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Old 09-27-2021, 02:16 PM   #1
blakemcelroy2000
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Default 6 Bolt B20 Forged internals?

Hey all.
I have a fully rebuilt B20 with an F head. Im starting to think about some future modifications to increase power to a pretty high level with a supercharger, megasquirt, variable timing, some head porting, and a new cam. Looking at the power and torque numbers Im hoping to make, Ive become concerned with the strength of internals. Ive heard multiple opinions, that all 8 bolt cranks and rods are cast and that 6 bolts are forged, or that only penta are forged, or that everything was cast. Anyone know for certain? If they are cast, should I get forged rods? Hoping to make around 300HP atc.
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Old 09-27-2021, 03:12 PM   #2
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IIRC cranks are all forged, rods and pistons are not until you get into turbo era cars, b21 forward there might have been some forged internals...

Ive been running stock rods in my B20 for the last 4 builds. 10psi, dropped a valve, 16psi popped the HG, 18psi blew ringlands off, 22psi blew ringlands off... At 22psi I was running mid 7s in the 1/8th. With a best of 7.2 on a prepped track and average of 7.6 on the unprepped air strip. so right in the neighborhood of 300 at the crank.

Probably should have opened the gaps up another 2 thou, maybe 4 thou. But oh well.

Forged pistons would be worth the money/effort, and if youre going to spend that kind of coin, a set of forged rods would be a great idea.
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Old 09-27-2021, 04:02 PM   #3
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Originally Posted by cwdodson88 View Post
IIRC cranks are all forged, rods and pistons are not until you get into turbo era cars, b21 forward there might have been some forged internals...

Ive been running stock rods in my B20 for the last 4 builds. 10psi, dropped a valve, 16psi popped the HG, 18psi blew ringlands off, 22psi blew ringlands off... At 22psi I was running mid 7s in the 1/8th. With a best of 7.2 on a prepped track and average of 7.6 on the unprepped air strip. so right in the neighborhood of 300 at the crank.

Probably should have opened the gaps up another 2 thou, maybe 4 thou. But oh well.

Forged pistons would be worth the money/effort, and if youre going to spend that kind of coin, a set of forged rods would be a great idea.
Was the ringland failure due to detonation from improper AF ratio? Or are the stock pistons simply not strong enough to survive the power. Are there stronger retainers to prevent dropping a valve? Looked at some rods and pistons on KG Trimning. Very pricey so Id hate to drop a valve on one.
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Old 09-27-2021, 04:12 PM   #4
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Was the ringland failure due to detonation from improper AF ratio? Or are the stock pistons simply not strong enough to survive the power. Are there stronger retainers to prevent dropping a valve? Looked at some rods and pistons on KG Trimning. Very pricey so Id hate to drop a valve on one.
ringlands were both due to insufficient end gap. The last set probably just barely butted, but at 7k for a lengthy auto-x course, it was bound to break something.

The dropped valves were stock springs/keepers/retainers.

The last ones I burnt the seat/edge of the exhaust valves, but only on holes that had failed ringlands, so who knows, chicken or egg.. but the ring ends were clean, so my guess is heat/expansion pushed it too far.

AFR's are stable in boost 12.1 ish, had been in the 11's, but didnt make the power. Ignition timing could be optimized, but its fairly conservative at the moment. No sign of detonation, and all my spark tuning as been with a set of DET cans, havent heard any noises.

I'm building it again this winter with some forged slugs, a set of forged H-beams, and plan to run 25-27psi on pump gas with progressive 100-400cc/min water meth above 20psi.

The car went through about 40 1/8th mile passes in one day, then another 15 the following weekend with no smoke, no issues, great in boost. So I decided to try the auto-x course, and it sucked. My gearing was way too long for it. So in order to maintain any speed on corner exit, I was in first gear for the majority of the course, and on the limiter way too long.
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Old 09-27-2021, 04:23 PM   #5
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ringlands were both due to insufficient end gap. The last set probably just barely butted, but at 7k for a lengthy auto-x course, it was bound to break something.

The dropped valves were stock springs/keepers/retainers.

The last ones I burnt the seat/edge of the exhaust valves, but only on holes that had failed ringlands, so who knows, chicken or egg.. but the ring ends were clean, so my guess is heat/expansion pushed it too far.

AFR's are stable in boost 12.1 ish, had been in the 11's, but didnt make the power. Ignition timing could be optimized, but its fairly conservative at the moment. No sign of detonation, and all my spark tuning as been with a set of DET cans, havent heard any noises.

I'm building it again this winter with some forged slugs, a set of forged H-beams, and plan to run 25-27psi on pump gas with progressive 100-400cc/min water meth above 20psi.

The car went through about 40 1/8th mile passes in one day, then another 15 the following weekend with no smoke, no issues, great in boost. So I decided to try the auto-x course, and it sucked. My gearing was way too long for it. So in order to maintain any speed on corner exit, I was in first gear for the majority of the course, and on the limiter way too long.
What cam are you running? Ive been trying to find one with very little overlap without any luck. Also, not looking to run the a lot past 6000, so Im trying to not have to modify the head to run double springs, but preferably find some stronger ones with better keepers that would take a potentially higher lift cam.
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Old 09-27-2021, 04:30 PM   #6
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What cam are you running? Ive been trying to find one with very little overlap without any luck. Also, not looking to run the a lot past 6000, so Im trying to not have to modify the head to run double springs, but preferably find some stronger ones with better keepers that would take a potentially higher lift cam.
I've also tried to find a lower overlap OHV cam and have come up short. As you go higher in lift your duration gets a lot longer. The higher LSA and lower overlap cams with higher lift seem to have come about with the OHC cars.

Your B20F should already have a stock D or K cam. Those are already pretty good as far as the factory stuff goes.
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Old 09-27-2021, 04:37 PM   #7
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What cam are you running? Ive been trying to find one with very little overlap without any luck. Also, not looking to run the a lot past 6000, so Im trying to not have to modify the head to run double springs, but preferably find some stronger ones with better keepers that would take a potentially higher lift cam.
I'm running a k cam, similar to a D, its probably one of the lowest overlap stock cams.

The last build I ran iPD doubles and steel retainers, stock valves. Good setup, but something took out the seats. Could have been the porting.... maybe nicked the valve grind. or could have been caused by burning oil.

This next build, I might have Schneider run me a custom cam. Not sure yet. But if I do it'll probably be a 274/240 on 116* lobe centers.

I want to say the k is 264/225 on 112* centers... but I cant remember anymore.
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Old 09-27-2021, 04:49 PM   #8
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Don’t do that. Tight squish, cool burn, crank boost. Less chance of building up hot spots, and running into detonation issues.

I’d run it 0 deck, with a cometic.036”.

I’m running like 9.2:1. Higher compression isn’t exactly the killer of a boosted engine
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Old 09-27-2021, 04:53 PM   #9
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Originally Posted by cwdodson88 View Post
Don’t do that. Tight squish, cool burn, crank boost. Less chance of building up hot spots, and running into detonation issues.

I’d run it 0 deck, with a cometic.036”.

I’m running like 9.2:1. Higher compression isn’t exactly the killer of a boosted engine
You're able to run 22psi at 9.2:1 static CR?! Do you have to run race gas or a huge intercooler? Or is it just timing retard with boost?
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Old 09-27-2021, 05:09 PM   #10
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You're able to run 22psi at 9.2:1 static CR?! Do you have to run race gas or a huge intercooler? Or is it just timing retard with boost?
I'm on an MS2 EMS with ls-coil on plug, so spark is controlled, and yes, slightly retarded in boost.

Not exactly a huge intercooler. It was 10x12x2.5 in a V mounted setup. intake temps were typically within 50*f of ambient during 1/8th mile pulls, and within 80f of ambient at my last auto-x.

The new setup is running an air to liquid IC, and should hopefully keep me at within the 50* of ambient. And a bit of water meth just in case.

These were all on 92 pump gas.

I'll probably end up running some 1850cc injectors this next go around, maybe some 2150's so that I can run e85 and crank up the boost even more. I was thinking that 30-35 on e85 would be fun.

edit: grabbed my specs. Bore 3.538 X Stroke 3.15 X HG .036 X Chamber CC: 58... So its like 9.3 ish.

Last edited by cwdodson88; 09-27-2021 at 05:16 PM..
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Old 09-27-2021, 08:07 PM   #11
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I'm on an MS2 EMS with ls-coil on plug, so spark is controlled, and yes, slightly retarded in boost.

Not exactly a huge intercooler. It was 10x12x2.5 in a V mounted setup. intake temps were typically within 50*f of ambient during 1/8th mile pulls, and within 80f of ambient at my last auto-x.

The new setup is running an air to liquid IC, and should hopefully keep me at within the 50* of ambient. And a bit of water meth just in case.

These were all on 92 pump gas.

I'll probably end up running some 1850cc injectors this next go around, maybe some 2150's so that I can run e85 and crank up the boost even more. I was thinking that 30-35 on e85 would be fun.

edit: grabbed my specs. Bore 3.538 X Stroke 3.15 X HG .036 X Chamber CC: 58... So its like 9.3 ish.
V mount in a 122? Or are you driving an P1800? Also, where do do your source your injectors? Looks like finding new stock Bosch Djet injectors is pretty expensive. Any other vehicles injectors work? Thanks for all the valuable info.
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Old 09-30-2021, 11:57 AM   #12
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V mount in a 122? Or are you driving an P1800? Also, where do do your source your injectors? Looks like finding new stock Bosch Djet injectors is pretty expensive. Any other vehicles injectors work? Thanks for all the valuable info.
Beck/Arnley 158-0438 injectors are an exact fit with matching flow rate for the Bosch 036 injectors on the D jet equipped cars. Flow rate is about 550 ml/min @ 43.5 psi. Rock Auto still lists them for about $50 each.
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Old 09-27-2021, 09:39 PM   #13
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Yep, v mount in a 122. The current set are 1000cc dekas. I’m running k-jet holders instead of d-jet. They have a tapped boss that I used to mount a custom fuel rail to. I’ll see if I can post something that shows the last setup and the current setup.
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Old 09-27-2021, 09:44 PM   #14
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Here’s some pics of the newest setup. Awic and a Borg Warner efr7163.
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Old 09-27-2021, 10:41 PM   #15
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Here’s some pics of the newest setup. Awic and a Borg Warner efr7163.
Wow!! Almost didn't see the b20 under all that!! I didn't realize you were running an Air to Water setup.
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Old 09-27-2021, 10:44 PM   #16
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It’s a b20 for sure… I’ll try to find the pics of the V mount.
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Old 09-28-2021, 02:49 AM   #17
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All B20 or B18 rods and cranks are forged and plenty strong for whatever you are able to throw at them.
It simply does not exist cast cranks or rods for these engines.
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Old 09-28-2021, 03:45 PM   #18
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All B20 or B18 rods and cranks are forged and plenty strong for whatever you are able to throw at them.
It simply does not exist cast cranks or rods for these engines.
You think they would take around 300HP? Ive seen one B20 block with a hole in the side of Cylinder 3, so I really don't want that or a lump under the hood if I run up the boost.
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Old 09-28-2021, 10:28 AM   #19
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And I stand corrected. They are forged rods. But there are differences between B18, Early B20, and Late B20. So take that into account. Also, B21 rods will fit. And I believe this was what Jens Gustafsson was running in his 500 whp B20.

http://forums.turbobricks.com/showthread.php?t=83476
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Old 09-28-2021, 03:42 PM   #20
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And I stand corrected. They are forged rods. But there are differences between B18, Early B20, and Late B20. So take that into account. Also, B21 rods will fit. And I believe this was what Jens Gustafsson was running in his 500 whp B20.

http://forums.turbobricks.com/showthread.php?t=83476
Don't B21 rods use the larger diameter wrist pin? So you'd need custom pistons to fit the bore of a B20? Im not really interested in getting my engine bored out to fit B21 pistons.
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Old 09-28-2021, 11:05 AM   #21
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I ran 'lightweight' B18 rods in my PV's motor (not boosted, about 160 - 170 HP) for a long while. When I had it apart to replace a cracked piston, I noticed odd wear marks on the rod bearings, right where they have the thinnest metal on the big ends - right where that red arrow is pointing in the last picture. /\ /\ /\
Not a whole lot of wear since the motor had been built, but it had shiny spots right there, seemed clear that the rod big ends were flexing there under stress.

Of course, the B18 rods themselves never caused any issues, but I put it back together with slightly heavier set of B20E rods.
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Old 09-28-2021, 11:47 AM   #22
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Here’s the best pic I have at the moment of the old v mount setup. And then the front mount that followed it… this thing has been through so many renditions…
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Old 09-28-2021, 02:49 PM   #23
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Rods from 74-80 B20/B21 are forged, but the material was not that good for high rpm engines. Better rods were introduced 80/81. There is cast "M" letter on big end.
These goes together with 8-bolt crank.

"Best" rods for 6-bolt crank were early (69-70) B20 rods. Those had long number in the beam.
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Old 09-28-2021, 03:43 PM   #24
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Rods from 74-80 B20/B21 are forged, but the material was not that good for high rpm engines. Better rods were introduced 80/81. There is cast "M" letter on big end.
These goes together with 8-bolt crank.

"Best" rods for 6-bolt crank were early (69-70) B20 rods. Those had long number in the beam.
Like a number stamped into the rod surface? Ill look when I take my oil pan off to replace a gasket if I have those.
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Old 09-28-2021, 04:41 PM   #25
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Like a number stamped into the rod surface? Ill look when I take my oil pan off to replace a gasket if I have those.
http://www.savarturbo.se/?sida=conte...ndelen&sidnr=1

Check those pictures.
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