TheSamba.com :: View topic

Sun Jan 22, 2012 2:07 pm

I need advise on a set of heads for a big block 40HP motor I'm getting together. Here are the parts I have already.
1. Rimco worked 40HP case with line bore and cam bearings cut.
2. Rimco Rebuilt 40HP Rods cut for 69mm crank (1600)
3. 69MM Stock 1600 Crank
4. NPR 92MM Piston & Cylinders (40HP Small Crank Pin)
5. 110 Cam
6. 40 Kads (Need to make manafolds)
7. 019 (Bosch VJ4 BR8) Dizzy
8. 12v Small Generator & Stand
9. Black Satin Powercoated 40HP Stale Air Tin Complete.

I really want some of the Brothers Big Valve heads. $1000 Ouch.
I really do not know what it really need since I will not be racing this above 5000RPM. I have a 58 Bug I'm using this motor in w/ a freeway flyer and thiss will be my second (Backup Motor). My main motor is a 2054cc 74x94 044 head dual weber 44 120 cam big motor. I want an oldschool motor for this ride and can take my time building it since I have the other ready to go now.

Sun Jan 22, 2012 2:30 pm

using the 92 pistons would they use the stock 1600 rods?

what did you do to use the 40hp rods.

ive moded the 40hp rods to work with 69 crank for mine but to use with 83 mm pistons

Sun Jan 22, 2012 3:49 pm

I,m using 40HP rods. The 92mm have the small pin like a 40HP piston.
They are old school 92MM P & C made by Nippon Piston Ring in Japan in the late 70's or early 80's. It makes a 1835cc 40HP Short Stroke!

Sun Jan 22, 2012 4:15 pm

would a 1300 head work? or are you looking to keep the 40hp heads?

Sun Jan 22, 2012 4:30 pm

I have 8 sets of used 40hp heads I just want Ideas on what would be the best setup. I'm thinking 40/35.5 valves and lots of work to make it work with a set of fresh 40 Kads set for the 1835cc. I will still need to tig up a few intakes out of the old dual port intakes and the bottoms of a 40HP intake.

Sun Jan 22, 2012 5:10 pm

cool.

looking forward to what you plan on doing.

have any pics?

Tue Jan 24, 2012 7:08 pm

Jake, I'll get some pic's up here shortly.

Wed Jan 25, 2012 6:30 pm

I think 40 x 35.5 valves are way too big for any 40hp head. The valve would be larger than the intake port on even a heavily modified port. You can only go so large with the port if you are planning to keep the original manifold flange configuration.

Also since you are using a 69mm crank, you can't call it a short stroke motor; a short rod motor yes, but it's not short stroke anymore. It's an interesting build; I like outside the box engines.

Mon Jan 30, 2012 4:33 pm

I think you might be correct that they would flow like crap. Does anybody know the largest flow I could get? Should I go with the Okrasa and speedwell intake route. I could always put a bigger crank like the 74MM I have laying around.

Mon Jan 30, 2012 7:29 pm

Since yor going to surface for 90.5 go up to stck 1600 valve size ,but us the 1965 heads ?

Mon Feb 06, 2012 12:10 pm

biger valve will not hurt the flow as long as there done corectly,and the chamber is unshrouded.40x35 should work great.or you could use a 37.5x35 if you wish.it's not so much big valves that hurt performance but too big of port or not ported corectly.a big valve wll out flow a small valve unless someone has effued up the head.if it were me I would make it a duel porthead.

Fri Mar 09, 2012 5:08 pm

If I were to use okrasa heads & the new speedwell repop intakes what are the carbs to use and what size are they and is it easy to get parts? IE...jets
Who would be a good shop to enlarge the valves.