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Penta Faq

Rod / Piston interchange
the AQ151 and AQ171 use the same 152MM long conn rods as the B230 engine, and use a 3MM shorter compression height (wrist pin to piston crown) to compensate for the longer stroke.
 
Is that reply a mistake? My question is sorta, well the increased stroke increases the output, but it is compensated for. Is it possible to not compensate for it and increase the output even more? Sorry we can just delete this if it's stupid questions, haha. Maybe you are still composing your answer, since I quoted what you said. Guess it goes to show I don't understand it.
 
Right, so there isn't a way to use a thicker gasket, or a spacer in a different spot? What about a shorter piston? Guess that would be the same thing as before. We can just delete all this, haha.

Well I guess a thicker gasket wouldn't make any difference, but maybe you could add a weld in a machined plate to the bottom of the block so the cylinder sat up higher. Well I guess this isn't done and isn't feasible. Guess I have a firmer understanding now anyway.
 
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I am not an engine builder and it took me a while to figure out some of the internal dimensions. As I understand, the 86 mm crank adds 6 mm stroke, but this can be compensated for by 3 mm shorter rods and stock pistons, pistons with the pin located 3 mm higher, or pistons that are 3mm shorter (i.e, with 3 mm taken off the top). These measurements have to be only 3 mm less, not the 6 mm of the longer stroke, because the internals are reciprocating -- they go up and down so the three mm you take off will change the dimensions at the top and at the bottom and add up to 6 mm.

You are asking about stroking the crank further. This is possible. Dave Barton's motor is apparently over 2.6L, and is done by increasing the stroke to about 88 mm (I am guessing - I have not done the math, which is complicated; I don't have a chart sort of like a mileage map with bore and stroke and number of cylinders). There have been posts here about 88 and 89 mm cranks -- TB members have had stock 80 mm B21/23 cranks altered. I have not read of anyone changing the stroke on a cast B230 crank and I don't know whether the fact that it is case makes a difference or not. Increasing the stroke is typically done in two ways -- either the crank is enlarged by welding on more metal to the journals (offset welding) and then that new metal is machined into a journal or the stock journals are downsized and different rods are fitted to match the smaller journal size. This sort fo work can be expensive. You will no longer be working with stock dimensions, so building the motor can be more challenging. To compensate for the extra stroke, you need either or both custom (or different) rods and pistons. These mods are usually also expensive. There is a limit to how much you can stroke the crank. At some point, the edges of the big end of the rod that are attached to the crank journals will hit the edge of the block. The block can be clearanced a little. Perhaps someone knows the biggest displacement that has been developed from a stock B21/23/230. I'll guess 2.8L.

I plan to consider these issues when I do my Penta AQ171 turbo. I have to decide whether it is better to spend extra money on increasing displacement from 2.5 to 2.6 or 2.7L or whether I should spend the money on mildly reworking the head. I'll guess that I'd be happier with the head work. If money is no object, do it all. If you plan to buy custom rods and pistons anyway, then offset welding and grinding the crank do not add as much expense. I have Penta AQ171 pistons and I have late B230 rods and have to decide whether to use these stock parts or spend the big bucks for aftermarket parts. I'll probably wait to see what others do since I don't need to start this project right away.

Philip Bradley
 
Ok, well I thought I understood something, haha. I thought that the increased stroke of 3mm on the bottom added up to .2L to go from 2.3L to 2.5L, and that 3mm was taken off the top to keep it in the cylinder bore. I understand reciprocating and 3 on top and 3 on bottom and all. Have an overall grasp, but one thing I don't get. 86mm stroker crank, and 3mm is taken off the top, reciprocated means 6mm is taken off total. Ok, if so, why aren't you still at 2.3L? Not a big deal, but sounds strange to take the extra stroke back off, so I'm confused there, haha.

Also yah, sounds like your talking about taking more off at the bottom to further stroke the crank. Guess what I was thinking was if you could get a taller block, say from the guy that does the aluminum ones, so that you could use the longer rods n taller pistons so that the stroke was as long as possible. New sleeves and machined, welded block extension? haha, don't pay attention to me. My brother used to get so mad at me because I had no engine knowledge and asked stupid questions. Common sense in these things is based on experience!
 
Ok, I just realized that the issue is how far the piston goes all the way down and back up, the stroke, and the piston still needs to rise to the same place in the cylinder, but it will drop down further with longer stroke. So you gotta shorten the parts at TDC. Think I got a handle on it now, maybe, thanks to the other engine geometry discussion enlightening me a bit.
 
Cool PDFs on these engines someone posted. Important to remember to search for 250a engines too, because I guess they are the same?


Hmm now what was the high performance motor someone talked about that was 250 or 251, seems like the 251 is just alternate naming convention for a AQ171. So there isn't a beefy 2.5L penta after all. The 251 is just considered high performance because it is DOHC.

So we made any progress on the differences in the model year/letter designations? AQ151A, AQ151B, etc? Seems like from what some have said that the differences are in bearings n stuff, and not in the crank, rods, cams, pistons, etc. Basically the blocks, but not the upgrade parts you want to scrounge from them? I guess ideal would be to rob a AQ engine and put the parts in a squirter car engine.



Feel free to delete my posts in this thread that are extraneous or whatever.
 
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Penta setup

Saw this on Sten Parner website! Anyone translate. Wonder if it is all forged.

http://www.stenparnermotor.se/default.aspx?NodeId=86

vevset2%20(WinCE).jpg


B 230 2,5 Liter Turbo
Marinvevaxel 55mm ram H-profil vevstakar-Smidda venolia kolvar 96,3mm 18700:- med moms
63mm ram + 3000:-
B230 2,5 Liters sug. motor:
Marinvevaxel 55mm ram H-profil vevstakar-smidda venolia kolvar 97mm- block-lager-monterat: 22500:- med moms. 63mm ram + 3000:-

St?lvevaxlar"Billet" h?gsta kvalite Pris 14800:- Se sida vevaxlar
 
B 230 2,5 Liter Turbo engine:

Marine crank 55mm main bearings H-profile connecting rods - Forged Venolia pistons 96,3mm 18700:- incl. VAT
63mm main bearings + 3000:-

B230 2,5 Liters N/A engine:

Marine crank 55mm main bearings H-profile connecting rods - forged Venolia pistons 97mm- block-bearings-mounted: 22500:- incl. VAT
63mm main bearings+ 3000:-

Steel cranks "Billet" highest quality (Doug Kiddie) Price 14800:- Look under cranks

<TABLE class=tborder cellSpacing=0 cellPadding=6 width="100%" align=center border=0><TBODY><TR vAlign=top><TD class=alt1>Yes its a comlete set of the forged Penta 86 mm stroke crank, with forged H-profile piston rods and forged Venolia pistons. Price is 18 700 SEK for the early model b-230 (55 mm mainbearings) and aditional 3000 SEK for the late model (63 MM main bearings).

He also says he has 86 mm stroke "Billet" cranks for 14 800 each if you need something even better.

1 US$= 6,86 SEK
1? = 9,20 SEK
<!-- / message --></TD></TR><TR><TD class=alt2>

<HR style="COLOR: #999999" SIZE=1> <!-- / icon and title --><!-- message -->

Very nice! Especially after dollar comes back up, and you can take back off 25 percent for the VAT I think? n put it towards shipping I guess.
</TD><TD class=alt1 align=right><!-- controls --></TD></TR></TBODY></TABLE>
 
Any speculation on how many HP an engine built with one of these all forged kits could hold up to before breaking? I'm assuming at this point the block itself would become the weak point.

Lets say assume a 16v head and a 93+ block.

Would also be interested to know if sten sell's these forged heads machined out for 16v clearance.
 
Yes, I would say something else would be the limitation for sure. As long as you don't run a lot of detonation. We have heard of 800hp 8v and 1100hp 16v, and that may not have been with all forged parts.


So what engine parts would be weak with those parts? Not much left to upgrade? Balance and blueprint block? I got no idea. Seems like all moving parts are covered??
 
People talk about offset grinding the cranks. Any idea what the limits would be for a factory crank to be offset? Factory b230 is a cast crank correct? Would that make it unsuitable? Seems maybe cheaper than scrounging AQ parts. Especially if it would work and forged custom rods n pistons could be ordered.
 
Nice work on the write up. (very cool)

I was just wondering if anyone could answer my questions???

1. To buy some penta cam shafts for my 16v engine what would it cost (avg)

2. Can I just buy the cam shafts and put them in my car

3. is the power gain worth the money

And any added information would be much appreciated

Thanks

David
 
a offset penta unit would be strongest, along with being a more stable. that is because offset grinding changes the centerline, moving it further from where it was designed from.
i'll add the main diff's.
for pz reviews click here
pz's are hard to come by, very, very hard.
pz's are a drop in
*EDIT*
all info, plus some now in orig post.
 
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davidmacq said:
Saw this on Sten Parner website! Anyone translate. Wonder if it is all forged.

http://www.stenparnermotor.se/default.aspx?NodeId=86

vevset2%20(WinCE).jpg


B 230 2,5 Liter Turbo
Marinvevaxel 55mm ram H-profil vevstakar-Smidda venolia kolvar 96,3mm 18700:- med moms
63mm ram + 3000:-
B230 2,5 Liters sug. motor:
Marinvevaxel 55mm ram H-profil vevstakar-smidda venolia kolvar 97mm- block-lager-monterat: 22500:- med moms. 63mm ram + 3000:-

St?lvevaxlar"Billet" h?gsta kvalite Pris 14800:- Se sida vevaxlar
mmmmm god they are sexy! dave dave dave...i want for my engine....!!! hmmmm penta cranks on its way, might as well do it proper, lol drooooool. Ill shut up now
Griz
 
Yes, I want that too. I think you really gotta get the pistons, and might as well the rods too. So the penta crank conversion will be proper. They say stock B230FT or AQ151 rods, pistons don't add up in a correct combination... If you want to get around the VAT you can ship the stuff to me!! :D
 
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