Jenvey Heritage throttle bodies anyone?

Does anyone have this setup? Thinking about dual 45's, pros, cons? How complicated is install and setup? I understand costs are higher but, do they increase drive-ability,reliability, gas mileage, horsepower?

Also, block is at the machinist getting zero decked and cleaned up. Is the increase to +40 pistons worth the squeeze of a few more HP's? If so, what kind of increase can I look forward to?

Thanks

I've looked into the DCOE throttle bodies, I was sort of planning on Megasquirting the PV's motor. But it's a cheap old fun beater, the price just sort of sticker shocked me out of the idea each time. The DCOE's on it already work pretty damn well, but you can tell they're a bit messy and random in the fueling. Especially around corners, lol.

I think going +40 on the pistons is going to be fairly subliminal in terms of HP increase. What you can do is go to B21 pistons, you will notice an extra ~100 cc's. With no other mods it won't raise peak HP much, but it will increase low end torque an appreciable amount. Add some breathing mods to the motor (carbs/head/cam/exhaust) and the peak HP will go up too.

Thanks John!
So stock b21 pistons will fit and work well with my b20 block? Better than +40?

They're a direct fit for the later 8-bolt flywheel B20's. For the earlier 6-bolt B20's you need to do something non stock, because the dimensions of the rod changed on both ends.

IPD used to make some custom pistons, you could do something similar. Alternatively, what I've done with my engine is to have the small end brass bushing removed, then just a *tiny* bit of steel need to be removed and you can push the 24mm wrist pins into them with an interference fit.

Haha....and so begins the slippery slope.... again! I have an 8 bolt in my car now and I was considering rebuilding my 6 bolt because it's lighter and less rotational weight.

If you have good B20 pistons, use them. It's not a huge difference. But if you're buying new pistons, you might as well go to B21 size. It's about the same cost, worthwhile improvement.

Unless you're planning on running lots of boost, the cylinder walls are plenty thick for normally aspirated use, maybe not for boost.

I wasn't planning on buying pistons unless the advantages tipped the scales. But if the increases are that small....then why?

Not going to turbo so there's no boost. Unless there's something I'm missing with the throttle bodies.

It's roughly 7% more displacement - 2126 cc's vs 1986. You will notice 7%.

It's the 40 over pistons that won't really make any noticeable difference.

But can I use the b21 pistons with a 6 bolt crank? Also, the 8 bolt won't work in the 6 bolt block correct?

AFAIK the 8 bolt crank will not fit in the 6 bolt block, and the rods don't interchange, or the pistons.

The 8 bolt block was basically the B21 bottom end showing up a few years earlier than the OHC engine. The main and rod bearings changed in size, as did the wrist pin diameters.

But like I said, have a machine shop take the 22mm brass wrist pin bushings out of the 6 bolt rods, and then just a *tiny* bit of the steel, and the 24mm wrist pins that the 8-bolt B20 and B21/23 used will be an interference fit. It's not the stock design, but it's what millions of other engines do (instead of using little clips and letting it float).

FYI, you can bolt an 8 bolt crankshaft in place of 6 bolt without modifications as they use the same crankshaft bearings. You can even use the very early B21 crankshafts as they are the same as the early B20 8 bolt crankshafts.

But you do have to use 8 bolt rods and pistons.

Another FYI, IPD is now selling the 2130 8 bolt pistons again and they have the special big bore B20 head gasket too.

However the pistons are Mahle cast aluminum and therefore should not be revved consistently over 6000 rpm.

I sell B20 forged aluminum B20 6 bolt pistons with 22 mm wrist pins that are .075" or .100" over stock. The .100" over set brings the displacement to 2101 cc. I chose these sizes because you can still use a stock head gasket.

I have the forged piston sets and rings on our website, but our site is down for about a week while we transfer to another server.

Thanks Eric! How much for the set?

Cometic also sells 'big bore' MLS headgaskets. You know exactly what the installed height is with those since they don't compress at all.

Topic drift...

ITB's only work well at rpms well above anything used on the street. You need torque to get it moving.

A long runner intake with a large plenum and a single throttle body work the best for the street.

The big issue I have with ITB's is that it screws up the air flow in the port at WFO. The ideal port design should carefully squeeze and accelerate the air past the valve opening. A butterfly throttle can reduce airflow by as much as 20% @ WFO. Halfway down the port is not where you want to slow down the air in your port. All the energy is lost and the air has to start accelerating again after the butterfly. FAIL!

Another issue with ITB's is modulating the throttle, butterfly throttles have a large air inrush at low throttle angles. Combine this with X4 and the problem is compounded. This can be somewhat mitigated with arm angles, but that is a bandaid for something that should not be there. Combine this with no low RPM torque and you have a vehicle that is near impossible to delicately drive. Combine this with a clutch disc with no damper spring and the only way to get it moving is to spin the tires.

In the end this leaves ITB's as nothing more than a masterbatory aid.

ITB's

Thanks Dirty Rick!

Those are some really good points, and yes....the car is more street with some track days as opposed to the reverse. I thought I was building the motor once this past fall but unfortunately that is not the case. I want an aggressive street car with drivability and reliability that I can also drive to the track, rip around for the day and drive home.

Thanks

I don't know how DCOE's compare to ITB's, specifically DCOE style ITB's (same manifold and throttle placement), but the DCOE's are a freaking hoot to drive. I did play around with the linkage angles when I first installed them (lololol at my first attempt!) but it's pretty good now. It's just a very sharp and instant throttle response. so that can be somewhat hard to deal with. The old SU's always had a sort of muted response.

The engine is all suited to making higher PRM power - the cam, exhaust headers, etc all sort of works together to make it scream from 3500 rpm on up (7 - 7500ish). So while it has comparatively less low end torque, I'd be very surprised if it has less torque down low than a stock B20 does. It's just got less than it does when it all 'kicks in'.

For what I do with the PV that's perfectly fine and fun.

ITB's

Are the throttle bodies overkill for what I'm going to do? Does anyone have throttle bodies that can help me drink more Kool Aid or, any purist out there that can definitively talk me off the ledge?!

Thanks

I certainly wouldn't bother with those 'Jenvey Heritage' throttle bodies. Why pay extra so they look more like carbs? Either put carbs on it or put DCOE pattern throttle bodies. Just my cranky opinion, take it for what it's worth.

Overkill is a very subjective thing. I can say that the DCOE's are a bit cranky:
- in the cold - snort sneeze snort
- around corners - in hard corners mine go rich or lean. Go over a big bump and they'll spike rich. Driven hard on a twisty road and they will make some gasoline smells
- initial setup is finicky and requires lots of little spendy small machined bits in sets of 4

All stuff than an injection system would avoid. Plus if you've got MS or something running the engine, you can also have it run the ignition and be free of the vagaries of the old stock distributor advance curves.

71142volvo said:

Thanks Eric! How much for the set?

Click to expand...

$160.00 per piston which comes with the lightest tool steel wrist pins we could find and spiral locks.

The piston ring set is not included and costs $100.00 and has chrome moly top rings.

I only have a .100" over set of pistons and rings in stock.