my friend wants to know if it would sound the best if he put glasspacks on his 81 Z-28?

IMHO NO!

get a good performance muff, glass pack's rob you of power when compaired to set of flow master's or dynomax muff's. the hooker aero chamber are nice too.

purple hornie's, cheerie bomb's and so on are old out dated tech and hurt you more then help you. i all so think they sound laim! compared to a nice performance muff that is.

Just my opinion here...I think glasspacks sound good on stock engines or very mildly modified ones...you start building a hot motor though and they are just way too loud. Smaller engines like 305's with a mild cam in them sound real nice with glasspacks without being overly loud. Good glass packs dont hurt power as much as many people think...car craft did a shootout of under $50 mufflers a few years ago and the thrush glasspacks were better than several of the supposedly hi-po turbo mufflers. Now, using an el cheapo muffler shop made in taiwan glasspack is a different story...most of those only have 1 3/4" or 2" cores...the shop just expands the nipples to make it fit whatever pipe size is needed.

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375hp 78 Chevy truck
77 Chevy Nova
95 Chevy Lumina 3.4L
and building a 78 Nova

Thats what cowboys here put on there cow trucks.