[Tomaso]

We have some stations that do have 94 octane( 10% ethanol as well I believe) in my area

[Gach]

It sucks today trying to do what your trying to do, I mean 10-12 grand is crazy. Its to bad you couldn’t get your hands on a good set of used e-heads. Here’s a quick quote. Your heads probably flow maybe 190-200 cfm. To get were you want to go, you’ll need 260-270. Sure you already figured that out. That 60 to 70 cfm more is the key. Just a 30 cfm pick up is wroth 10% more hp, Maybe a set of speed masters heads, but I get what your saying its not just the heads. Its everything else push rods…Lifters….Cam… and intake. Its tough

[Gach]

Originally Posted by Tomaso

We have some stations that do have 94 octane( 10% ethanol as well I believe) in my area

Thats great! Perfect ! I don’t know, but I’d give it a shot if it was me, just pick the right cam. Sorry I meant ethanol

[Gach]

Its not hard getting those 16’s to 250- 265 cfm. I’ve done a few sets. Good value job rising the roof.

[Gach]

That 4” stroke vs the 4.21 on 455 makes all the difference in the world. 4”Definitely tolerate more compression.

[Gach]

The valve timing on the Crower 60919 is perfect for bleeding off compression. But the other thing I’m thinking about is convertor you’ll be running. Might need a tight 3200 stall convertor vs a stock convertor.

[Tomaso]

Unless, I sell the 389 that I have complete that was in the car, the parts from the 428. And just bite the bullet and go all out on the 428 with that builder kit…
Heck, it’s a 4 bolt main. Just go with a 4.5” stroker crank too instead of the 4.25?

[PunchT37]

Originally Posted by Tomaso

Unless, I sell the 389 that I have complete that was in the car, the parts from the 428. And just bite the bullet and go all out on the 428 with that builder kit…
Heck, it’s a 4 bolt main. Just go with a 4.5” stroker crank too instead of the 4.25?

I would not over cube those already small heads. The 4.5 stroke will also put more stress on the block, even though it`s got 4 bolt mains. Course, it will be a low rpm engine with a 4.5 stroke and small runners, and that includes the intake.

I would leave it as 4 inch stroke. Those 428`s are a "small block" big block. 421`s and 428`s are some of Pontiac`s best running engines.

[Gach]

I would definitely not go with 4.5 stroke, that would definitely push compression way Beyond what you could run on 94 octane. Unless you went with E-head even then I wouldn’t

[Tomaso]

So is the consensus to keep the stock crank or the 4.25 crank and E-heads?

[Steve C.]

Stated- "I would not over cube those already small heads. The 4.5 stroke will also put more stress on the block, even though it`s got 4 bolt mains. Course, it will be a low rpm engine with a 4.5 stroke and small runners, and that includes the intake."

Good point.

Related, from the internet....

"Increasing the stroke greatly changes the angular relationship of the rod and cylinder. The rod is at a much sharper angle in relationship to the angle of the cylinder, generating enormous amounts of friction between the piston rings and cylinder walls, causing both friction and ring sealing problems. At lower RPM ranges this friction is easily overcome, but as RPMs increase, the friction reaches higher levels. The second factor is directly related to the first. The increased rod / cylinder angularity also increases the piston velocity. That is, the piston will move up or down within the cylinder bore at a far greater rate of speed than a shorter stroke engine. Also, the piston "dwell time", that is the amount of time that the piston remains at TDC, is decreased. These factors have the effect of making the engine extremely sensitive to detonation, as well as making the engine sensitive to under-flowing heads. To illustrate, grab a bicycle tire pump sometime, and first try to operate it as quickly as you can. Then, slow down the pumping action. You will notice that it is far easier to move the pump handle slowly. Your engine is no different- slow down the piston, and the engine has less work to do. Again this condition is aggravated by high RPM conditions. The important thing to remember is that no matter how fast or slow the piston goes, the engine moves exactly the same amount of gasses during the same number of crank degrees. This situation could be improved by using the longest rods possible, which would increase the rod ratio and somewhat alleviate the angularity problem."



.

[tc]

Depends on what you want from your car. I have never really cared about hp and tq numbers. I just wanted my car to run high 11's to race in a 12.00 class. The engine is a 428, iron heads. 9.6 compression, HFT cam, .508 actual valve lift. Fun street car.

[Tomaso]

If I can get away with the stock heads and stock crank. Even if the heads need to be rebuilt and ported. And use the 91-93 octane. I would be happy..
or should I get the edelbrock heads and keep the cast crank?

[Stan Weiss]

Dennis Jensen post this build here some time ago

Dmac, My brother Dan and I rebuilt a 1970 360 hp YH code 455 (std. in the
Bonneville's) using the 100% stock #15 small valve heads (combustion chambers
measured 89 cc's after a minimal cut to true them up) at 9.9 to 1 static
compression. The block had been previously been bored .040 over with new cast
pistons, so we had it honed to provide .0025" - .0030" clearance (we know, not
ideal) for the new moly rings. The cast rods were replaced with Eagle H-beams
and the factory crank cut .010/.010 with new bearings. The #15 heads had new
Ferrea 1-pc stainless steel valves (1.96/1.66) with new CC valve springs and a
Summit 2802 cam & lifter kit (224/234/112 @ .466"/.488") installed straight up
(4 degree built in advance IIRC). We had the stock pressed in rocker studs
pinned too rather than going to the screw in studs (cheap move on our part
...and, again, not ideal). Again, the ports on the #15 heads were untouched
and are known to flow 190/195 cfm on the intake side and 145/150 cfm on the
exhaust both at .450"+ lift. With the factory cast iron intake, Q-jet, and
exhaust log manifolds it made 390 hp at 4600 rpm and 512 lb-ft torque at 3400
rpm. With RA manifolds or headers, it would have easily been in the 420 hp/540
lb-ft range.

Stan

[locomotivebreath]

Just a for what it’s worth . I did a 68 400/406 , original engine for my GTO . The 16 heads are mildly ported to flow 230 cfm , small bullet HR 226/230 (280/288 adv ) .518 lift , 1.5 Harland sharps , 0 decked block , 10.00.1 comp - I added oversized ram air manifolds . Engine made 420hp & 485 ftlb on a tight dyno and 93 octane . Pulls good vacuum . Car is still in assembly but I’ll try to upload a short clip . Your stock parts will get you what you want with the 428 is my point with the right cam .

[locomotivebreath]

I cant upload the clip , something about a security token missing but the engine idles nice and appears it will have good street manners .

[Tomaso]

I would be happy with those numbers..

[MarkS57]

As other have said, depends on what you want in the car. Track numbers or just a big fast car. I had a 69 428 Bonneville. It was the only stock big car I owned that would chirp the tires on the 1-2 upshift. As a big fast car, it was lovely. If that's your goal, keep it a 428, not likely you'll be disappointed.

[Gach]

Originally Posted by Tomaso

If I can get away with the stock heads and stock crank. Even if the heads need to be rebuilt and ported. And use the 91-93 octane. I would be happy..
or should I get the edelbrock heads and keep the cast crank?

Mike…I’d get Edelbrock heads and keep cast crank. The thing that makes the power is definitely the heads. Those 16’s probably flow 195-200. Which probably restrict you to right around 350-360 hp. Think about first thing we do to make more hp…port the heads. The e-head flow 270-280 out of the box. That 16 head maybe with allot of port work trick valve job 265. (I know guys have gotten 270 )
But your talking allot involved doing those 16 iron heads. By a competent head porter. But the key thing you’ll be battling with 16’s is the compression issue. Mike you want something you can pull up to the pump and not have to worry about donation. Its a know fact that with aluminum head you can run at least a full point of compression, you could run 11.1 no problem. I’ve ran 12.1 with no problems. With aluminum heads. Its kind of rule of thumb more flow more
compression.

[Gach]

Here’s what you don’t know about your 16’s yeah they may look good, ran good. But what condition are valve guides and the valve seats. Are you going to end up with sunken valves with new valve job. The other thing is valve spring and install height. What I would do is get those heads to a machine shop and go through them. Find out what they need and the cost to port them. Then consider the compression issue. If it was something were you were going to run say 068 cam then there wouldn’t be no worries. But you’ll never reach your hp goal with 068.
Increasing the head flow definitely going to need more cam then that.