OK, I have the 88 305 TBI out of the car and I am in the process of changing out the flexplates. The one on the 305 looks like it was externally balanced and has a huge weight I believe on on side. The 86 350 flexplate was larger, but has no weights on it. If I put the old 305 externally balanced flexplate on the 350, will this cause me issues?
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OK, I just got finished comparing the 86 350 flexplate to the 88 305 flexplate and the centering hole in the plates are different sizes, so I know this is not going to work. I need a new flexplate. What do I buy for this application? Do they make a smaller flexplate like the one off of the 88 305, but has the larger center hole opening like the 86 350? Thanks for your answers on this as I can just see me going to Auto Zone and trying to get the correct part being a real cluster.

 

If we're really talking about '86 and '88 engines, they use the same flexplate.

But, if they in fact aren't the same, the wrong one won't bolt on, anyway, so the "correct" one is the only option.

And don't get started on the "externally balanced" thing - it wasn't. That weight takes the place of what used to be part of the crankshaft, outside of the rear main seal, before the factory went to one piece rear main seal. The '88 is still technically "internally balanced", because the damper on the front of the crank is neutrally balanced.

 

They aren't the same, hence my question. The center hole is different, and the diameter of the flexplates are also different. The old flexplate off of the 86 is bigger diameter center hole, along with outside diameter of the flexplate itself. So, why they are not the same? Beats me, I just know that they are not.

 

Sounds like you don't REALLY have an 85 350.

The 86 350 would have the same flex plate as the 88 305; with the small center hole and bolt circle.

You just need a flex plate for 85-back 262 / 265 / 283 / 302 / 305 / 307 / 327 / 348 / 350 / 366 / 396 / 402 / 409 / 427. Basically, the one for any 55 to 85 Chevy V8 except the 400 or 454.

Diameter goes with the starter you have. For that car, it should be the 12.8" one. Buy the flex plate for 83-85 Camaro/Firebird 305, and it'll be the right one.

Be aware though, that since you don't know what 350 you have, it's possible that it's a pre-80 one; and those don't have the later-model bolt pattern for the starter that fits the small flex plate. Your block will be missing the inboard hole, nearer the crank. So get a machine shop to drill that hole into your block BEFORE you drop it into the car, while it's easy.

 

OK, I was wrong about this being a 1986 block. That is what I thought it was sold to me as. This is what I have.

1969-79 3970010 350 185 370 2 or 4 car, truck, Vette.

I took this off of Nasty Z-28's site. So, can I use an earlier model starter, or will it not fit in a 1988 Trans Am?

 

One other question on this swap. I have picked up an Edlebrock performer intake so that I do not have to mess around with the center bolt holes on the TBI intake. What I plan on doing is using the Holley adapter plate so I can mount the TBI on the perfprmer intake. The question I have, is can I use the EGR that mounts towards the rear of the TBI intake onto the center mount of the performer? Reason being is the car has to be emissions legal. Here is a link to the adapter I am looking at.

http://cgi.ebay.com/ebaymotors/tbi-t...em320153465607

 

OK your 350 is a 2 peice rear main seal and the 305 is a 1peice rear main seal. The difference in your outer dimensions is the smaller is a 153 tooth and the larger is a 168 tooth. Yes you will need to get the starter for the larger flexplate/flywheel. try and get the narrowist diameter starter you can, there is room for the fat ones but hurt worse when dropped on head while installing (dont ask how I know) check on the edelbrock site for the egr issue.

 

What heads does the engine have? 350 heads of the era of the block were pretty poor.

The adapter you linked should work, although the bore sizes weren't mentioned.

 

Thanks guys, I will get the narrowest starter I can, as I to have seen first hand the damage a heavy Pontiac starter can dish out to one's head. LOL. The heads I will get that information later today when I get back home. The guy I bought the engine from had me change out the heads from the engine I bought to another set he game with the engine. He said they were fresh rebuilt, and were decent heads. The Adaptor I believe in the description says it will adapt a 50 mm bore TBI to a square bore intake.

 

The heads are 882's. I have only read a little about Chevy heads, and I heard they aren't great, but I imagine there are worse heads out there. 76cc chamber might be a little big on a 350, but then again my old 78 Trans Am had 111 cc heads on a 400. Then again my Pontiac had flat top pistons, and the 350 I have now have dished pistons. Looks like a trade off on one end or the other and a low comp motor this will be.

 

the 882's are the worst of the better flowing iron heads they have 194 intakes and 150 exhaust, they do prefer having flattops for a 9:1 ratio or domes to get higher. I believe the dished will net you 8-8.5 compression.

 

That will be fine for now. I just want to get this motor in there and get the car back on the road. It has been on jackstands now for a year. Then when I can get my hands on some money I may look at some Vortec heads, and a decent cam to go with it. I will just be happy to have a bit more power than the boat anchor 305 had.