[goquick]

B-Man has a good Idea, stroke it! But it is getting very hard to not buy aftermarket steel rods instead of redoing weaker stock ones. Plus the cycle time on the stockers adds up to unmeasured metal fatigue. And alot of the redone rods I have seen would have been far better left alone.
I still say if your head porter has experiance, open up the combustion chambers into a fast burn style and gas octane at the pump won't be a problem. I did that on a small domed piston 389 combo and it does not ping on 93 octane. In fact, it does not ping on 89 octane. The car runs hard, 12.40's with a larger cam than you want. 093 heads on it.

[Bill Eveland]

If you really want to stroke it, you could use a 4.25 stroke crank and go up to 447-453 ci depending on bore. But those pistons would have to be dished quite a bit to keep compression down.
The 744 is a Pontiac manual trans Ram Air cam.

[66GTO Jim]

I went the stroker route with my 389 for the reasons you stated (see link below for full story). I wrestled with porting my 093s or going with the 6X8s. I finally went with the 6X8s. I wouold stay away from the 744 cam, as I remember Pontiac having problems with them due to the flattened out nose. I went with the Comp Cams XE274H which is probably more than you want and probably more than I want! I am currently researching other cams to possibly replace it with. I think the suggestions of the Crower 60916 or Summit 2801 are good candidates.

Good luck on your project! Jim

http://forums.maxperformanceinc.com/...d.php?t=430014

[Z Code 400]

66tri-hb,

In your case, I would seriously consider keeping the engine configuration (CID) as close to stock as possible, with modifications limited to compression reduction and a custom camshaft profile with valve events optimized for your final static compression ratio.

I would likely select a profile with 225° - 230° intake duration @ .050" on a 114° to 116° LSA if you were to remain around 9.75:1 compression and 220° -225° on a 110° - 112° with a drop in compression to 9.00:1.

With the common TRW 288P pistons (which yield about 0.025" deck height) you will likely end up with 9.80:1 with a 72cc combustion chamber. I recently had a set of TRW L2269F pistons dished for a 'restification' 389 GTO project engine. I paid about $530.00 for the set.

One area where you can increase your combustion chamber volume is opening the chamber around the valves. This serves to unshroud the valve and enhance flow in addition to lowering the compression ratio without changing the quench distance. I fitted the heads with the larger valves (2.11" x 1.77) at the customer's request. The bowls were blended under the cuts for the larger valves, but the ports were left stock.

I would advise against porting the heads on a street car. You simply will not see a benefit on the average street engine with moderate camshaft profiles and compression ratios.

I prefer to keep the modifications simple...Robert

[Z Code 400]

P.S. I don't have my assembly notes with me, but as I recall, the finished product had a - 0.010" deck clearance with a 77cc chamber (modified for larger valves) and a 12cc dish in the piston. This worked out to right at 9.00:1 compression...Robert

[JKrull66]

You have a lot of options,
On my 66 389 I had to go 60 over. This was before all the cheap rods out there, but with the shorter stroke adding ARP rod bolts is all I did. I spent most of my money on the small hyd roller cam 276 282 .536 .544 w/ 1.6 rocker that Butler sells, and on the heads. And keep the RPMs below 6000
The heads I added 1.94 and 1.60 stainless valves, springs and offset retainers to handle the lift. Screw in studs and roller rockers. It won't break the bank to get those 093's to flow 220 - 230. And with the tri power this cam makes good torque and a nice rumble. but still pretty tame for acc's.
I did open up the heads to about 74 cc's. and get along fine on 91 gas.
I figure it is in the 430 - 450 hp area and pushes the 66 and me 4000 plus at a 13 flat in the 1/4.
Have fun and do what you want, that will keep you out there beating up on those pesky Stangs.
John

[66tri-hb]

Well all the options are here so I must decide. I am leaning with the stock build and stock to maby a custom buttler cam. The roller cam has been on my mind alot, can I go roller for another $500 and stay stock and get any advantage? Hey JK you went this rout could feel the differance in performance?

My pistons are my subject now I just spoke with Diamond this morning $80 each plus $10 pins .They were super to deal with
Robert you mention the other 66 you did what pistons did you use and where do I want my compression to be ? I have 93 octane and this will just be a weekend driver. I checked the trw numbers the first is obsolete sence trw is out but they are looking up[ the other. Did you have to get it dished or did it come that way.

I may just leave the heads alone if you think I want get anything from it but a lit work if I will .

Hunter

[mchell]

I wouldn't waste a dime on a roller cam for a stock type rebuild.......you can get a custom piston from a few vendors who frequent this site.....Pdude, PPR, SD Performance etc...

I would keep your compression in the 9.5 to 1 range......

If its gonna be a Sunday driver and stock show car and your set on using the 93 heads and tri power setup, I wouldn't be spending much on trying to port those heads or running a roller cam etc... spend your rmoney on a GOOD basic rebuild that uses solid factory parts and drive it on Sunday's.... be happy..even thats probably gonna run you 4g's..

[Z Code 400]

Hunter,

As you probably know, the closer the piston is to zero-deck, providing the compression is at a reasonable level, the more detonation-resistant the engine will be. In the case of a 389 with small chamber heads, you can't really do zero-deck because there is only so much piston you can dish. I used TRW L2269F pistons and dished them on a lathe.

I added the big valves for two reasons; Number one, the seats were sunk and this allowed me to bring them back to the correct setting and number two, I was able to open the combustion chamber wall around the valves to both unshroud (enhance low lift flow) and increase chamber volume, which reduces the static compression ratio.

If your seats are in good shape, you can retain the smaller valves, but the 'unshrouding' in the chambers is a must to reduce the compression ratio. Even with the small bowls, the larger valves will provide a modest flow advantage.

I think 9.00:1 to 9.25:1 is a very good street compression ratio with a healthy, yet well plotted camshaft profile. If you plan on running 87 octane, then 8.75:1 would be more appropriate (yet difficult with small heads) and a milder camshaft profile.

Flat tappet hydraulic is the best way to go for your 389. Crower #68404 Dual Springs will install exactly as stock and work to about .550" lift. Porting the heads would be a waste of money since you will never exceed the stock head's flow capability on a mild street engine.

A carefully chosen camshaft profile should be used to improve cylinder head flow. I prefer camshafts with the same amount of lift on both intake and exhaust since everything in the valve train 'sees' the same load. Higher lift on the exhaust means higher valve spring pressures, increased heat and wear. Most of the stock Pontiac D-Port Heads I have seen on the flow bench peak at around .450” valve lift and I can see no reason to shoot for really high lift values on a street engine with a flat tappet camshaft and stock heads.

The diameter of the .842” lifter places a limit on how much valve lift can be employed and .300” to .320” is about the practical limit for flat tappet camshafts in the 220° to 230° @ .050” range. I like to see net valve lift in the .465” range for a street engine. This gives long cam lobe life and adequate lift for basically stock heads. It is also very easy on springs, rocker arms and pushrods since it keeps valve-open pressures moderate and even.

In your case and providing you can arrive at 9.25:1 to 9.50:1 compression, I would like to see a full 6° to 10° additional exhaust duration to promote cylinder scavenging. For a stick-shift car, I would likely choose around 225°- 233° @ .050” on a 113.5° LSA and for an automatic, I would likely choose around 222° - 228 @ .050” on a 111.5° LSA, both with about .465” lift with stock 1.50:1 rocker arms.

The 9.00:1 compression 389 I recently built was backed by a four speed and 3.90:1 gears, so I designed a hydraulic flat tappet camshaft specifically for this application. The lift was .461”/.461” with 227°/233° @ .050” on a 115° LSA. Power was very broad and smooth with this configuration and cranking compression was in the 165 psi range. The engine runs very strong, cool and does not ping even on 89 octane fuel.

I designed a very similar camshaft for a forum member with a tri-power equipped 462 and it is quite impressive.

Keep your rebuild close to stock, but use quality parts and modify your compression ratio, while keeping the piston as close to zero-deck as you can. Refer to post #25 in this thread for an idea of the measurements you will need to achieve your desired compression ratio.

Feel free to email any questions you might have…Robert 10851man@gmail.com

[Z Code 400]

Originally Posted by goquick

Oh, and open up the oil pump entrance in the block so the oil doesn't smack the block and give the oil pump a false pressure read.

You mean like this???....Robert

[goquick]

That works.

[JKrull66]

Originally Posted by 66tri-hb

Well all the options are here so I must decide. I am leaning with the stock build and stock to maby a custom buttler cam. The roller cam has been on my mind alot, can I go roller for another $500 and stay stock and get any advantage? Hey JK you went this rout could feel the differance in performance?

My pistons are my subject now I just spoke with Diamond this morning $80 each plus $10 pins .They were super to deal with
Robert you mention the other 66 you did what pistons did you use and where do I want my compression to be ? I have 93 octane and this will just be a weekend driver. I checked the trw numbers the first is obsolete sence trw is out but they are looking up[ the other. Did you have to get it dished or did it come that way.

I may just leave the heads alone if you think I want get anything from it but a lit work if I will .

Hunter

JMHO
If you want it stock, put in a 068 cam or new upgrade of it and be happy. If you want more HP....
Its all in what you want, The roller is more like 1,000 add on with the 093 heads. This is with the additional head work to run the springs & screw in studs.
Was it worth it, I thought so, The porting and roller dropped me a whole second at the track. Over stock heads.
The feel and driveability was about the same as running my Crane Commander cam. ( witch was my favorite Hyd)
HP is in the heads (2.1 or 2.2 X Flow). If you want more power from a small 093 head (180 ish stock) you have to open them up, Cost more money... Yes. Have to spend time getting work done here and there ...yes.
Burning the tires down the block will put that smile back on your face.
John

[Z Code 400]

Hunter,

Porting is not a requirement at your desired performance level. In fact, your combination will benefit more from careful selection of parts to ensure a 'streetable' compression ratio and optimum valve timing for the application.

How good are the 'small 93 heads' in reality???

The 389 335,338 & 360 horsepower engines and the 421 256 & 376 horsepower engines both use the '93' head with a 1.92" intake and 1.66" exhaust valve.

My suggestion would be to add the bigger valves (to ensure perfect seats and stem height) and open the combustion cahmabers up to unshroud the valves and reduce combustion chamber volume for a more 'pump-gas friendly' compression ratio.

I am sure I will be most unpopular when I recommend against factory Pontiac camshafts, or those that mimick the factory camshafts, like the K2801. Why continue to use 40 year old camshafts when the technology in valvetrain components has come so far???

People do the same thing with Chevorlet...everyone uses the old 327/350 horsepower hydraulic, even though much better camshafts are available.

I can tell you that 227°/233° @ .050" on a 115° LSA with a 4 speed is more power than you can possibly put to the ground with DOT tires. It idles nicely, has high vacuum, good cold start/driveability and broad power...Robert

[Z Code 400]

I was chatting with the 389 owner this evening and he provided me with flow data for his stock 93 heads. This was done during the engine's first rebuild, completed by the owner in 1985. No porting was performed. These are as-cast 93 heads with 1.92" x 1.66" valves:

Intake Flow @ 28 in/H20:
.100" 63.0 cfm
.200" 116.7 cfm
.300" 146.3 cfm
.500" 149.6 cfm
.600" 152.8 cfm

Exhaust flow @ 28 in/H20

.100" 35.4 cfm
.200" 69.1 cfm
.300" 99.3 cfm
.400" 103.6 cfm
.500" 105.7 cfm
.600" 108.2 cfm

Larger valves would likely improve the low lift flow numbers, but I think Pontiac kept the numbers low and the valve sizes small for a reason. For any of you that have driven a stock 389, you know they have great low end, pull hard and run good, right up to redline.

My vote is for the 93 heads...Robert

[mchell]

Yikes!!!...............are those flow #'s for real?

Unless the 389 owner is looking for a concourse restoration, I would toss those things and get just about ANY other D port head............a head thats choked like that ain't gonna support a lot of ponies..........

[b-man]

1966 389 360HP Tri-Power. Log exhaust manifolds, 093 heads with small valves and ports, 068 cam.

1967 400 HO 360 HP. Free-flowing exhaust manifolds, 670 heads with big valves and ports, 068 cam.

Which one makes close to a 'true' 360 HP?

It sure ain't the 389.

The 400 has 11 extra cubes and far-superior heads, I'm betting there's a 40HP difference between these two 360HP-rated engines, 30HP from the heads alone. Pontiac redesigned the heads for a reason, the 389 heads were lackluster to say the least.

[JKrull66]

093 can go 220 - 230- easy just take some in intative,
it all is in you hands
John

[Z Code 400]

Nice historical input B-man....So what factory performance numbers do we choose to believe and which do we choose to dismiss??? I personally believe that 335 HP is accurate for a 389.

In this case, the owner wants to improve performance, but does not want to abandon the 93 heads.

Of course later (modern) heads would be better, but that is not within the confines of Hunter's question...Robert

[goquick]

When the chambers are opened up to a proper fast burn style on the sides of the valves (when done should ressemble the outline of a 8 ) the flow goes up dramaticly. The closed chambers are basicly enclosed on the top of 75% of the valves. Also without opening the chambers, A 45-50 degree seat with a high lift cam can overcome this restriction. Larger valves really won't help half as much as chamber reshaping and narrowing of the valve guide, and grinding the sharpness off the the intake port wall next to the head bolt and rounding off the pushrod bulge. There is nothing wrong with using these heads, just a few areas to make them far better and continue to look stock. And when it's done with hard exhaust seats, pump gas isn't an issue as far as 'ping', because there will not be any 'ping'.

[Z Code 400]

Jkrull66,

Consider that Alan Mandella's 1974 Trans Am (Sept 05 HPP Shootout) with a 462 and 228°/235° @ .050" camshaft with stock 4X heads featuring 2.11" x 1.66" valves is running consistent low 13's - high 12's (corrected) on DOT tires through the mufflers, and considering that stock D-Port flow is around 200 cfm intake and 150 cfm exhaust, I can't see a 389 'weekend cruiser' needing 220-230 cfm.

Also, those 93's will take considerable work in the ports (volume) and the bowls (diameter) up to and including larger valve sizes to reach that goal...Robert