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Discussion in '1979 - 1995 (Fox, SN95.0, & 2.3L) -General/Talk-' started by Venom351R, Sep 10, 2010.
If you want a strong N/A car you better run some flat tops or deck thoses heads.
My thoughts about the piston to valve clearance problems is that the trickflow heads have will probably have more clearance than the AFR 185's. The Trickflow heads valve angle is is more vertical at only 15 degrees vs the AFR's 20. If the clearance turns out to be to little though isky makes a tool to flycut the pistons with the engine in the car. I believe there is a write up on here or corral about how to do it.
GMkillr on here has a set of the TFS 205's from CI he could probably tell you alot more than I could about them. He had some pics of them in the link at the bottom
edit, I would put the engine together using these parts then buy a fordstrokers 408 diy shortblock kit and order a custom cam for the stroker combo and when all the parts were there and assembled I would pull the current engine out swap the topend onto the new shortblock. IMHO why swap pistons and bore the block doing a basic engine rebuild when you could build a stroker for not that much more. Either that or put a 150 shot on it and be done.
im not stroking it to more cubes and i hate nitrous. the cost of buying a stroker kit is just to much added with the cost of machineing the block to a 408. The whole point of this upgrade is bigger heads and thats it. Better pistons are an option but a stroker kit another custom cam and block machine work far exceeds the budget of this project and goes against what im trying to do in the quarter mile
I e-mailed trickflow asking them which of their pistons they would suggest for my set up and to raise my compression into the 10 range. This will mostly come down to "COST" I was not looking to make this a major project, $2,000 heads is enough but if the cost of pistons and the price of machine work to hone the bores on the block and to install the pistons is not to much then I will consider pulling the engine out. The other issue is how I am going to get it out. I think I may be able to get my hands on a hoist but I'm still undecided if I would be better off just pulling the engine or pulling both the tranny and engine connected together. Ive read both being done even when just wanting to pull the engine.
The other plus is if I do pull it out it will be much more easy to re assemble the engine with it on a stand VS doing it in the engine bay and then just dropping it back in as one whole piece.
I know I went .3 seconds and 4mph faster with 10.5:1 over 9.5:1. I probably have a mph or two I could pick up with some more tuning, but you get the idea. That's about a 30-40rwhp difference.
You can get a set of forged Probe pistons w/rings and wrist pins for about $500. (Going off stroker pistons, standard may be less...) I had a little over $600 in machine work on mine for cylinder honing, cleaning, cam bearings, line bore, balancing, and mounting pistons on rods. You'll probably want new bearings too, so figure around $1000-1500 total for everything.
Damn Mike ****s expensive where you live. I Paid a little over 1,400 (i think) for all the work and building my engine. That was cleaning, boring, all new bearings, and building the long block. All I had to do was put the intake and vc's on. I'll see if I can find the exact price one of these days
If Im looking at $1000 to $1,500 to get it done then it wont happen now. I dont want to dump that much more into it at this time. If I went into this project with the intent of doing that and the expectation of what it would cost then it would be different. But like I said I have to hear back from one machine shop I contacted and there is another I can call tomorrow as well. Also I would not need forged pistons so I save money there. I'm already saving a lot by deciding not to do any porting and if I dont go ahead and do the pistons then I'll probably put the extra money I planned on spending on all of that and get a nice set of Accufab long tubes and a different mid pipe.
Do you know what combustion chamber size your 185's are? Looking at AFR's website, they have 72cc, 58cc, and 60cc. The TF heads you're looking at have a 65cc chamber which will change your compression. My guess is the AFR's are either 58cc or 60cc(pedestal rockers). By going to a 65cc head your compression will drop by around .5 or .6.
I looked at pistons on summit's website and you can find a set with rings for $300-400. Flat tops with 6cc valve reliefs put you around 9.8:1 CR with 65cc heads. I figured up a 0cc piston(no valve reliefs) puts you around 10.6:1. I don't know the stock piston cc, but I'm guessing at 15cc dish which puts you at 9.0:1 with the 65cc heads and 9.6:1 with 58cc.
The AFR's had 72CC combustion chambers. If the Trickflow heads are going to drop my compression then I would be more inclined to do the pistons if I can get the block work done for the right price. If I can get pistons for $300-$400 then thats fine its just a matter of what amount the machine work for the block comes out to.
I would like to have 10 for compression but would no valve reliefs cause issues with PVC?
Well the 72cc heads had you in the 8.4:1 range. The trick flows will bump you up to around 9.0:1. Again, guestimating a 15cc dish on the stock pistons. It looks like 1cc is worth about .1 CR, with smaller cc raising compression and larger cc lowers it.
Also would I have to have all that was mentioned above for block work? There are not that many miles on this engine I dont know if it would really need new bearings or not
Did some more searching and it looks like stock pistons should be around 11cc which gives you 9.3:1 with 65cc heads.
I figure you'll need it balanced if you change pistons, which means the crank and everything has to come out. It might be ok to reuse the bearings, but I wouldn't if it was my car. You could probably get away with just honing the cylinders on the block.
How much do bearings usually run, Cam bearings were not that much. I'm going to have to call some places tomorrow for block work to find out for sure. Every place is different.
So overall the current pistons and AFR heads gave me some really low compression. This was set up for boost prior to me buying it so that would explain why Im getting 344 RWHP out of a H/C/I 351
The Plus side is that 9:3 CR is better then what I was probably getting before if I decide to hold off on pistons for now
ball park what kind of HP increase can I expect going from an approx 8:4 to a 9:3 CR?
If you're not going to put spray on it, or a blower, just get some Speedpro hyper pistons. They are like $240 on ebay. If it's a standard bore piston, should be $10/hole to get a fresh hone job. So that's $80 plus $240 for the pistons, call it another $100 to get the pistons and rods mounted, and another $100/gaskets. Rod bearings are dirt cheap. That will fix your valve relief problem and your compression problem. The crank does not have to be rebalanced because you get new pistons. The two have nothing to do with each other.
If the new pistons weigh more/less than the old ones wouldn't the crank need re-balanced?
Thats more of a price range I would be ok with. Also why would the crank not have to be balanced?
Cranks are rotationally balanced. It has nothing to do with the weight of the pistons. Pistons don't really get balanced. When someone says they have balanced pistons and rods, it means they have weighed each one, and made sure each one is within a certain weight of the others. There are spots on the pistons and the rods to shave metal off to get the weight down. This is done independent of the crankshaft, which is put a on a balancing machine, and balanced essentially the same as a tire.
Thanks kurt. Trickflow got back to me and said to contact probe pistons for a set that would put me in the 10 range for compression. What they have would get me in the 9:5:1 range
Sounds like good advice. Probe pistons are very very good, but they are also extremely expensive.
Yeah thats what concerns me as well.
Honestly if i can get 9:3 with my current pistons and not have PVC issues I would rather do that then do the whole new piston pulling the block thing. I did not want this to turn into a back and forth type thing where I cannot make up my mind on what to do or where to go with the whole tear down. I think that just going with the 205's and a set of Accufab long tubes will be good for now. I'll be fine with the 9:3 CR with my current pistons b/c its still an improvement over the 8:4 I was getting before with the 72cc with the AFR heads.
I just dont want to get to far ahead of myself, I dont want this whole project to get to far ahead of what I originally planned. I was hoping to just take the heads off and reverse order with the new ones. Like Ive said the only thing I'm concerned with is PVC issues but if that is a problem I'll be in better shape this spring to have the block taken out and better pistons put in. Also I would not even have to do this as well b/c of the Insky valve relief cutting tool
I got on the whole compression thing b/c I was not aware just how low it actually was and the fact that the 65cc 205's would raise it up to a better number for me being NA