# 389 RPM's



## Piedog (Feb 14, 2013)

Driven my 64 twice now and not sure of how hard to push it. It's a 389 3 x 2 that was professionally built less than 1000 miles ago under previous owner to the tune of $10k. Nothing wild just solid. What kind of rpm's is reasonable for a solid 389?


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## geeteeohguy (Feb 2, 2008)

5200 max for a stock engine with factory rods. Without knowing what's inside, I wouldn't push it. Also, know that these engines will wind up like a small block Chevy, but won't hold together doing it. Keep an eye on the tack and keep the revs at 5k or under. I've had these engines up to over 6500 rpm, but it is _very_ ill advised.


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## Piedog (Feb 14, 2013)

Got it. The build was all top stuff crank, rods, pistons, cam, lifters, headers, etc but I'm not wanting to find out the hard way. Previous owner had tach redlined at 5,500. It gets there pretty quickly & my only current frame of reference is my LS2 which winds up a bit more, so this is a new experience...a very good one I might add. Thanks


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## BearGFR (Aug 25, 2008)

If you know for certain that it has good aftermarket forged rods in it, then you don't have to be quite so cautious. Factory rods were always the weak link. Keep in mind though that Pontiacs are torque motors and they make it all on the bottom end. Depending on which cam you're running, it's probably going to be all done a good bit before 6000 anyway.

Bear


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## 67GTO4SPD (Oct 4, 2012)

BearGFR said:


> If you know for certain that it has good aftermarket forged rods in it, then you don't have to be quite so cautious. Factory rods were always the weak link. Keep in mind though that Pontiacs are torque motors and they make it all on the bottom end. Depending on which cam you're running, it's probably going to be all done a good bit before 6000 anyway.
> 
> Bear


I agree with Bear. The truth is without more specifics, we really can't accurately answer this question.


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## Piedog (Feb 14, 2013)

Thanks guys I got the answer I was looking for. 

The invoice shows Impastato Racing Engines Chesterfield Twp MI did the build. There's a 3 page list of work and parts. Honestly I don't know what "squared and parallel decks" even is. I know what honing is but I'm not sure about "bore hone to 4085 with plates"? I can figure out "pin fit to pistons, cut & mag crank, balance blue print & dyno"! It goes on; Diamond pistons, Eagle rods, Competition cam & lifters, Trend moly pushrods, performance oil pump, etc etc., 

Bottom line is it the 389 is not a hi rev engine and I'll treat it accordingly....if it ever quits raining! Appreciate the help!


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## Instg8ter (Sep 28, 2010)

You got ALL the goodies, but no need to push them to the limits...5500's a good number. Hope to see you and your car at the Dreamcruise...:cheers


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## 67GTO4SPD (Oct 4, 2012)

Piedog said:


> Thanks guys I got the answer I was looking for.
> 
> The invoice shows Impastato Racing Engines Chesterfield Twp MI did the build. There's a 3 page list of work and parts. Honestly I don't know what "squared and parallel decks" even is. I know what honing is but I'm not sure about "bore hone to 4085 with plates"? I can figure out "pin fit to pistons, cut & mag crank, balance blue print & dyno"! It goes on; Diamond pistons, Eagle rods, Competition cam & lifters, Trend moly pushrods, performance oil pump, etc etc.,
> 
> Bottom line is it the 389 is not a hi rev engine and I'll treat it accordingly....if it ever quits raining! Appreciate the help!


The specs you have listed above pretty much means everything was done right. "Squared and parellel decks" means the decks were cut and they were cut at the correct angle in respect to each other (90 degrees for a Pontiac). "Bore hone to 4085 with plates" means the engine was bored .030" over using a deck plates, which a plate that bolts to the head using the head bolts simulating the head being bolted on the engine. This is a better way to bore an engine because the normal distortion that is caused by the head being torqued is being duplicated by the plate. Most regular engine machine shops bore it with nothing bolted to the engine, and when the head is bolted on after it is bored, the bores aren't truly round (although the distortion is slight). 

NOW - you've got me curious - Does it have the cam specs, and dyno numbers? What heads are on it? This has nothing to do with your question, I'm just curious what they did and what they used now!  

It sounds like a very nice build!


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## ALKYGTO (Mar 29, 2010)

67GTO4SPD said:


> The specs you have listed above pretty much means everything was done right. "Squared and parellel decks" means the decks were cut and they were cut at the correct angle in respect to each other (90 degrees for a Pontiac). "Bore hone to 4085 with plates" means the engine was bored .030" over using a deck plates, which a plate that bolts to the head using the head bolts simulating the head being bolted on the engine. This is a better way to bore an engine because the normal distortion that is caused by the head being torqued is being duplicated by the plate. Most regular engine machine shops bore it with nothing bolted to the engine, and when the head is bolted on after it is bored, the bores aren't truly round (although the distortion is slight).
> 
> NOW - you've got me curious - Does it have the cam specs, and dyno numbers? What heads are on it? This has nothing to do with your question, I'm just curious what they did and what they used now!
> 
> It sounds like a very nice build!


:agree Sounds like a solid build! Nice find OP.


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## Piedog (Feb 14, 2013)

67GTO4SPD said:


> NOW - you've got me curious - Does it have the cam specs, and dyno numbers? What heads are on it? This has nothing to do with your question, I'm just curious what they did and what they used now!
> 
> It sounds like a very nice build!



All I have on the cam is the part number Competition Cams xe262(either H or 11) - 10. It has the original 9770716 heads. The block is from a 64 Catalina. I have the original 76x but it is shot. (The previous owner spent a ton having it built by a less than pro outfit only to find afterwards it was full of cracks. So long story longer this time he had a real pro do it.) I don't see any dyno numbers but I'm going to see if I can get them. The list of stuff is hand written on carbon paper & some is hard to make out.
I could try to copy, scan, & send pm if you are really interested.


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## BearGFR (Aug 25, 2008)

Ok, so if you can help with some details I've got an engine simulation program here that does a pretty decent job of running a theoretical model on an engine. That ought to give you a reasonable estimate of where the power and torque curves are on it.
Mostly, I need:
Cam (Comp XE 262H - I can get the cam details from that - do your build sheets say how it was installed? [look for phrases like "straight up", x-degrees advanced or retarded, or x-degrees ICL/Intake Centerline])
Heads (got - but need a way to get to actual compression ratio if it's not listed in your data)
Carb (type, model, cfm rating)
Intake manifold (if stock, or if aftermarket which brand/model)
Exhaust (headers? manifolds?)

To arrive at an accurate compression ratio (if you don't already have it in your build sheets) then we need to know:
Cylinder head chamber size
Piston deck clearance (sounds like yours might have been zero decked)
Which head gaskets (compressed thickness and gasket bore size)
Which pistons (brand and model - flat tops? dished?)
Bore and stroke (which we already know is 4.085 by 3.750 - unless it was stroked)

Sounds like you've got a nice one there.

The better information I have, the more reliable the results from the simulator will be.

Bear


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## geeteeohguy (Feb 2, 2008)

Now I'm really curious, as I'm a huge 389 fan. I hope the info will be forthcoming. I neglected to post, but others did, that the whole Pontiac experience is about rip-your-head-off-torque, not high rpm horsepower. A 389 has no need to wind to give you whiplash. It's a different animal than a small block or an LS-1, and different in a GOOD way, IMO. Agreed, you have a nice solid combo there.


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## Rukee (Feb 8, 2007)

Also keep in mind that the tack is not going to be able to keep up with the engine, so at WOT if you wait for the tack to hit 5500rpm chances are it's doing more then that. I run an MSD unit with a 5500rpm rev limiter chip.


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## BearGFR (Aug 25, 2008)

Ok, I couldn't stand it. I made some wild assumptions and ran some simulations. I assumed 72 cc chambers, zero deck, flat top pistons, standard head gaskets. That put's it a 10.2:1 compression which is scary close for iron heads on the streed on pump gas, so I hope it's not really that high.
But, with that combo and also assuming 1.50:1 rocker arms, a 750 QJet with factory iron manifold, plus headers, the simulator predicted a peak of 413 HP at 5350, 433 lb ft. at 3400.

More information --- which rocker arms are you running, and if you've got headers what is the tube diameter of the primary tubes?

Not too shabby though, I'm going to post a graph of the run with two tweaks - namely an 800 cfm carb and 1 5/8" primary tube headers.
Take a look at that torque curve. Now -THAT- is a Pontiac. The GTO didn't earn it's street cred by making a habit out of losing to the SS 396.... 

Bear


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## geeteeohguy (Feb 2, 2008)

I wish I still had the cam card so you could do mine! From what I know, though, the old 389's had small chamber heads...really small. The '77' heads on my '65 are about 64-68cc. Even the milder '10.5:1' 092 heads measured 69cc. So, a ton of compression with an iron head. In '67, the 72cc number showed up and became pretty common on down the line.


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## Piedog (Feb 14, 2013)

Sorry I had domestic duties - a granddaughter 1st birthday. Manifold is original with 3x2's. Hooker Headers - Super look like 1.5 inches /final exhaust 2.5.

Here is what I have to date retyped from the rebuild sheets w/ part number where shown. 

Disassemble
Degrease case heads etc
Media blast case heads etc
Debur cyl case
RR cam bearings
RR core plug
Ck align hone
Square & parallel decks
Bore hone to 4085 with plates
Cut crank mivns? 020 rods @hevy? –Moldex
Mag crank
Pin fit rods and pistons
Balance assembly
Repalce 2 cracked guides
Install guide liners in 14? Hone
Comp valve grind
Cut for pc seals
Resurface heads
Blueprint Assemble Complete Paint
Curve Distributor
Renew Carbs Plate Carbs Plate metal carb parts
Fabricate oil pickup
Dyno
Change carb plates on dyno
FM main bearing set 113m?20
Mnn ? rod bearings m77743pstd
Dura Bond cam bearing set dur4
Diamond pistons with pins 01055
Eagle BBC connecting rods crs670030
Total seal ring set cr08
Seal BOP rm501
Cloyer timing set 9-3612x9
Pioneer freeze plug kit
Meuing? Select performance oil pump 10540
Felpro gasket set fs8518it3
Meuing oil pump pixkup
Com cams cam xe262h-10
Comp cams lifters 852-16
Trend moly pushrods 5-625x080x5116
Comp cams springs 988-16
Comp cams retainer 743-16
Comp cams locks 601-16
Pro fit Viton valve seals 1132-500
SI inlet valves1-160
SI exhaust valves 1-660
Grade 8 fastners
Ace carb kits ends & center Ace floats
Autolyte spark plugs 86
Mr gasket curve kit 927
Mr Gasket header gasket
MSD distributor 8528
MSD coil 8202 & wire set & cap

I think the owner told me it gained about 30 hp. Whatever it is, it runs and sounds pretty sweet. I really appreciate all the help & dialogue. Mind you the only thing I can take credit for is right place right time to buy it but can't say I mind the nice comments from everyone! Much appreciated!


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## 67GTO4SPD (Oct 4, 2012)

BearGFR said:


> Ok, I couldn't stand it. I made some wild assumptions and ran some simulations. I assumed 72 cc chambers, zero deck, flat top pistons, standard head gaskets. That put's it a 10.2:1 compression which is scary close for iron heads on the streed on pump gas, so I hope it's not really that high.
> But, with that combo and also assuming 1.50:1 rocker arms, a 750 QJet with factory iron manifold, plus headers, the simulator predicted a peak of 413 HP at 5350, 433 lb ft. at 3400.
> 
> More information --- which rocker arms are you running, and if you've got headers what is the tube diameter of the primary tubes?
> ...


Did you use an actual flow numbers for 716 heads or a generic airflow file?


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## BearGFR (Aug 25, 2008)

I SWAGGed it 

If'n I had actual flow test data, I could use it though.

Bear


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## Piedog (Feb 14, 2013)

Bear et al. Here's what I got from the builder. Not sure if there's enough here if you wanted to to rerun your calc's & see how it compares. After you did all the work I feel kinda bad I didn't think of contacting the builder in the first place! Thanks again! :cheers

******
Nice little engine,
434.5 lbs ft. @ 3500 rpm
345.9 h.p. @ 5000 rpm
Timing @ 35*---- checked @ 4000 rpm, curve ends @ 3500 rpm
Autolite # 85 spark plugs----gap @ .040
10.03 to 1 compression
Center carb jet 62------end carbs 66
Comp cams 262 H 10
.462 218 inlet .470 224 exhaust 110 center
1.5 comp cams magnum rockers
6 quarts Valvoline VR1 20/50 non synthetic oil
Marathon 93 octane fuel
I would use a liter oil for the street in the summer VR1 10w30 non synthetic
*****


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## 67GTO4SPD (Oct 4, 2012)

The actual flow numbers for your heads, if they are unported, are below. 

1963-64 No. 9770716 (1963 421 HO & 1964 421 HO/389 GTO)
Valve sizes: 1.92/1.66
Intake(S) Flow (cfm) Exhaust(S) Flow (cfm) Exh./Int. 
.100 65 .100 33 .51 
.200 115 .200 64 .56 
.300 143 .300 86 .60 
.400 149 .400 102 .68 
.500 153 .500 110 .72 
.600 155 .600 113 .73 

These numbers are measured at 12" of H2O and will need to put in the simulator this way to be accurate. 


Using my simulator and these head flow numbers with your added specs, I came up with 361 HP @ 5000 RPM and 448 TQ @ 3500 RPM. 
These simulators are usually a little optimistic, but it makes for great bench racing rhetoric. Its also fun to "build" wild 700 cu in engines with 16 : 1 compression, turbos/superchargers pushing 80 psi of boost AND a 400 shot of nitrous!!!  

I'd be interested to see what your program comes up with, Bear. I used 900 cfm as a guess at what the Tri Power should have.


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## Piedog (Feb 14, 2013)

Bear & 67GTO4SPD,

The builder told me he uses a Superflow 901 engine dyno. Whatever the numbers are it's an experience every drive. I can see it will be hard to keep my right foot under control. I thought my 05 Vette w/ Corsa exhaust had a robust sound. Yesterday I uncovered it & had them side by side idling together. Different cars for different purposes but the real muscle car was pretty obvious! I'm hooked! arty:


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## geeteeohguy (Feb 2, 2008)

As a side note, you're running pretty small jets. In my '65 GTO with a 389 and big cam/tubing headers, I'm running 71's on the outer carbs and 68's in the middle carb. You may realize more power by going up slightly in jet size. You'll use more fuel, too, though. If it's running well now, though, and it sounds like it is, I probably would leave it alone.


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## Piedog (Feb 14, 2013)

geeteeohguy - Good information to have. I'm going to heed your advice and leave well enough alone at this point. I have some things to fix that are broke! Thanks!


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