[blubomber]

I don't think they were all that common since so few guys, including long time Pontiac guys I know, had even heard of it for the most part. I never see it on other GM models at car shows or junk yards even though it is a GM, not Pontiac specific, part number. The ones that were installed likely went by the wayside as mentioned. The second or third generation owners by the mid 70's and beyond were not interested in the "cool little features" we are all so intrigued with now.

Very interesting about the compression ratio on the motor being a full point lower than advertised.

[north]

My convertible Instant air was missing the engine bracket and the spare tire hold down but the actual pump was in the trunk along with the unique vacuum fitting on the intake. I bought an NOS kit a few years back but waited for the engine rebuild to install it.

My 4 door has the complete original kit including the spare tie down bracket and the cardboard tube that holds the pump. Surprisingly it works perfect.

The weakest link seems to be the white plastic adaptor on the engine bracket, when you open it the bale is very stiff, feels like it wouldn't take much to crack it.

[north]

As for the compression I noticed that cars with the 48 heads are actually about 10 to 10.2 to one due to a smaller combustion chamber than the 62 or 16 heads. I'm curious about the 428 small valve head, I'll measure them next week, the chamber looks identical to the 62's but the smaller valve might slightly increase the cc's.

The factory advertised hi compression engines as 10.5 and 10.75 but the distinction made no sense since mechanically identical engines from compression point of view were advertised with different compression ratios. I think the distinction between the two was just a code word for high performance with Firebird and GTO 400's and 428HO's being rated at 10.75 to distinguish them marketing wise from the "regular" high compression engines.

[blubomber]

I'd be tempted to not install it except for static display. the plastics back then weren't as good as today AND its 47 years old. If you had access to one of those 3 D printers you could fabricate a spare.

As you know I had an Instant Air kit for my Bonneville. It was complete including the cardboard package tube and the spare tire hold down bracket.

[north]

Fired up my Bonneville Wednesday and was greeted with a loud banging noise! Pulled the belts to eliminate possible water pump or alternator or fan noises but it was still there. Placing my hand on the front of the oilpan while it was running I "felt" the noise.

[north]

Oil pressure was fine and I guessed it was the crank hitting the pan. Three hours later I pulled the pan (had to release the engine from the trans to get it high enough) and sure enough to impact marks from the crank, pan was dented (before rebuild) about where the crossmember was (forward of where it is on GTO's). In fairness to the engine builder the dent was very uniform looking so it appeared ok, I suspect at some point in it's past someone probably lifted the engine with a jack in the car. The reason it started hitting now is probably the 455 crank which has an almost 1/4" longer throw.

[north]

I had a few nice original pans kicking around so we painted and gasketed one and yesterday spent 3 hours getting it installed carefully. Engine ran great for the cam break-in so first drive tonight if the thunder storms hold off.

I was surprised what a PITA this turned into. I thought with the frame cross member much farther forward removing the pan would have been easier but no dice. Jacking until the TH400 pinned the floor pan didn't give enough room to even wiggle it off (never mind installing a pan with a fresh gasket) so we had to remove the fan, disconnect the trans, drop the steering linkage, loosen the left exhaust manifold (to get the starter out-long branch) and even remove the oil filter bracket and adapter-spacer to clear the bottom of the AC box.

Speaking of the long branch oil filter adapter, the Allan bolt provided with it was about 1/2" too long so it bottomed out in the block before it could do its job.

[David Brown]

Did you use a mini starter or the OEM? I had mine installed with the OEM and long branch, but decided it would be a major PITA to change the starter if it went bad and switched to a mini. Problem is, the mini is almost as much of a PITA to get in as the OEM. How about heat to the starter causing problems?

[north]

Stock starter, unlike the GTO style HO manifold these ones are clear of the solenoid so shouldn't have hot start problems per say. Long term I'm sure it cooks the starter armature itself but at a few hundred miles a year I'll sleep well.

By the way I was a bit disappointed with Waldron exhaust; in the end it fits nice and sounds great, nice and low like a Gardner system, stock but you know it has the big engine kind of sound, perfect. But the flares were too small and the wrong angle for the factory flanges, made it work but a pita one head pipe was too long and also needed angle adjustment, resonators were nice with beautifully cut tips but missing the stock length adjustability feature seen on NOS ones I've had. Biggest issue was that the over axle pipes were sloppy, the other stuff I can see but when one over axle pipe has the axle loop visibly wider but lower than the other when obviously they should be mirrors it speaks to lack of even visual quality control. She took a look of cutting, welding and tweaking.

I'd be happy to pay even 50% more and have a bolt in system. If Gardner can do it why can't they. I've installed 7 or 8 Gardner systems and all of them were flawless, well worth the money.

[north]

Put about 100 miles on her over the weekend and running quite well, actually cooler temperature than the old engine but I notice a bit of surging on the primaries on the highway at higher speeds. I guess the 34 extra cubes and a bit lower compression both demand extra fuel. I'm running the stock carb (7029268) so if my memory is right its probably running 71 or 72 jets, I'll bump it 2 sizes to 73-74 and see how it feels.

[blubomber]

Yes, that's the stock carb 7029268. I think its the same as used on GTO's (non-Judges). That makes sense about increasing the jet size one or two points due to the changes from the original factory spec's.
428 HO distributor is coded 1119. Different weights and springs than base 428 IIRC.

Did you paint or powder coat the LB's or did you leave them bare metal?

[north]

I don't have it in front of me but the distributor is also the correct one for an HO automatic, I believe it's the same as an automatic base GTO engine. All I did with the manifolds (exhaust) is brush them quickly with a plastic bristled floor brush and then rub them down with engine oil, they smoke for ten minutes but you are left with a nice dark natural color that will never get rust colored. The trick is to oil them long before you fire them up so the oil really penetrates. If you start with very rust ones you can wire brush them or if necessary blast them, but oil them before you blast them then oil again after, the look is great, free and will never peel or look painted.