper parts and modifications is an iconic engine, the engine that started the muscle car craze. These engines could perform mightily in stock form. I believe Dick Boneske's 65 turned some 13 second ET's, in the day. That tells us exactly how well engineered those engines were/are!!! Send those 093 heads to SD Performance, and the performance increase is amazing!!!

[Jay S]

With forged rods and forged dished pistons won’t the expense for an aftermarket nodular stroker crank be a good value compared to the aftermarket heads or the hyd roller cam? DSS makes the 3.75” dished pistons, but the strokers pistons are priced similarly. They might be a little more for less than 4.12” bore. DSS has a 18cc dish and a 28cc dish option for all their Pontiac pistons. That is the 28 below.

I have a 4.125” bore 66 389 I am working on, we had a 4.21” N crank reworked to 3” mains, kept the Pontiac journals. DSS pistons.

[geeteeohguy]

Originally Posted by b-man

I’d rebuild it using the original 093 heads. Just upgrade all the components to allow it to run well on today’s questionable fuels. Hardened exhaust seats, good quality stainless valves and screw-in studs would be wise. Forged dished pistons to adjust the compression ratio to where you feel safe for driving under all conditions it might see along with a good set of aftermarket forged connecting rods bushed for floating pins.

If it’s just a cruiser why upgrade to aluminum heads at all? I’d keep it looking as ‘original 389’ as possible under the hood for that classic Tri-Power 389 GTO look. Those neat factory chrome valve covers with the pentroof pressing at one end look so cool, topping off the special high-compression 093 heads that were standard equipment on all ‘66 GTOs. Be a shame not to run the 093 heads.

Keep it looking factory correct, those ‘66 Metallic Blue 389s have a factory hot rod look that’s hard to match. I’d even run the old school 068 cam in it, plenty of punch and more than fine for a cruiser. Easy to tune and maintain, great all around performance.

This^^^. Helped a friend about 8 years ago with his '65 389 and we used all the factory stuff except for custom dished pistons. About 8.5:1 CR. He used a Comp XE 268 cam, and stock rockers. He didn't want to upgrade the rods. It was a budget build with the main cost being the pistons (Ross). That engine flat out screams and runs on 89 octane fuel without detonation. It runs cool and smooth at all rpm ranges, gets decent mileage as well. I wish dished pistons were available when I rebuilt the 389 in my own '65 GTO back in 1981....I wouldn't have to use race gas in it today. Sigh.....

[leeklm]

Will be interesting to see what this motor currently has for pistons. Guy has been running 91/92 octane fuel and no noticeable detonation with timing set at factory spec. My adjustable light gave out so was not able to see how far it was advancing at higher rpm. The balancer on my motor has the advance marks, so had no need to replace the adjustable light

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[JEC3039]

Follow-up to the pic in JayS post. I'm working with DSS on a 389 build at present. Here's a new 389 dish shape they just introduced. Perfectly mimics the squish flat on the 093 cyl head. Will be a 20cc dish in my case.