New member - Building Mopar powered '41 Chevy streetrod

Hello fellow Mopar fans,
I'm building a '41 Chevy street rod and will be building a Mopar LA engine and 727 transmission to put in it. I'v e always loved Mopars, especially '60s - early '70s so when a co-worker offered me a 360 block I got it. Did some research and learned about the 408 stroker kits. Scored some 340x heads and a six-pack manifold. I recently came across a deal on a 340 block and picked that up. It turned out that the 340 block is "virgin"; it is a '71 casting and has never had a piston in it. Apparently, it was a spare parts or replacement block from the '70s that a dealer had squirreled away. The cylinders have never been honed and according to my measurements with a non-calibrated micrometer, the bore is just under 4.04". If I go with the stock bore on the 340 and stroke it to 4" it will be a 408 or I could bore it and get up to 416. I'm thinking the 8 extra cubes are not really worth unnecessarily boring a good 340 block. I'm not looking to build a race car, just a reliable driver street rod with loads of torque and a good highway cruiser. Opinions welcome. Advice will be considered.

I'm sure it won't take long before someone offers you a complete engine for that block. Good luck with your project

If you have any sense at all you will build a 360. That 340 NOS block is a SCORE! Let the bidding begin.

R.

I wasn't planning on selling the 340 block, I know it is extremely rare.... Not saying there couldn't be an offer I can't refuse.

I mentioned that I have a 6-Pack intake manifold for it, but the manifold is not in great condition. It was over-ported for W2 heads and I have 340X heads. There are epoxies that can be used and should hold up, but I would rather have a new, or used manifold that hasn't been ported already. The problem is that Mopar or Edelbrock no longer make a 6-pack for the LA engine. If anyone knows of a source for one please let me know.

I was also hoping to outfit it with fuel injection units in place of the 3 carbs. There are sources to do that, but it would be much more expensive than the already costly 3 Holly 2bbl set-up.

I always welcome opinions and advice, but don't get your feelings hurt if I don't always follow them. I am pretty hard-headed. If I had followed the advice of most of my street rodder buddies, I wouldn't be putting a Mopar engine in a Chevy!

Question: I understand that the serpentine belt system from a magnum engine can be fitted to an LA engine. Is this true? If so, are there any issues such as water pump rotation direction?

Not easily.

The Magnum uses a shorter cam snout, no fuel pump eccentric provisions, with a correspondingly thinner timing chain cover.

You'd have to swap cam and cover or play spacing games to line everything up.

Well okay then. I'll keep that in mind. Thanks for the heads-up.

One thing for sure is I would not bore a virgin 340 block! Good 340 blocks are getting harder to come by, there is no reason to shorten its life span by a needless overbore, there are plenty of 340 seasoned blocks out there if you want to overbore one. In a street motor, unless your street racing, your not going to miss those few CI the overbore would provide. Throw the stroke kit at it, and add a power booster if that is not enough for you. I would also do the EFI. I would think as time moves forward the EFI is going to be easier to tune and dial in properly. Gene

Yeah, I won't be boring the 340... and in that case I may as well use the 360 block for this build and save the 340 block for something more worthy.