Briggs Raptor block/ Briggs "Standard" 5HP block

The_Ruppster_86

The_Ruppster_86

New Member
#1
#1
Gentlemen,

I would like to know if there are any significant differences between a Briggs Raptor block and your "standard" Briggs 5HP Kool-bore block. Is one block more desirable for building up to higher RPM such as 6-7000? Also, are there any differences between the various generation Briggs Raptor blocks?

I've read that a Briggs Raptor block can be spotted by checking the block for an internal governor hole. No governor hole means it's a Raptor block. Correct?

Thanks for any help you can provide,
Jeff
 
The Restore Kid

The Restore Kid

New Member
#2
#2
Sounds right to me..

There are DIFFERENT kool bore blocks.. Like the Raptors and newer motors have a lot bigger valve guide area, and the third bolt hole for the carb.. The BLOCK itself has more aluminum in it, therefor it's a little bit (stronger) all around... But if you use the older 1974 style block....

You still are never gonna explode the engine block, unless you go building some retarded monster engine....

But then you'd be running something sleeved anyways with bearing crank.. If you want to build ANY kind of racing motor and plan on getting it hot and spinning the hell out of it, you might as well just buy a sleeved engine to start with, as it will have a hell of a lot longer life trying to be an airplane motor it was never intended to be...

There are buhed and ball bearing engine blocks as well... Most people want to use the dual bearing engine when talking about high RPMS

But there is ALSO an engine block (DU bushing) which is a bushing block, BUT the bushing is made from a bronze/oil brass, type material, to reduce friction and ad a lot more life to the block.... So it is better than a standard aluminum bushing in that respect, but still is a bushing and offers a bit more drag than a ball bearing... So you'd want maybe a ball bearing over DU bushing for going 11,000 rpms.....

BUT I have heard from Gokart racing guys that in ALL REALITY, the DU bushing block is the strongest block, as it has much more aluminum engine block material holding the DU bushing in place.... The GAIN in very little friction loss that you gain by using a dual bearing engine....

ACTUALLY DOES NOT out weigh the block strength of the DU block..... And when you are talking about building 11,000 rpm engines, The DU bushing works just fine and is no problem with drag or oiling...

But a Dual Bearing engine block, built the same way, will explode, because there is far less aluminum engine block, because it has all been cut away to make room for the ball bearing.....

So in a perfect world I guess you want a DU Bushing iron bore block, which is not a Raptor.... It would just be some unsuspecting 1992 Briggs 5 horse Industrial Plus motor bolted to an air compressor somewhere...

Then ya gotta take the junk crank out and replace it with an old 70's 80's one...
 
Last edited:
Minimichael

Minimichael

Well-Known Member
#3
#3
I'm bumping this thread since I came across it while digging around for Briggs 5hp info...for the current build I'm doing. This thread looks to have a lot of info packed into this tiny post.

I'm researching to be sure no billet will be necessary.

Next stop, I think Affordable Gokarts has an article on hopping up 5hp flatheads.

PXL_20230424_214344525.jpg
 
Last edited:
creia

creia

#4
#4
The "Bible" on performance-building a Briggs 5Hp engine is Jimmy Glenn's book "Building a Race Ready 5HP Briggs". My son (14 at the time - he is 28 now) purchased a signed copy from Jimmy back in 2012 and used it as his guide to rebuild/hop up a Raptor 3 which he put on a 1967 Bonanza BC-1200 which he still has today. Glenn is an iconic engine builder for race karts from back in the day. Unfortunately, the book is out of print and NLA , although every once in a while a used one will come up on eBay. Fortunately, Jimmy was kind enough to provide Bob's 4 Cycle Karting Forum permission to reprint it on that website in its entirety. I have provided the link below.
Michael
Sidebar comment; By the way, the member who started this thread back in 2012 "The Ruppster86" is my son Jeff.
https://4cycle.com/karting/forums/building-a-flathead-jimmy-glenn.94/
 
Last edited:
sparkwizard

sparkwizard

#6
#6
Last summer, I bought an old racing kart from a young Marine who had it thrown in the back of his truck at Auto Zone. He did not know what it was and it was given to him. I gave him $200 for it and threw it in my truck. It was an old Margay frame, but the engine was a Raptor with the gas tank below the carb and no choke. It ran really well. The only thing I found to be different from any other flathead I had was no hole for governor, no choke, no linkage for governor and the piston and rings were strange. The connecting rod did not even look special.
I made a nice profit on that kart.
 
You must log in or register to reply here.
Top