Where to go from here?

Guys - Have been working on restoring a 70 swinger which came originally with a slant 6. I have been collecting parts and geting ready to put it all together, but would ask if any of you could offer advice on how to proceed from where I am at. I received a 68 340 block which is 30 over with a clean bore, included a forged crank and a set of bare J heads as well as a bellhousing, flywheel and a 4 speed. I have a set of TRW pistons which are 30 over, formerly 13 to 1 but cut down to about 11.25. I am looking for thoughts on should I get these cut a bit more? I would like to use pump gas on this. The J heads do have hardened seats installed, but no valves. I did pick up a set of adjustable rocker arms with shafts, etc. At this point I need to find a set of connecting rods and make a decision on the pistons and what to do for valves, cam etc. This will be a driver, any assistance would be appreciated.

Unless you're trying to use a good amount of nitrous, why not just hit the easy button and pick up a set of KB hypers and some Scat i-beams. Perfectly reliable and reletively inexpensive. Then maybe you can sell the TRW's to get a little of that money back. I wouldn't hang onto the TRW's just because they're forged, for a driver they're not needed. The KB pistons are plenty strong for a street screamer and lighter to boot.

X2. You would need to have the piston deck thickness measured. My guess,someone machined the down to minimum thickness. Unless going full strip,really hot street car,go the hypers. The engine bores,will thank you for it.

11.25 on iron heads on the street ??

UOP said:

Unless you're trying to use a good amount of nitrous, why not just hit the easy button and pick up a set of KB hypers and some Scat i-beams. Perfectly reliable and reletively inexpensive. Then maybe you can sell the TRW's to get a little of that money back. I wouldn't hang onto the TRW's just because they're forged, for a driver they're not needed. The KB pistons are plenty strong for a street screamer and lighter to boot.

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dustoff440 said:

11.25 on iron heads on the street ??

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They were 13 originally when I purchased them in 1977, gas was different then. Had them cut to 11.25 in 1983, then pulled them out 12 years ago when I retooled the motor for pump gas, which is now running in my T/A at 9.25. I realize 11.25 won't run today which is why I raised the question. I believe the pistons could be cut to less than 10 which should be functional on todays pump gas. Looking for some friendly advice from this group which appears to be generally friendly and well informed. Also looking for a set of rods if anyone has some available.
Thanks for the feedback.

Just helped a buddy re-hab a 69 Charger. We went crazy on holleys and edelbrock carbs, timing erratic. etc

So paid the big$ for the msd atomix fuel injection. Allready had the brainbox installed. So put it on; screw the instructions and their pump; you need a return system. I think it is tanks.com . Pump a pain to install, cutting hole in tank, but if you buy the reader-passenger sit in car, and see what enginge is doing, and re-program the computer, on the fly.

You need to know which parameters fit your engine.

UOP said:

Unless you're trying to use a good amount of nitrous, why not just hit the easy button and pick up a set of KB hypers and some Scat i-beams. Perfectly reliable and reletively inexpensive. Then maybe you can sell the TRW's to get a little of that money back. I wouldn't hang onto the TRW's just because they're forged, for a driver they're not needed. The KB pistons are plenty strong for a street screamer and lighter to boot.

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Abodybomber said:

X2. You would need to have the piston deck thickness measured. My guess,someone machined the down to minimum thickness. Unless going full strip,really hot street car,go the hypers. The engine bores,will thank you for it.

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X3. KB's and Scat's are the easiest way. Valve wise, whatever fit's, I assume 2.02/1.60's. I'd be careful cutting too much out of TRW's. I once dished enough out of a forged 455 Pontiac piston to bring it from 12.2 to 10.0. Pretty scary, but they were a custom piston that had enough meat too get there. As far as the cam choice, the final compression ratio, your gear, tire size and torque converter choice, will help with a recommendation.

Thanks, I am putting this into a 70 swinger as a driver, looking for 400 HP as a target, not a race car, no nitrus, simple carberator. Trying to operate on a budget and own the pistons so thought it might be usable. Guess I will need to take them to someone and see if it can be put together for a minimal cost, if the pistons are questionable or other options are less then I will pursue. Thanks for the feedback.

You could make the money on those pistons, as stated, to help costs with the hypers.

Another thought would be some Cometic head gaskets, made to your spec for about $100. Maybe drop comp, ratio without changing quench and use parts you have now.

On a budget, I'd look at what a set of those forged pistons would go for 2nd hand, before paying to have them trimmed, if I were going to use those pistons, I'd go with a different head gasket at about .060" compressed thickness from Cometic. They are reusable and are high quality, to boot.

If it were my engine, on the street, I'd go with 10.5:1 KB hypers and sell the forged set.

The forged rods you have in there will be perfectly fine. You could resize them with new studs and nuts for cheap and do just fine with the KBs. Those TRW's will probably need some balance work with the crank and rods, which is more $, but it depends on what's already been done.

If what you have is balanced, some Cometics may be the cheaper route, but if not, if these are just on the shelf and you haven't set them up on those rods and crank, it may actually be cheaper for you to run the KB's, because of the balancing that would likely need done on the forged TRW pistons.

I'd go with the KB's, because it's a street engine and it will be nicer on the block in the long run.

I built my spare 340 with Mahle 10.5-1 forged pistons , not that expensive , lighter than the stock forged pistons . See what they are priced at .