[A.J.]

Got my hands on a out of a car running Pontiac 428, #16 heads (small valves) 9792968 YH dated K098 (november 9th, 1968).
Previous owner said it might be 4 bolt mains but was not sure. Cant find any info of whether this is true or not and it's not really that important for my intents of use but it would still be nice to know. Any way to to know wihout lifting the pan?

[b-man]

The '69 model year YH 428s generally have been known to have ben produced with 2-bolt mains and small-valve #46 heads, rated at 360 HP they were the standard Bonneville powerplant. Depending on assembly line conditions some did slip through with 4-bolt mains.

No small-valve #16 heads were produced for that year, only 1970 model year #16 heads had the smaller 1.96"/1.66" valves. I would question whether the #16 heads on it are original to it.

Pontiac downgraded the 'normal' performance-oriented big-valve head/4-bolt main 428 to use cheaper small-valve heads with press-in rocker studs and 2-bolt mains so they could maintain a certain price point and offer it as a standard Bonneville engine that year.

Pulling the pan is the only way to be sure, but I'm betting it's a 2-bolt main engine. Either way, it's a fine start for a good street engine build up to about the 600 HP mark if you so desire.

[Cliff R]

To date all the 1969 428's with the #46 heads that I've seen have been 4 bolt main blocks but only 2 bolt caps installed. Nearly as I can remember all other years and HP were 4 bolt main with 4 bolt caps, or at least all the ones I've worked on and rebuilt over the years have been that configuration.......Cliff

[A.J.]

Wallaceracing shows this as a 375Hp 428 with 16/62 heads. This if its rated as a 68 but if 1969 it should have #46 heads (360 Hp)?
Small valve was merly a thought. Better check the date codes on those as well.

[b-man]

A November 1968 built 428 would have been slated for a 1969 model year Pontiac.

[A.J.]

Ok, the headcode and date stamp made me think it would still be seen as a 1968 engine.
Will be back with more info on the heads.

[Tom Vaught]

I have also heard over the years that the 67 & 68 428 engines were pretty consistent with drilled for 4 bolt mains and 4 bolt main caps on the block. I have only owned two 428 engines, so my knowledge on them is lacking. Both were 69 engines and both had 2 bolt main caps but drilled for 4 bolt mains.

Tom V.

[Cliff R]

Correct Tom. All 67 and 68 428's that I've seen have been 4 bolt main with 4 bolt caps.

In 1969, the lower performance 360hp 428 came with 2 bolt caps on a 4 bolt block.

The higher HP 428's that year will have 4 bolt caps on a 4 bolt block, I have one of them in my car at the moment, the 390hp version.

I'm certainly not saying that what I posted above is the cardinal rule, just what I've seen in my many years of working with these engines.........Cliff

[The Boss]

I have 4 bolt caps & bolts if you end up needing/wanting them.

[John Eiseman]

I have 2 YH blocks here. One is dated I108 and the other is L168. Both are drilled for 4 bolt caps and both have 2 bolt caps. Side note: The later block has 2 A's stamped to the right of the YH, not stamped as deep as the YH, but looks like the factory font.

[A.J.]

Well, the heads are#16 with screw in studs and date coded J109 (Oct, 10 1969) on drivers side and J159 (Oct, 15 1969) on passenger side so I guess one could assume that their not original to the engine, maybe not even a pair?

[Goatracer1]

I have 2 1969 YH 428's in the cellar and they are both drilled for 4 bolts but only have 2 bolt caps. I bought a NEW 428 YH in 1969 out of a wreaked new car and was surprised it only had 2 bolt caps.

[Kenth]

1968 #16 D-port heads are 2.11"-1.77" large valves, screw in studs, drilled and threaded outer exaust manifold holes.

1970 #16 D-port heads are 1.96"-1.66" small valves, pressed studs and no outer exaust holes drilled.

The dates on your heads indicates 1970 #16 heads.

[A.J.]

They definitly have screw in studs. Not unlikley that they have been tampered with though. It has a carb done by you kenth

[geeteeohguy]

Years ago I had a '69 428 with the #46 heads. It was a two bolt main motor, but was drilled and tapped for four bolt mains. So, pretty consistent with the information posted.

[Will]

Nearly every Pontiac engine I've torn down has been drilled for 4-bolt mains but almost none of them have had 4-bolt caps installed.*

The only block I've had in my grubby hands with 4-bolt caps was a '65 421.

I currently have one 455 block and 3 400 bare blocks in my garage. all are drilled for 4 bolts except one of the 400s. IIRC, it's a late '73 casting date for the '74 model year. That block is also one of the beefiest blocks I've seen as far as thickness in the main webs goes.

Up to acquiring that block I'd read about blocks drilled only for 2 bolts but never seen one.

* - exception being 350 blocks. I've torn down 2 or 3 over the years and honestly don't remember whether they were drilled for 2 or 4 bolts. I'd suspect 2-bolt only because, AFAIK, no 350 ever came with 4 bolt mains.

I have a '73 350 complete engine also but its going to be awhile before I tear into it.