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advice for mild 36hp build
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esde
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PostPosted: Mon Mar 05, 2018 5:40 pm    Post subject: advice for mild 36hp build Reply with quote

I've been collecting 36hp cores and parts for a while, and finally have enough to start building one. It's either for my 50 (on a 56 pan) or 57. Most of my experience is with 1500-2+ liter engines based on the later case, though I have had a few 36hp apart. Just not recently, that was maybe 20 years ago..
Rough plan, based on what I have collected:
several cases dating from 53-57. May need line bores
I have several cranks, some just need a light polish
set of NOS rods
set of NOS pistons and cylinders
Berg full flow cover with the offset washers to use with 6mm studs
2 sets of heads, the nicest I will have rebuilt
dual 28 carbs and manifolds with old deano linkage
010 and BJUR 4BR8 distributors
to purchase:
cam from air cooled research
machine work:
8 dowel the crank and flywheel
Balance rotating assembly
Cut heads to increase compression

Questions!:
will the stock heads benefit from a port/ polish? If so, are there any specifics to address, or leave alone? I have done some 1500sp heads with success, but not the small 36 heads.
I'm looking to increase compression to 8:1, what other mods should be done as well?
I have NOS rods, at what point do the bolts become a concern? For a little mouse motor, are they ok? Or should I upgrade?
Do the 36hp wrist pin clips need upgrading?
Many thanks in advance, I'm looking forward to getting into this
SD
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RichardinNZ
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PostPosted: Tue Mar 06, 2018 6:13 pm    Post subject: Re: advice for mild 36hp build Reply with quote

I have only worked on/upgraded the top end of my engine, with reworked stock heads, Speedwell ratio rockers, dual 28PCI and have had no issues.

I think the greatest difference between your plans and mine are that you plan on a different Cam rather than ratio rockers and that I also had 33mm inlet valves installed and the heads cut for higher compression (7.5:1).

More details of the car in the photo link in my signature....

Hope this helps.
regards
Richard
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esde
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PostPosted: Tue Mar 06, 2018 10:51 pm    Post subject: Re: advice for mild 36hp build Reply with quote

RichardinNZ wrote:
I think the greatest difference between your plans and mine are that you plan on a different Cam rather than ratio rockers and that I also had 33mm inlet valves installed and the heads cut for higher compression (7.5:1).


Interesting, 33mm valves. I've done some reading about improving the stock 36hp heads, but nothing that really calls out what needs to be improved.
For instance, what becomes a restriction first, the intake port, or the intake valve size? As most people looking for performance just go straight for the Okrasa heads, there doesn't seem to be much info online for the stock heads.
Not looking for a screamer, just free up the intake and exhaust wherever possible.
SD
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PostPosted: Thu Mar 08, 2018 1:48 pm    Post subject: Re: advice for mild 36hp build Reply with quote

Stroke it. The 69.5 cranks will a huge difference. I built a similar engine as yours with the stroker and ran it in my old 58 bus. Had no issues keeping up with traffic running a crash box trans.
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esde
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PostPosted: Thu Mar 08, 2018 11:37 pm    Post subject: Re: advice for mild 36hp build Reply with quote

Braukuche wrote:
Stroke it. The 69.5 cranks will a huge difference. I built a similar engine as yours with the stroker and ran it in my old 58 bus. Had no issues keeping up with traffic running a crash box trans.

I would, but I've got all the parts for stock bore x stroke. I've gone overboard on most engines with bigger this and that, so I'm trying to keep this one based on the stock hardware, to see what it can do.
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RichardinNZ
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PostPosted: Fri Mar 09, 2018 12:17 am    Post subject: Re: advice for mild 36hp build Reply with quote

The 33mm valves are the same size as used in the Okrasa heads. I took advice from people on here and the Cal Look Lounge on the valves and increased compression.
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PostPosted: Fri Mar 09, 2018 5:07 pm    Post subject: Re: advice for mild 36hp build Reply with quote

Do 40 horse pistons fit in the 36 horse and would they boost the compression? Just a thought, espcially if one is running a single carb.
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esde
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PostPosted: Fri Mar 09, 2018 9:06 pm    Post subject: Re: advice for mild 36hp build Reply with quote

EVfun wrote:
Do 40 horse pistons fit in the 36 horse and would they boost the compression? Just a thought, espcially if one is running a single carb.


Copied from another post:
"later 40 hp pistons are 1mm higher in piston height. you can machine a 10-15mm circle high 1mm around the top to eliminate possible contact toward flat side of head.

other evident difference is that later pistons are stronger and then heavier by about 40 grams each (!) that stopped me to use them

if using these on used barrels, check if these has a little groove near top ring race, you do not want that the top ring works agaist the race. remember the 1mm different height between the 2 pistons, top ring position is a little higher."

Not sure that machining a 40hp piston to raise compression gets you a better scenario than a tight deck and fly cutting the heads. For sure swinging an additional 40 grams from the dinky 36hp rods isn't my favorite idea. But, interesting thought..
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PostPosted: Sun Mar 11, 2018 9:38 am    Post subject: Re: advice for mild 36hp build Reply with quote

The sweetest Pistons you can drop in Are domed top 77(40hp) They were in Mexican 40 hp industrial engines They give an exellent hp and comp boost and they are light . Rev fast! Tom Brucks head porting
showed You can get the same results from a SP 36 as a okrassa. Secrets though
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PostPosted: Mon Mar 12, 2018 12:42 pm    Post subject: Re: advice for mild 36hp build Reply with quote

I also run these 77mm mexican domed top pistons and work well, but indeed had to machine the heads to avoid contact at higher rpm. Also run stock crank, lightened flywheel. Make sure you use a good exhaust with bigger diameter tubing and something like 32 PCBI carbs and you will enjoy some more oomph.

I think its cool to stick to the 1192cc!

(although... i have thoughts to build a 72x80 combo...)
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PostPosted: Mon Mar 12, 2018 4:15 pm    Post subject: Re: advice for mild 36hp build Reply with quote

I'll edit my last post, as I figured out the answer to my stupid question..
But I do have a few more that I can't find the answer to..
AirCooledClassics wrote:
The sweetest Pistons you can drop in Are domed top 77(40hp) They were in Mexican 40 hp industrial engines They give an exellent hp and comp boost and they are light . Rev fast! Tom Brucks head porting
showed You can get the same results from a SP 36 as a okrassa. Secrets though

Who has the domed top 40hp pistons? Are they the same or different than the domed top 36hp pistons I see listed? Does anyone recall the height of the dome? If stock compression is 6.6, what did the domed pistons bump it to?
Someone earlier brought up the possibility of using a stock 40hp piston, and machining the added 1mm height into a dome. But they are a good bit heavier, and the dome would be very slight.
Thanks for the info this far.
SD
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PostPosted: Sat Mar 17, 2018 4:27 pm    Post subject: Re: advice for mild 36hp build Reply with quote

Still looking for a supplier on the dome top 40hp pistons. Anyone?
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PostPosted: Fri Mar 30, 2018 4:40 am    Post subject: Re: advice for mild 36hp build Reply with quote

Dome top 40hp was standard from sometime in 1973.

About cores for 36hp, the better cores are from sometime in 57 or later. Mine is from september 57, installed as factory refurbished engine in 1964, it has 160.000 km since then, half of it in my possesion. Still going strong.
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PostPosted: Sat Apr 28, 2018 7:18 pm    Post subject: Re: advice for mild 36hp build Reply with quote

I've been collecting parts, and have changed the plan a little:
56 case, full flow oiling
stock crank and flywheel, 8 doweled
set of NOS rods
I've sourced a set of NOS domed pistons to use with my NOS cylinders
Berg full flow cover with the offset washers to use with 6mm studs
Stock heads, light polish and 33mm intake valves
010 and BJUR 4BR8 distributors
single Zenith NDIX
NOS muffler
I've contacted aircooledresearch, and will be purchasing a cam and lifters from them, and asking for a recommendation on compression ratio.
At this point, most of my questions lie around the cylinder heads, and what can be done to make them work better. It seems that most people go straight to the Okrasa heads instead of working the stock heads, but I've read that it can be done.. but where do I look or who do I talk to?
SD
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PostPosted: Sat Apr 28, 2018 9:25 pm    Post subject: Re: advice for mild 36hp build Reply with quote

If you are going NOS stock exhaust you may want to think about less restrictive tailpipes. I used TDE tailpipes on my stock exhaust. They look standard but have a larger internal bore.
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PostPosted: Sun Apr 29, 2018 8:31 am    Post subject: Re: advice for mild 36hp build Reply with quote

RichardinNZ wrote:
If you are going NOS stock exhaust you may want to think about less restrictive tailpipes. I used TDE tailpipes on my stock exhaust. They look standard but have a larger internal bore.

Thanks, I had been told that I may have to modify the internal baffles, and enlarge the tailpipes. I wasn't sure if it was just a larger bore pipe that would bolt on, or if I would be welding a larger tube into the muffler itself.
The last post resulted in a number of PM's that may yield some cylinder head decisions, I'll update soon.
SD
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PostPosted: Sun Apr 29, 2018 10:13 am    Post subject: Re: advice for mild 36hp build Reply with quote

If you will use the stock crank I weould think twice about adding duration to the camshaft. It is common knoiwledge that the stock crank does NOT like a lot of rpm. So it would be better to find some power in the lower to mid rpm.
Definitely bump the CR as much as you can. If memory serves you can flycut to just above 7-1. More than that requires welding in the chambers or dome pistons. I have gotten 1200 heads welded in the chamber several times. Then I aimed for 8,1-1 with stock cam. and 33 mm inlet valve + porting of the channels of course. Never used 28´s though. Always used 32 mm PCI´s . In that set up, along with either a gutted stock muffler or a copy 4 tip muffler I usually reach 42-43 hp @ 4000 rpm. One actually made 45 hp @ 4250 rpm. (From 30 hp Din)
With dual 28´s and 7-1 CR you will most likely not hit more than 40´ish hp, but the torque increase will be significant. Most likely something like 20%

Have fun.

T
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PostPosted: Sun Apr 29, 2018 12:40 pm    Post subject: Re: advice for mild 36hp build Reply with quote

Alstrup wrote:

Have fun.

T


That is the reason I do any of this.
Thanks for your input Torben, I do appreciate it. I was thinking of using the 28pci solex carbs as I have them, and a nice old Deano linkage, but no manifolds or air cleaners. Then the complete Zenith kit with 36hp manifold and air filter found it's way to my shelf, and I figured I would give it a try.
What can be done (if anything) to help a stock crank live in the upper RPM? Will DPR do counterweights and does that help?
SD
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PostPosted: Mon Apr 30, 2018 2:16 am    Post subject: Re: advice for mild 36hp build Reply with quote

esde wrote:
Alstrup wrote:

Have fun.

T

What can be done (if anything) to help a stock crank live in the upper RPM? Will DPR do counterweights and does that help?
SD

Yes, definitely. Just ask him to let the counterweight "fingers" go all the way up to the opposite rod journal on the webs. I have had some cranks stroked to 76 mm and Porsche rod journals and there has been no problems with 90 hp and 6000 rpm redline. The next crank I am going to have made will be 78 mm stroke and Honda rod journals. This crank will be full circle though to get the best strength in it. This engine is only on the drawing board as of now, but the goal is a 1700 cc displacement street engine pulling 115 - 120 hp below 6000 rpm.
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PostPosted: Mon Apr 30, 2018 4:53 pm    Post subject: Re: advice for mild 36hp build Reply with quote

I'm expecting two quotes back on the heads. One is from Brothers Machine, the other from an independent builder here on the east coast. I've requested Okrasa sized valves, open the intake/ port and polish, new valves and guides, etc.
I'll see how the prices and work offered compares. There was the suggestion to open the intake to 1500 single port size, and use a shortened 1500 manifold... but as I'm sticking with the stock displacement that might be too big. Lots more reading to do here to help me figure out what might work well.
SD
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