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I have ROL's that are .045 compressed, and that is putting me just below 10 to 1 compression, what is felpro compressed thickness? Stock head gasket compressed thickness?? With the ROL's my compression worked out to 9.8 to 1 but I am trying to get closer to the factory 68-9 4 barrel 10.25 to 1 rating. Thanks.
Understanding is FelPro's PermaToque Blue head gaskets
#8266 PT-1 are .043-.045 compressed thickness.
Per Performance American Style
stock 343-360-390-401 was .048
stock 304 was .028
stock 290 was .022
SCE Gaskets and others offer thinner in COPPER but require O-Ring-ing the block.
That' as far as I know, others may know otherwise.
Thanks for the specs! This is on a 343 bored .030 and cast replacement pistons the compression after everything was ccd worked out to 9.8 to 1 with the .045 ROLs so if felpros are basically the same I think I'll stick with the ROL's they are a better designed gasket. Can a stock . 028 304 gasket be used on a 343 to bump compression or is the bore of the gasket smaller???
I may be able to get OEM steel gaskets that are supposed to be thinner than the aftermarket stuff. In any case would there be more power going to 10.25(or at least closer) over 9.8 to 1 compression??
The 290 & 304 gaskets won'y work on a 343 / 360, hole's to small 3.88 I think.
Yeah, I think more compression makes more power,
especially with a cam with a late intake valve closing angle.
Are yours cast pistons ? with a big dish top that's about 3/16 deep with 4 valve reliefs ?
Are they .080 down in the hole ?
or was the deck milled ?
what's the deck clearance ?
Watch your piston to valve clearance, did ya clay a piston ?
Probably too late, but the block could be deck milled to raise CR.
Can't believe no one makes a "good" cast piston for 343 / 360 bore, but hey don't.
The block was squared but just enough to get it square so not much was taken off. The heads were milled .020 - the chambers ccd' at 51.8 Pistons definately werent that far down less than .060. I think the valve reliefs worked out to 7.5 CC's but I'll post the exact numbers when I get the spec sheet from the builder. Cam has .491 on intake and .501 on exaust, no clearance problems. I think the factory 10.25 to 1 rating could vary from one engine to another due to production tolerances. Pistons were .030 badgers.
I have a '69 343 block with Badger cast 360 pistons, actually Zollner's but same as Badgers.
Stock 343 deck clear was .060, Zollner's were .020 shorter than stock, 1.58 Comp Ht
where stock 343 was 1.600 Comp Ht.
So the Zollner's ended up .080 down in hole with the 3.28 stroke 343 crank.
But I used a 304/360 3.44 stroke crank and came out with 0.000 deck clear.
The specs I have for Badger pistons says a big ~27-29cc dish.
Badger part number I have is P891, but those are for 360's
Ahhh, do you have Badger #P886 343 Flat Top cast pistons ?
If so, ok I see how your's has the 9.8:1 CR & 1.588 Comp Ht & ~.065-.070 deck clear.
Man, where's you find those Badge P886's ??? Egge ?
Yes they are the Flat top badger 343 replacements P886 +030. I asked the builder about the compression height and they are the same as the OEM high compression 343 and the ring lands look beefier than the stock pistons. I bought them from Maddog racing on ebay at what I thought was a great price of 260 for the set brand new 2 years ago they still should have them, quality looked better than the stock pistons.
There was a guy on here that runs the 343 flat tops in a jeep with a 360 and it gave him 11 to 1 compression, no durability problems and he mud races it.
Badger is still making them as far as I know so there should be plenty out there. I know that you can contact badger directly and order them.
What is your compression now with the dished pistons??
Well I had the 304/360 3.44 stroke crank offset ground .010 for a 3.46 stroke
and the Zollners were 1.580 Comp Ht, not 1.588 like the Badgers
and stock was 1.600 for 343 I thought per Perf American Style.
Got the Zollners from MadDog Fast Engine also, like $108 to my door :t:
anyway, with the 3.46 stroke the pistons stick out .007 above deck
since rods were reconditioned and are now 5.872.
'70 Heads mild porting and unshrouded, milled .060, 48cc chambers
Fel-Pro .045 head gaskest, gives 10.2:1 CR with the 27cc dished pistons
and .038 piston to head clearance around the rim at least of the huge piston dish.
Just fired it up like May 1st, but lost 1 stinkin' cam lobe :smile:
and now it's completly apart again, hope the crank polishes up ok :smile:
My rods were resized for ARP bolts too so the piston could be down the hole further than stock I guess but probably not much.
Yours Sounds like a great combo must have a lot of torque!, what brand cam was that?? Sounds like faulty manufacturing or bad lifter prevented it from spinning on the lobe while you broke it in? I am going with a Reed 218/223 @ .050, 272/276 advertised and there lifters are available with an optional anti friction coating-not visible to the eye but they look glossy compared to untreated lifters. The degree wheel matched the spec sheet for the cam perfectly and the builder said that does not happen with cams very often, so they are very high quality cams and they have done development work for AMC back in the day. Only problem I had with them was the retainer inner step didnt fit the double spring supplied in the kit, so we are going with stock retainers, they fit perfectly and are actually lighter than the reed retainers.
Was your cam a comp cams???
It was kinda my own fault cause I re-used the same cam that was in it before, forgot to keep the lifters in order on dis-assembly, and re-assembled new lifters on the old cam with new double valve springs without removing the innners, #120 closed #315 open.
Cam was a stock AMC piece reground by Chet Herbert back in the 80's .512/.529 & 280/295 and had worked well, have ran this combo for 15+ years, but last time it was just std 3.44 stroke and CR was a little lower.
Piston to Valve is pretty tight and had trouble finding another cam that had ""low" overlap and would work. Ended up this time with a Elgin/Clevite cam .488/.488 218/218 284/284. May be a little "mild" compared to that old regrind, we'll see.
Guess torque was good before, would barely lift the drivers front tire at launch with slicks and thru full exhaust.
Yikes I am suprised only 1 lobe went flat? Sounds like it was a really nice cam too. I guess that is a mistake that has probably happened to the best of them so dont be too hard on yourself, you'll have it back up and running as strong as ever. Good luck with it, I'll post more specs of my 343 later and what we decided on as far as head gaskets..I might just stick with the ROL's 9.8 should make plenty of power.
Fel-pro .042-.046
Rol high temp racing gaskets are about the best gasket for a AMC V8. They even have nitrile beads silkd screened around the water ports. :t:
Yes I know they have a lot more features than the felpros, I was just wondering if there is a big differnece in power/torque going from say the 9.8 that I have now to 10.2 to 1 for example? I just wanted to get as close to factory advertised compression for the rebuild but I gusess 9.8 is close enough not to make a difference from the factory 10.25 to 1 as it is less than a point?
Don't forget, we had leaded gas back in the day. Be careful of going too high on the compression ratio if you want to run it on today's pump gas.
A friend of mine built a small block chebby 10.2cr, and he has to atleast run about a 50/50 mix of 93 and 110.
We ended up with 9.5 static and 8.5 dynamic on the 401, and it's running fine on 93 octane unleaded pump gas. I was really worried about whether it would. Didn't try any lower octane ratings yet.