Newbe with a ton of questions about the 1997 MarkVIII DOHC Motor

[RCReevesPhotography]

Hey all, I have a 1997 Cougar XR7 Sport. I Found/bought a 1997 Mark VIII LSC DOHC Motor with low miles. (Don't fear the car was destroyed) I plan to swap the Mark Motor in to the Cougar.

This is what I have for my swap so fair.

1 1997 Mark VIII LCS Motor with 100% all the extras from under the hood.

1 1997 Mark VIII 4R70W Transmission fully rebuild with J-MOD

1 Complete 1996 Cobra intake, every thing from the EGR to the IMRC's.
Pulled from a car with 8k miles.

1 Set of Composite IMRC's with MDS RPM Window switch to control them.

1 1993 Mark VIII Drive shaft.

1 1998 Mark VIII Differential with 3.27 gears and a Trac-Loc swap.

1 8k mile Factory 1998 MarkVIII LCS dual exhaust setup, every thing from the manifolds to the tips. 100% complete.

1 set of new High flow cats, and Cobra shorty headers (If I can find out how to make them fit)

Plus 10hours of Dyno/Tune time after it's all together.

Here is my question, since this motor stock should only push 290 Flywheel H.P. What should it push with the Cobra intake, Cobra shorty's and the High Flow cats?

Next what is the best bang for my buck at this point with out buying Kooks or adding new cams? I have been a long time member of TCCoA but the people over there just don't this motor.

Any and all help would be appreciated.

Thanks all!

P.S. Dose any one know the factory Lift duration of the 1997 Mark VIII LCS Cams?

 

[rayner601]

Hey all, I have a 1997 Cougar XR7 Sport. I Found/bought a 1997 Mark VIII LSC DOHC Motor with low miles. (Don't fear the car was destroyed) I plan to swap the Mark Motor in to the Cougar.

This is what I have for my swap so fair.

1 1997 Mark VIII LCS Motor with 100% all the extras from under the hood. OK

1 1997 Mark VIII 4R70W Transmission fully rebuild with J-MOD OK

1 Complete 1996 Cobra intake, every thing from the EGR to the IMRC's.
Pulled from a car with 8k miles. Really not needed..will only make a marginal amount of more power and will shift the power peak more into the upper part of the rpm range. Even with your planned gear set, you still need a good portion of the power down low, but not truck engine low.

1 Set of Composite IMRC's with MDS RPM Window switch to control them. Don't need the IMRCs unless you didn't get them with the engine. 97s already have this. Will need the RPM switch

1 1993 Mark VIII Drive shaft. Will help a lot

1 1998 Mark VIII Differential with 3.27 gears and a Trac-Loc swap. Will help but not much, really need something over 3.55 (can't remember exact ratio but most agree 4.10s are the best for these cars)

1 8k mile Factory 1998 MarkVIII LCS dual exhaust setup, every thing from the manifolds to the tips. 100% complete. Other than the manifolds and possibly the mufflers, the rest won't fit I think.

1 set of new High flow cats, and Cobra shorty headers (If I can find out how to make them fit) Cats good. Headers prob won't fit with extensive mods.

Plus 10hours of Dyno/Tune time after it's all together. WILL def. need this

Here is my question, since this motor stock should only push 290 Flywheel H.P. What should it push with the Cobra intake, Cobra shorty's and the High Flow cats? Flywheel, generally speaking with you not changing cams, about 300 or a touch higher. Can't remember which it is but the intake or exhaust cam has a bit longer duration and therefore is the reason for some of the difference in power between a cobra and an 8. the rest is in tuning and exhaust system. I think the heads are the same.

Next what is the best bang for my buck at this point with out buying Kooks or adding new cams? I have been a long time member of TCCoA but the people over there just don't this motor. Install engine and trans with rpm switch, install 4.10 gears (trac-loc is almost mandantory at this low a ratio), swap out driveshaft, get a good base tune, and go to dyno and tune from there. You may have to upgrade the fuel pump, but the tuner can tell you if you are starving the engine of fuel at wot. One more thing, you may have to lengthen some sensor wiring, but it will be apparent.

Any and all help would be appreciated.

Thanks all!

P.S. Dose any one know the factory Lift duration of the 1997 Mark VIII LCS Cams?

I hope all this helps. I was planning on doing this on my 95 Cougar before it got totaled

Someone correct me if I am wrong in anything...don't want to give out bad advise

 

[RCReevesPhotography]

Thanks for all the info rayner601, I got the Cobra intake more for looks than power. Some thing about that don't mess with me cobra on the top I just love lol.

I found put that the dual exhaust setup will work buy I'll need to shorten the tail pipes by 5'' (more or less cutting off the tips).

I could not pass up the deal, I found an OEM setup with only 8k miles the cats are as clean as could be, the manifolds don't even have rust and all the 02's were tossed in for around $120.00 plus gas and time.

 

[RCReevesPhotography]

Thanks for all the info rayner601, I found out the LCS dual exhaust setup will work but I need or shorten it by 5'' at the end since the Mark VIII is longer by 5'' I could not pass this set up it came off an 8k mile car has almost no rust and looked like new inside and out for next to nothing.

As for gears, I have always run 3.27 in my Ford's and 3.73's in my Mopars. I'll need to look into 3.55's

I'm hoping I can make the Cobra manifolds work so I can add high flow cat's and dump the cat manifold combo.

Your right about the Fuel pump, S.C.P. Marks a 255gph swap for around 125.00

 

[Rich88LSC]

1 Complete 1996 Cobra intake, every thing from the EGR to the IMRC's.
Pulled from a car with 8k miles. Really not needed..will only make a marginal amount of more power and will shift the power peak more into the upper part of the rpm range. Even with your planned gear set, you still need a good portion of the power down low, but not truck engine low.

I disagree. The 97-97 Mark intake is the weakest of the b head intakes. The Cobra one is worth the swap. Since you are aready going to have to splice some wires etc for the 4V swap this isn;t going to be any more work for you.

1 1993 Mark VIII Drive shaft. Will help a lot

+1

1 1998 Mark VIII Differential with 3.27 gears and a Trac-Loc swap. Will help but not much, really need something over 3.55 (can't remember exact ratio but most agree 4.10s are the best for these cars)

The Mark had an aluminum housing over the MN12 iron one but I agree but some gears in there and a trac lok is a must especially with the gears.

1 8k mile Factory 1998 MarkVIII LCS dual exhaust setup, every thing from the manifolds to the tips. 100% complete. Other than the manifolds and possibly the mufflers, the rest won't fit I think.

Most likely right. Possibly if you shorten it up you can peice it back together but the Mark mufflers are big and heavy I wouldn't use them anyway.

1 set of new High flow cats, and Cobra shorty headers (If I can find out how to make them fit) Cats good. Headers prob won't fit with extensive mods.

+1 Flaming river steering shaft is a must even then I think your going to have trouble getting them to fit.

Plus 10hours of Dyno/Tune time after it's all together. WILL def. need this

+1 most important part of the swap.

Here is my question, since this motor stock should only push 290 Flywheel H.P. What should it push with the Cobra intake, Cobra shorty's and the High Flow cats? Flywheel, generally speaking with you not changing cams, about 300 or a touch higher. Can't remember which it is but the intake or exhaust cam has a bit longer duration and therefore is the reason for some of the difference in power between a cobra and an 8. the rest is in tuning and exhaust system. I think the heads are the same.

The dyno tune alone should put you over 300HP. I'm not going to try and guess other then that. You will have rwhp numbers after the dyno that you can estimate from.

Next what is the best bang for my buck at this point with out buying Kooks or adding new cams? I have been a long time member of TCCoA but the people over there just don't this motor. Install engine and trans with rpm switch, install 4.10 gears (trac-loc is almost mandantory at this low a ratio), swap out driveshaft, get a good base tune, and go to dyno and tune from there. You may have to upgrade the fuel pump, but the tuner can tell you if you are starving the engine of fuel at wot. One more thing, you may have to lengthen some sensor wiring, but it will be apparent.

I agree a trac lok is mandatory no matter what gears you go with. 4.10s are good and your still under 3000rpm at 80mph. If you are ok with more revs go with more gear. I would get a good high stall converter. The deeper the gears the bigger stall you can get away with without losing to much drivability. I would look into have the Cobra intake ported and runners shorted. Places like Pauls High performance and I cant remember the other relativly well know shop that does them but they are expensive. There are a few mustang guys that do them for a few hundred $. You will notice the gains over just the stock Cobra and it will pull much harder past the peak.

P.S. Dose any one know the factory Lift duration of the 1997 Mark VIII LCS Cams?

Exhaust is the same as the 96-98 Cobras. Intake I spend a lot of time searching and could not find out for sure. My best guess based in my own research is same lift and duration as the Cobras but retarded 3 degrees to try and improve torque production for the heaver Mark over the Cobra.

 

[RCReevesPhotography]

1 Complete 1996 Cobra intake, every thing from the EGR to the IMRC's.
Pulled from a car with 8k miles. Really not needed..will only make a marginal amount of more power and will shift the power peak more into the upper part of the rpm range. Even with your planned gear set, you still need a good portion of the power down low, but not truck engine low.

I disagree. The 97-97 Mark intake is the weakest of the b head intakes. The Cobra one is worth the swap. Since you are aready going to have to splice some wires etc for the 4V swap this isn;t going to be any more work for you.

1 1993 Mark VIII Drive shaft. Will help a lot +1

1 1998 Mark VIII Differential with 3.27 gears and a Trac-Loc swap. Will help but not much, really need something over 3.55 (can't remember exact ratio but most agree 4.10s are the best for these cars)
The Mark had an aluminum housing over the MN12 iron one but I agree but some gears in there and a trac lok is a must especially with the gears.

1 8k mile Factory 1998 MarkVIII LCS dual exhaust setup, every thing from the manifolds to the tips. 100% complete. Other than the manifolds and possibly the mufflers, the rest won't fit I think.
Most likely right. Possibly if you shorten it up you can peice it back together but the Mark mufflers are big and heavy I wouldn't use them anyway.

1 set of new High flow cats, and Cobra shorty headers (If I can find out how to make them fit) Cats good. Headers prob won't fit with extensive mods.

+1 Flaming river steering shaft is a must even then I think your going to have trouble getting them to fit.

Plus 10hours of Dyno/Tune time after it's all together. WILL def. need this

+1 most important part of the swap.

Here is my question, since this motor stock should only push 290 Flywheel H.P. What should it push with the Cobra intake, Cobra shorty's and the High Flow cats? Flywheel, generally speaking with you not changing cams, about 300 or a touch higher. Can't remember which it is but the intake or exhaust cam has a bit longer duration and therefore is the reason for some of the difference in power between a cobra and an 8. the rest is in tuning and exhaust system. I think the heads are the same.

The dyno tune alone should put you over 300HP. I'm not going to try and guess other then that. You will have rwhp numbers after the dyno that you can estimate from.



I agree a trac lok is mandatory no matter what gears you go with. 4.10s are good and your still under 3000rpm at 80mph. If you are ok with more revs go with more gear. I would get a good high stall converter. The deeper the gears the bigger stall you can get away with without losing to much drivability. I would look into have the Cobra intake ported and runners shorted. Places like Pauls High performance and I cant remember the other relativly well know shop that does them but they are expensive. There are a few mustang guys that do them for a few hundred $. You will notice the gains over just the stock Cobra and it will pull much harder past the peak.




Exhaust is the same as the 96-98 Cobras. Intake I spend a lot of time searching and could not find out for sure. My best guess based in my own research is same lift and duration as the Cobras but retarded 3 degrees to try and improve torque production for the heaver Mark over the Cobra.

Thank you for all of your help, I'm thinking about taking off the rear mufflers since as you stated they are very big and rather heavy I would guess.

Gears I'm still looking into and what I want to do with the intake in unclear.

 

[RCReevesPhotography]

"I would look into have the Cobra intake ported and runners shorted." How short have you seen them go? I have never seen that but it makes for a good thing to put in the pot.

Just to be clear would the point of that would be making a shorter line from A to B in turn making things flow faster?

 

[Blenderhead]

Shortening the runners will give you more top end power, at the expense of some bottom end torque. Depending how far you want to go with the motor, and also what gears and stall you wind up running, would affect whether it is worth it to you to do this or not. Personally, I wouldn't do it unless you are running at least 4.10s and a 3500stall.

 

[Rich88LSC]

Shortening the runners will give you more top end power, at the expense of some bottom end torque. Depending how far you want to go with the motor, and also what gears and stall you wind up running, would affect whether it is worth it to you to do this or not. Personally, I wouldn't do it unless you are running at least 4.10s and a 3500stall.

Without going overboard on shortening the runners what upi lose down low will be minimal and more then made up for up top. But yeah this is a mod best left after you have done gears/stall. If RC didn't already have the Cobra intake and ask for other mods I wouldn't have suggested it.

 

[RCReevesPhotography]

To tell you the truth I like low end more than hi end.

How does it go, Horsepower Burns gas and Torque burns tires?

Dose any one know the factory gears of an 1996 SS Impala? I understand that car has 340lbs of Torque so it's going to have more pull than a DOHC but I remember the gears/hook feeling real good.

 

[rayner601]

Rich88, thanks for the clearing up. A steady diet of lorcet+ and late night TV makes the brain mush. I was under the impression that a Cobra intake swap with out cobra cams would give a minimal power increase and move the peak higher up, with most daily drivers not seeing that high of a RPM...now I need clarification so I don't make this mistake again.

 

[Rich88LSC]

To tell you the truth I like low end more than hi end.

How does it go, Horsepower Burns gas and Torque burns tires?

Dose any one know the factory gears of an 1996 SS Impala? I understand that car has 340lbs of Torque so it's going to have more pull than a DOHC but I remember the gears/hook feeling real good.

4V 4.6 and low end torque don't go together. I still say go with as much gear and stall as you can live with.

I believe the Impalas came with 3.55s.

 

[Icedphoenix]

I was going to do this to my t-bird till she got totaled so just skiped it and got a mark. Anyways im throwing this out cause always thought of this myself but never asked. You are changing gears i was thinking like 4.30 but thought that might be to high and was wondering, and im hoping that someone could answer this cause some people don't think about it..... Wouldn't the cougar t-bird diff housing be stronger then the marks so wouldn't you swap the gears into one of those over a mark aluminum housing to keep it from dynamiting itself just a thought hope someone knows for sure.

 

[chicken]

ok scratches head.............
95 bird
95 mark dohc (gen 1 intake)
kooks headers, no cats
circle d converter
4" (i think) DS
mark pumpkin with 4.10's and a trac loc
mark alum real lower control arms
lowering springs
rear diff brace
rear strut tower brace
blistein (sp?) rear shocks
j mod and resealed trans at uhhh 170~ish k and still running strong
rpm switch for the imrc's
uhhhh paint....theres lots more just cant remember, if you are on tccoa its midwestbird's car, i built it. heres a vid from the dyno if the vids dont load (dont work here, click the link at the top)
project thundermark dyno run Video by chicken - MySpace Video

 

[Icedphoenix]

hey chicken where did you get the loc and 410s from lovethe car btw mine was a pearl 95

 

[Blenderhead]

I was going to do this to my t-bird till she got totaled so just skiped it and got a mark. Anyways im throwing this out cause always thought of this myself but never asked. You are changing gears i was thinking like 4.30 but thought that might be to high and was wondering, and im hoping that someone could answer this cause some people don't think about it..... Wouldn't the cougar t-bird diff housing be stronger then the marks so wouldn't you swap the gears into one of those over a mark aluminum housing to keep it from dynamiting itself just a thought hope someone knows for sure.

No! In fact the tbird/cougar guys swap it out to the aluminum housing to save weight. The weak point of the diff that usually breaks with lots of power is not the housing itself but rather the diff cover, which is also aluminum on the tbird/cougar diff, so there would be no strength advantage to running the heavier cast iron diff over the aluminum one. If you are worried about breaking it though, there are several companies that make a brace that bolts onto the housing with the cover bolts and reinforces it.

 

[chicken]

hey chicken where did you get the loc and 410s from lovethe car btw mine was a pearl 95

not my car, i just built it. but if was ever to go for sale it would go to me

 

[RCReevesPhotography]

I understand that the DOHC motors are crappy on the low end I don't see why I could not use the factory Mark VIII T.C., Rebuild my Trans with a nice J-MOD, install 3.73 Trac-Loc gears and maybe have some shift options done in my dyno tune and still get a nice low end feeling with my stock 97 Mark motor?

Any ideas?

 

[Rich88LSC]

No! In fact the tbird/cougar guys swap it out to the aluminum housing to save weight. The weak point of the diff that usually breaks with lots of power is not the housing itself but rather the diff cover, which is also aluminum on the tbird/cougar diff, so there would be no strength advantage to running the heavier cast iron diff over the aluminum one. If you are worried about breaking it though, there are several companies that make a brace that bolts onto the housing with the cover bolts and reinforces it.

Exactly.

I understand that the DOHC motors are crappy on the low end I don't see why I could not use the factory Mark VIII T.C., Rebuild my Trans with a nice J-MOD, install 3.73 Trac-Loc gears and maybe have some shift options done in my dyno tune and still get a nice low end feeling with my stock 97 Mark motor?

Any ideas?

You absolutely can you the stock TC. Gears will help personally I would look at a min of 4.10s but 3.73s are still better then the 3.27 gears you have now.

However a good TC will make big difference getting the car into the powerband. IMHO it's worth doing especially if your pulling the trans already.