3.0 with 2.8 Heads What Say The Gurus?

[D001264]

Ok definitely over my skies here, but let’s give the question a whirl.

With the scarcity on non-rotted 2.8 blocks. Is it feasible to use a 3.0 block even fire crank, pistons and liners while retaining the 2.8 heads and intake? I don’t think there would be a difference between an even and odd fire cam as the pistons in a bank will reach TDC at 120 degree intervals in either configuration. The issue would appear to be the 30 degree splay on the even fire crankshaft that could not be accounted for in camshaft timing by the limit of 19 teeth on the crank timing gear. Retarding the camshaft for the crank journal splay by moving one or two teeth on the cam to chain interface would offset the cam timing by 18.9 or 37.8 degrees (checks math)...

Seems solutions would be custom camshaft, adjustable camshaft gear, or cutting a new slot in cam for locating cam gear to provide the required offset.

Love to hear about any thoughts on the feasibility, issues or successes with this type of a build.

All Gurus or mortals welcome.

[RamblinDMC]

I built the opposite actually. 2.8L block, crank, pistons, and liners with eagle 3.0L heads. But I used the 2.8L cams and sprockets. And my valve springs are from a Renualt Alpine A610 Turbo

[D001264]

I built the opposite actually. 2.8L block, crank, pistons, and liners with eagle 3.0L heads. But I used the 2.8L cams and sprockets. And my valve springs are from a Renualt Alpine A610 Turbo

Sounds interesting, is there a thread on this adventure?
I freely admit I am in over my head hear, but very interested how parts from different PRV models play together. Did you have any issues with the hydraulic lifters with the 2.8 cams for mechanical lifters?

End result, where you happy with the modified engine?

[RamblinDMC]

I didn't have a build thread, but I did make this post when I finished everything up. I have a few more mods to do on my interior, and then I'm going to make a detailed video going over all of it. There's definitely some affordable performance gains to be had by mixing and matching PRV parts.

I didn't use the hydraulic lifters from the 3.0L heads. I used the normal 2.8L rockers.

[D001264]

Great info on the interchange ability on the 2.8 vs 3.0 rockers.

My high level goals in researching this would be:
Replace 2.8 block with more available 3.0 block.
Even fire operation with 3.0 crank
2.8 heads and intake to reuse MS EFI and optical trigger mounted in 2.8 dizzy.
Learn more about PRV variants

[Josh]

Bill has alot of expertise here if you want to ask him.

This has been done before. You can put 2.8 heads on a 3.0 block, then the intake manifold and everything will bolt right up.
If you try to bolt the Kjet setup to a 3.0 as is you will find the angle is wrong and you are lacking a distributor. Bill has made adapter plates that get around this but I am not sure of the availability.

After this you are faced with another issue. you now have a odd fire distributor with a even fire crank. You need to run an even fire distributor, Bill has done this, Im not sure what is all involved. Ideally you just need an even fire distributor cap that fits on the stock delorean distributor assembly. The stock ignition module will work fine with this setup.
Alternatively you can install the 2.8 crank into the 3.0 block. Since the 3.0 gains its displacement by bore, the stoke of both engines is the same at 73mm. You can leave the pistons and connecting rods in the 3.0 and bolt them up to the 2.8 crankshaft. You will need to get into the bottom end of the engine anyway as you swap out the lower crankcase that interfaces with the engine mounts.
If you install the 2.8 timing cover and balancer you can run all of the stock delorean accessories in either case.

http://www.dmctoday.com/showthread.php?2404-Progress-Update&

[RamblinDMC]

Or you can run MS3X and do sequential spark and fuel. It can accommodate both even and odd fire. My 2.8L with 3.0L heads works fine without a dizzy. :)

[D001264]

Thanks Josh and RamblinDMC, looks like some good reading material! Looks like Bill must be the guy for PRV mods.
I am currently installing sequential MS EFI and Spark, I think Jimmy was a bad influence :). I had to grab his setup when it was for sale, wish I could have gotten his engine.

P.S. shoutout to Jimmy he has been great to work with on the sale of his EFI setup!

[Josh]

Oh, I didnt put two and two together. I can talk with Jimmy, but if you run a trigger wheel off the crank, and throw on the 2.8 heads you will be able to make everything work.
The cam sensor that jimmy sold you would no longer be used. Im sure another owner could use it though if you sold, its a nice piece.


EDIT: sorry, I am WRONG!
you can put everything Jimmy sent you right onto a 3.0 block, provided you swap over the heads. You will need to change the settings in the megasquirt to even fire and you will be off to the races.
At the end of the day you have a small increase in displacement and a even fire engine. Swap over the timing cover and front drive as well as mentioned.

[D001264]

Thanks Josh, of course this is just temporary, until I do an LS swap :)

[Andrew]

I have researched this build setup. From what I have determined, the secret to the timing / cam issue is the 3.0 timing chains. One timing chain is Eagle specific based upon the timing marks. The other side chain crosses to a Volvo 760 etc. Thus, as long as you use the Eagle chains and follow the correct procedure to set the same from the shop manual, you can use the 2.8 cams and heads on the 3.0 block.

With Bill's build he utilized the 3.0 block and 3.0 heads with 2.8 cams. Bill confirmed that the 3.0 and 2.8 cams are the same, but for the timing gear and mechanical fuel pump lobe on the 2.8 cams. From my understanding he opted to go with the 3.0 heads due to their improved flow. However, Bill need to drill a hole in one head for the distributor and a hole in the other head for the mechanical fuel pump. Bill's 3.0 build was carbureted, but if one wanted to run K-jet with 3.0 heads, that would require some serious modifications to the heads.

The previous posts are correct regarding the need to source an even fire 6 cylinder distributor. Bill used a modified distributor from a 4.2 AMC I-6 engine. In short, the distributor modifications included shortening the AMC distributor to remove the oil pump drive and swapping the drive gear from a stock DMC distributor. Bill posted pictures showing the measurements of the distributor modifications. Since it worked, I would defer to Bill's distributor mod procedure. I happen to have an 82 AMC Eagle, so, just for fun, I test fit an AMC distributor in a stock 2.8 PRV head and confirmed that it fits from a diameter standpoint. The AMC distributor sits higher than a stock DMC distributor, thus, I don't think that distributor would work on a K-Jet build.

Disclaimer: I have not actually built this engine, I have only researched the build.

Hope this helps! Keep us posted!

Andrew
4194
5052

[Josh]

Im not sure why Bill didnt just swap heads. Leaving the 3.0 heads on created more work.

Great note about the timing chains.

The distributor no longer matters as it is an EFI setup and the RPM pickup is installed in place of the distributor and the computer can be configured for even fire or odd fire easily.

[Farrar]

Im not sure why Bill didnt just swap heads. Leaving the 3.0 heads on created more work.

In addition to either failed head gaskets or detached cylinder liners, the 2.8 had a bad case of block rot. I had filled two holes with engine epoxy but oil was starting to leak out again.