The dampner that came on my crate engine is the 6.75" size. Is the Standard 350 L98 dampner an 8" unit? Currently I have a 305 TPI but I'm building up a 350 for it. I just want to be similar to an L98 setup for part reasons. My 305 TPI dampner is also 6.75"

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1985 Z-28 305 TPI
165 ECM,STB,SFC,GW "wonderbar"

 

The L98 damper/harmonic balancer/etc etc... is the same size as the 305 one, so its 6.75" and not 8".

 

Yeah, its the 6 3/4", the 8" is only used on some big blocks.

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1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission
Borg Warner 7.75" 9 Bolt Rear End with 2.77:1 Gears.

Current Mods: LT4 HOT Cam, Comp Cams 1.52:1 Roller Rocker Arms, Edelbrock TES 1 5/8" Headers, Catco High-Flow Catalytic Converter, Hooker 3" Aerochamber Cat-Back System, Transgo Shift Kit, Performance Resource Chip, Accel Ignition, K&N Filters, JET TPI Air Foil, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET (w/o LT4 cam): 14.32 @ 97.7mph
(corrected for elevation)

Soon to Come: 7.625" 10 Bolt with 3.42s and Accel TPI Intake Base

 

Guys, not to rock the boat, but my 1988 GTA 5.7 (350) has the 8" balancer. Just went and checked it. When the engine was rebuilt a couple of years ago, I compared it to a known 305 balancer and it was larger (the 350).

I had a 305 TPI '88 GTA (the one Frankie Rider has now) and I think it had the smaller balancer. Almost positive. It was a hollow on the backside version.

I'm working on an '82 Z-28 (changing oil, etc.), with the 305 and it has the small, hollow on the backside, balancer.

I had an '89 TPI 305 RS with the 305 and it had the small hollow balancer.

As did the '87 Firebird 305 I owned five years ago.

I parted an '86 T/A with a 305 and it had the small, hollow balancer.

I've looked at other guys 350 TPIs and they had the 8" balancers.

I'm not saying that all the 350 TPIs have the 8" balancer, just the ones I've seen.
jms

 

I have the balancer that came off an 88 L98 that was in an Iroc (helped pull it myself) and its 6 3/4. Its exactly the same as the replacement 305 balancer I got for my 86 about 6 months ago, and matches the one that came off my 86 as well. The timing pointer lines up with the 6 3/4 as well. I have a 91 305 in my car now, and the balancer on that is the same as the rest, none of them are the smaller hollow style.

Ive actually never seen an 8" on anything later than mid 70's and a few trucks. I suppose its possible like anything else with GM, but I dont think its the norm.

 

An 88 with an 8" balancer?

I do no think that would clear the 1 piece accessory mount bracket.

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Hybrid Black 5.7L 5 Speed
'95 Competition Yellow Corvette Coupe ZF6

 

That is interesting about the timing pointer location.

My 350 timing pointer and balancer are such that they time at about the 2 o'clock position.

Is your timing location at 2 o'clock or 12 o'clock?

Here is a quoted section from "Chevrolet Small-Block V-8 Interchange Manual" by David Lewis (pages 33, 34 and 35).

"Balancer dimensions vary according to engine size. For the 262 ci and 307 engines, a 4-3/8 in. hub supports a balancer measuring 6 1/8 in. in diameter by 3/4 in. width. The base and intermediate 327 ci and base-only 350 ci engines use the same 4 3/8 in. hub but the outer ring is larger and wider--6 3/4 in. in diameter and 1 3/16 in. in width. The 267 ci and 305 ci engines also have the small 4 3/8 in. hub and the 6 3/4 in. ring diameter, but the ring width is increased to 1 11/16 in.

The remaining balancers all use the large 6 1/4 in. hub. The intermediate-performance 350 ci balancer measures 8 in. in diameter with a width of 1 1/2 in. The 400 ci small-block has an 8 in. diameter, 1 1/2 in. wide balancer that has been unbalanced by removing weight from one side. This 400 engine balancer should be used only with the 400 crankshaft.

The special high-performance 302 ci, 327 ci and 350 ci engines have the largest balancer because these engines are intended for high-rpm use. High performance engines come with forged-steel crankshafts that have a denser structure. This heavy-duty structure makes these engines more resistant to component failure during repeated wide-open throttle acceleration. However, the same feature that makes the engine so tough also makes it more susceptible to frequency vibrations, which could cause other failures, so more vibration damping is necessary. The high-performance balancer is heavy. It measures 8 in. in diameter by 1 3/4 in. in width."

There is also included a chart with the various sizes and part numbers---

"6 1/8 x 3/4 in., 262, 307, part # 6272223, base performance, 4 3/8 in. hub size;

6 3/4 x 1 3/16 in., 305, 327, 350, part # 6272221, base performance, 4 3/8 in. hub size;

6 3/4 x 1 11/16 in., 267, 305, part # 458653, base performance, 4 3/8 in. hub;

8 x 1 1/2 in., 350, part # 6272222, intermediate performance, 6 1/4 in. hub size;

8 x 1 1/2 in., 400 only, part # 6272225, unbalanced intermediate performance, 6 1/2 in. hub size;

8 x 1 3/4 in., 302, 327, 350, part # 3947708, special high performance, 6 1/2 in. hub;

8 x 1 3/4 in., 302, 327, 350, part # 364709, nodular iron ring, off-road racing."

There are several photos in these pages which also show the differences.

Also, please forgive any typos.

jms

 

well I need a new dampner. I guess I'll go to the dealer and ask for a dampner for an 89 350 TPI IROC and see what size it is. If it's 6.75" I'll save my money because I bought a new GM dampner for my 305 a year ago. If it's 8" I'll get it and let you guys know.

The caprice replacement 350 I'm using as my base engine, less heads and cam, came with a 6.75" but the timing marks are at 12:00, not 2:00, which make it kinda hard to time a TPI car

James

 

I went to the dealer and for an 89 350 TPI (IROC) he brought out a 6.75" dampner.

Now that the 6.75" is standard, will my 6.75" dampner of my 1985 (1-piece RMS)305 be OK on my 93 (2-piece RMS)Caprice replament engine?


James

 

Over the past couple of days I've tried to verify my observations on balancers.

Double checked the 1982 Z-28 I'm working on right now (original owner car). 305 with replacement Goodwrench engine. I swapped this in two years ago. Had to use the original balancer. It has the hollow balancer.

Checked the 1987 Firebird 305 I owned five years ago. The girl I sold it to works the same place I do. Hollow balancer.

Got a hold (by phone) of the guy I sold the 1986 T/A 305 (carbed) engine to. It went into a work van! He loves it but starting to show its age. He had to put a timing chain on it not too long ago. Hollow balancer.

I couldn't find the guy I sold the 1989 RS 305 car to.

Got to thinking. These guys on this site are sharp and they can't all be wrong.

Went back to my GTA to recheck it. Anyone that has worked on one knows it is tight down there.

Couldn't easily-quickly get to the balancer (from up top) so I held an 8" piece of paper across the pulley. Hmm. Looked about the same as the balancer but it was way back there. Better check some more.

Jacked the car up, after finding a cloth tape measure like seamstresses use. I measured the distance between the accessory brackets and found an 9" balancer (if there was such a thing) would probably fit. Then I got to thinking that 383s use 400 cranks and they use 8" balancers with no clearance problems.

I then took the tape and snaked it around the balancer (which is solid).

Right at 21".

Divided by pi equals right at 6.75 inches.

ARRRGHHH!

Guys, I'm sorry. I was wrong on the size of a L98 balancer. I guess GM doesn't consider the L98 a performance engine! At least it didn't get the hollow balancer.

I've been messing with cars since the very early 1970s and have been wrong before and I guarantee I will probably be wrong again.

But it is kind of tough to be wrong in front of thousands of other car nuts.

At least I hope I showed that not all small-block balancers are the same.

Forgive me?
jms

 

Hey it happens to all of us... admitting it is something entirely different.

I would not be the least bit surprised if there were some 8" balancers floating out there... I wanna go out and check my dads van, see what it has. Its probably 6.75.... I hope I'm wrong

btw, thanks for checking... thats what I love about this board, seems alot of the time people go and check out stuff and bring back some good info.

[This message has been edited by madmax (edited June 28, 2001).]

 

My dads 85 G20 van has an 8" dampner.

James

 

I checked it... 25 1/4 (or close) circumference. Its an 8". 94 G30 van.