Used Engine Block Options

[S2Jay]

Considering sourcing a used Block to rebuild for the S2, while keeping the original engine bagged. It has 42k original miles [although this cannot be documented, I believe it correct, since the car came to me in 1984 with what appeared to be 26k orig miles].
Following is a list of Blocks now available from a noted Lotus prep, racing & engine shop.
I do not have any pricing for any of these as yet, and some may be out of my budget [well, all could be out of budget for all I know], but I am very interested in any opinions on what would be a good choice for an S2, mostly road car for spirited driving, mountain roads, etc, with a possible track day or 2 in its future.

List of Blocks available
Lotus “L” Block 6015
Bored & Honed to 84.25mm
Pressure Tested & Crack Tested
Tall 701M Main Caps [aka “Square” caps?]
Liners in # 2 & 3 cylinders From a Strong Running FB car

120E Block
Finish Honed to 83.50 mm
Tall 701 M Main Caps

Lotus “L” Block
Bored to 84 mm, needs final Hone
Steel Caps
Polished Inside From a Strong Running FB car

120E Block, 2731-6015
82mm, needs to be bored
Round Main Caps From a Good Running 1500 Pushrod Engine

701M Block [416 B]
Finished Honed to 84mm
Liner in #2 Cylinder
History Unknown

[rgh0]

I would go for the 120E block at 83.5mm and square main caps assuming the work on it has been done right.

84+ mm bores and liners is pushing the boundaries in my opinion unless you have been lucky with casting thickness and offset bored it well

cheers
Rohan

[2cams70]

I'd go for the 2731 block and fit with square main caps. It is the one with the smallest bore. It's best to buy the pistons first and have the block bored and honed to suit rather than buying a block already bored and honed to size and then hoping any pistons you buy will suit.

[rgh0]

I'd go for the 2731 block and fit with square main caps. It is the one with the smallest bore. It's best to buy the pistons first and have the block bored and honed to suit rather than buying a block already bored and honed to size and then hoping any pistons you buy will suit.

As I said buying the bored and square cap block depends on it being done right, The 82mm round cap block will cost a fair bit to bore and hone the cylinders and line bore square caps if you also want those which is what I would want. Really depends on the individual blocks wall thickness details and details of any work done on then and the price they want for each

I agree desirable to buy pistons first and then bore and hone a block but if you have a completed 83.5 mm block then you can get pistons to suit this, if thats the bore you want.

cheers
Rohan

[S2Jay]

Thanks much to all for the advice & suggestions.
I had already sourced a set of Square Caps, so I could use those with the 120E / 2731 block, then of course add the machining cost.
If I go with that 120E - 2731, then I may end up with a spare set of square caps to sell back into the market.

I did expect to order pistons made to fit whatever bore the Block needed after boring.
I also expect to use the 3.060 stroker crank I have acquired.

Here is some further info just received about the 120 / 83.50 bored Block:

"It has fresh bores actually at 83.65mm making 1600cc [with the “stock” crank].
The bores are spot on size. This is quite a common size now as many blocks are worn at 83.5mm

The top deck face has also been milled clean [no word on deck height, suggesting it remains close to original, and of course this would be confirmed before purchase & ordering pistons].
Water jacket looks really good and rot free.
Main caps are the late type and the bore is .015” as you would expect [suggesting that it has been align bored, and again to be confirmed].

It does need jackshaft bearings - well the front two as we generally block off the rear.
The jackshaft bores are slightly oversized, I have seen this on a number of blocks and struggled to find the oversized bearings.. so it may be a case of turning up a couple from alloy tube."[/size]

Pictures were then forwarded which appear to confirm what he described. As a side note, this is a shop in which I do trust, and has a great reputation.

Is the Jackshaft bore an issue, or is it a relatively common item to just have a shop “turn up a couple from alloy tube” at some “reasonable” cost?


The 2731 block does need some additional machine work that has already been done on the 120 block, so it is likely that pricing & final cost will be similar.
I do understand the advantage of the 82mm bore, but there is additional cost needed to bore, hone & deck that block.
I do have a set of square main caps.

Assuming I use the 3.060 stroker crank previously sourced, then this would make a 1708 cc engine.

Pricing for the 83.65mm block seems reasonable, although I have not yet seen a price for the other 120 block. It is beginning to appear that this will be within my limited budget. Any further comments & opinions gratefully appreciated.

[seniorchristo]

I had intended to add square main caps to the block of my recent engine rebuild. My engine builder (Quicksilver Race Engines) convinced me that for fast road only the center main cap needed replacing and he was able to line hone it. Other than the center caps breaking, I think he said he has seen only one round main cap break.
Chris

[S2Jay]

seniorchristo
Thanks for that background info from your builder. This does seem to be more of a concern for the all-out race engine guys, but “better safe…” as they say & doing a rebuild is the time to do any upgrades. The proposed block already has the upgraded caps & I had secured a set also.
Even if I end up with an engine capable of “safely” doing 7k rpm, it is unlikely I will ever go there [intentionally].I do feel better about [possibly] eliminating / reducing one more possible concern, it is a different issue when you are the one paying the bills!
And this is just a “street” engine after all & not intended to win any races [and certainly not w/me @ the wheel]. I do hope to put “a lot” of miles on this thing, but that does become relative at this age.

I did forget to add a few of the pix I did get of this block.

[2cams70]

If you are buying the block pre-bored and honed make sure you have pistons sized to fit. We are talking tight tolerances here. Back in the day production pistons were selectively fitted to bores. It’s better now with accurate Cnc machining but you still can’t assume pistons sized nominally from one manufacturer will be the same as another. At 82mm you’ll have at least another rebore possible 83.5mm maybe none, 84mm definitely none.

[S2Jay]

2cams70, Thanks for the cautionary.
I was expecting, and now must, have pistons custom made to the block [possibly JE, but open to other suggestions]. I am considering sourcing a used block such as this in order to “save” the original block, which I believe has 43K orig miles on it.
Perhaps a waste, but to machine my current block would cost at least as much as this block. At this age, I don’t really expect to put enough miles on the thing to need another rebuild, the only purpose of bagging the orig block/engine is to [possibly] increase the value of the car as a “package” to some future collector. I have no intention of ever selling this car, but it is possible that it will be of some greater value to my wife, who is likely to outlive me by several decades.
More difficult, I expect will be to locate a used/rebuildable T/C head to port for this project. I imagine there are heads available in various conditions, but are very likely out of my budget range from what I have heard about T/C head values. I don’t really want to attempt to port the “original” head from this car, but I do want to have a bit of fun while I can still enjoy the drive.

Speaking of tolerances, would I be expecting about 0.004” piston-to-wall for forged aluminum pistons in a “fast road”, stroker engine with about 10:5 c.r. & 420 cams?

[2cams70]

Forged pistons can run tighter clearances these days compared to old times due to new alloys of aluminium. You shouldn’t guess. The piston manufacturer will advise what the clearance should be.

[seniorchristo]

S2Jay
If you are in the US I would recommend Tony Ingram for pistons, parts and other technical info
Chris

[S2Jay]

Thank you again, 2cams70 for the clearance advice. I have been out of the loop for too long, and technology has again managed to move along nicely without me. I will refer to recommendations from the piston mfr & have a shop check all measurements since I don’t have access to instrumentation accurate enough.

Thank you, seniorchristo for the reference; I will follow up with that shop.
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Possibly final question about this block:

Is the Oversized Jackshaft bearing issue of any significance to anyone? This was not in the original description of this block & a note was added later after a closer inspection by the shop.

“It does need jackshaft bearings.. well the front two as we generally block off the rear. The jackshaft bores are slightly oversized, I have seen this on a number of blocks and struggled to find the oversized bearings.. so it may be a case of turning up a couple from alloy tube.”

I have heard of this only a few times on this board. I expect it is likely more common with race engines, as this block likely was, although no history was available for this one.
It does sound as if it would be a fairly basic procedure for a shop to turn out o/s bearings for this.
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[StressCraxx]

And then there is the opportunity for a new block....https://iveyengines.com/about/

Jay Ivey started talking with Ford Motorsport over 10 years ago to reproduce the Kent blocks (both the 711 and the 701) because the availability of good used blocks started to become difficult. It was not just Formula Ford and Lotus owners who were having hard time finding blocks, but numerous other users of these engines. The availability of replacement "service engines" had long since dried up. Bobcat skid steer loaders, Zamboni ice machines and Clark forklifts all used these engines all over the Americas.

Jay had significant input into the molds and castings of the new blocks, including reinforced motor mounts and better oiling flow to the rotating assembly. The new blocks came available in 2012 and they have proven very reliable with very clean castings that can take larger bores.

Tony Ingram and other builders are using these blocks to rebuild engines that were otherwise no longer repairable. Tony's work is first rate.

Jay and his sons Cameron and Colin (yes you know who he was named after) provide great service during their rebuilds and after the sale. Jay had 77 engines out of 700 entries at the 2019 Monterey Reunion vintage races. Jay saved my weekend at Portland 3 years ago when he helped me diagnose a bad brand new condenser. It was a home built motor that I bought a set of pistons, bearings, and valve springs from Cameron for a refresh. I finally had Jay and his sons rebuild mine with a new block (old one was found with a crack under the motor mount and causing a mystery oil leak). Engine is still going strong.

[rgh0]

I have never seen a block with the jackshaft bearing bore oversize and not sure how it would happen. Perhaps if you spun a bearing or if the block distorted and it was line bored over size ?

You could always fit a thin steel sleeve to bring it back to the standard bore but perhaps machining up an aluminium bearing to fit in is just as easy it does not carry much load so should work fine.

Whether I went with this block given it has a few issues and perhaps a hard racing life or the 82mm block would now be down to a bore wall thickness survey.

cheers
Rohan

[2cams70]

A small number of blocks did have .015" OS camshaft tunnel bores from the factory but near on impossible to get replacement bearings to suit these days. 0.015" OS main bearing tunnels also means difficulty in obtaining replacement bearings. Ford were pretty canny and only scrapped stuff as a last resort. Out of spec pushrod engine camshafts with chipped lobes were even recycled and used as twin cam engine jackshafts instead of going to waste! Small quantities of 0.015" OS main bearings are still available but only in certain sizes and choices are limited when it comes to bearing material. Not worth considering this block in my opinion. An 84mm block would even be better than this. If considering an 84mm block you'd need to know what it had been bored and honed to down to +/-.0005" accuracy and see if any available pistons with 0.060" nominal oversize would suit (the piston manufacturer will state a recommended bore size down to +/- 0.0005" tolerance).