[scld1354]

Looking through the 67 fsm, I noticed the 376-horse 428 came with a few different parts than the 360-horse 428.

All 360-horse, and most 376-horse engines came with "H.D. TWO" valve springs (whereas all 400-inch engines came with "STD TWO" valve springs"). Two of the 376 horse engines (WJ and XK codes) came with "H.D. SPECIAL" valve springs.

Next, all four of the 376 horse engines (WJ, Y3, XK, and YK codes) all came with "SPECIAL EXHAUST MANIFOLDS".

Im just curios, but does anyone know the difference between the different valve springs, and what are these "special" exhaust manifolds???

[goatless]

I can only guess that the HD valve springs were a little stiffer than the standard springs.

The "special" exhaust manifolds were the long branch cast header type free flowing manifolds. Lesser motors got the regular log manifolds.

[north]

Originally Posted by goatless

I can only guess that the HD valve springs were a little stiffer than the standard springs.

The "special" exhaust manifolds were the long branch cast header type free flowing manifolds. Lesser motors got the regular log manifolds.

Those are things of beauty

[scld1354]

Are the short blocks the same between the two 428 motors?

[b-man]

Originally Posted by scld1354

Are the short blocks the same between the two 428 motors?

Same except for the camshaft, 067 vs 068.

[blubomber]

I think, but don't know for certain, that all 428's in 67 and 68 had 4 bolt main caps.

In 69 only the H.O version had them.

The 068 cam was used on manual transmission cars IIRC as well. Automatics got the 067 grind.

In 67 and 68 both versions used the same heads as well I have been told. The long branch exhaust manifolds enable the higher power rating.

The blocks are all the same.

[PONTIAC LARRY]

Yep the 376 HP HO is one up on cam, a touch stiffer springs, and of course the good exhaust manifolds originally designed for the 421 HO TriPower . ALL 67-68 428's are 4 bolt mains period and short blocks are the same except cam, 360 hp 67 auto is 066 cam, 67 360 hp stick is 067 cam, 376 hp auto is 067 cam, 376 hp stick is 068 cam. The hp ratings are always based on the stick motors. HP increased to 390 hp in 68 due to better power made with open chamber #16 Heads versus the closed chamber 670 heads in 67

[65WJ]

there is one exception to all 428's having 4 bolt mains. that is the YH 428 for the Bonneville only. It is drilled and tapped for 4 bolt but only has 2 bolt.

patrick

[ANDYA]

Originally Posted by 65WJ

there is one exception to all 428's having 4 bolt mains. that is the YH 428 for the Bonneville only. It is drilled and tapped for 4 bolt but only has 2 bolt.

patrick

It's funny, most of the 428's that I run into for sale seem to be the 69 YH 2 bolt variety.

[north]

That's because of production rates; because the YH 69 engine was standard in bonnevilles they made 100,000. The only relatively high volume 4 bolt 428 was the 69 XF which had about 20,000 copies because it was standard in the 69 SJ GP. All other 67-69 428's were very low production by comparison.

[blubomber]

My friend North might have entered a typo. I think he meant to say that they made about 2,000, not 20,000 unless he is referring to the 370hp version that was std in the SJ which would have represented less than 1 in 5 of all GP's made that year.

The '69 YH coded 428 had the .066 cam, #46 heads, std exhaust manifolds, 262 Q'jet. This was the std engine on Bonneville's only in '69. You could special order the 428 HO 390hp or either of the 400's; 290hp or 265 hp.

They only made 726 automatic 428 HO's for B body cars in '69, code YK. There were a few 428 HO's out there in Catalina's and Ventura's or Executives although I suspect most were in Bonneville's.

GP 428's came in two versions: 370 hp and the 390 hp which was just like the B body version. Std engine in GP's and Model J's was the 400.

All the 428 short blocks are identical.

[scld1354]

Originally Posted by blubomber

All the 428 short blocks are identical.

Glad you brought that up. I was wondering about that, and instead of starting another thread, perhaps y'all can jump in here. I know for the most part, Pontiac dictated performance by carb selection, dizzy selection, cam selection, and most importantly, head selection.

So what differences are there between the blocks, cranks, rods, and pistons of 400s of various years? It seems that some 400s received 4 bolt mains (RA and non-RA). What other differences are there in the 400 shortblock? Different pistons? Different rods? Different cranks? For example, I keep reading to avoid the 577 block for any type of performance build because of thinner cylinder walls(?).

[WDCreech]

Originally Posted by scld1354

I keep reading to avoid the 577 block for any type of performance build because of thinner cylinder walls(?).

The "557" block is thinner in the main saddles. I don't know about the cylinder walls as I have never had one soniced.

[scld1354]

Originally Posted by WDCreech

The "557" block is thinner in the main saddles. I don't know about the cylinder walls as I have never had one soniced.

I knew it was thinner something, and I took a stab with "cylinder walls".....

[blubomber]

Here are the 1969 400 & 428 GP and Pontiac Production numbers by code

GP

YF 400 Auto reg fuel 1,000 265 hp
WX 400 man 569 340 hp
XH 400 auto 89,975 340 hp


WF 428 manual 333
XF 428 auto 19,611 370 hp
WL 428 HO manual 142
XG 428 HO auto 989 390 hp


Pontiac

YB 400 auto 2bbl 47,283
WD 400 man. 2 bbl 799

YD 400 auto 2bbl 228,746
WE 400 HD clutch man 2bbl 197

XZ 400 auto prem. auto 3,981

WG 428 manual 171
YH 428 auto 101,020

WJ 428 HO manual 25
YK 428 HO auto 726

XJ 428 Police 176
XK 428 Police 67

[PONTIAC LARRY]

Originally Posted by 65WJ

there is one exception to all 428's having 4 bolt mains. that is the YH 428 for the Bonneville only. It is drilled and tapped for 4 bolt but only has 2 bolt.

patrick

Yes the 69 only 2 bolt Bonneville 360 hp 428 is the only year of a two bolt but is far and away the most common to find due to it being the new standard for the Bonneville base automatic car that year thus being much higher than before as 428 were options upgrades previously. This thread was about a 67 376 hp 428 and as I said ALL 67-68 428 are 4 bolt. 69 4 bolt blocks would be more likely Grand Prix applications.

[scld1354]

Good info on the 428 so far. I had no idea the 428 was the "standard" bonneville motor in '69. Probably a stupid question, but what are the differenecs in the 2 and 4 bolt caps (besides the obvious...)? Does the 4 bolt have more "meat"?

I referenced the 67 because that is the only fsm I have, and I can actually see the differences in components between the 8 428s they had.

If anyone wants to chime in about the 400, please answer here: http://forums.maxperformanceinc.com/...d.php?t=750603

[blubomber]

The blocks are all the same; 67, 68 and 69. They are ALL drilled for 4 bolt main caps.

NOTE: the caps hold the crank shaft in place. 4 bolt caps use 4 bolts per cap, 2 for each side, to hold the cap; 2 bolt caps only use one on each side.

The GP 370 hp and 390 hp and the full size 390 hp all used 4 bolt caps. The 360 hp in '69 used 2 bolt caps. All '67 and '68 428's were 4 bolt caps. It doesn't affect performance at all. Just lower motor strength for heavy duty racing. Lots of guys have opinions on that. I really don't other than for regular driving 2 bolt caps are just fine.

[north]

Originally Posted by blubomber

My friend North might have entered a typo. I think he meant to say that they made about 2,000, not 20,000 unless he is referring to the 370hp version that was std in the SJ which would have represented less than 1 in 5 of all GP's made that year.

The '69 YH coded 428 had the .066 cam, #46 heads, std exhaust manifolds, 262 Q'jet. This was the std engine on Bonneville's only in '69. You could special order the 428 HO 390hp or either of the 400's; 290hp or 265 hp.

They only made 726 automatic 428 HO's for B body cars in '69, code YK. There were a few 428 HO's out there in Catalina's and Ventura's or Executives although I suspect most were in Bonneville's.

GP 428's came in two versions: 370 hp and the 390 hp which was just like the B body version. Std engine in GP's and Model J's was the 400.

All the 428 short blocks are identical.

I was referring to the 370 horse 428 (XF) of which roughly 20,000 were built.

[north]

Here is a meaningless question but still interesting... The basic 360 horse 69 bonneville YH was the the two bolt small valve engine. but the 171 manual WG's which were I understand a four bolt engine likely the same as the 370 horse GP engine. Was it rated 360 or 370? And has someone ever seen one?