2.8 w/ E cams & Webers

[Roger 911]

Here is the current "dream" for my 2.4L motor, when it is time to rebuild. I'm looking for a good street motor that will see occasional DE and auto-X use. The starting point is a 2.4T motor (yes, 7.5:1 CR!!!) w/E cams & Webers, 4R case. I would want to retain, or reuse, as much as I can.

Bruce Anderson describes a 2.7L motor using E cams and Webers in his book. If I recall, that was using the 8.5:1 RS pistons. Given the current availability of JE pistons and QSC cylinders, it seems like a 2.8L, 9.5:1 CR, w/ E cams and Webers would be fairly easy to do, and would be a similar, but slightly more powerful motor (200+ HP?). Heads currently have the "tiny" T ports, so probably 35/34 would work there. Twin ignition would be nice, but I don't want to spend the extra $$$, plus I think 9.5:1 will make it easier to find gas, anywhere in the country. It's not a race car.

I'd be curious to hear from anyone who may have experience with a motor like this. Especially if you built it on a 4R/5R case. I know there are a lot of people who feel you have to have a 7R case for any sort of "material" power increase. On the other hand, I have seen posts from engine builders (Steve Weiner) claiming a 4R is good as long as you keep it under 7K RPMs, which would be the case here (actually, I currently have a 6500 rev limiter, which I think is just fine).

Thanks.
Roger

[RoninLB]

I run the Mahle 2.7 8.5:1 and E-cams etc

are you asking about the 2.4 into a 2.7 or just about the 2.7 w/E-cams ?

[Steve@Rennsport]

Go for it, Roger......................

My best advice would be not to forego the mandatory modifications to your engine case that are required for durability & longevity.

Be sure your oil cooling system is up to snuff since that's the real key to magnesium case reliability.

[al lkosmal]

5 years ago or so, I built a 2.7 w/E-cams, JE 9.5:1 pistons, single-plug, Webers, SSI's and Dansk 2in-2out sport muffler. This was built on my 2.7 7R case, so a bit different than your starting point. This was one of the best street engines I have driven.

regards,
Al

[Evans, Marv]

There is still decent availability of 2.7L cores out there. If it were me, I'd just spend the money on that rather than machine work on my 2.4 case to make it work. Besides with 2.8 compared to 2.7, there isn't a lot of difference in displacement. With the 2.7L case you can get the features you will have to mod the 2.4 case for. Plus with people cutting up the older cases, there are fewer & fewer left as time goes on - just like the older cars. Just my .02.

[Walt Fricke]

I'm with Marv. You won't get much of a boost with 130 more CCs with an affordable and streetable build.

The 2.8 RSR made its power because it had larger valves in one of a kind heads, huge ports, exotic parts (titanium rods), and made its HP up high - max HP at 8,000 rpm. Hardly the way to go for a street motor, even if dual purpose.

Especially with your weaker case, a bump to 2.7 might be easier, less expensive, and more durable. You might find good used cylinders, or not so good ones cheap you could have Nikasiled. And there are a variety of Mahle performance 90mm pistons around. I have their 10.5/1 version in my 2.7 race motor (head work, big cam, 46s, 224 rear wheel HP), but there are other CRs out there. 200 crank hp is reasonable of achievement, I think. After all, the 2.4S was 190 advertised, and the 2.7RS was 210.

[Roger 911]

Originally Posted by Evans, Marv

There is still decent availability of 2.7L cores out there. If it were me, I'd just spend the money on that rather than machine work on my 2.4 case to make it work. Besides with 2.8 compared to 2.7, there isn't a lot of difference in displacement. With the 2.7L case you can get the features you will have to mod the 2.4 case for. Plus with people cutting up the older cases, there are fewer & fewer left as time goes on - just like the older cars. Just my .02.

Yes, I thought about that. However, I've read that in many instances 2.7 cases may actually be in worse condition than 2.4s due to the increased heat stress of the emissions equipment. At least with my 2.4T case, I have a fair amount of history on it, and being a T, it has not really seen high heat or RPMs.

[Walt Fricke]

Roger

I think the coveted cases are 2.4 7R cases, and if they are Ts so much the better, for the reasons you state. Just takes a spigot bore and you are good to go up in displacement.

And because the 7R has case reinforcing not found in earlier cases.

Not clear what case you have. A '72 would not have had a 7R case. I think the 7R came in about '72, but not sure (and too lazy to look it up).

[Roger 911]

Originally Posted by Walt Fricke

Roger

I think the coveted cases are 2.4 7R cases, and if they are Ts so much the better, for the reasons you state. Just takes a spigot bore and you are good to go up in displacement.

And because the 7R has case reinforcing not found in earlier cases.

Not clear what case you have. A '72 would not have had a 7R case. I think the 7R came in about '72, but not sure (and too lazy to look it up).

I have a 4R. I guess the question is, for a street 2.7 motor, are you better off with a '76 7R, or a '72T 4R???

[Henry Schmidt]

For a 2.7 or SS 2.5 you would want to use the 7R case.
If you want to build something fun using the 4R case build it with 86mm cylinders. They are slip in with no machining necessary.
I have always thought that the E cams were a lazy compromise.
With carbs and 8.5 to 9.5:1 compression I would use Solex and Mod Solex cams.
The Solex cam was designed from a clean sheet of paper with the singular purpose of offering the widest power band when using carbs.
IMHO, they (Solex cams) offer a much more enjoyable power band than the E.

[Roger 911]

Originally Posted by Henry Schmidt

For a 2.7 or SS 2.5 you would want to use the 7R case.
If you want to build something fun using the 4R case build it with 86mm cylinders. They are slip in with no machining necessary.
I have always thought that the E cams were a lazy compromise.
With carbs and 8.5 to 9.5:1 compression I would use Solex and Mod Solex cams.
The Solex cam was designed from a clean sheet of paper with the singular purpose of offering the widest power band when using carbs.
IMHO, they (Solex cams) offer a much more enjoyable power band than the E.

That was my original thought, but then you start listening to that little voice that says "bigger is better, no replacement for displacement", and you wind up looking at 92mm pistons. I'm sure I would like Solex cams better. I was focusing on reusing what I could. However, I guess if I really want to stay on that path, I should probably just bore my iron cylinders out to 85mm and put some JEs in there.

[ericb]

Henry, are those 86mm cylinders Biral or all alum.?

[RoninLB]

I'd use early solex's [or i guess Mod-solex] w/some head work in a heart beat if my engine was used for something other than trucking around the country

I took the safest route for my act and can flip them any time if I ever get info that my 3-4.5k rpm torque would improve without killing gas mileage or plugs. Right now the E allows enough torque to cleanly zip around in traffic at big interstate speeds and give me 17-18 mpg. And if I'm lazy and wind up crusing at 2.7k rpms in 5th gear it won't lug when accelerating although it'll do that slowly.

Solex in a 2.7 can be a dynamite package imho

[Henry Schmidt]

Originally Posted by ericb

Henry, are those 86mm cylinders Biral or all alum.?

New manufacturer Biral.

[larrym]

Did that back in 1977 on my 914-6, vintaged raced it until 1988

used original 2.4 case & heads, did all the "bruce's book" stuff plus advise from Woods, Stoddard, et al

- much machine work to race prep including the head chamfering - 10.5 CR - originally was 14:1 CR when bolted up so I had to space out the cyls 080 to get it to wher i could run 100 octane street gas of the day -

it had lots of torque, pulled strong from under 1500, but it generally ran out of breath at 5800 on track, tho you could keep winding it to 7000 - in all the car was pretty competitive at the time and once won pole position at Willow - always ran in top 1/3

over-revved it at Lagiuna Seca and broke a couple rockers - but the extra spacing saved the pistons & valves

I swapped off the 2.8 parts for 2.7RS heads & p/c's and solex cams - built on a new 7R case with the same old 2.4 crank and 8.5 CR; Runs on pump gas

don't like the result - makes good power on a flat curve all the way to 7000, but doesn't start making torque until about 2000 so it is not nearly as good a street engine - and it is no longer competitive in the current track enviro - "cubic money" as they say

- plan to go back to E cams - have already got the CIS set to regrind - all i need is TIME to do the change

meanwhile, i drive it regularly and fill it with 91 octane

[Roger 911]

Originally Posted by larrym

Did that back in 1977 on my 914-6, vintaged raced it until 1988 used original 2.4 case & heads, did all the "bruce's book" stuff plus advise from Woods, Stoddard, et al

Larry,

Do you recall if the 2.4 case you used was a 7R, or a "lesser" case like my 4R?

Thanks.
Roger