Getting Your Slant to Breathe

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Location: Tiegerpoort, Pretoria

Getting Your Slant to Breathe

Post by 68barracuda » Fri 11 Jul 2008, 23:09

Right At this stage you and your slant have met and you have started to enjoy her. Great - things can be improved!

As previously mentioned - the well know 225CID slant six is a long stroke motor with a narrow bore - not a problem as such 'cept that Ma Mopar kept the same head design and Valve size from the 170CID mill a n engine which can develop 196BHP with a hyperpak and headers OK and 10:1 CR - take it as said that the 225 slant has the same stroke as the 440 V8 just to put things into perspective

But the 225 was strangled. Modern tech comes to the rescue - CNC combustion chamber milling, porting and gas flow techniques improve matters, but icing on the cake is the 1.7inch (1.62 stock) and 1.44 inch (1.36stock) EPN stainless steel valves - at $64 a set good value - a good thing to as the modifications to allow these valves is more expensive, but as they say in for a penny.

So porting, installing bigger valves is the way to go.- BTW do not over do porting - you have to keep mixture velocity up - and a mirror polish of the ports is totally unneeded - chambers is another matter - especially if you start pushing the CR higher. Good bowl work, unshrouding the valves etc all helps. - a side effect of the bigger valves is that they move the valve seat back into the chamber on high mileage engines- it is less shrouded - while you are at it have the seats hardened it prevents seat recession and allows you to run unleaded - 95 octane do allow higher CR to be run.

Due to the THICK cylinder head deck you can mill .1 inch of the head with out fuss.
The BIG question is who to use to do the head work - who will allow you to keep a sledge hammer over their private to prevent them from going over board

On the inlet side there is a couple of options - the late model local 4bbl manifold with a carter AFB or Holley 4160/50 listnumer 8007 - a 390CFM unit
, The Atkinson’s PowerPaK 2 x 36dcd7 Weber's on a ram type manifold - this setup is in the process of being reproduced, the stock 2bbl Carter BBD manifold - if you use a BBD from a 318 V8 you will also improve matters

Clifford performance offers the Clifford plenum Ram manifold, the HyperPak reproduction manifold, Ausiespeed offers he Hurricane Ram manifold - so there are choices - all these manifold come with provisioning for multipoint EFI

Please remember as rule of thumb - don’t go above 500CFM airflow.

Slants turbo charge very easily if you keep the stock 8.4 cr and that makes serious hp an efi turbo slant regularly turn 8 second times at Santa Pod in England - it installed in a Ford prefect....OUCH.

So induction is a personal preference -for restoration purposes I will stick to the original option bits - RSA 4BBl, hyperpak, and Atkinson’s - and the 318 BBD on stock 2 bbl manifold - keep it period looking.

Exhaust manifold is also a choking point which can be addressed.
Stock manifold extrusion honed collector milled out to 2 1/2 inch - it look's stock add ~ 20 Hp - on this not PLEASE do not match exhaust port on head to manifold - the smaller port on the head side acts as an anti-reversion device - prevents exhaust gas pulsed back into cylinder.

Dutra duals - Cast iron Shorty header - they work and they last but will put you back $500

HyperPak Cast iron headers - not available - period - helped push experimental slants to over 230BHP

Tubular 1 5/8 inch primary 34 inch long headers in a true dual exhaust system - 2 1/2 inch with an X -pipe and flowmaster mufflers - that is my design aim - it boosts torque, improves volumetric efficiency looks cool sound great and gets rid of the drone caused by the inline six cylinder.

Here you can go to Clifford - $650, Hooker -$ 700 or you can have it made up - I have the specs for the Factory performance tubular headers.

Last part in this peace of the puzzle is the CAM - and it just a phone call away - US connection can import you a compcam, iskederian or what you desire - ERSON however is the leaders in slant cam technology and offers mild to FREAKING wild - for my build I have ordered a 270seat to seat, 220@ 50. .465 inch lift cam from Erson - RSA performance stock cam - 244 seat to seat, 208 @50 .414 inch lift. dual roller timing chain and 340 valves are amongst the tings going into the cuda head - remember I am recreating the PHASE III PowerPak my CR is 9.5 BTW.

So there you go you can have a 230 BHP, 300lbFt torque slant six with my recipe (Weber’s etc) or a 280 bhp 270lbft torque with a 4BBL

I prefer the high torque route,and in theory my vollumetric effieciency will be just over 90% up from 68%

The long and the short is do not throw out your slant and stuff in a V8 and stuff up your car - a period look upgrade with hidden modern tech is so much more apealing.

In the next chapter - your oiling system and how to blueprint it

Enjoy your weekend
Fanie Gerber
It's never junk, it's just a part you're not currently using
Just say I own a few Mopars

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