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Interesting page on 3800 development


wws944
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Here is a fun page that talks about the development of the 3800 from '88 to '95 in some detail:

Rebuilding the 3.8L Buick Engine: Engine Builder

One thing I've wondered is if it was possible to retrofit the roller rockers from a L26 back into a LN3? (Not going to do so in my car, but just curious.) The heads look almost identical - except for that big hole on the left for crank case ventilation.

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He mentions two cams for 88-90, but doesn't specify which goes where. However his part numbers do match up with the Reatta illustrations pdf. (#12339315 for '88, and #12338325 for '89-90.) I've read here that the '88 cam has slightly more lift than the later one.

Seems like retrofitting roller rockers, if it were feasible, would be a fun upgrade for someone who had the heads off anyway.

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I looked into retrofit of those roller trunnion rockers several years ago, but there are a couple of issues. The stud size is different (smaller) and the offset of the pivot point appears to be different also. The hole in the cross shaft can be made larger, after dissassembly, but I couldn't solve the rocker geometry issue. Can also make the rocker adjustable but the rest didn't work out.

The '88 cam has more lift and duration, but nothing to write home about. Still pretty mild but it does feel somewhat stronger (very subjective, I know). Air flow indications through the MAF do seem to indicate greater airflow. Easy to check for anyone that has both models and compare.

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A roller cam can have less lift but more "area under the curve" due to the shape of the camshaft lobes . . . rounded rather than "peaked". More crank duration at and near peak lift with a roller cam, compared to peak lift on a flat tappet being about 1 degree of crank rotation.

I suspect there are cam kits to put roller cams in the place of flat tappets in the Buick V-6, but these would be aftermarket. Aftermarket will use different methods to keep the roller lifters aligned with the lobes and also a means to keep the cam correctly positioned in the block. Flat tappet cams have the lobes ground with a slight tilt to them. This uses valve spring pressure to keep the camshaft in the block and also to help the valve lifters turn as they go up and down.

Many roller cams use a "button" on the front end of the cam to accomplish this same location activity. Siimilarly, there were "alignment bars" which connected the pairs of valve liters, to keep them from turning in their bores. OEM normally used different methods.

The roller rockers will usually have a more consistent "ratio" than stamped steel rockers. Using rocker arms with a roller tip should drastically reduce the side loading on the valves as they are pushed down in their guides by the rocker arm. Longer guide life and related valve seal life should be benefits.

There are many Buick 3800 V-6 performance websites, with links to aftermarket parts. One used to be www.3800performance.com . Many might be listed on the RegalGS.org and Pontiac Grand Prix-oriented websites.

Regards,

NTX5467

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I like roller lifters, it is roller rockers I was questioning the value. BTW does that mean a roller bearing on the pivot or where the rocker contacts the valve stem, or where the pushrod contacts the rocker, or allathe above ?

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The 3800s in our Reattas already have roller lifters. GM switched all 3800s for the '87 model year. (Look at the illustrations pdf. For the '86 vs '87 Riv 3800, about the only difference in the top end of the engine is the lifters.)

Here are some aftermarket roller rockers with higher ratios. Apparently they make them with both bolt diameters.

HOLDEN HIGH RATIO ROLLER ROCKERS TO SUIT BUICK 3800 V6s - Mace Engineering Group

The roller refers to the center of the rocker itself - not to the pushrod or valve ends.

By supporting both bolt diameters, one would hope they would also make the appropriate geometry corrections that 2seater mentioned. If someone were really interested, it would be worth an email.

medium.jpg

Edited by wws944 (see edit history)
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In many cases, "roller rocker arms" also have rollers on their tips, too. But you can also purchase non-roller rocker arms with roller tips . . . for many engines. "Rollers" with the bearings at the pivot point are good for decreased friction, but it's the ones with roller tips which affect the valve stem side loading of the valve guides.

Looks like the ones pictures are rollerized at the pivot point.

Regards,

NTX5467

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Yep, the roller trunnion rockers I looked at look like those, sans the polished finish. I am not quite sure what the extra bar is? A stud girdle over the top or a new support to bolt them down tight like the originals? In any case, the Aussies are very creative and have many models of Holden spec. variants of domestic GM models, generally higher performance.

I looked over a new police car at a dealership. Labeled as a Caprice on the trunk with wide steel wheels and dog dish hubcaps. An LS engine under the hood (6.2 liter?). Mean looking car. I looked over the build sheet and it was over 60% Australian content with several percent more from Mexico and Canada leaving about 13% U.S. content. It looked like it meant business, (was going to a local small town police department), but it struck me as odd that it was essentially a foreign car. Maybe not so odd with worldwide sourcing of parts. Holden Commodore SS, maybe, for almost $50k.

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