best approach to a rebuild/mild upgrade for a Late bay

[wizrod]

Hi all,

I have a '75 bay with its original T1 1600 motor, which I think would, sooner or later, benefit from a complete strip & rebuild - its 40 years old after all.

I'd like to take this opportunity to perhaps give it a bit of an upgrade. I'm not looking for an all-out fantasy race motor, just a little more grunt to make passing & hills a little less of a challenge, while retaining reasonable gas mileage & good reliability.

I'd like to spend up to somewhere around $750 on this (or less) - I intend to do the majority of the work myself - only outsourcing any precision machining.

I also have the following that could potentially be used:

• A low mileage 1700 T4 motor

• A set of 87mm Bs&Ps (1641cc T1 upgrade )

• A pair of 36IDF carbs jetted for a 1915cc motor

• A s/s big-bore 4->1 collect & mufler for a T1 (I forget how big, but originally used with the 1915cc motor)

• A fair amount of assorted T1 spares

What would be my best approach to achieve my stated aims, within my approximate budget? The following are some options that came initially to mind:

• 1 (On the assumption that fitting the T4 motor, as is, wouldn't give much of a boost in performance...) upgrade the T4 to 1911cc, but retaining the stock carbs & exhaust

• --- would need new Bs&Ps to be bought and heads machined to accept them...nothing else?

• --- Apart from the machining, I assume this would be a simple bolt-on upgrade...?

• 2 as above, but adding the 36IDFs but retaining the stock exhaust

• --- as above but would additionally need T4->IDF manifolds & linkage

• --- would it be reasonable to expect the jetting to be about the same?

• 3 as above, but adding a 'performance' the exhaust

• --- as above but would additionally need a new exhaust

• 4 upgrading the (existing) T1 to 1641cc, but retaining the stock carb & exhaust

• --- NO COST - already have the parts

• --- an extra 56cc probably won't so much on its own!

• 5 as above, but adding the 36IDFs (re jetted appropriately) and the big-bore exhaust

• --- NO COST - already have the parts.

• --- I'd have thought this would be well over carbed..?

• 6 as above but also splitting the case and fitting a 74mm crank/8-dowl flywheel combo

• --- would just need the crank and flywheel to be bought (and dynamically balanced?..not intending to do big RPMs)

• --- I've suggest a 74mm crank here, to minimise the case clearancing needed...also, would a longer stroke be worthwhile with an 87mm bore?

• 7 as above, but adding an aftermarket cam to match the other upgrades

• --- just the cost of the cam (something like a C25...?)

• 8 ...other?(TBH, I can think of a bunch of other options...this list is perhaps just the simplest to actually implement...?)

• 9 Or even do nothing...if achieving the stated goals in not feasible within the stated budget?

Options 4 or 5 would of course be the cheapest but, would one or other of the T4-based options be a 'better' approach with regard to the stated goals. I don't think there would be much of a price difference between 1 & 6 or 2 & 7?

I'd appreciate the forum's thoughts on this.

Thanks in advance

cheers

Paul

[Piledriver]

Z: Put the 36 idfs on the 1700 and drive it.
New exhaust valves and valve job + decent exhaust.
Will walk all over the 1641.

A T1 in a Bay bus is likely to need align bored etc as well.

[wizrod]

Fair enough. Always prefer a simple solution.
TY.
P.

[helowrench]

my $.02
take the 1.7L, add 94mm pistons and cylinders to bring it up in displacement, then add a good cam.
use the IDFs on it.

[Piledriver]

In a Bay Bus I'd personally prefer to keep the bore at 90mm or 90.5.
I'd look for a set of reman style 90.5s (REPCO etc) before going AA.

Mahle 90.5 "A" pistons are just about the right pin height, but the rods would need bushed smaller.
(install in slightly overbored stock 1700 jugs)
May get away with just a rering?


The 1.7s had few head seal issues due to far more meat in the heads.
93mm is 1800 cc, but you have to open the heads up to 105mm or cut the top OD of the jugs down to 100mm.
More to lose than gain there.

He's had a 1600 DP in it, so the gearing will be kinda short, so the 1.7 will be in its element.

The effect of vehicle weight/drag etc is also a consideration, if I was going to run it on the highway in the USA I'd avoid 96s in a Bus.
(also require cutting the heads and thinner wall)

[wizrod]

Thanks for your input...
So the general consensus seems to be to use the T4 motor after increasing the bore (but not by too much?) and running it with the IDFs..?

[Marc]

Don't forget that you'll need to replace the transmission input shaft with the longer version in order to use the Type IV engine. Not difficult, you'll need a bellhousing gasket and I strongly suggest a new snapring.

Thin cylinderwalls are a real bad idea on a heavy vehicle, so if you go with the Type I motor forget about using the 87s. For that matter, 94s are only ~.007" thicker. 90.5s have the thinnest walls I'd use for a Type I baywindow motor; AA makes thickwall 92s and 88s which would be much better choices. The 88s don't require any machining to the case (just the heads). I used to run a 1679 Type I in my `73 (with a mild Bugpack 4061 cam, 7:0 CR, 34PICT-3 and 1½" "street" header) and its performance was comparable to the stock dual-carb 1700 it replaced.

The Type IV with 36IDFs remains the most expedient solution for you - if it's low-miles and not in need of rings, I wouldn't even bother to up its displacement.

But, if I was going to build the Type I I'd be inclined towards a thickwall 1835, which'd be big enough to make good use of the IDFs and still have decent longevity. Rather than open the case all the way up to the "94" register, I'd cut it to 90.5/92 size and turn the barrel spigots down to leave more meat in the case. Keep the C.R. and cam conservative (like, 7½:1/Engle W-100 conservative) - it is a Bus, and low-end grunt makes for a much more enjoyable driving experience.

[Piledriver]

What transmission is in your van?
What vehicle is the 1700 out of?
Reason I ask is the flywheel/input shaft setup varies, and we are not sure where you are.

We are somewhat at a disadvantage as we are only familiar with the North American versions, elsewhere VW had a variety of engine trans combos not seen here, the Brazilian busses were swing axle with redux boxes until the end of the line, so T1 trans.

If the 1700 is out of a 914 or 411/412, it has ~8:1 CR and is good for ~90HP with the IDFs, with no cam upgrade etc.
The T4 has about a 30% cooling capacity advantage, so that will probably work great in a bus, particularly with a mild cam and good exhaust.

If out of a Bus, ~7.3:1 CR w/dished pistons and ~70 HP, ditch the head gaskets when you freshen the heads and put ~.020" cylinder base spacers/gaskets in to regain the deck to a reasonable level around .045". This will improve the head seal and be worth a few HP while running cooler.

If the engine/flywheel is from a 914, the flywheel is slightly different, it also has the input shaft bearing in the flywheel already, so will work on the t1-ready trans.

Other T4 flywheels can have the input shaft bearing installed in the flywheel in a similar fashion, eliminating the need for a new input shaft.

The 914 ring gear on the flywheel is extra deep, will actually clear and work fine on a late 091 bell housing, but it may need to be turned back a few mm to clear YOUR bell housing, depending on the trans. Only way to know is try.

The 914 flywheel requires the matching 914-specific pressure plate, but it will also work fine with the std TO bearing setup.
(The difference is mostly 3 dowel pins for alignment of FW and PP on the Porsche setup)

[Marc]

To hang the Type IV you'll also need the crossbar and the end bracketry (fortunately the brackets are a simple bolt-in swap) - I think any `72-up Bay's parts will fit...throttle cable's different, too, but for the IDFs your present Type I cable will probably work.

[wizrod]

Thanks again for the additional replies...to answer the questions...
The 'box is a 3 rib IRS and assuming its original, whatever gearing that was standard for the middle eastern market in 1975 (It was originally delivered to Oman, before coming to the UK).
The T4 is an ex-mulitary static engine, originally used to power a field generator or pump. It has a magneto and a 24v alternator. As such, I would not expect it to have been thrashed to the limit and certainly not under the kind of load a full T2 or T25 would give. No idea off the top of my head about the current flywheel.

My plan has been to get it up and running as it is, on a stand, to confirm it does run and then to consider any appropriate upgrades.

I definately appreciate the need to keep the barrel wall thickness up and agree with the need for torque over powed.

If that can be achieved with a minimum of machine work...so much the better.

Thanks again

P.

[Tony Z]

Rebuild the 1600 with a counterwighted crank and Engle 100.
Keep everything else stock.
up the CR to 8.3:1
use the 87mm pistons if you have to, but rather source new 85.5 piston kit
run with the 36IDFs.
Get a cheapy exhaust like an EMPI 4-1 in 1 3/8" size.
Simple, easy and you will never look back.

[craigvwdude]

I've never heard of a late bay come with a type 1 engine??
It should have came with a type 4 engine.

[Piledriver]

I've never heard of a late bay come with a type 1 engine??
It should have came with a type 4 engine.

~Everywhere but USA it was an option.
There was even a mutant CZ 1600DP motor that was T1 but the fan/housing setup looked like T4.
(not sure where those were sold other than Europe)

The last of the Bays had a water cooled 5 banger lying on its side driving through a swing axle (with redux boxes?) to the very end of production in Brazil in December, 2013.(only ~a year and a half or so ago)

The Vanagon was available with a similar 5 banger setup in S.A. too, at least as far as the engine went, I think it was more a road going beast, but the Vanagon suspension is pretty beefy in any case.

Ruggedness and ground clearance beat out handling where the word "road" often means something the off road guys would probably prefer to go around...
We didn't see those models either.

[craigvwdude]

learn something new every day!