What would you do? - engine spec choices

Right so I’ve sourced myself a good stock bore Mexican 302 block and it’s getting time to decide on my final spec.

It’s going to be 99% street driven, 347ci, 6500rpm limit near on 500hp build. Idea is for a snappy revving responsive engine.

What I can’t decide on however is heads and CR combo.
What I was thinking:

-fully prepped 302 block
-ARP mains studs
-K1/RPM/Liberty 4340 internal balance crank
-Scat 4340 H beams
-Mahle powerpak -6.5cc flat top pistons (1.0/1.0/2.0 rings)
-Clevite 77 H bearings
-Morel link bar lifters
-double timing chain
-Custom cam from Ed Curtis at FTI
-Davies Craig electric water pump + controller
-melling standard flow oil pump
-arp bolts throughout
-kevko sump
-harmonic balancer
-Jim Inglese 48mm 8 Stack ITB’s running on Emu Black ecu.

What I cannot decide on, either:

185cc AFR renegade heads with 58cc chambers and #8019 spring upgrade. With 0.041 head gasket and 0.213 crown to top ring the static CR to just under 10.6:1


Trick flow 11R 190cc heads, 56cc chamber.
With the same 0.041 HG and -6.2cc pistons this brings the static CR to 10.9:1

Obviously with cam specs I can bleed off dynamic CR to counter detonation, the Ecu has dual knock sensors with timing control. The car will be run on 98/99 octane and will also have flex fuel for up to e85 for European road trips. The plan is to have provision for 95 fuel if I get stuck.

Im open to peoples inputs to what you’d go with if it was your choice and why?
FYI the trick flows work out about $150 cheaper.
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Mike Pass

UK? IVA? Block date? Emissions level? Cats?
Main girdle? One piece crank seal? Neutral balance harmonic damper? Different piston notches for AFR or TW.
Steel neutral balance flywheel? How much rotational inertia to get a zippy response without needing too many revs in traffic.
Clutch for 450+ torque with reasonable clutch pedal pressure?
Exhaust system to get target dB noise level.
Pumps, filters swirl pot, two tank return system to supply enough fuel for 500hp.
Yes UK, it’s a 1971 D1 block.
No cats, visible smoke only.
No mains girdle, not even sure they’re designed for the Mexican mains caps without machining.
One piece rear seal yes.
Neutral balance damper yes.
Am aware of the different cuts for the pistons (is part of my reason for asking peoples thoughts on CR and head choice)
Am thinking of something along the lines of a 15-lb or so steel flywheel. Depends what’s on offer to suit the box. Am not concerned about inertia for pulling away, it’s a light car and will have good torque.
The AP clutch that SGT offer should be more than enough for the torque.
Target db noise will be sorted for IVA but will be planning v banded mufflers with interchangeable megaphones if I decide it.
Yes to the aforementioned fuel system :)

Has anyone on here run these twisted wedge heads or Afr’s to give any real world opinions on them?
I like all of it ! I had a 347 strokes in mine and it was exactly what you are describing, but don't forget 1 thing gurtle on the lower end !

Mike Pass

1971 block. Great - easy emissions as you say. The SGT steel flywheel and AP Racing clutch is a good compromise and will be just right for mostly road use. I have the same clutch on my GTD. Your engine builder will advise on fitting a mains girdle and necessary machining. I think the neutral balance is a very good idea as the beating the main bearings get at high rpm cannot be a good thing. Also many of the neutral balance stroker kits have a forged steel crank.
If you can't find someone who has run both heads then the best info is to check out the Richard Holdener videos on YouTube which have the power and torque graphs so give a good indication of torque. I suspect that there is not much between them as both are very good heads. With the intake you plan you should be well on the way to 500hp. I hope your gearbox is up to the job!
I’ll have a look at the videos. Thanks!

I’ll be going with the Quaife transaxle once it’s available again. Am hoping can get a discount through some contacts there haha.

With the head choice it’s more down to the two CR options with the out the box options.
It’s either 10.6:1 with the AFRs or 10.9:1 with the trickflows.
Am just under sure whether that extra .3 is going to make much of a difference potential detonation wise and whether to go with the 2618 pistons over 4032. Mahle said that 4032 would be fine for my power level it’s just down to detonation resistance of the material.

anyone on here run 2618 pistons? Do you get much of a slap when cold? Ring gap will be 0.0046-0.0054 if I ran those pistons.
I can't recall seeing anyone offer an internal balance crank in a 347 stroker kit - That extra stroke means there is not enough counterweight available for neutral balance. 331 seems to be available though.
I can't recall seeing anyone offer an internal balance crank in a 347 stroker kit - That extra stroke means there is not enough counterweight available for neutral balance. 331 seems to be available though.

Basically of the manufacturers offer internal balance 347 cranks :)
I’m going to use a k1/rpm/liberty internal balance crank. From everyone I’ve spoken to they all come out the box to very good tolerances and good finish - unlike the varying scat and eagle versions. They have enough on the bobweight to balance.

Callies internal balance cranks do normally need heavy metal to balance however.

Mike Pass

I had an Eagle 347 internal balance stroker kit a few years ago. Forged steel crank, H section rods, JE forged pistons, Was very easy to balance. No heavy metal needed - just a bit of metal removed. I don't know if they still do them but they are available from others