early 389 rebuild

Hi I am a new member in need of a bit of advice. After a 120k miles my 389 is getting difficult to fire up. I am rebuilding a 1962 Bonneville that's a factory 389 303hp engine, carter carb, roto-hydramatic trans, factory rears. The hydramtic was recently gone over and I will continue to run it until it gives any grief. I am not looking to build a ten second car just the odd cruise night and some highway trips to the lake. I am just getting into tear down and want to get some parts ordered. Everything will be stock other than a cam, distributor and port and polish.  I would like to replace the connecting rods but do not want to break the bank. I picked up a new cam at a swap meet that is Jegs 262/272 duration, lift 440/442, 1500-4000rpm range.

So my questions are does the cam seem suitable for a cruiser ? Suggestions on where to get connecting rods and stock pistons ? Is there a stock set of rods from a 400 ci that are suited for my application ? Do I need to install hardened seats on the valves ? (having trouble finding a shop that is experienced)  

Hello oldskool

I see you are new to the forum as am I. Welcome

Nice sounding car you have there, I love those big ole bonnie's.

I can just offer you my personal thoughts regarding your questions.

Is the cam in it now stock and if so do you want similar performance or more of a lope at idle and stronger mid range etc?

Do you commonly rev it to the max?

Do you know what your orig cam specs are? Be interesting to know if any one can post that info.

Does it have cast iron high perf manifolds small stockers or headers?

Does it detonate [ping]under any level of acceleration or a heavy load like accelerating up a hill? The reason I ask is because the head chart on this site says your current [not worn out] static compression is around 10.5. Most people seem to experience "pinging" at compression levels above 9.5 with 91 octane pump gas. If you have compression caused pinging it is easily addressed in your case during a rebuild with dished top pistons.

CAM - Just curious, what brand and part number is it exactly. The jegs catalog does not show a jegs brand? It sounds fine but I personally would run a comp 265DEH in your situation since I am more familiar with what it is. Your rpm range sounds like an rv type cam to me and the lift seems low. Your rpm range also seems very "narrow".

HEADS -  In addition to your porting I would back cut the stock valves for improved flow. But I wouldn't over port it like for racing etc.

RODS - There is a post on the site somewhere that lists which factory rods were cast and which were forged. Frankspontiacparts.com lists a set of forged "fits all" factory rods for $195.00. You could call him for info if you need. If those won't work or are sold then I would use Eagle forged rods. Any rod new or used should be checked for size and proper rod bolt strength by your machine shop. Although the less expensive tomahawk rods sound tempting and may be fine I personally would not use them but that's just what I would do.  

keep your rods they are forged! from 1958 to 62 pontiac used forged rod in 389s. just get new bolts and resize.  i have a set in a 406 that has seen 7000 rpms and a 200 shot of nos its at least 15 years old.  
76 455/4spd TRANS AM
69 GRAND PRIX 406/5SPD

Welcome to the forum Old!

There are several versons of your 62 389.. here's one and al lthe 303hp versions are very similar.

Year  Engine HP  Engine Trans CR     Cam     Head Code BBL carb
1962    389 303HP 16K    A   10.25   472     538177    1-4 3326S

You factory cam specs are;
Application  Stamp  Dur.  CL  1.50:1  1.65:1  O.L.  Dur.  CL  1.50:1  1.65:1
1959-62 4bbl   4    273  106  .407"   .447"   55    282   116 .411"  .452"

I think the specs on the cam you picked up are ok.. But I'd really want to know who manufactured it.. And I'd degree it in no matter which cam you end up with.
As Row said.. keep your forged rods and just about any manufacturer will have pistons for it (TRW etc..)
That 10.25:1 CR might be a bit much on todays pump gas.  
Jim,

I agree, your cam specs are fine for the kind of driving you've indicated. The Bonne is a big car and you want to keep the torque down low to get all that mass moving, especially since you indicate the rest of the drivetrain will remain stock. My71 makes a good point concerning the compression ratio, you will want to have the heads cc'd and the deck height measured to determine the true compression ratio and shoot for somewhere in the 9:1-9.5:1 area at most for reliable operation on today's pump gas, either way you're still looking at buying premium fuel. This means buying dished pistons after you determine the cc's of the heads. You can choose the cam specifically for low rpm torque and you'll never miss the extra compression.
The stock rods should be fine with correct resizing and ARP bolts. Rebalancing is always recommended when rebuilding but if the new pistons are similar in weight to the stock ones and the rpm is kept in the range you indicate I would consider it a luxury.
Steve  
A little help... 'cause we don't all have to learn the hard way!

Hello old skool and my71

my71 thanks for posting those specs unfortunately those are the same ones I found and was hoping for durations at .050 also but couldn't find them.  

I did find the cam but am having some issues accessing the jegs website at the moment. Everything on the car is stock. I wont be redlining the engine. I have a 50 chevy pickup with a 302 out of a late 60's camaro I beat on and wanted this as cruiser. I currently add 1 gallon of race fuel per tank that helps helps the pinging.

I will cc the heads to verify. I can bore it .060 over and run 400ci pistons but really seems like a waste boring that much for a fairly stock engine. Other than stacking 3 head gaskets with duct tape to drop compression is there a source for a dished 389 piston. I would prefer not using the race fuel as it is a pain to get and not a fan of storing it in my shop.  

Hello

RE DISHED PISTONS – Below is a link to someone that may have them. You will need to call because their catalog does not list whether their pistons are dished or not. If you don’t find any or they can’t make them you can always get them custom made by je pistons or others. They may cost around $700.00. Phone 800-866-3443

Getting custom pistons or any piston information direct from piston mfgs is very easy, just look their sites online for their number and call them. Most have xlnt customer service lines. Some sources are JE, probe, trw.

REDUCING COMPRESSION – I used the Wallace free online compression calculator to generate the following numbers for you. I entered the following specs, 389 std bore, -64 cc chamber, -.020 deck height. 64 cc = 10.47 comp, increasing bore size to +.030, 76 cc chamber = 9.4 comp. This means that If in fact your heads do cc close to 64 cc then if you remove 12 cc’s from the chambers you will have approximately 9.40 static compression. You would have to ask an experienced machinist if this is possible to remove that much material or perhaps someone here with first hand experience in doing this can let you know. This process may save you some money if that’s a concern. I personally might go the dished pistons way irregardless of cost simply to preserve the original heads.

As I mentioned in my original post I think 9.5 is the max you want to run but going around 9.2 or less will add in a bit of a safety margin to allow for high loads under hot weather conditions etc.




Egge machine pontiac piston page at egge.com

http://www.egge.com/parts?make=PONTIAC&category=2

PO389M59HP          1959 PONTIAC, 389, V8

PO389M60HP          1960 PONTIAC, 389, V8

PO389M66W8.6CR   1966 PONTIAC, 389, 8.6:1 CR, V8  

i just happen to have a cam card for a 066 witch is the same as the 472.
273/282 advertised 200/210 at .050, 407/411 lift.  
76 455/4spd TRANS AM
69 GRAND PRIX 406/5SPD

Hello old skool

As I mentioned in my original post and Barneyformula also mentioned the cam you have will work however the reason I am trying hard to get more orig cam spec info other than what has been supplied and your opinion of how you like your existing cams perf is that I think there may be a different cam than you purchased that will give you the type of performance you are looking for.

I personally hate to see anyone just throw a cam in without knowing how it may perform or in your case how it may perform when compared to a known factor like your orig cam and end up disappointed in the results.

Rowsley - Thanks for the additional cam info.

Any "lsa" on that card  to compare to the lsa posted by my71 or valve timing events etc. and if not is there a mfg and p/n so I or others can look it up if they want?

In the absence of any more additional orig cam specs, I personally would still use one of the cam's I suggested for the reasons I mentioned. I can assure you they will provide plenty of bottom end but won't fall off at 4k like your newly purchased cam says it does, not that you will need or use the extra rpm.

Does it have hp cast ex manifolds?

Thanks  

Hello

Here’s a few cam specs from comp, plus your [purported] factory cam and the jegs cam specs you supplied. Thought I would post them for you and in case others might want to look at your stocker and jegs and offer any alternatives to the jegs.

255deh  244 261   202 212 .420 .425   io 21  ic 53 eo 16  ec 64 lsa 110 1000-5000  overlap 32.6

Xe256h  256 268   212 218 .447 .455   io 22  ic 54 eo 20  ec 68 lsa 110 1000-5200  overlap 42

265deh  265 269   211 221  .442 .465  io 25  ic 59  ec 21  eo 67 lsa 110 1200-5500 overlap 46

275deh  275 277   219 228  .462 .480  io 31  ic 63  ec 24  eo 72 lsa 110 1500-5800 overlap 55

Xe262h  262 270   218 224  .462 .470  io 25  ic 57  ec 21  eo 69 lsa 110 1300-5500 overlap 46

xe268h  268 280  224 230   .477 .480   io 28 ic 60  ec 26  eo 74 lsa 110 1600-5800  overlap 54

529472  273 282  200 210  .407 .411                                     lsa 111 1700-5200 overlap  55

jegs       262  272               .440 .442                                                 1500-4000


NOTE – It looks like the 529472 is most likely your stock cam p/n and specs per my71, and Rowsley’s info. The site listed below in the url had the cam number and other specs. The first 6 cams are comp cams.


RPM range and LSA for 529472 from Howards cams p/n 417131-11

OPTIONAL OEM CAM - Howards factory P/N 9779066 is a slighty lower rpm cam 1600-5000.

The jegs cam specs you provided so far are most similar to the 265deh comp listed first above however more specs on it would be helpful to better compare them all for you.

Here are the hp/tq ratings between the comp cams using the same specs for all tests which are similar enough to the ones you have provided so far except I used high perf cast ex with mufflers instead of base type cast manifolds for a general comparison.

255deh 275 hp 4000, 404 tq 3000 rated as RV cam by comp

Xe256h 281 hp 4000, 404 tq 3000 slightly bigger than RV cam rating

Xe262h 285 hp 4500, 400 tq 3500

Xe286h 293 hp 4500, 393 tq 3500

265deh 284 hp 4500, 398 tq 3500

275deh 291 hp 4500, 385 tq 3500


Is your intake stock?

Thanks  

Hello old skool

I just had an epiphany. Just in case you are not aware, if you are happy with the way the existing cam performs [other than the motor being worn out], then you can get a replica of it, Howards cams has a version of it. The only problem I can see you having is using the stock cam is that if you reduce the compression then it will not perform as well then one of the other style cams might still be a better choice.  

Hello old school

Here’s an interesting item. An article written by Jim Hand says the ideal “cranking” cylinder pressure for a street performance engine to run on 93 octane without detonation is between 160 and 170 lb’s. I decided to calculate the dynamic cylinder pressure for some of the comp cams using the Wallace dynamic pressure calculator and this is what I found out.

At the very least, in your particular case, if I use the existing static compression criteria below, the calculator produces the dynamic compression and cylinder pressure numbers listed. This means that if I understand the article correctly, according to Jim Hand, in your particular case, you would be able to use a cam with an intake valve closing time of a minimum of 57 degrees at sea level if you can reduce your existing purported static compression of 10.5 by at least a minimum of .5, it's feasible to run all the cams below. That being said he also recommends that, due to possible irregular fuel octane levels, it is best to run the cranking compression on the low side, which would still be around 9.5 for the cams below.    


 Cam         Elevation             Intake valve closes                     Dynamic compression                 cranking pressure

Xe262h           0                                 57                                             8.42                                             169.85

265deh           0                                 59                                             8.30                                             166.74

Xe286h           0                                 60                                             8.22                                             164.66

275deh           0                                 63                                             8.06                                             160.52          


The calculator says your cranking pressure reduces by approximately 5 lb’s for every 1000 feet of elevation. So the higher above sea level you are the less likely your motor will detonate.



EXISTING STATIC COMPRESSION – If in fact your current combustion chamber size is around 64 cc’s as estimated then you only need to remove 5 cc to arrive at the following compression which was used to generate the cranking cylinder pressures above which are deemed acceptable by Jim Hand with the lower number of 160.52 being the most detonation resistant of the ones listed. 389 ci, +.030 bore, -.020 deck height, 69 cc chamber = 10.06 static compression.

Reducing the static compression from 10.0 to 9.5 lowers the dynamic cranking pressure numbers listed above by 10 lbs across the board.

The intake valve closing time is required to calculate the oem or jegs cam.

I personally would try to run a little less than the static compression and cranking compression numbers above just for a safety margin.

Thanks  

Good post 70bird.

 
When The Flag Drops,,,



The Bull Chit Stops,,,


P. Engineer, Engine Builder

066 cam specs at .005 lift

intake opens at 30 btdc closes at 63 abdc
exhaust opens at 77 bbdc closes at 25 atdc  
76 455/4spd TRANS AM
69 GRAND PRIX 406/5SPD