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Old 06-28-2009, 03:10 PM
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305 to a 350 motor swap...

I could use some advice & opinions. I have an 85 chevy truck. I wanna swap the stock 305 for a 350 & beef up the 350 a lil bit. Nuthin too serious, jus some good horsepower & maybe churn a lil buttermilk while I'm sitting at the red light.
I have located 2 350 blocks. the stamp code on one of the blocks is 3970010. The guy wants $500 for the 350 LT1 block disassembled, 186 heads, a camshaft & is also throwing in pistons w/ rings installed, the crank, factory 4 barrel, intake manifold, oil pan, fuel pump & harmonic balancer.
The other block's stamp code is 3970014. a 4 bolt & This block is already cleaned w/ the crank installed & balanced by a local machine shop, Hyperutectic flat top pistons.He is also throwing in a cast intake & cast heads, valve covers & distridutor.
Which is the "better" block of the 2? Or which If there is any difference.
I am interested in putting vortec heads & intake on whatever motor goes in to my truck. Is that possible with either of these motors?
Thanks for the input in advance

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Old 06-28-2009, 04:16 PM
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According to Mortec, both those blocks are flat tappet cam units. I see no reference to LT1 on either casting number.

What I would do is be looking for a motor from a '96 to '99 Chevy truck. Look for a 5700 Vortec L31 rebuildable long block that came from the factory with a roller cam. I've seen them on craigslist here in the Phoenix area for $200 or less. This motor will have the L31 Vortec heads on it. Look for a hacksaw tooth design on the front of the heads and casting numbers of either 12559062 or 10239906 under the valve covers. You'll need a Vortec-specific intake manifold. Here are some part numbers that will work well.

Edelbrock Performer RPM Vortec #7116
Edelbrock Performer RPM Vortec w/ EnduraShine finish #71164
Edelbrock Polished Performer RPM Vortec #71161
Weiand Stealth #8151
Weiand Stealth w/Everbrite finish #8151C
Weiand Stealth polished #8151P
Weiand Stealth Air Strike #8502
Weiand Stealth Air Strike w/Everbrite finish #8502C
Professional Products Crosswind Vortec #52028
Professional Products Crosswind Vortec polished #52027



It's better to start with a roller cam block because of the oil formulations from the oil manufacturers. They've stopped including the extreme pressure lubricants that used to protect the flat tappet lifter interface at the cam lobe, so many of the fellows building motors with flat tappets have had problems with cams going flat.
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Old 06-29-2009, 11:02 AM
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Thanks techinspector1!

I appreciate the info & feedback!
I will do some searching for the block you suggested. See what I can come up with.
I have been looking at some motor packages on sites like JEGS & Summit Racing. The 350 HO motor by GMPP is 330 hp for around $2800. It has a one piece rear main. Would I have to change transmissions? Since I believe the 85 employs a 2 piece seal.
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Old 06-29-2009, 11:18 AM
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Nope you won`t have to change transmissions but you will have to change the flexplate and starter if you go with a 1 piece rear main seal and I certainly would. a 350 will need a 168 tooth 14 inch flexplate and a staggard mount starter. The flexplates from the 1 piece blocks are different from the 2 piece blocks and they will not interchange.
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Old 06-29-2009, 11:31 AM
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Thanks DV...

I honestly have no idea what I'm gonna do lol! All this is stuff is some what over whelming to me, I'm kinda getting frustrated & aggravated a lil bit.
I'm wondering if I can just save myself sometime & some of the aggravation by getting the 350 HO motor from GMPP. 330 hp is plenty for me I think lol!
Or can I build a motor using an older block like the ones I mentioned & go w/ old school heads like the 186's & build up the motor some to get more horses out of it?
This is turning out to be more than I originally thought LOL!
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Old 06-30-2009, 02:05 PM
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Quote:
Originally Posted by JCK13
I could use some advice & opinions. I have an 85 chevy truck. I wanna swap the stock 305 for a 350 & beef up the 350 a lil bit. Nuthin too serious, jus some good horsepower & maybe churn a lil buttermilk while I'm sitting at the red light.
I have located 2 350 blocks. the stamp code on one of the blocks is 3970010. The guy wants $500 for the 350 LT1 block disassembled, 186 heads, a camshaft & is also throwing in pistons w/ rings installed, the crank, factory 4 barrel, intake manifold, oil pan, fuel pump & harmonic balancer.
The other block's stamp code is 3970014. a 4 bolt & This block is already cleaned w/ the crank installed & balanced by a local machine shop, Hyperutectic flat top pistons.He is also throwing in a cast intake & cast heads, valve covers & distridutor.
Which is the "better" block of the 2? Or which If there is any difference.
I am interested in putting vortec heads & intake on whatever motor goes in to my truck. Is that possible with either of these motors?
Thanks for the input in advance
Both are 4 inch bore Heavy Duty blocks, they show up in things from 302 Camaros to 350 trucks either is an excellent choice. Yes the original LT1 was built on these blocks but these blocks saw most of their use in trucks and as industrial engines. The 010 is more familiar to people but the 014 is just as good.

Head selection needs to be done with the piston in mind. GM, and everybody else for that matter control overall compression with combustion chamber volume in the head and dish volume in the piston crown. A flat top piston with a small chambered head such as a Vortec can get you into excessive compression ratios, especially if combined with a zero decked block and or milled heads which are commonly done steps with old castings that needed flattening across the decks. So you must be aware of what the dimensions are of the block and head decks, and the chamber volume before you put pistons in. Or the reverse, if you have pistons in the block, you need to know their clearance to the head deck and the size of any dishes or domes before you pick chamber volumes for the head. So just deciding to buy a block and strap a set of Vortecs to it doesn't work without some prior computation of compression ratios.

Bogie

Last edited by oldbogie; 06-30-2009 at 02:06 PM. Reason: clarify the sentence meaning
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Old 07-09-2009, 12:33 AM
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Thanks for the input Bogie!

I appreciate all the help fellas! I'm still debating on what route I'm gonna go & whether it will be a 350 or small block 400 I use for the swap. (Oh yeah, I posted a thread about a 400 as well lol!) I really do appreciate you guys taking the time to read & respond tho...thanks again!
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