Switching harmonic balancers?

[Telecasterjoey]

Hey guys, I'm swapping the motor from my 1990 van into my 86 truck and the harmonic balancers are different sizes. Can I simply put the harmonic balancer from my trucks 305 onto the van's 350 so that my belts all line up again? The balancer on the 350 is thinner than the trucks 305.

Thanks!

[Telecasterjoey]

anyone? or are the harmonic balancers engine specific?

[80SPORT]

If your 90 engine has 1 pc rear seal and the 86 has 2pc rear seal the balancer is different and should not be swapped.....I assume your 90 is efi and the 86 is carb so you are sorting some other issues out as well.

You should be able to retain all the accessories inc the serp belt drive on the 90 engine and keep it complete

[mongoose]

timing marks are different? or can be..

other than that it will work..

[Telecasterjoey]

OK... I'd really like to keep my original 2 belt set up as I have all brand new accessories for the 86 and I'd like it to look stock.... New question then: Am I able to put spacers behind my pulley to achieve the same spacing? I'm pretty sure my 86 is a 2 piece main seal but I'm not 100% how can I tell?

[wyattglock]

1986 model year is when GM started getting away from the 2 piece seal. I know that is true with the cars that had small blocks, not sure about trucks.

[Hotrodrobert]

Leave the balancers alone. The pulleys will just unbolt from one engine and bolt onto the other. There is NO difference in the pulley alignment. All the drives and accessories from any SBC genI since 1968 will fit any SBC GenI.

[lanconcj]

my 86 truck had a one pice main

[Hotrodrobert]

One piece or two piece mains, any size displacement the bolt holes and balancer face are exactly the same but the ballancers can have differences that affect the motor but the pulleys and brackets, etc. are THE SAME.

[rfmaster]

Originally Posted by Hotrodrobert

One piece or two piece mains, any size displacement the bolt holes and balancer face are exactly the same but the ballancers can have differences that affect the motor but the pulleys and brackets, etc. are THE SAME.

305 and 350 engines are neutral, internally balanced and can use identical balancers - i.e 6-3/4'' or 8" diameter depending on the year/application. The 400 engine is not internally balanced and requires a 400CID specific external balanced flex plate and balancer. This should cover stock configurations. For stroker engines (383, 377, etc) consult with your machine shop.

Main crank pulley will bolt to to either 305/350/400 CID balancer - there is not need to swap balancer. Balancer is press fit and requires correct installation tool to press it onto the crank snout. Harmonic balancer retention bolt should NOT be used for installation - threads are easily stripped and crank can be damaged. Pounding balancer onto crank with a hammer will destroy main bearing thrust surface - the old David Wizard book (How to rebuild small block Chevy) should be revised!!!

//RF

[Telecasterjoey]

Hey guys thanks for all the replies! So after all this the pulley lines up just fine. The harmonic balancers are different sizes but the thinner one is further from the timing cover to make up the difference! So I'm back in business.

Thanks a lot!

[BigBlocksRule]

rfmaster, don't forget that the 1-piece rear main blocks are neutral on the dampener but external balance on the flexplate/flywheel. GM had to do this since part of the weird shaped crank flange is actually there for balance.
There are a few things that Vizard was wrong about, same with Smokey Yunick, but you hear folks quoting the incorrect stuff every day...but keep in mind that waaaay back, GM didn't drill the snout of crankshafts for a bolt, the dampener was held on with friction fit only, there's no way to pull one on with an installation tool. That said, anyone that uses a hammer to install a balancer gets shown the door of my shop PDQ.

[rfmaster]

Originally Posted by BigBlocksRule

rfmaster, don't forget that the 1-piece rear main blocks are neutral on the dampener but external balance on the flexplate/flywheel. GM had to do this since part of the weird shaped crank flange is actually there for balance.
There are a few things that Vizard was wrong about, same with Smokey Yunick, but you hear folks quoting the incorrect stuff every day...but keep in mind that waaaay back, GM didn't drill the snout of crankshafts for a bolt, the dampener was held on with friction fit only, there's no way to pull one on with an installation tool. That said, anyone that uses a hammer to install a balancer gets shown the door of my shop PDQ.

Absolutely correct on 1-RMS! Flexplate/flywheel has an equivalent counter weight that used to reside on the crank due to a 3" diameter 1-RMS.
When I re-build early 60's and older SBC which did not had a retention bolt I have crank machined for one - it is an easy operation and cheap insurance. Hammers (for the most part) are not a precession tool for engine assembly.

//RF

[BigBlocksRule]

Yeah, the only early engine I built with no crank bolt hole got the crank hauled to the shop and left with the bolt hole. I agree, there's no use for a hammer when you're dealing with a crankshaft and bearings...