# Whats the diff. between a JH and GX block?



## EuroVeeDub (Nov 16, 2001)

I found a 8.5/1 CR motor here locally, which I need for my turbo build up... the guy says its a hydro headed motor from an 80's non-GTi. Im assuming this is a GX motor found in the A2's.
From what I know they are both 8.5/1 CR, but the JH is a solid lifter and the GX is hydro (not that it makes a difference...I only need the block).
I'd like to know if there are any differences in the bore, stroke, pistons, rods, crank, ect.
The guy is offering a good deal, so I'd like to pick it up. As long as the internals are the same, I'll take it.
Any help would be much appreciated 
-Drew


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## BastardBunny (Sep 24, 2002)

*Re: Whats the diff. between a JH and GX block? (EuroVeeDub)*

Curious as well, i have a 86 GX block... just would like to know the difference since its a code that is rarely talked about.


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## EuroVeeDub (Nov 16, 2001)

*Re: Whats the diff. between a JH and GX block? (BastardBunny)*

I know man, seems like everybody always brings up the JH...what about the po old GX


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## BastardBunny (Sep 24, 2002)

*Re: Whats the diff. between a JH and GX block? (EuroVeeDub)*

EXACTLY!! I thought i had a freak under my hood!! Nobody talked about it, made posts, and nobody brought it up, even did a search and nothing. Till somebody knew about the O2 sensor on a GX, made me feel much better.
Now you!!
Thing is their not that old either. You said this GX was on a 80?? Mine is from a 86... strange...
I can't find more info, but would love to know!
Quinn


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## racinrocco (Sep 26, 2002)

*Re: Whats the diff. between a JH and GX block? (BastardBunny)*

well,ya know every family has a weird relative that no one ever talks about


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## BastardBunny (Sep 24, 2002)

*Re: Whats the diff. between a JH and GX block? (racinrocco)*

and that relative is usually a mistake =( I hope not, my car runs great, when the timing is advanced it goes like a bat out of hell, but all i have is a few small problems that need ironing out when it warms up. I will stand behind my GX damnit!


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## gcarson (Apr 25, 2002)

*Re: Whats the diff. between a JH and GX block? (EuroVeeDub)*

I believe that you will find the only factor that changes between the GX block and the other more popular blocks is the piston dish. Hence the different comp ratios. Crank, rods, bore and stroke between all the 1.8 engines are the same.


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## citat3962 (Oct 15, 2001)

*Re: Whats the diff. between a JH and GX block? (gcarson)*

I'm going to venture a guess and say theres not a difference.
They have the same compression and internal parts.
The difference would probably be the fact that it's setup for the Early A2 Golf..
I'm going to also guess the GX in the 80 is a replacement block.. as I don't think there were 1.8's in 1980.
They are the 8.5:1 low compression blocks and so are great for low boost turbo using the usual CIS trickery.
Came in 85-87 GL Golfs and Jettas. It's just as good as any 1.8L from an A1 and only a piston swap away from a 10:1 compression block.
I know about them but I find that the non GTI GLi's Got sold for cheaper and we're thus abused.. SO the blocks usually sit in the yard til they seize... and the cars they come in are not enthusiast cars compared to the GTI GLI's.
Now when crazies like us start thinking Turbo and want low compression motors We'll be wishing we hadn't tossed out that GX or passed up that GX you saw in the yard with crosshatching on it...
I dunno. I'm guilty I tossed a GX block at one point because I had no more room. No one wanted it. Now if I offered the $50 for it it might actually sell..
But strangely I offer a 1.8 10:1 for 75 and I can't sell it to save my life...


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## BastardBunny (Sep 24, 2002)

*Re: Whats the diff. between a JH and GX block? (citat3962)*

So the JH's is the higher compression engine with the bigger valves that came on the GTI/GLI's, and the GX is the lower compression GL's.
Simple enough... Either i gotta go turbo or switch piston's








Quinn


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## Racer_X (Jul 14, 2002)

*Re: Whats the diff. between a JH and GX block? (BastardBunny)*

quote:[HR][/HR]So the JH's is the higher compression engine with the bigger valves that came on the GTI/GLI's, and the GX is the lower compression GL's.
Simple enough... Either i gotta go turbo or switch piston's








Quinn[HR][/HR]​No, the JH is the 8.5:1 compression big valve engine that came in the 1983-1984 Rabbit GTI's. It was also used in some Scirocco 8Vs and Cabriolets through 1988 or so. 
The 1985-1988 8V Golfs had HT and RD engines. These were the 10:1 engines with the big valves and hydraulic lifters. I'm pretty sure the compression increase was in the head, not the pistons, but I could be wrong on that.
The GX was listed in Bentley as a 9:1 engine, not 8.5:1. It also has smaller valves in the head and hydraulic lifters. 
According to Bentley, the GX has a 81.0mm bore, a 86.4mm stroke and a displacement of 1781cc. The compression ratio is listed as 9.0:1 (but so is the RD, and I know that's wrong in the chart). Power was 85HP at 5250 RPM and the torque peak was 96 ft. lb. at 3000 RPM's. It's not quite as powerful as the JH engine, but that's most likely due to the slightly smaller valves. 
The block and crank in the GX should be the same as the JH engine. The pistons might be slighly different if that's where the extra 0.5 compression comes from. The oil pump is probably larger due to the hydraulic lifters. You don't really want a GX head, even with forced induction. The JH head has bigger valves, solid lifters and maybe slightly lower compression.


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## EuroVeeDub (Nov 16, 2001)

*Re: Whats the diff. between a JH and GX block? (Racer_X)*

I'd be using the JH head... so the CR would be 9.0-1 then with the GX(block)/JH(head) combo?
I guess I just have some strange idea that the JH is better for some reason...who knows







I also wanna make sure all my bearings,rings,gaskets will fit the block and that it has low enough compression (with the JH head) to handle forced induction.


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## need_a_VR6 (May 19, 1999)

*Re: Whats the diff. between a JH and GX block? (Racer_X)*

quote:[HR][/HR]I'm pretty sure the compression increase was in the head, not the pistons, but I could be wrong on that.[HR][/HR]​As far as I've seen, all compression increases were done through piston dish alone. Counterflow heads almost always cc right at 30ccs.
The difference between the JH and GX bottom ends is probably just the oil pump.


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## citat3962 (Oct 15, 2001)

*Re: Whats the diff. between a JH and GX block? (need_a_VR6)*

Yup
oil pump and I think the port on the front of the block for the WUR is blocked off by a plate...?? Can;t remember how that works..
The JH is the same compression as the GX the 9:1 in the bentley is a misprint ( I could be wrong) they're exactly the same.
Guess I learn something new everyday..










[Modified by citat3962, 12:24 PM 3-4-2003]


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## A1Rocco (Oct 6, 2001)

*Re: Whats the diff. between a JH and GX block? (citat3962)*

JH iss 8.5:1
GX is 9:1.
Both are controlled by the piston, bnoth have same bore stoke.
Both will have the same compression as listed above regardless of using hydro or solid head.


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## Racer_X (Jul 14, 2002)

*Re: Whats the diff. between a JH and GX block? (A1Rocco)*

quote:[HR][/HR]JH iss 8.5:1
GX is 9:1.
Both are controlled by the piston, bnoth have same bore stoke.
Both will have the same compression as listed above regardless of using hydro or solid head.[HR][/HR]​Well, it looks like I am wrong here. Two different people have pointed out my error.
I stand corrected, the pistons probably are different then.


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## vwpat (Oct 25, 2000)

*Re: Whats the diff. between a JH and GX block? (Racer_X)*

quote:[HR][/HR]JH iss 8.5:1
GX is 9:1.
Both are controlled by the piston, bnoth have same bore stoke.
Both will have the same compression as listed above regardless of using hydro or solid head.
Well, it looks like I am wrong here. Two different people have pointed out my error.
I stand corrected, the pistons probably are different then.[HR][/HR]​I agree with you. The GX is 8.5:1 and uses the same pistons as a JH.


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## A1Rocco (Oct 6, 2001)

*Re: Whats the diff. between a JH and GX block? (vwpat)*

Hmmm... I've been wrong before.


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## veedubfreak03 (Feb 23, 2003)

*Re: Whats the diff. between a JH and GX block? (A1Rocco)*

i have the ht engine i heard it is rare?!?


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## lotus7 (Oct 30, 2001)

*Re: Whats the diff. between a JH and GX block? (veedubfreak03)*

HT 10:1 advertised comp ratio. Found in 85-87 GTI.


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## vwpat (Oct 25, 2000)

*Re: Whats the diff. between a JH and GX block? (lotus7)*

HT was only used in 85, 86-87 used an RD. They are essentially the same. Cam and oil pump different as well as different ignition map.


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## D11RCD (Sep 18, 2014)

*Chasis & Engine Codes*

I realize this is probably a dead thread, but I landed here tonight looking for the same info. So I am going to post this link to a page that clears up the basic questions.

http://www.autotech.com/appchart.htm

It's worth bookmarking.


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## G60 Carat (May 14, 2004)

That website lists the GX as a 9.0:1, but I'm pretty sure it's a 8.5:1


This is my go to website for engine specs.

http://www.a2resource.com/

Particularly this page. As there is some Canadian spec engines, like the MZ, that the Americans never got. 

http://www.a2resource.com/eandt/allengines.html

And for that matter, I'm not sure we ever officially got the GX, although I did have 85 American 'Westy' Golf that had one in it.


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## Seax_Smith (Jun 1, 2007)

I had an 85 wolfie jetta with a GX and that wierd CIS-E variant (vac advance distrib, no knock box and a DPR). That thing LUVED 12*BTDC and super high mileage with an ACN trans.


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## G60 Carat (May 14, 2004)

LOL, yeah I swear there is no knock threshold with those old low comp 8v's.

I would always run way more base timing on them as well, made them so much more punchier down low. Still had no real guts up top though.


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## Seax_Smith (Jun 1, 2007)

Yeah, you could get up to highway speeds well enough, but after that... well I didn't pass many people, but the MPGs were amazing. I was driving from Amherst MA to Toronto pretty much bi-weekly in that car.


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## ps2375 (Aug 13, 2003)

G60 Carat said:


> LOL, yeah I swear there is no knock threshold with those old low comp 8v's.
> 
> I would always run way more base timing on them as well, made them so much more punchier down low. Still had no real guts up top though.


My GX on MS made 95whp with an exhaust and a "G" grind cam. It ran pretty well up to about 6500rpm and actually made better highway mpg's w/ an AT280 cam.


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## Legoguy (Sep 18, 2002)

EuroVeeDub said:


> <p>From what I know they are both 8.5/1 CR, but the JH is a solid lifter and the GX is hydro (not that it makes a difference...I only need the block).



I didn't see anyone clarify this, but not all JH engines had solid lifters; those between 1988 and 1989 installed in Cabriolets had hydraulic lifters, before the 2H took its place in that model in 1990. This information comes from http://www.cabby-info.com/engine.htm#Specifications


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