Sd1 Front cover on 3.9lt

Gavin RS · Post by **Gavin RS** » Mon Mar 09, 2015 8:27 am

Morning everyone.

I need some expert advice please.

My race Sd1 full bare metal re spray is now complete and I can start assembly. I was going to fit my spare 9.35-1 comp 3.9lt efi motor (but with Weber 500cfm) to the car keeping the serpentine belt system etc but as I run an electric water pump I thought I would rather go the route of fitting the SD1 front cover etc..my 3.9l has the crank driven oil pump and still uses the Distributor.

My original 3.5l that came out of the car is an untouched motor since new so I was thinking of fitting my new piper cam kit in and use it that way but the 3.9lt will give me better performance.

I have never actually seen the fitting of an SD1 front cover fitted to the later type motor. what would I need to do this conversion, I have everything at hand from other 3.5lt motors I have. One thing I do not have though is the damper pulley from the 3.9lt but I can get one.

Any info and advice would be appreciated.

Thanks
Gavin

kiwicar · Post by **kiwicar** » Mon Mar 09, 2015 8:56 am

Hi
the front cover off the 3.5 should go straight onto the 3.9 engine, they are basically the same block and crank, the 3.9 has better strengthening webs but they are in the middle of the engine away from the front cover.
As this is a race engine have a think about power bands and gearing for a given cam heads and inlet set up the 3.9 will make peak power a few hundred revs lower than the 3.5 and the power band will be about 5% narrower than the 3.5 with less over rev beyond peak power. If you generally run on short twisty circuits then the extra torque low down that the 3.9 will make may be a big advantage. However if you run on long open flat tracks you may find it better to stick with the 3.5 and add a cam with a little more exhaust timing and drop the final drive ratio and rev it a bit more. There is also the option of using the 3.9 and up camming that, this will give it a much narrower power band compared to the other two options but could worh very well if you run oval cinder track and a close ratio box.
Best regards
Mike

Gavin RS · Post by **Gavin RS** » Mon Mar 09, 2015 10:10 am

Thanks for the reply Mike.

I run the car in Historic racing in a road legal class called Marque Cars. The engine is not full race as the car gets driven to the track. Basically I am looking at torque and will not rev over 6000rpm anyway. My 3.5l has been very good over the last 8 races but I fall short at tracks like our Kyalami with longer straights. I just need that little more as the car is very consistent anyway.

With the front cover issue, would the Sd1 gasket be used as well. The sump and pick up I take it would also need to be from the Sd1. As for the damper pulley I know the 3.9lt crank nose has the longer keyway, would I be able to use the Sd1 pulley.

Thanks

kiwicar · Post by **kiwicar** » Mon Mar 09, 2015 11:03 am

Hi
I can't comment further on the swap beyond that the blocks are basically the same (obviously the bores are different), I have not done it myself. I would swap the whole SD1 stuff across using the gaskets (again though I am pretty sure they are the same) as I know mix and match dipsticks tend to end up with over full sumps. The blocks changed with the 4.0/4.6l engines and although they can be swapped they need more work.
best regards
Mike

DaveEFI · Post by **DaveEFI** » Mon Mar 09, 2015 1:42 pm

Gavin RS wrote:Thanks for the reply Mike.

I run the car in Historic racing in a road legal class called Marque Cars. The engine is not full race as the car gets driven to the track. Basically I am looking at torque and will not rev over 6000rpm anyway. My 3.5l has been very good over the last 8 races but I fall short at tracks like our Kyalami with longer straights. I just need that little more as the car is very consistent anyway.

With the front cover issue, would the Sd1 gasket be used as well. The sump and pick up I take it would also need to be from the Sd1. As for the damper pulley I know the 3.9lt crank nose has the longer keyway, would I be able to use the Sd1 pulley.

Thanks

The standard EFI 3.9 has pretty well the same peak BHP as the standard 3.5 EFI. The 3.5 has a higher CR as standard. Where the 3.9 gains is in torque at lower revs. So depending on your gearing, may not improve the top speed.

unstable load · Post by **unstable load** » Mon Mar 09, 2015 6:07 pm

GavinRS, where do you live in SA? I'm down in Cape Town.

Gavin RS · Post by **Gavin RS** » Tue Mar 10, 2015 7:24 am

Thanks for the replies guys, gives me a good idea now what to do. I have 2 spare engines, 2 spare g/boxes, 2diffs with different ratios, loads of parts used and plenty new in packaging as well as a brand new 3.9lt block still in its crate and 3, SD1's to play with

I might just remove the LSD unit out of my road going 4.6l UK import SD1 Vitesse and put that into the race car.

I will go with the 3.9lt and 3.5 front cover and with my new block I will build a nice strong spec motor to handle some endurance events

John.

I am up in JHB, my Sd1 has just had a full bare metal re spray and in the colour scheme of the Andy Rouse Group A car that was restored last year in the UK. I hope to be back on track for the 6th June race . hopefully at next years international event in Feb I will come down to Killarney for second leg of the event.

Gavin

unstable load · Post by **unstable load** » Tue Mar 10, 2015 4:47 pm

Gavin RS wrote:John.

I am up in JHB, my Sd1 has just had a full bare metal re spray and in the colour scheme of the Andy Rouse Group A car that was restored last year in the UK. I hope to be back on track for the 6th June race . hopefully at next years international event in Feb I will come down to Killarney for second leg of the event.

Gavin

Sounds great! I hope I am in CT for the race.

Gavin RS · Post by **Gavin RS** » Wed Mar 11, 2015 8:22 am

will post some pictures up soon of the build.

It would be great to run at Killarney, never been to that track as yet

unstable load · Post by **unstable load** » Wed Mar 11, 2015 12:09 pm

It's an interesting track from the guys that race it. My best was watching Sarel van der Merwe steering the Bobby Olthoff Ford Galaxie round there.

Gavin RS · Post by **Gavin RS** » Wed Mar 11, 2015 1:30 pm

Yip, always watch it on TV a few weeks after the event. awesome to see

Gavin RS · Post by **Gavin RS** » Fri Mar 27, 2015 12:36 pm

Greetings all.

My SD1 race car is now back from bodywork and full re spray so it is now time to assemble it.
I am contemplating what to do with the 2 engines I have and after trying the SD1 cover on the interim 3.9l I decided I will go that route for now.
I need to install my new cam kit as well, does anyone have a nice detailed pdf file or pictures for me to set up the cam timing properly.

Thanks

Gavin

DaveEFI · Post by **DaveEFI** » Fri Mar 27, 2015 2:07 pm

Never quite understood just why an aftermarket cam needs 'setting up'?

If they can grind the profiles accurately, why can't they put the key slot in the correct place?

DEVONMAN · Post by **DEVONMAN** » Sat Mar 28, 2015 9:14 am

DaveEFI wrote:Never quite understood just why an aftermarket cam needs 'setting up'?

If they can grind the profiles accurately, why can't they put the key slot in the correct place?

Sometimes it's the slot in the cam gears that is not machined spot on.

Gavin RS · Post by **Gavin RS** » Wed Apr 01, 2015 6:43 am

Fortunately I have a proper double roller chain with vernier pulley so the cam timing can be set properly