Hello, and thanks for any info you can provide...

I have a BVM Agressor II with a KBV 71 engine (I believe this is a K & B engine manufactured for BVM).... My question is: can I replace it (as is "direct bolt-in exchange) with a BVM 91 DF engine?

I also have a KBV 82 engine that came with the plane that the previous owner was going to install... Is this a direct bolt-in replacement? Also, how much more power does this have over the 71? If I replace the 71 with the 82, can I use the same pipe?

Lots of questions from this DF rookie... Hoping for some good info.

Thank you in advance for providing any help you can

John Adams
San Jose

John,

Well I will try to answer a few of the questions here. The KBV .72, .82, BVM .81, .91 and .96 will all bolt into the viojet unit. The .72 was a great engine in its day, the .82 was good, and the .91/.96 were by far the best you could get.

The .82 has more power than the .72, but the .72 is no slouch. The .72 used a stinger type tuned pipe if memory serves me correctly, but I could be wrong here. The pipe for the .82 was a little longer so hence the .72 pipe probably won't work with the .82 (would be real tough to neddle).

The same pipe was used for the .81, .91, and .96. You could get either the standard pressure or puffer pressure pipe for these engines.

If I was you I would search the world for a .91 engine. It was by far the best and will definitely work for you.

John Redman
Team BVM, Jet Cat USA

John,
I have the Aggressor 2 with a KBV .82 it works outstanding I have around 150 flights on mine. I have been told by those more knowleagable than I that I can't put the bigger fuel tanks in the plane. They won't fit and you need them for the .91. I recomend that you contact BVM they have always been very helpful with any and all questions. Although the look I get from BV when I show up at a jet fly is always precious when I bring out my Antique.
I think I have the info for the guy who did the KBV for BVM. He has worked on my engines at a very reasonable rate.
Sparky

I have two KBV82s and one BVM91 and they are bolt in replacements, definately. I have tried it. Not sure on the 72 but I'd be suprised if it was any different externally. I am guessing the only way to tell them apart is to measure the bore/stroke.

I have a Viper that has the small tanks and a KBV82. I am thinking of putting the 91 in it. If I find I have too little fuel I will replace the header tank with a much larger one. There is heaps of room in the canopy (just a little hard to get things in there).

Hi,

As my memory serves... All of the BVM engines use the same bolt pattern and mount.
VERY early fans may need a little dremeling in front to clear parts of the forward case of the larger engines. Minor stuff.
Otherwise, engine should bolt right in.

David

This is good information.. I appreciate it.

I do have a BVM91 on hand and want to install it (after my initial flights with the originally installed equipment)... I don't want to go tearing into it yet.

Sounds like the only thing I'll need to do is change pipes and increase the fuel volume to get the BVM91 online... Too cool ! !

John Adams

Hi John,

You can not fit the bigger tanks in an Agg II, but we run ours 5 minutes with a 91 with the smaller tanks no problem, there just is not much fuel left when you land. Our Agg III and Mav have the bigger tanks, with those we get ready to land at 5 minutes rather than being on the ground at 5.

Steven

Yep, just plan on a 5 minute or so flight with a 91. With a little creativity, you may be able to fit 4-6 oz. worth of 'hoppers' in there... May get you a tight go arround.

(I still have an original Viper with a .91... very cool!)
You can stretch it a little longer if you fly more at reduced power.

David

I use the 2 sadle tanks and a 2 oz header. A standard pipe. with pipe preasure and have my timer set at 6 minutes and am comfortabel with another minute for loiter if I need to.
Sparky