GTA cam grind specs

Seasons greetings and all the best for 2017 from here in New Zealand fellow Alpiners.
Ive just bought my wife a 1.2T Captur for Christmas. She loves it! (she has previously owned a Clio and a Megan, and as a family we have owned and 12 (way back), a Scenic and a 2.0T Espace, so we know Renault reasonably well!
My blue '90 Atmo is part way throught the total respray project. Been all stripped, and prep started.
My black '86 Atmo has had everything execpt the engine done, and that is underway now.
The car is getting a total engine refresh, and the heads are being modified to improve flow, similar to those on my '90, but better.
The car will also be getting a free flow mainfold system, and we are looking at replacing the existing Weber DGAS with a Quickfuel 450 cfm four barrel (similar to a Holley, but better and easier to tune).
Does anybody have any info on mild street grind cam grind specs to help take advantage of all of this?
There are a couple of cam whizz's here in NZ, one of whom had specs for a previous GTA atmo grind, which he cannot find! The other wants to experiment a bit but I'd much rather go with something of a known quanity.
Any advice/help would be appreciated.
Happy Days!!
Graeme

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Happy New Year Graeme, hope you have a great year!

Any pictures of your setup? I guess PRVert folk on here are quiet as they are waiting details and pictures... pictures really, but let's ask for details what inlet manifold are you running, is this a std engine or has it been modified? What valve gear are you running, and do you know where in the rpm range you wish to move the peak power with a hotter cam?

Smiles,
Martin

Hi Martin
Happy New Year!
I have two cars, and 86 D500 which is getting this work done now, and a 90 D500 which had already had a head job by a local race engine expert, Lynn Rogers before I bought it.It has also had a compression increase, but we do not intend to go as far with the 86.
My son who is an automotive engineer and performance car specialist, has been undertaking a complete engine refresh on this car (when stripped it was in very good condition), and he largely copied 90's head work, along with some further improvements suggested by local local tuners. That included building up and re-shaping the head inlet and exhaust ports to increase gas velpocity and flow.
Both cars currently run a Weber DGAS carb, but I plan to fit a 4-barrel Quickfuel 450 to this one as they are easeir to tune than a Holley and have a fantastic reputation. The inlet maniold will be modified to suit, and has already been carefully matched to the engine head inlet ports. We will be ditching the inlet manifild water heating and the quickfuel has an electric choke.
The car is also receiving three into one extractors on each side.
I am simply looking to give it a bit more lift up around the 3000 mark, while retaining as much as possible of the tractable bottom end. The car will not be used for competition.
Any thoughts will be appreciated.
Before we get to the reassembly stage I will post some pix of the heads and the exhaust setup, plus the quickfuel and the inlet manifold mods.
Regards
Graeme

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Hi Graeme,

Sounds like a good plan.

These are some results I got with the earlier head, so they do work well with some rework. I didn't move the port up for my applications. So it would be good to see what you are getting with yours if you have had them on a bench?

From here:
viewtopic.php?f=8&t=5769&start=30

Hi Chris

Hope you are out there enjoying your holidays! Well, when you catch up I have developed the port and happy with the overall result - bulk flow, flow down force (cylinder filling), and mixture motion (wet flow)... results look like this (.. and that's my best reworked 46mm inlet valve 3ltr head by comparison, not the OE 3ltr head performance):



I'm quite pleased with the that given the complexity and extreme care needed with the 2.5ltr port SSR compared the 3ltr.

Martin

From here:
viewtopic.php?f=8&t=5612&start=60

Right I thought I would go back to some flow development and testing of the various PRV heads, and further previous results to compare the PRV in 12V form to other V6 engines and see how we stack up. Let’s face it this is what we are all looking to do, compare other marques and the technology of the day.

Well the airflow potential of a head will give the power potential of an engine, really the head if the build is such it can support the flow potential efficiently (remember the restrictions in the manifolds etc need to be accounted). If you want to read more then, you pick a good guide from the Superflow manual:

http://www.superflow.com/support/brochu ... ations.pdf

So I thought I would put some numbers around this by way of comparison out of interest. The Alfa 12V 2.5 and 3ltr engines make good comparison, 2V technology, but better chamber than the PRV from the point of even flow characteristic (pressure recovery) around the valve curtain area. The PRV is not so blessed in this regard, and this does affect our fuel distribution pattern, something I am currently trying to improve. Anyway, the Alfa 3ltr stage II engine here, with 11.5:1 CR and 292 deg cam gave 236hp at 6490 rpm, so good direct comparison. The standard 2.5 12V Alfa engines in 10:1 CR form were 200hp, >11:1 versions with hot cams and ported heads on 46mm inlets show 215+hp , and the Essex V6 head here went on to give 175hp at the wheels. So looking at the 3ltr Alfa and PRV 3ltr both in stage II trim on the same diameter valve give very similar performance, with the PRV beating it at the higher flow, big cams would pay dividends here. I will have to dig the data out for the OE 3ltr heads for both the Alfa and PRV, just to give some comparison, but not essential for this discussion. As you can see from the following, with careful flow bench development the PRV 3ltr head porting, seats and valve shape can be made to perform, and potentially more with larger still valves, but this would get into offsetting the shrouding and measures needed to achieve that.

So I think the P4 replica should be looking good for around 200hp given it’s a top end only rebuild, and the lower 9.5:1 CR. Andreas 12V n/a 3ltr with the high CR pistons, full build and fresh rings should see him to the 230hp hopefully, and that will be a lovely engine. So hopefully there should be some interesting articles on here this summer, John Law’s set included.



Column order (left to right):
PRV OE 2.5 44mm, PRV 2.5 stage II, Alfa V6 2.5 OE 44mm, PRV 3ltr 46mm stage II, Alfa 3ltr 46mm stage II, and finally Essex V6 3ltr 46mm stage II

Lift thou
50 17.1 18.5 13 17 18 15
100 38.9 37.4 25 35 36 29
150 58.2 55 42 53 57 44
200 73.7 72.2 55 71 74 57
250 85.6 89 68 87 92 69
300 91 104 77 102 104 78
350 93 114 83 114 110.4 86
370 xx xx 85 118 112 xx
400 96 119 86 122 114 91

I have it in Excel if you want it, bit difficult to drop it in here. Flow numbers in CFM, as mentioned above at 10" depression.

DallaraX has also posted some results, and I will pull these into one Excel to share, so all leveled on the same baseline as best as I can get it. If nothing else will give folk better data to run on power analysis software along with cam specs etc to do more informed analysis. So anything you have would be great.

As to the DGAS carbs, what size were you using the 38 or 40mm, and standard or bored chokes? I know from some time back this was popular mod in Aus, and Oddfire chap and others were running them in competition. Did see some dyno results, can't remember now, do you have any dyno results for yours on the DGAS? Pictures of your head and manifold work would be great too, email if you prefer, certainly happy to share mine, and critical dimensions. Happy to share my cam data if that helps, no point shipping cams around the world.

Cheers,
Martin

hi Martin
My DGAS were both 38mm chokes.
I have my Quick Fuel BDS 450 carb in transit. I got the black diamond teflon coated version as they say it lowers the fuel temperature in the carby by 6 degrees compared to a standard bare metal housing.
The engine is up Nathan my son's in Auckland, but he is going to send me some photos of the heads.
Will send phiotos of the manifold and exhaust later.
We have not had either engine on a dyno etc, but the fellow that did the heads on my blue car is recognised as New Zealand performance head guru.That car goe quite a bit stronger than my black one, although local GTA fans say they always considered that a quick ATMO anyway. The main difference can be felt around 3,000 rpm.
We took the heads off the blue car, stripped them, and compared with the heads on my black car to check out what had been done.
So the heads we are talking about now are very similar, but with some detail improvements including re-shaping of valve guides etc.
Nathan is going to email me some pics which I will flick to you.
Re the cams, my engine is the 2.9 normally aspirated, so the cams will be different to the 2.5 which is an even-fire engine.
So the cam grind details I am looking for are for the 2.9. I note the valve timing on one bank of the 2.9 engine is also slightly different to the other.
Again, any help would be appreciated.
My email is graeme@purches.co.nz.
Regards
Graeme

Hi again Martin
Here (hopefully if I can get this to work) are some pix of the intake ports for my 12V head on the 2.9 litre Atmo.
I have resized these so the files aren't' too big (originals were 4 mp).
Bear in mind some of these aren't finished yet - in some areas the ports are being built up (reduced in size) and then reshaped to not only improve flow but gas velocity. My son has had huge success doing this on the some Nissans, including his racecar.
I can't seem to get the pix across, so if you email me Martin I will reply and attach to that.

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Hi Graeme, email sent, thank you