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LT1 rotating assy into a Vortec 5.7 block opinions

29K views 43 replies 12 participants last post by  Jim Rockford 
#1 ·
Just picked up a(nother) sweet 77 impala coupe. has a decent running 305 2 brl engine in it now,but I'm looking do do a budget 350 i have a vortec 350 short block that has a bad bottom end, haven't pulled the pan yet to see if It can be saved, but I also have a very low mileage lt1 that came out of a road master with an electrical fire, few burn sensors , but that all, wondering about installing the pistons rods and crank into the vortec block and topping it with a set of l98 heads I have laying around and a used edelbrock performer .. What do you guys think...?
any thoughts on a good roller cam?
 
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#2 ·
What are you looking for in a roller cam? Low end torque? Mid range?
Swapping the parts over from the LT1 bottom end to the Vortec should work out okay. Not sure what style pistons the LT1 engines use, but since the L98 heads have such a small chamber you'll have to keep a close eye on the compression ratio. I have a roller cam for sale that I used in my Vortec engine. It has less than 2000 miles on it and in excellent shape, it would save you a few bucks compared to buying a new one. Shoot me a PM if your interested. Not sure if you know also but Vortec blocks require a special timing chain so I'll include it in a link:
http://www.summitracing.com/parts/CLO-9-1157/Application/?prefilter=0
 
#3 ·
Well the L98 heads I have are Iron 64cc heads, the vortec engine has dished pistons and the LT1 has flat tops...but the LT 1 heads are 64 cc to I think ..I have both the roller LT1 and the Vortec cams and I think I have a roller cam from a l98 also , Just looking mainly for low and mid range power.
 
#7 ·
Mainly wondering if I would gain anything from useing the flat tops from the LT1 along with having the shorter piston skirt, over the dished vortec pistons? Opened up the bottom of the vortec today and found the crank broken between the #7 rod and the 4th main web.



 
#8 · (Edited)
Whether to use the FT or dished pistons comes down to simply entering the numbers (rod length, intake valve closing point and SCR) into a calculator to see if the DCR (using the cam(s) you have on hand) falls into the range of pump gas or not.

Personally, I'd spec the cam to work w/the heads and the LT1 FT pistons- even if it means buying another cam. The advantages in the quench/turbulence created by true FT pistons shouldn't be discounted. If you need more chamber volume, work the chambers to deshroud the valves and gain volume. It's not that the valves are shrouded w/1.94" intakes, but the idea is to get some benefit other than just enlarging the chambers if possible.
 
#13 ·
Jim Rockford said:
Mainly wondering if I would gain anything from useing the flat tops from the LT1 along with having the shorter piston skirt, over the dished vortec pistons? Opened up the bottom of the vortec today and found the crank broken between the #7 rod and the 4th main web.



Jim you wouldn't by any chance know the cc of the vortec dish piston would you?
 
#14 ·
onlyfnway said:
If i am not mistaken the lt1 cam does not have a gear for the dist. being it is driven off the front of the engine. Lt1 heads should be 58cc?
You are thinking of the LS series engines,,
the LT1 has a stuby shaft that sits under the intake

louis165 said:
Jim you wouldn't by any chance know the cc of the vortec dish piston would you?
What I found on the Interwebs..
I measured the dish and found that they are 10.5 CCs, and they are .028" in the hole. I was trying to decide if not changing pistons was going to cost me too much power vs. how much money it would cost to change them.
 
#15 ·
Jim thanks I've been trying to find these numbers for a while now I'm using the vortec block with dish pistons I didn't know any better and used 041 head gaskets with stock deck hight 9.025 put me with 66 quench not good ! Now that you have helped me out I can take it back apart an change head gaskets 015 or 020 thanks
 
#17 ·
louis165 said:
Jim you wouldn't by any chance know the cc of the vortec dish piston would you?
From another thread earlier:

I found the notes from the Vortec engine (880 block) I pulled apart recently. The piston on that engine has an 11cc round dish and is 0.080" deep.
FWIW, my pistons were spotless, and I measured pretty carefully. But 1/2 cc won't make that much difference either way.
 
#19 ·
Jim Rockford said:
damn .080 is pretty deep, wonder if that was checking all 8 or just one...
I'll check mine toda i'll do the 2 front cyls.
The depth is less important than the volume being 10.5-11 cc, right? I mean, w/a round dish all the quench action is lost where the dish is even if it were half that depth. If anything the diameter of the dish would be more important than the depth, unless you have something else in mind...
 
#20 ·
I got .024 deep in the hole on both sides...

Sorry missed the new post.. You want to get the deepest part of the piston as close to the head as possible with out any part of the piston touching the head..lol so Depth plays a decent part in the equation.
 
#21 ·
well got around to tearing the vortec apart and come to find out the block is ruined... the #4 main bearing spun in the block and they much have just kept on driving it with the crank broken...so its scrap.






The rear main bearing was turned in the bore and I had to beat the back part of the crack and bearing out with a hammer.

So I think I'm just going to suck it up and buy a carbed LT1 intake and refresh this LT1 I have, took it apart and it is super clean in the bottom end..



it came out of a grandma roadmaster that had some fire under the hood, but the engine didn't get very hot, hell all the front seals are still there and the block still has the factory powdercoating on it, so Its gonna be a nice engine. has no slop in the timing chain.
 
#25 ·
Jim Rockford said:
Just picked up a(nother) sweet 77 impala coupe. has a decent running 305 2 brl engine in it now,but I'm looking do do a budget 350 i have a vortec 350 short block that has a bad bottom end, haven't pulled the pan yet to see if It can be saved, but I also have a very low mileage lt1 that came out of a road master with an electrical fire, few burn sensors , but that all, wondering about installing the pistons rods and crank into the vortec block and topping it with a set of l98 heads I have laying around and a used edelbrock performer .. What do you guys think...?
any thoughts on a good roller cam?

Why is my thread in Hotrodding basics It should be in the engine section... please move it .
 
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