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Old 08-13-2007, 04:08 PM
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early model vs. late model 350 blocks

what was the difference in the one piece and the two piece rear main seal motors? i just bought an 87 camaro and was told it had a one piece rear main seal. i was also told id be better off gettng an older motor. what are the specs between the two as far as rod length, stroke, etc. any info would be appreciated.

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Old 08-13-2007, 04:47 PM
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In 1986 chevy changed the 2 piece rear main seal to a 1 piece rear seal, The 2 piece was notoriously famous for oil leaks. When they made it into a 1 piece the rear flange was made completely round and a smaller bolt pattern was used, so the flywheel/flexplate from a older 2 piece block will not fit on a 1 piece and vice versa. The rod lenth remained unchanged, as did the bore and stroke lenths of the same cubic inch engines. Whoever recommended using a older 2 piece block hasn`t got a clue about small blocks. They also started using roller cams in passenger car engines in 1986, a roller cam is far superior to any flat tappet cam design. They also changed the heads in those years to a center bolt valve cover with higher paremeters, the valve covers on the older blocks were also famous leakers.
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Old 08-13-2007, 04:51 PM
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The one piece seal uses a crankshaft designed for the seal. You cannot use an older crank in a newer block. You can however use the newer crank in an older block with the GM one piece rear main seal modification kit. The one piece seal is a vast improvement in an area the small block Chevy has needed ever since it's inception. Rear main seal leaks are almost a thing of the past in the newer small blocks.

I don't know who told you they were less desirable than an older block, but IMO they do not know what they are talking about. The only way I would use an older block would be in a period correct restoration.

Vince
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Old 08-13-2007, 04:53 PM
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Basic same motor. Crank is different, flywheel, Pan, most heads are different, Blocks tend to be thin castings with very few four bolt main motors produced.

Internally, some are drilled and fitted for hydraulic roller lifters, whether they have them or not. Some just have the extra bosses. Some have no provision for mech fuel pump.

Still good for street and mild race motors, just different from the old school blocks..
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Old 08-14-2007, 05:17 AM
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Quote:
Originally Posted by 302 Z28
The one piece seal uses a crankshaft designed for the seal. You cannot use an older crank in a newer block. You can however use the newer crank in an older block with the GM one piece rear main seal modification kit. The one piece seal is a vast improvement in an area the small block Chevy has needed ever since it's inception. Rear main seal leaks are almost a thing of the past in the newer small blocks.

Vince
Vince
I don't know where you got this info from but I hate to tell you but you CAN use an older crank in a newer block and can not use a newer crank in a older block.

Think about it when those Bowtie blocks came out in 1986 we used a lot of older cranks in those blocks in the circle track engines we built back then.

We use quite a few of the newer blocks for the circle track engines we build and we use a different seal adaptor for using the older cranks in newere blocks.

Believe it or not here is a pic of a newer block with a older crank
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Old 08-14-2007, 05:46 AM
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I stand corrected, sorry for the confusion.

Thanks
Vince

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Old 08-14-2007, 04:26 PM
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thanks guys. ill stick with the block and crank that i have then instead of lookin for an older one. hopefully the camaro will run as good as my malibu did. the 79 malibu i had years ago had a 350 with the double hump heads. this one will have the 305h.o. heads reworked by dart. 2.02 intake valves, 1.6 exhaust valves. dual valve springs, arp rocker arm studs. 64cc combustion chambers, 171cc intake runner, 75cc exhaust runner. $580 for the heads. im hopin they work as good as my last set.
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Old 08-14-2007, 09:21 PM
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For that price you could get a set of RHS vortec heads, or with a little bit more a set of Iron Eagles. I would not invest in a set of reworked factory castings. But that`s just me.
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Old 08-14-2007, 09:28 PM
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Quote:
Originally Posted by BOBCRMAN@aol.com
Basic same motor. Crank is different, flywheel, Pan, most heads are different, Blocks tend to be thin castings with very few four bolt main motors produced.

Internally, some are drilled and fitted for hydraulic roller lifters, whether they have them or not. Some just have the extra bosses. Some have no provision for mech fuel pump.

Still good for street and mild race motors, just different from the old school blocks..
I also heard the newer blocks were thinner but I've always ran the older blocks so I really don't know. I have seen a few of the newer blocks with hydraulic roller cam and also a mechanical fuel pump-but very few. For the guy who wants to run a mechanical pump it can be tough finding one of those.
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Old 08-15-2007, 07:22 AM
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it has mechanical fuel pump. wether it has a roller cam or not i dont know. really i dont care. im just ready to get this damn thing goin. also the heads im getting were not just reworked with dart parts. dart assembles them and sells them. its the GM casting of the 305H.O. head but all worked by dart. oh and also the RHS heads that have close to the same specs as the ones im getting from dart are $581 each. im paying $580 for both heads from dart.

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Old 08-15-2007, 11:00 AM
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Quote:
Originally Posted by baddbob
I also heard the newer blocks were thinner but I've always ran the older blocks so I really don't know. I have seen a few of the newer blocks with hydraulic roller cam and also a mechanical fuel pump-but very few. For the guy who wants to run a mechanical pump it can be tough finding one of those.

Don't go by here say as we sonic test all the blocks tha come through our shop and to tell you the truth we find more of the older blocks with inconsistant cylinder wall thickness, We have about 45 of the older blocks in the shop that we only rate under 400 horse do to poor cylinder wall thickness.

The later blocks seem to be more consistant as far as cylinder wall thickness as we have machined quit a few of them for our shop and other shops accross the U.S.

If everybody went by here say everything would be junk.
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Old 08-15-2007, 11:12 AM
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alot of the early 1 piece seal blocks crack in the lifter valley.mainly from thin castings and stress. later blocks the castings changed to reinforce the valleys. so if you have an early block it is something to check.
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