[leeklm]

I had another thread started regarding a 389 build for a friend of mine... the thought was to use a +.030 dished piston with the oem 093 heads, but sounds like an 8 week order delay (talking to Butler) which is not an option here.

Engine builder is suggesting the cast replacement pistons with multiple valve reliefs, thinking that with the piston cc and sitting down in the hole a little, we can get to a manageable CR.

Any thoughts to this approach, or other potential options?

Thank you!

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[b-man]

Horrible piston choice, sitting far below the deck isn’t a good thing though others may have gotten away with it.

Not an option in my opinion.

Wait for a special order, going to those 8 relief cast pistons would be a mistake.

[steve25]

All of those multiple valve notches in those Pistons and there sharp machined edges are ping and knock creators just waiting to happen irregardless of having a low enough compression!

Why no go direct to a piston manufacturer, see what they can do, and bypass having to pay a middleman like Butler.

I just called Ross pistions and there wait time is 5 weeks, so there's a option for your buddy!

[ponyakr]

Have you already contacted DSS ? They show a 14cc dish piston for a 389.

https://dssracing.com/Pontiac-piston...55-stroker.htm

https://dssracing.com/contact.htm

[leeklm]

Originally Posted by ponyakr

Have you already contacted DSS ? They show a 14cc dish piston for a 389.

https://dssracing.com/Pontiac-piston...55-stroker.htm

https://dssracing.com/contact.htm

Dss does have the 14cc available, would need a thick gasket and leave in the hole a little ways to get 9:1 CR with the 68cc heads.

We have a set of 6x heads available. Instead of spending 1k on pistons, Really thinking we just do a Butler stroker kit with the 6x heads. Would make a bunch of power for the same cost in the end, and not deal with custom pistons in the event of an issue down the road. The 093 heads can sit in the garage for the next owner...

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[Baron Von Zeppelin]

You picked the best overall option there.

If he wants to keep vintage appeal under the hood -
could even grind the 6X and date codes off - and have 093 stamped in its place.
waa laa - Service Replacement heads

or leave them blank after grinding off 6X

[leeklm]

But looks like I got ahead of myself here... Butler just got back to me. Due to the 389 bore size, they still need to order custom flat top pistons if going with 6x heads!

I did not realize that! Again, my first 389 project

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[geeteeohguy]

Originally Posted by b-man

Horrible piston choice, sitting far below the deck isn’t a good thing though others may have gotten away with it.

Not an option in my opinion.

Wait for a special order, going to those 8 relief cast pistons would be a mistake.

THIS^^^. Regardless of your build route, do NOT use the 8-valve relief cast pistons. Their design guarantees detonation, low performance, and short service life. Have done a couple of 389's with Ross dished pistons using the stock 64-68cc heads, and they ended up screamers that ran on 89 octane. I have forged flat-tops in my own 389 built almost 40 years ago, and running my milled #77 GTO heads, it needs race gas which is a real drag. When I built it, it ran OK on 94 octane leaded fuel I was able to get back then. On today's 91 crap, not so much.
389's aren't seen much these days, but are excellent engines that make a surprising amount of torque and HP. Plus, '389' sounds way cooler than '400'.

[leeklm]

"389's aren't seen much these days, but are excellent engines that make a surprising amount of torque and HP. Plus, '389' sounds way cooler than '400'."

Valid point!

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[Baron Von Zeppelin]

Originally Posted by leeklm

But looks like I got ahead of myself here... Butler just got back to me. Due to the 389 bore size, they still need to order custom flat top pistons if going with 6x heads!

Yeh , you'll have to bore about 0.060 +/- oversize to use pistons "off the shelf" type slugs.
But figured you already had that accounted for.

Block would need a sonic check first to see if it can take that much cut.
Some will, some won't.
Its hit and miss on 66 389 blocks

You might could hit eBay or post a wanted ad on here and source some old stock 389 pistons (forged) - or even quality cast ones.
Then have those massaged for CR

Could have chamber work done on the 093's also

it gets into extra money any way you go with a 389 on pump gas
They have gotten to where they are mainly just for #'s cars anymore.

[Jay S]

I am curious what the engine builder was using for pistons? Where they boring it out to 4.12”....058” over???

There are no 8VR pistons for the smaller bore (less than 4.12” bore) 389s pistons that I am aware of...

Go direct to D.S.S,there is more chance of someone like Butlers making an error, and DSS know’s their piston options and costs better. And they can alter the quote better. Go straight to DSS.

8 weeks??? Maybe it has changed as of late? The last set here was a few months ago during the COVID deal and the turn around was 2- 3 weeks. They were custom FX series pistons with rings and the cost was around $800. The ring were probably $150 of that. They have a std 14 cc available, or custom you can get a 18cc or a 28 cc. I have a set of flat top DSS’s and the were $550 without rings. It isn’t that much more to go custom as long as you pick from there standard piston options. Usually the dished pistons run $590

The aftermarket cast 389 pistons are expensive for what they are.

With the stock heads the factory rods with arp bolts is what I would do. Get the lighter DSS pistons, order the dish that accommodated the compression they want. Then have it balanced (the DSS pistons and pins are close to 200 grams lighter than stock pistons and pins.

And if your going to use forged rods, do a stroker.

[leeklm]

"Go direct to D.S.S,there is more chance of someone making an error and they know their piston options and costs better. And they can alter the quote better. Go straight to DSS. "

Right, I spoke with DSS who commented they could get the 14cc pistons out in about 1 week. I will ask DSS about their custom options, as an additional -6 or 7 cc might be the best route with the 68cc heads.

The 7-8 week comment was after talking to butler about their custom Ross pistons.

I do like the idea of the lower end eagle forged rod's for $370 vs using the factory rods. Seems like good insurance. I know many here are comfortable with HFT cams, but I have been soured enough that a roller cam with quality lifters has been a much better option with my limited experience, especially for a owner that is likely not doing his own oil changes, etc.

Thank you all for the feedback, it is appreciated!



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[Jay S]

I agree with your logic on the HR cam. For tight funds and staying with the stock heads they could do the HR cam and punt on the aftermarket connecting rods. The lighter DSS pistons will help the stock rods a lot. I know of some 3.75” stroke E headed street engines running around with stock rods and ARPs and lighter forged pistons. They can break, but so can a lot of other stuff.

Or just do both..LOL

[ponyakr]

"...I do like the idea of the lower end eagle forged rod's for $370..."

I've posted this many times. But appears needed here, again.

Rather than paying that much for those rods, why not pay $30 more & buy RPM H-beams. They're lighter, stronger, & you can buy the floating pin type.

https://rpminternationalinc.com/conn...80-stroke.html

Cliff has posted that most cheaper Chinese H-beams check out good. But, if you prefer the Eagle brand, I think they're still under $500.

https://www.ebay.com/itm/Eagle-6625P...IAAOSw1s9esHvq

To me, it just doesn't make sense to buy a heavier, weaker rod, just to save $30, or even to save $100. Has anybody priced the TOTAL cost of ARP bolts + having cast rods resized, LATELY ?

[ponyakr]

For custom pistons, have you checked with Auto Tec ? Don't know how quick they could get 'em to you.

But, they're made with the 4032 material & you can get the pins located where you need 'em, so you can get near zero deck height without cutting extra material off the deck.

To make 'em cheaper & quicker they use what they call "shelf blanks". These blanks are in stock for the more popular bore sizes. So, if one of those sizes is a size you can use, they can just take those off the shelf & machine 'em to your specs.

Paul Knippen here can order Auto Tec pistons. He can find out how long it would take & give you a price.

https://www.facebook.com/PaulKnippensMuscleMotors/

I once priced some Auto Tec 350 pistons thru Shannon's Engineering. He doesn't list any 350 or 389 pistons. But, as mentioned, they can make some using popular sized shelf blanks.

https://shanonsengineering.com/produ...at-top-pistons

According to the Summit bore size chart, 4.090, 4.0925, & 4.100 look to be common piston sizes.

"...Yeh , you'll have to bore about 0.060 +/- oversize to use pistons "off the shelf" type slugs.
But figured you already had that accounted for.

Block would need a sonic check first to see if it can take that much cut.
Some will, some won't.
Its hit and miss on 66 389 blocks..."

If a .058 overbore is OK, then the std 400 Pontiac piston will work. Many have posted about machining a dish in the forged SP L2262F pistons. That dish should make 'em compatible with the 389 heads.

Here's a set for $350.

https://www.ebay.com/itm/Speed-Pro-T...MAAOSwB4NWvhvs

If by chance the block will go 4.125, you can go with Olds 455 pistons. Already have an 18cc dish & a 1.735 pin height.

https://www.summitracing.com/parts/s...ake/oldsmobile

[Jay S]

Originally Posted by ponyakr

"...I do like the idea of the lower end eagle forged rod's for $370..."

I've posted this many times. But appears needed here, again.

Rather than paying that much for those rods, why not pay $30 more & buy RPM H-beams. They're lighter, stronger, & you can buy the floating pin type.

https://rpminternationalinc.com/conn...80-stroke.html

Cliff has posted that most cheaper Chinese H-beams check out good. But, if you prefer the Eagle brand, I think they're still under $500.

https://www.ebay.com/itm/Eagle-6625P...IAAOSw1s9esHvq

To me, it just doesn't make sense to buy a heavier, weaker rod, just to save $30, or even to save $100. Has anybody priced the TOTAL cost of ARP bolts + having cast rods resized, LATELY ?

The I beam RPM and SIR Eagle rods are probably the way to go if your using an OEM style pressed fit piston. Floating pin is when it is time to start looking at the H beams.

Cost probably varies a lot depending on were your at and the shop. IRC several of the smaller shops here charge $12 per connecting rod to machine the big end. Rod bolts are about $68. I spend about $160 total. Bigger shops in the big cities you can add $40 do that. I did a Chevy W engine that used 454 rods last year and had them machine and converted to floating, that was around $180 in just machine work. I probably should have went aftermarket on that.

I have a couple sets of Eagles, one an H the other a I beam, each one took machining on the small end to get them correct. People often forget that these aftermarket rods do not always work out of the box. The fun surprise is on the rare occasion when they need work on both ends. All of a sudden you have a $700 set of rods.

Our 66 389 stroker has Pontiac journal Eagle H beams. I have several with Scat rods and bbc H beams. The lightest steel connecting rod for one the Pontiacs has been the 6.625 Eagle H beam Pontiac journals. They didn’t require any machining. You just never know what to expect. Lol

I have an Eagle 6.8 H beam and an Eagle 6.8 I beam set I just compared. I have to look up the H beam numbers. I checked the bbc 6.8” I beams. They ran about 800 grams. I have 6.8” scat H beam bbc rods in my w72 stroker, I think they are 78x something grams. Not really much difference in weight between the h and the I beam there. Those I beams were rated for 700 hp and the H beams were rated for 800. On a street engine either one is fine. I am not sure, I might like the I beams a little better on that.

I have another engine I am working on with 6.7” Scat bbc 2.2” h beams and they weighted 767 grams. The stock Pontiac rods ran 868 grams with most of the extra weight on the small end of the pin. The Eagle H beams 6.625” Pontiac journals were 678 grams. Pretty light for what they are, nice rods.

[ponyakr]

"...The I beam RPM and SIR Eagle rods are probably the way to go if your using an OEM style pressed fit piston. Floating pin is when it is time to start looking at the H beams..."


Don't understand your reasoning.

The RPM & Eagle H-beams are available in press-pin versions. So, why go with the weaker, heavier rods, just to save a very few bucks ?

https://rpminternationalinc.com/conn...80-stroke.html

https://www.dragracecarparts.co/eagl...free-shipping/

It was a different story back when the Chinese 5140 rods were just over $200. But, those days are gone.

Another note: RPM discontinued the Pontiac spec 5140 rods, a while back. So, I suppose the Eagle version is the cheapest Pontiac forged rod now available. I suppose it's just as well. Cliff posted that he has seen several problems caused by those rpm 5140 rods being out-of-spec.

Don't know the cheapest source for the Eagle SIR 5140 rods. I suppose you'd have to include shipping AND tax. Some vendors still don't charge tax. Summit & Jegs started charging me tax a couple of years or so back. Amazon also charges tax if it's shipped directly from them. Have bought from several Ebay stores that didn't charge tax. But, I've read that it may become law that all online vendors MUST charge applicable tax. For these rods, you have to add around $30 tax, for my location.

https://www.jegs.com/i/Eagle/356/SIR6625PP/10002/-1#

https://www.competitionproducts.com/.../#.X2OVEozYo4g

Went to checkout at this Ebay store. No mention of adding tax.

https://www.ebay.com/itm/Eagle-SIR66...-/133478678972

I'd still go with the RPM H-beams, for lighter, stronger rods. But that's just me. The small savings may be worth it, for some.

[Jay S]

This photo in this thread is one main reason why you should do I beams with pressed fit pins, H beams for floating.

http://forums.maxperformanceinc.com/...d.php?t=844201


The H beam gets its strength and lighter weight from the cross section of the H. The I beam rods are thicker through the center and their strength come through the thicker metal in the center of the I beam. When the small end of the rods are heated up for pressed pins, the I beam heats up fairly evenly. More mass in the I, thick flanges on the ends. The H beams the end of the flanges in the H are thin, it is easy to get that really hot. It is thinner, not much mass to heat up. They can distort a lot easier than a I beam. Having the ends of the H glow red doesn’t help the metallurgy either.

Plus if the engine has pressed pistons hanging on the end of the rods it probably isn’t a 800 hp engine and the pistons is likely heavy. 800 hp rod in a 400 hp engine isn’t bring much to the table, the forged I beam rod have a plenty safe safety factor for that. IMHO. H beam and Pressed Fit are two terms that should not be used together, I would much prefer the I beams on that.

Each too his own though. It someone wants to use H beams so they can say they have H Beams. Cool

[leeklm]

All makes sense. We ended up ordering the eagle bushed h beams and will order the proper DSS pistons once we determine where the final bore size lands. Think it will be 4.080 or 4.100 at the most.

I will report back with the end result once everything is up and running in a few weeks.



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[JEC3039]

leeklm - don't know if your 093 heads still have the stock pressed-in rocker studs but if they do here is one more item for your consideration. The standard compression height of a DSS 389 piston is 1.710. For a small premium they will move it to 1.720. While that 0.010 doesn't seem like much it's that much less that you'll have to cut from the decks to achieve zero-deck if that's on your design list. The more you cut from the decks the more you bugger up the valve train geometry with stock rocker studs in the heads. Just something to think about. I'm about to place an order with DSS for 389 pistons with 20cc dish and 1.72 CH. Like you, need to complete the block bore work first to provide DSS the finished bore diameter.