Home 
Home Search search Menu menu Not logged in - Login | Register
> Jensen Healey & Jensen GT Tech > Engine & Transmission > Differences between MkII engine and GT engine?

 Moderated by: Greg Fletcher
New Topic Reply Printer Friendly
Differences between MkII engine and GT engine?  Rating:  Rating
AuthorPost
 Posted: 09-14-2015 08:11 pm
  PM Quote Reply
1st Post
answerman
Member
 

Joined: 09-10-2012
Location: Little Chute, Wisconsin USA
Posts: 382
Status: 
Offline
Hey guys. Considering buying an engine for Ms. Jenavieve. Are there any differences between a MkII 907 and a GT 907 that I need to know about? She currently has her original engine, MkII type (later style with lip style rear seal, not a rope seal). Joe Mazurk has a GT engine available. I know there were some differences with peripherals like air pump and such, but should it be a straight swap otherwise?

Back To Top PM Quote Reply  

 Posted: 09-14-2015 08:30 pm
  PM Quote Reply
2nd Post
NigelK
Member
 

Joined: 07-16-2014
Location:  
Posts: 165
Status: 
Offline
I think it depends what engine was fitted to the GT. Jensen used whatever engines they had available at the time, including A74 (Dellorto), B73, B74, and T75 (Stromberg). According to Ric Calver, all Federal market GTs had the T75 engine, which may also have been fitted to very late JHs. It would be an idea to compare engine numbers between your JH and the GT. I think the main differences between B74 and T75 engines will be emissions / ignition related, and perhaps also the air box setup.

Last edited on 09-14-2015 08:31 pm by NigelK

Back To Top PM Quote Reply

 Posted: 09-14-2015 08:44 pm
  PM Quote Reply
3rd Post
answerman
Member
 

Joined: 09-10-2012
Location: Little Chute, Wisconsin USA
Posts: 382
Status: 
Offline
Good information so far. The current engine in her is B74.03.6527. I think the items you mentioned will fall under the "peripherals" I was talking about and won't be included with the engine anyway. I was more worried about core items like the block/head/clutch/tranmission/etc itself since I'll likely be pulling the Strombergs and all the current ignition components from my current engine for transfer to the new one. Consider it a bare T75 engine for the purposes of this question.

Long term plan, assuming the new engine is a decent runner in its current condition, is to swap the new engine in and then do a proper rebuild on the old engine as time permits.

Back To Top PM Quote Reply  

 Posted: 09-14-2015 09:12 pm
  PM Quote Reply
4th Post
t4brew
Member
 

Joined: 03-11-2010
Location:  
Posts: 12
Status: 
Offline
Some of the 907 emission heads had eight air injection ports on the exhaust side where the air injection rail was attached. The GT 907 engine may have these ports.  I have seen two 907 emission heads with air injection ports.  One still had the original air rail attached and the other had plugs in the air injections ports.  If the GT 907 engine you are looking at still has the air rail you may need to find plugs for the air injection ports.

Attachment: air-injection-port-small.JPG (Downloaded 168 times)

Last edited on 09-14-2015 09:59 pm by t4brew

Back To Top PM Quote Reply

 Posted: 09-14-2015 09:30 pm
  PM Quote Reply
5th Post
NigelK
Member
 

Joined: 07-16-2014
Location:  
Posts: 165
Status: 
Offline
A few more thoughts...

1. The water pump and fan setup may be different, as T75 engines had the later viscous shrouded fan and crossflow radiator (this is probably also "peripheral")
2. Check if the GT had A/C - this could mean a different cambelt tensioner and crankshaft (amongst other things)
3. RH engine mountings will be different (in order to make space for the air pump)
4. Valve timing is different for Federal engines after # 10480

Presumably your JH already has the 5-speed Getrag box fitted? If not, the bell-housing will obviously be different on the GT engine too...

Back To Top PM Quote Reply  

 Posted: 09-14-2015 09:46 pm
  PM Quote Reply
6th Post
answerman
Member
 

Joined: 09-10-2012
Location: Little Chute, Wisconsin USA
Posts: 382
Status: 
Offline
Nope, I have the 4-speed. I would assume the bell housing will have to come off of the current engine and transferred. The GT engine has the water pump installed yet (no idea of condition) and the cambelt installed, so the tensioner etc is all there though obviously I'd replace the belt and bearings before swapping. How would the engine mount be different?

Back To Top PM Quote Reply

 Posted: 09-14-2015 10:07 pm
  PM Quote Reply
7th Post
NigelK
Member
 

Joined: 07-16-2014
Location:  
Posts: 165
Status: 
Offline
The GT parts manual shows different RH engine mountings and subframe for T75 engined cars. With the T75 engine, the subframe bracket to which the engine mounting is attached is located where the subframe swings upwards from horizontal to sub vertical. On non T75 cars, this bracket is a completely different shape and is mounted halfway up the sub vertical part of the subframe. The engine mountings need to be a different shape as a result. I think these differences were all to create space for the air pump. But there is nothing in the parts manual to indicate anything different in the block casting, so provided you retain the B74 engine mountings you should not have a problem.

Back To Top PM Quote Reply  

 Posted: 09-15-2015 02:15 pm
  PM Quote Reply
8th Post
Brett Gibson JH5 20497
Member
 

Joined: 03-17-2005
Location: Hilton, New York USA
Posts: 713
Status: 
Offline
Mike, a GT engine will bolt right into your JH, water pump is different comes out the side instead of up front like yours, you would need to switch yours onto the GT engine and it also sounds like you would have to use your JH engine mounts, otherwise you are good to go, what is the problem with your original engine ??? and don't forget you would be buying a used engine that if I know Joe would be AS IS, I'm sure he would be honest about it's condition as much as he knows about it but there would be a question mark.
Brett

Back To Top PM Quote Reply

 Posted: 09-15-2015 05:46 pm
  PM Quote Reply
9th Post
answerman
Member
 

Joined: 09-10-2012
Location: Little Chute, Wisconsin USA
Posts: 382
Status: 
Offline
Thanks for the info. Brett, there is nothing wrong with my current engine other than that it is going to turn the odometer over in the next few weeks and I think it may be time for a rebuild. My thinking is that if I am going to do a rebuild, I would rather do it on the original "numbers matching" engine. So, the plan would be to (assuming the new engine can be made to run fairly easily) swap the new engine in and then rebuild the original engine at my leisure for reinstallation later. Though, I went through the service manual last night and the rebuild doesn't look as complicated as I expected, so maybe I am worrying about nothing and can easily get it done this winter. I just don't want to be caught without a running engine next spring, so this was a backup plan.

Joe was very clear that the GT engine is "as is". It came from a car with 45,000 miles on it, he has never run it, but it is complete, spins freely, and has plenty of compression according to him.

Back To Top PM Quote Reply  

 Posted: 09-15-2015 07:19 pm
  PM Quote Reply
10th Post
wtberks
Member
 

Joined: 09-18-2006
Location: Long Beach, California USA
Posts: 33
Status: 
Offline
On my GT, the engine has the air injection ports, which you can plug, a slightly different oil pump housing, a different water pump. the dreaded air pump, an A/C compressor and no place for the rear engine damper.

The oil pump housing has the top mount cut off and a taller one bolted on, presumably to mount a larger alternator. The water outlet from the thermostat also connects to the radiator following a different, less cramped path. The rear damper is missing as the air box fan on the firewall is in the way of where the mount would be in a JH.

Back To Top PM Quote Reply

 Posted: 09-16-2015 02:02 am
  PM Quote Reply
11th Post
Screenplay
Member
 

Joined: 07-12-2013
Location: San Francisco, California USA
Posts: 121
Status: 
Offline
I'd second Brett on the "e caviat emptor." No need to rehash old stuff but just go in with your eyes wide open.

Back To Top PM Quote Reply  

 Posted: 09-17-2015 06:45 am
  PM Quote Reply
12th Post
Esprit2
Member
 

Joined: 05-01-2005
Location: Minneapolis, Minnesota USA
Posts: 293
Status: 
Offline
t4brew wrote:
If the GT 907 engine you are looking at still has the air rail you may need to find plugs for the air injection ports.The plugs are 1/8" BSPT, Allen drive. If Delta doesn't have them, then JAE does.

Back To Top PM Quote Reply

 Posted: 09-18-2015 02:57 am
  PM Quote Reply
13th Post
Art DeKneef
Member
 

Joined: 03-12-2005
Location: Mesa, Arizona USA
Posts: 298
Status: 
Offline
I'm not sure but I believe there was a discussion on the differences between the MKII engine and the GT/later 907 engine somewhere on the board.

All the GT engines I have seen her have had air conditioning, air pump and fittings, different subframe, different water pump and radiator. There might be a couple of other minor differences I don't remember right now.

1. Engine block is the same. The difference in mounting has been mentioned. The passenger side engine mount is different because of the air conditioning compressor.
2. Since your car is a 4-speed you will need to use the bell housing for your current JH.
3. Water pump, fan and radiator are different. You need to use your current water pump and fan on the GT engine. Otherwise you need to swap radiators and then you lose the cooling shroud.
4. You can remove the air pump and fittings. Delta has the plugs.

Like Brett mentions, it will fit. You need to take the changed parts of the GT engine off and replace them with your parts. Then reconnect the fittings and electrical and hope it starts and runs. If not just repeat the process in reverse and you can still use the old engine.

Also, depending on the age of your current engine, it's possible that the heads on the GT might have larger ports. Given the choice I would probably leave the current engine in the car and rebuild the GT engine instead.

Back To Top PM Quote Reply  

 Posted: 01-17-2016 03:43 pm
  PM Quote Reply
14th Post
Lash Russell
Member


Joined: 07-23-2005
Location: Franktown, Colorado USA
Posts: 69
Status: 
Offline
Gents,
Regarding the different engine mounting locations for the GT (and I think on later JH's), was this strictly to accommodate the air pump of for the AC compressor, or both?
Thanks,
Lash

Back To Top PM Quote Reply

 Posted: 01-17-2016 04:43 pm
  PM Quote Reply
15th Post
Frank Schwartz
Member
 

Joined: 02-18-2011
Location:  
Posts: 248
Status: 
Offline
Definitely use your original water pump...the one in the GT has a longer shaft and will not accommodate your belt driven fan...the viscous coupled fan very often does not work well anyhow. Other than plugging the air holes and using a single bend hose on the upper radio connection instead of the crazy S hose, all should be interchangeable.

Oh, yes, the GT uses a three row radiator whereas the JH uses a two row radiator...and the GT radiator mounts differently... I have found the tensioner to be identical and I cannot see where you would have trouble replacing it or using the one on it, assuming it will come with it. Just replace the bearings, which is a good practice in the tensioner. If the GT engine is stripped, I think you can pretty much swap it without much trouble using most of your stuff such as the alternator etc.... I have a low mileage (24k) GT engine that I am going to put in a JH which has no compression on #3 and was driven very hard for a long time by the owner with the distributor stuck at 45 degrees of advance. I think it will be easier to replace the engine than to try to repair all the damage he has done.

Back To Top PM Quote Reply  

 Posted: 01-18-2016 07:44 pm
  PM Quote Reply
16th Post
Art DeKneef
Member
 

Joined: 03-12-2005
Location: Mesa, Arizona USA
Posts: 298
Status: 
Offline
Lash,

My experience, with my cars, is that the only engine mounting difference is on the passenger side because of the compressor. The engine mounting brackets are different between a non AC car and one that has AC.

The driver side bracket is the same. The air pump is located on the driver's side and uses a different bracket for mounting and a different fan belt.

Back To Top PM Quote Reply

 Posted: 01-21-2016 01:42 pm
  PM Quote Reply
17th Post
Lash Russell
Member


Joined: 07-23-2005
Location: Franktown, Colorado USA
Posts: 69
Status: 
Offline
Thanks Art,
I was pretty sure of that but glad you confirmed.
Lash

Back To Top PM Quote Reply  

Current time is 05:43 am  
> Jensen Healey & Jensen GT Tech > Engine & Transmission > Differences between MkII engine and GT engine? Top




UltraBB 1.172 Copyright © 2007-2011 Data 1 Systems