A20 details and B20 rods/pistons thread

[ShiRen]

I would like to lay all the A20 specs out because they are a little hard to find. Some of these measurements may not be 100% accurate, I will mark those, but as far as I can tell it is good enough for a compression calculator program. Input is very welcome. The purpose of this thread is largely due to the fact that B20 pistons fit in the A20 with an overbore. B20 pistons are 84mm, but B18 pistons can come in 83mm sizes, but options are limited. This thread also assists in blueprinting the engine I am building soon and I will post progress here.

Service manual:Section 6-3 to 6-21 (pg 49-68) Section 7-3 to 7-18 (pg 72-85) Dropbox - 1989 Accord Service Manual.pdf - Simplify your life

Useful threads: https://www.3geez.com/forum/performa...hlight=pistons
Is high compression on the cheap possible on an A20? (pump gas)
A20 Head Build Thread | Honda Prelude Forum

Useful apps: CR Calculator - Apps on Google Play
Punch in A20 custom specs as if it were a B series.

Head

Cams

Stock:

Delta 272: .415" lift, 220 duration @.050" lift

Intake valve dia: 30mm

Exhaust valve dia: 35mm

Valve stem dia: 6.6-7mm ??

Valve OAL: 120.4mm

Valve guide OD: 12mm

Combustion chamber volume: 47cc ??

Block

Deck height: 213.25mm ??

Bore size: 82.7mm

Max recommended bore: 83-84mm. Most pistons come in 84mm.

Piston to cylinder clearance: .02-04mm

Piston to cylinder service limit: .08mm

Service manual does not specify a maximum overbore or service limit. The cylinder walls should be strong. Bore at your own discretion, pistons can come as large as 85.5mm

Crankshaft

Stroke: 91mm

Main journal min std size: 49.985mm

Main journal max std size: 50mm

Main bearing clearance 1, 2, 4, 5: .026-.55mm

Main bearing clearance 3: .032-.061

Main bearing service limit: .07mm (the only time this matter is with a min size bearing and your crank is FUBAR)

Main bearing width: 20mm

Main journal width:

Rod journal min std size: 44.981mm

Rod journal max std size: 45mm

Rod bearing std clearance: .026-.038mm

Rod bearing service limit: .07mm (the only time this matter is with a min size bearing and your crank is FUBAR)

Rod bearing width (A20): 19.5mm*

Rod bearing width (B18/B20): 18.5mm*

Rod bearing width (B18B): 19.5mm*

Rod journal width:

*Not to make this confusing, but I have varying bearing widths, yet I've seen B series rods fit snugly on an A20 crank. First measurement is More Information for ENGINETECH BB2200, 2nd is More Information for ENGINETECH BB2208, 3rd is https://www.rockauto.com/en/moreinfo.php?pk=2989791. GET THE RIGHT BEARINGS!

Piston assy.

Rod length: 137mm

Wrist pin size A20: 20mm

Wrist pin size B20: 21mm ??

Piston comp. height: 30mm ??

Stock piston flycut depth:

Stock ringland height:

Rod big end width (B20): 23.7mm*

Rod big end width (A20):

Stock piston dish (A20A1):

Max piston dome/height:

*https://jhpusa.com/collections/rods/...=1655850106900

Other

Stock head gasket manufactured height: .0470" - .0530"

Compressed height: ~.030" (.762mm) ??

Stock head gasket bore size: 83.82mm (3.3")

Careful with an 84mm bore, Cometic suggests .01" larger than your bore. 83mm bore works with stock head gasket, any larger and you will require a custom gasket or carefully scribe and cut the stock one.

Rod/stroke ratio: 1.51:1

B series piston list

83mm

CP-Carrillo SC7112 +.1cc / 10:1
CP-Carrillo SC7013 +4.9cc / 10.87:1
Supertech P4-H83-P6 +5.9cc / 11.07:1
JE 338090 +3.5cc / 10.6:1
JE 338092 +8.2cc / 11.57:1

84mm

Wiseco K623M84 0cc / 10.17:1
Wiseco K594M84AP/Skunk2 316-05-0017 +8.25/8.26cc / 11.8:1
Wiesco K567M84AP/Skunk2 316-05-0013 +2cc / 10.52:1
CP-Carrillo SC7120 +5.8cc / 11.26:1
CP-Carrillo SC7117 +1.6cc / 10.45:1
Supertech P4-H84-P1R +1.4cc / 10.41:1
Supertech P4-H84-P5 +5.5cc / 11.19:1
JE 302413 +7.4cc / 11.6:1
JE 302412 +3.2cc / 10.74:1
Arias A3330521 +7.3cc / 11.58:1
Arias A3330511 +5.29cc / 11.15:1
Arias A3330490 +.5cc / 10.26:1
Honda 13010-PHK-000 -4cc / 9.22:1 - piston has 29.59mm comp height

If you would like dished pistons see SpeedFactory's site
Or RealStreet
Compression ratios based on 47cc combustion chamber and 213.25mm deck height

Rods

Skunk2 306-05-1130
Speedfactory SF-02-104
Manley 14025-4
Manley 14412-4 I beam
Supertech CR-HB20B-H137
Eagle CRS5394A3D
CP-Carrillo HN-B18>-65394H-4
CP-Carrillo HN-B18>-65394S-4
Speedmaster PCE274-1108 I beam... but cheap?
Crower B93728B-4 I beam
Callies C22103
Saenz SS-HB18B-A00-T
Saenz PS-HB18B-A00-T I beam
K1 015BR16137
Brian Crower BC6019
Brian Crower BC6029
Scat 2-5394-1771-935-827
Honda 13210-PR4-A00

My Parts

Intake valves: Supertech HIVN-1102

Head Diam: 31.00mm (+1)
Stem Diam: 5.48mm
Length: 118.50mm

Intake valve springs: Stock exhaust valve springs

Intake valve retainers: Manley 23100

Intake valve lash cap: Supertech LC-55 Required due to shorter valve than stock

Intake valve guides: B18C

Intake valve seals:

Exhaust valves: Stock

Exhaust valve retainers: Stock

Exhaust valve guides: Stock

Exhaust valve seals: Stock

Cam: Delta 272

Pistons: Arias A3330511

Rods: Skunk2 306-05-1130

Rod bearings: King CR439AM

Main bearings: King MB5168AM

[Oldblueaccord]

Honda A engine - Wikipedia

some of the specs are here and there is a "3geez' wiki also floating around someplace in internet space.

[ShiRen]

Honda A engine - Wikipedia

some of the specs are here and there is a "3geez' wiki also floating around someplace in internet space.

3geez wiki

Neither of those really have much to offer... I'd love to get a good measurement of the combustion chamber size, mine won't be perfect

[Oldblueaccord]

Is high compression on the cheap possible on an A20? (pump gas)

you can paw thru the numbers on this one.

[ShiRen]

I had low expectations for that thread until page 2 lol. Cygnus said he measured his stock head at 47cc, I'll take that with a grain of salt if a welded head is 44cc though. Its a start though, gets me a decently accurate compression ratio. I am going to be careful of milling the head or block, but I will do what I have to, I'm just wary about flycutting a new set of pistons. I am going to make a list of 83 and 84mm pistons that are in the reasonable compression range. I am not chasing any number, not welding the head, just probably somewhere around 11:1, a 10cc dome is asking for trouble.

[Oldblueaccord]

Hes a reliable source for whats its worth...and I think the 44cc Open loop number is also creditable.

Doubling checking everything is important.

For pistons I would just have them made to what you want from one of the big piston makers.

[ShiRen]

I'm just saying its old info and it seemed like an off the top of the head answer. I assume the head was roughly 45-50cc. I can't visualize how big a cc is, I just figure that huge quench zone would be more than 3cc. A b16a head is 2.3cc smaller than a b18b head and I doubt there is a ton of difference in there and I can't visualize a cc with my brain.

I updated the post with a list of pistons and rods. I should be pretty good unless I need an 83mm with a really small dome. I think I can find some dished pistons though. There are several Arias part numbers I was unable to list because I can not find anything on them... I hate that everyone advertises pistons with a compression ratio instead of piston cc. Its really confusing because they list the same things under B18 LS non-vtec and B18 LS vtec but just change the compression. I shouldn't have to do math to guess the cc. Only Speedfactory lists Arias though and they lean heavily towards boosted applications, so I assume they are dish, one might be really close to flat.

Doesn't really matter what dome you go, 84mm bore will boost compression and increase displacement to 2011cc, very likely it will be considerably more spicy than an 83mm bore.

[Oldblueaccord]

The Open loop head and motor was at the time the most horsepower made NA. Old 3gee lore.

The chamber was welded to reduce the CC and increase the compression.

[Oldblueaccord]

A20 motor build threads.

I been trying to put motor builds up on the sticky if you find any others floating out there. I think I added the Open loop build to it what little is left on the internet.

[ShiRen]

Man I should have paid more attention to the threads you linked there, makes me want to do more to the head. I'm going to link a few in my post once I get a chance.

A20 Head Build Thread | Honda Prelude Forum In this one though he has an a18 bottom end. He listed the deck height in there and it was about a mm shorter than my estimation, but same length crank, pistons and rods as our a20s, is that right? I was kind of skimming because I'm on my phone and I didn't see if he shaved the block.

[Oldblueaccord]

yeah thats a great thread and looks like some missing pictures are back up. The head cut aways are really cool.

I have and xtra head I just never found any body local worth a shit on Honda heads that would run it on a flow bench for me and rework the valves.

[ShiRen]

I've ordered about everything for my head except intake valve guides, I think, no big deal I need another set of exhaust valve springs. I think I picked out my pistons and rods, everything is in the top post. So depending on how much the head and block needs skimmed, I am looking at a 11.19:1 cr, I'll check valve and piston dome clearance, but if its skimmed a mm it'll bump the compression into the 12s, I don't want to go more than 12.5:1, so combustion chamber cc needs to be around 41.5cc minimum with a stock height block and 44.5 with half a mm off the block (212.75mm)

[Oldblueaccord]

The two big unanswered questions for me are:

1. how far can you safely bore out an A20 block....and that means sonic checking the cylinder walls.... not checking FB 27 times in an hour.

2. How much does our head flow...never hear a word on this even on the facebbook pages. Thats the answer on how much power we can make. The answer always come back to the head flow.

Those two questions cant be answered unless you have a good engine machine shop and so far I have not found one close enough for me to really fool with it.

I dont think any one ever settled in on the deck height either...and thats not the piston height.

One thing with your pistons is the compression height and ring pack. With our rod ratio the numbers I did for the piston speeds at RPM over 8000? were higher than any engine produced at the time,Type R Ferrari etc. Ring position and ring pack would be critical to keep the motor from jamming a piston ring which is what I see on Rjudeguys engine pictures.

[ShiRen]

I will probably bore the block first thing once its pulled and if the shop has any concerns I will have them call me. As far as sonic checking it, I don't think I will go that deep, but I'm not adding boost. I might be able to get the head on a flow bench... might...

What happened to Rjudeguy? I don't think I've heard of him. I can't do much about the pistons unless some of the ones that cost twice as much do a little tweaking... I will probably not spin it over 7750. I mean he made 180hp at 7250.

[Oldblueaccord]

The quarter mile time mph and the power don't add up. Not sure if a dyno in Mexico is considered a gold standard.

You want the block final hone to match the Pistons size so make sure that your machinist has them.

Sonic check is to make sure the thickness supports the bore. It's more important to have a strong cylinder wall then max bore.

[ShiRen]

I just looked at his dyno to see where it made peak power, it carries on good a little passed 7500, but even he stopped before 8k.

84mm should be about the limit, I've at least got another block if I "learn anything" after some track time. If anybody can do a sonic test I will have them do it.

[Oldblueaccord]

I should add his 13.2 at 106 mph is over 200 wheel hp especially on a front drive car.

[ShiRen]

Nothing says the dyno numbers aren't low lol

[Oldblueaccord]

Whats that song we learned as a kid "one thing doesnt look like another"

Not trying to spend your money but those Supertech pistons are made in Argentina im pretty sure and the company is in Cali. thats two strikes in my book.

[ShiRen]

My second choice would be the CP-Carrillo +5.8cc pistons, but my wallet would probably force me to buy the Skunk2s, which are Wiesco, so that's nice, but only +2cc. Supertech is a fairly reputable brand, they aren't the nicest pistons, but I don't have much of an issue buying them.

Edit: Found some more pistons. The JE 3.2cc and the Arias 5.29cc would also be a good choice, but they're in a higher price bracket. Found some more for 83mm but nothing spectacular, to compete with 84mm they'd need to be in the ballpark of 6.5cc

[ShiRen]

I think I am actually going to go with the Arias 5.29cc

[ShiRen]

Took me this long, but I finally bought the 2nd cylinder head to rob the valve springs from. That being said I bought intake valves and lash caps. Hopefully I will have something going in the way of builds here soon. I have everything but the rods, pistons, and machine work to go.

The price almost doubled on the manley 23100 retainers and I'm a tiny bit butt hurt about it. The valves and caps were in stock at Speedfactory. I had all this on order in April, but my order was canceled, that was at No Limit though. Exhaust valves would be nice, but supposedly they're impossible to source.