Jump to content
HybridZ

E31 head, what is needed to make it perform?


pjo046

Recommended Posts

I'm not positive on this but i seem to remember 1 fast Z telling something about not putting in bigger valves, correct me if i'm wrong, 1 fast Z.

If you want to use the car for street and live in Norway, i would recommend you not to go with a cam that is to big, you will need low end touqe and as far as i remember the 40 Dellorto's will run out of air at 6500 RPM on a 2.8.

I also have a set of 40 Dellorto's and i think they look and sounds great, but when it comes to that build i think the SU's will be just fine, they should handle a little above 200 HP, witch i think will be close to what you can expect with that build.

I'm not a guru or wise ass on this subject, all i know comes from using the search function and reading this and other forum's and of course my "How to" Datsun bible.:hail:

 

There is one selling some E31 heads on zcar.com, so if you want to have it build in US, it will be cheaper buying one of those, than shipping yours from Norway.

 

Chris

Link to comment
Share on other sites

The alternative will probably be roundtop SU's with a N36 manifold. So, how do these two options compare? I know the SU's are much easier to tune etc, so that's a good reason for going with those. But, will the dellortos offer much better power despite them only being 40mm?

 

If you guys were to give a ballpark guesstimate, where would we be power- and torque-wise with these dellortos (or the SU's), L28, flat tops, street cam (typical stage 3 grind), E31 with the bigger valves installed, headers and a crank-fire ignition?

 

My E31 head (suppossedly) had extensive work done to it. 1mm larger then 280 valves, new cam, ported etc. It's got a very large cam. I can get the lift/duration if your interested. It is quick.

 

The car came w/ OER 45mm and I didn't feel like trying to find parts for the rebuild. So I bolted on the SU's w/ the N36 manifold. Supposedly my motor was dynoed at 200 crank HP w/ just SU's. I'd guess anywhere from 20-40 HP increase if I kept w/ the 45mm. I think the heavy cam could have really benifitted.

 

I say suppossedly because the information I got was from the person who built the car, not the guy I got it from.

 

My car is pretty quick, but no where near turbo fast.

 

I run the E12-80 Zx dist which triggers the MSD 6AL.

Link to comment
Share on other sites

I'm not a guru or wise ass on this subject, all i know comes from using the search function and reading this and other forum's and of course my "How to" Datsun bible.[/color][/u]:hail:

This is the internet opinion for sure, but my suggestion is get some people who have actually run a bigger cam to comment. Experience > theory.

Link to comment
Share on other sites

I would do what the E Production racers do. Or, if you want to go all out, send your head to Sunbelt and tell them to do what they did to Zredbaron's head.

 

Just a FYI, and maybe a little off topic- Sunbelt was bought by Kinetic Racing and is largely occupied with Spec Miata, Porsche, and BMW motors these days. However, if you can get Jim Thompson and the crew to do any work on a Datsun head you absolutely need one of his cams. Most, if not all of the typical aftermarket "performance" cams are copies of copies of very early R&D on the Datsun motor (some are probably even BMW grinds scaled for a Datsun motor). Harvey Crane and Ed Iskyderian did some of their own original work back in the day, but alas, since their passing their companies and products are not quite the same (IMHO). Sunbelt was heavy into cam development for the Z before, during, and after John Coffey's killer N/A motor (which had a unique jet like exhaust sound on Sunbelt's dyno, BTW) and was making cams with typical performance lifts and durations but with none of the typical bad spring harmonics and way less spring force required. Less spring force = more available horsepower. Don Potter used to claim a stock Z cam at 5000 rpm took 75 hp to drive. Imagine how much hp a big lift cam takes. I don't remember the lift on Mr. Coffey's cam (.5 something?) but if I'm not mistaken the spring force was below that for a stock cam.

 

My guess is the most current knowledge bank regarding Z cams lies with Sunbelt (and maybe Rebombo, er, I mean Rebello, but since a Rebello never beat a Potter or a Sunbelt head to head I tend to side with the latter). Look at where Z's are racing today and that's where your cam guru's will be. Street sales mean little- that's all marketing hype and misinformation. Jim Thompson at Kinetic/Sunbelt is the only person I know of that's done Z cam development recently with current technology and robust dyno testing and on track wins. I could be wrong, like to hear if anybody else doing the research.

 

Up until about the time Kinetic bought them out (nearly 2 years ago?), Sunbelt was getting real Nissan billets for grinding their own cams but I think they're all gone now. That may be a problem now, not sure.

Link to comment
Share on other sites

Thanks for all the detailed feedback people!! :) It's nice to have all of you share some of your knowledge with the less wise amongst us. ;)

 

I don't have time for a long and detailed post now, but I just wanted to say that the dellortos are probably not in the picture anymore. He wanted 600$ for them, and they will need a service as well.

So, unless using SU's will be a major performance-stopper on our build, we'll probably buy a newly rebuilt pair (rebuilt at ztherapy) for 300$ (or is this too expensive? It's only the two carbs, no manifolds or throttle linkage etc), and just slap them on when the time comes.

 

I'll get back to all the other stuff soon, but if you guys think the SUs will be too small (or that they're not a good deal at that price), do speak up.

Link to comment
Share on other sites

I would strongly disagree with the characterization about the Isky company. Ed was the one that used the existing grinds, and many copied Isky's grinds at that time. It was when Ron Isky got out of the USAF got his engineering degree that the Isky Designs were reworked to asymetrical profiles and incorporated modern and proper design techniques. And that was some time ago. Racer Brown cams from the early 70's also incorporated the asymetric profiles that are required for proper Nissan OHC stability.

 

And Ron is VERY much alive. And he does grinds that are custom. He knows the L Series Valve Train, and if you talked to him...when he has the time...you can learn a LOT.

 

Iskendarian was instrumental in the cam grind that holds the F/PRO record at El Mirage and Bonneville...

Someone on 'another site' recently flamed me quite severely for contradicting their statement that a '0.550" lift cam was required' on an engine making 320HP to the rear wheels. Our Bonneville engine does just that, and is well below that lift figure!

 

I agree there is a lot of misinformation out there regarding cams, but if you scrape around in history and find the people out there that have knowledge... They know a lot and are more than willing to let people know what is right and wrong.

Link to comment
Share on other sites

how exactly might a relatively inexperienced chap go about getting to talk to mister iskendarian (that was fun to type out.. say it out loud :) ) without purchasing an expensive cam grind??

 

I have a feeling that there is something about these awkward angles in these ports, that has something to do with this assymetrical grind, that is just a smidgin beyond my ken... one of these days, it will be within my grasp, and I am curious to know how I might be able to get those last few stones set in place.... but I'm probly boned if I'm not trying to order a camshaft from him, huh??

Link to comment
Share on other sites

Assymetric grind has everything to do with valvetrain stability. Port configuration has little to do with it.

 

Have you read the Racer Brown Articles? They are very good, and nothing has changed since they were written in the early 70's regarding cam airflow basics in relation to piston position, bore, etc...

 

For the cost of the cam...what? $180 list price? Is it that much to ask that you actually be a buyer to get the technical support?

 

I'd say read the Racer Brown Articles on DMS' webpage. JeffP was so impressed by them, he actually downloaded and printed them hardcopy so he could re-read them while indisposed, or when he had additional time to devot to resoaking the sage words.

 

It's kind of like the Bible...only practically applied to Camshaft Design!

 

Links to the aforementioned articles abound. They are still good far as I know.

Link to comment
Share on other sites

Assymetric grind has everything to do with valvetrain stability. Port configuration has little to do with it.

 

Have you read the Racer Brown Articles? They are very good, and nothing has changed since they were written in the early 70's regarding cam airflow basics in relation to piston position, bore, etc...

 

For the cost of the cam...what? $180 list price? Is it that much to ask that you actually be a buyer to get the technical support?

 

I'd say read the Racer Brown Articles on DMS' webpage. JeffP was so impressed by them, he actually downloaded and printed them hardcopy so he could re-read them while indisposed, or when he had additional time to devot to resoaking the sage words.

 

It's kind of like the Bible...only practically applied to Camshaft Design!

 

Links to the aforementioned articles abound. They are still good far as I know.

 

I started reading them shortly before my old PC futzed, and haven't dug up a link since then.. I have my old hard disk. and I think I had bookmarked it, so it shouldn't be a major ordeal to find em.. but priorities come up, and spending an hour digging up hours of reading material is not an easy thing to find time for. Thanks for answering the question though; valvetrain stability. My brains will be chewing on that for a few nights, rest assured.

Link to comment
Share on other sites

I would strongly disagree with the characterization about the Isky company. Ed was the one that used the existing grinds, and many copied Isky's grinds at that time. It was when Ron Isky got out of the USAF got his engineering degree that the Isky Designs were reworked to asymetrical profiles and incorporated modern and proper design techniques. And that was some time ago. Racer Brown cams from the early 70's also incorporated the asymetric profiles that are required for proper Nissan OHC stability.

 

And Ron is VERY much alive. And he does grinds that are custom. He knows the L Series Valve Train, and if you talked to him...when he has the time...you can learn a LOT.

 

Good to know!

Link to comment
Share on other sites

Well you can call Jim Thompson at Kinetic Sunbelt Engines: 770-271-1577 and ask. I haven't been up to the shop in 6 months. Here's what has been a problem for Sunbelt, and proly a lot of Z performance shops for the last 10 years- an L series Z enthusiast will call you up and you'll spend 3 hours on the phone with the guy, several times, and after spending the equivalent of a day on the phone you'll never hear from him again, or at most he'll spend 5 grand. Racers are better, they know they have to pay to win. Contrast that with a BMW or Porsche enthusiast- you spend 15 minutes on the phone with the guy and he's writing you a check for 15 grand. So you go where the money is easier to come by. Sad, but I've seen this happen a hundred times. I'd like to think that Jim will still do a Z head for the right customer. Got my fingers crossed for any HybridZer that wants to go that route.

Link to comment
Share on other sites

  • 3 years later...

Found this thread doing a different search. What Keith says above is so true. Jim Thompson has a beautiful F54/P90 turbo long block and some ancillary parts sitting in his shop for sale. Jim says its built for a reliable 600hp and I've been trying to sell it for two years to a number of Z folks who call me about getting a turbo engine built. All of them have said they are really interested at the $12.5K asking price and then I never hear from them again. I'm not even getting a cut of the deal, I'm just trying to turn the Z community on to a great engine at a cheap price. A similar BMW build from Epic sold in 5 minutes for $17.5k.

 

Here are the specs on what's available:

 

9:1 compression

Forged CP pistons

Carrillo rods

Ported, polished, big valve head

Sunbelt special turbo cam

ARP studs

GTX3071R turbo

Link to comment
Share on other sites

I'll add to this necropost that Nathan at BC Gerolamy has ceased doing L-Engine Heads. What Nathan couldn't get, his dad could. The last two heads done by them are in the possession of Mr. Priddy.

 

The "Fat Old White Guys" are slowly petering out, or fading away. Someone with a 5Axis Profiler might be well advised to jig up someone's head to be able to reproduce this stuff some day in the future...

Link to comment
Share on other sites

Found this thread doing a different search. What Keith says above is so true. Jim Thompson has a beautiful F54/P90 turbo long block and some ancillary parts sitting in his shop for sale. Jim says its built for a reliable 600hp and I've been trying to sell it for two years to a number of Z folks who call me about getting a turbo engine built. All of them have said they are really interested at the $12.5K asking price and then I never hear from them again. I'm not even getting a cut of the deal, I'm just trying to turn the Z community on to a great engine at a cheap price. A similar BMW build from Epic sold in 5 minutes for $17.5k.

 

Here are the specs on what's available:

 

9:1 compression

Forged CP pistons

Carrillo rods

Ported, polished, big valve head

Sunbelt special turbo cam

ARP studs

GTX3071R turbo

 

Just the rods, turbo and pistons cost almost $4000 new.

Link to comment
Share on other sites

I'll add to this necropost that Nathan at BC Gerolamy has ceased doing L-Engine Heads. What Nathan couldn't get, his dad could. The last two heads done by them are in the possession of Mr. Priddy.

 

The "Fat Old White Guys" are slowly petering out, or fading away. Someone with a 5Axis Profiler might be well advised to jig up someone's head to be able to reproduce this stuff some day in the future...

I remember being quoted from our machine shop about $1200-$1500 if he scanned the head/wrote the program (you keep it) and another $800 or so to run heads with the program. If he keeps the program for his own use, rather than giving it to you, then he only charges you the cost to run the heads, I suppose only if he feels there is money to made from future heads. Don't you know though, that even if you paid the extra to own it yourself, he will probably keep a copy for himself anyway. ;) Worth it though.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...