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Engine basics => Engine set up tips => Topic started by: Allan Perret on December 09, 2017, 03:35:28 PM

Title: LA40>46
Post by: Allan Perret on December 09, 2017, 03:35:28 PM
So can you drop LA46 piston & sleeve into the 40 case ?  If so, are the p&s from RC engine same as the CL engine ?
Title: Re: LA40>46
Post by: Gerald Arana on December 09, 2017, 04:19:18 PM
No. The VF 40-46 are interchangeable.

Jerry
Title: Re: LA40>46
Post by: Dan McEntee on December 09, 2017, 05:29:41 PM
   The LA.40 and .46 use the same case, but you can NOT swap cylinder liners between them because of the difference in the O.D of the liners. That is why the .46 is a bit lighter than the .40, because more metal has been removed to let the bigger liner fit. The R/C and C/L versions of both the engines are the same within the displacement. The only difference being the carb on the R/C version and the venturi on the C/L version.  There has been MUCH written here on the forums on parts interchange over the years and can be found with the search feature.
   Type at you later,
   Dan McEntee
Title: Re: LA40>46
Post by: Tim Wescott on December 09, 2017, 05:54:52 PM
   The LA.40 and .46 use the same case...

They look similar, but at least the one 40LA that I have is about 1/8" shorter in the snout than my two 46LAs. 
Title: Re: LA40>46
Post by: BYU on December 09, 2017, 08:47:08 PM
They look similar, but at least the one 40LA that I have is about 1/8" shorter in the snout than my two 46LAs.

Snout?

Title: Re: LA40>46
Post by: BYU on December 09, 2017, 08:51:29 PM
The case is very similar but not the same.

The head bolts on the 40 are closer together, the case is bored for the smaller p &l

To fit the 46 parts you would need to fill the head bolt holes with aluminum and redrill and tap for the 46 head bolt location, then bore out the case to take the larger p & l.









Title: Re: LA40>46
Post by: Reptoid on December 09, 2017, 09:49:28 PM
They look similar, but at least the one 40LA that I have is about 1/8" shorter in the snout than my two 46LAs.
That's somewhat surprising since they use the same crankshaft and thrust washer
Title: Re: LA40>46
Post by: Tim Wescott on December 09, 2017, 11:22:48 PM
That's somewhat surprising since they use the same crankshaft and thrust washer

I'm gonna have to go check now.
Title: Re: LA40>46
Post by: Steve Helmick on December 10, 2017, 12:43:20 AM
Yeah, Tim's probably thinking about something else being shorter now... :-[

I put one of my .46LA's into the Skylark that Don McClave had a .40LA in, and Jerry Eichten raffled off with a .40FP in it. Same snout length. The head bolt pattern is indeed different. Way more trouble than it's worth, anyway.

B.Y.U. ..."snout" = "nose", "shaft", or "front end".   :! Steve
Title: Re: LA40>46
Post by: RandySmith on December 10, 2017, 01:04:11 AM
They are the  same mount  and outside dimensions, BUT they are   NOT  the same  case, the 46 has its own  piston  sleeve  head  wrist pin , gasket set  and  case,   The crank shaft is the same for the  35  40 FP  40  46  LA.

The  VF 40 and 46  uses   BOTH a  different  piston/sleeve set, head, and crankshaft

Regards
Randy