Too Much Compression!

[Hack]

Hmm, I'm not sure about the '86 5.0 from the Tbird. I know the '86 5.0 HO they put in the Mustangs had an undesirable piston and head combination. "High swirl" I think Ford called it. Then in '87 Ford made a new head that was the preferred iron head at that time until Ford started making the GT40 and GT40P heads which were first in the '93 Cobra and then Exploders.

I wouldn't put Ford iron heads on anything, port work notwithstanding. The one exception is 4V Cleveland heads, but you don't want those.

I think you should call someone who makes aluminum heads and see what they recommend. Just for kicks at least.

 

[bdepedro]

I've decided to replace the domed top pistons with flat tops. Just kept worrying if different heads would do what I wanted. I'm looking at Speed Pro pistons as I've been told they are a good piston and certainly fit my budget. Want to keep compression to at least 9.5:1 but most I see list it more in the 8s with a 60.4cc chamber. Not sure how much the decking adds though.

 

[Hack]

Since you are already 0.030" over you might consider finding a standard bore 302 and building that. You can't just swap pistons without doing any machine work. If there's any lip in the bore at all the cylinders will need boring. Don't buy pistons until you know how much the cylinders have to be bored in order to clean up. I'm not sure what your wants are, but I would build an 80s 302 with a 347 stroker kit from coast high performance. I rebuilt a 302 before and was surprised that adding a stroker really wouldn't have been that much extra money. I know you said you are on a budget, but an 80s 302 that's built for a roller cam is the way to go IMO. If you just want to do pistons you could just do pistons in the roller cam block. Even sticking with a 302 you would have more cubes. Also, when you start going 0.040" or more over with your bore the cylinder walls can start getting a little thin, which leads to more issues with heat. Not saying this is something you have to do, just it's what I would do.

Ultimate budget just find a good running 80s 302 and swap your intake, timing cover, etc. onto it. With EFI those engines tend to last a really long time. Some options for you to consider.

 

[bdepedro]

I'm going to have the engine checked out by a machine shop. Hoping I can get away with a hone job but will go 0.040 over if needed, have pistons balanced, check crank and rod balance and assemble rods and pistons. I'll get block checked and see what they say before getting pistons.

 

[bdepedro]

It's been a while since I updated but things are finally progressing. After debating between crate engines and rebuilding my 289, I'm going with a full rebuild. Just ordered new AFR heads with 165cc intake runners and 58cc combustion chambers. The machine shop will do a .040 over cylinder bore, line bore, etc: and order new 10:1 flat top forge red Pistons a new roller cam, pushrods and lifters. I'm having them assemble the short lock and then I'll complete assembly. Hoping to get the short lock done mid to late July so I can install and get car back on the road by late August. I'll keep you posted as things happen.

 

[302 coupe]

I'd steer clear of the 86 5.0 heads, especially if they are the E6whatever casting.

I think a good value for you would be a set of the late model GT40 heads, not the GT40P. They are very similar performance wise to early 351 heads but will have bigger combustion chambers to get your CR down (64-65 cc chambers versus your 60cc before decking heads). The GT40's can be found rebuilt and ready to go for $300-400 usually.

oops, just saw your last post, nevermind.

 

[blown65]

0 deck on a 289 crank with a .040 gasket is 11-1 compression. Should be able to run on pump gas if you just keep timing in check.

Whats the cranking compression come out to?

 

[Hack]

AFR makes good heads. I hope you end up happy with the results. I would always want to go bigger, but your way should work great.

 

[bdepedro]

Got a call from the machine shop today. Apparently one of the cylinders has a small area that is beyond a 40 over bore which would mean going 60 over. They are going to do an ultrasound to make sure there is enough wall to safely go 60 over. If not, I'll have to replace the block. I'm getting a little ahead of myself but if I did, could I include 302 blocks in my search or would too many engine components not work between the two blocks?

 

[bdepedro]

Ultrasound shows less than ideal material between cylinders and water passage if we go 60 over but I found a complete 289 pulled from a '68 mustang. Guy says it was running and believes it had never been rebuilt before so I'm hoping it would have more life left in it and all my other parts would work with it. Anything other than mechanically turning the engine over I should look for when I go check it out this weekend?

 

[bdepedro]

Forgot to say, price is $150 for complete engine.

 

[bdepedro]

Well, here we go again. New block measured a 30 over bore with a little wear. We were hoping to be able to go 40 over but shop just checked and it's too far out for that. Hack, looks like I may be going your route after all. The shop has an '80s 302 block I can use. Depending upon whether he has the crack and rods I may look into a 347 stroker kit. Shop is going to do a cost projection for me and we'll see where we go from here. I know the end result will be a better build but I see why crate engines are so popular.

 

[bdepedro]

got some new info from the shop. Apparently my 289 that had 351W heads, also had 302 crank and connecting rods. So, we can use those to build out the 302 block in budget.... But I asked them to let me know what additional costs to do a 347 stroker (other than the kit). Found a kit with Scat modular crank, Scat forged rods and Wiseco forged Pistons with rings, bearings, etc for $1k. If build costs aren't too much more, I may go for it.

 

[a91what]

Your new combination with a 347 will definitely be far above what you had before. I however would build a 331, very similar power with better longevity due to stroke/rod length ratio.

 

[bdepedro]

I was thinking 331 for that reason but wound up ordering the 347 kit. The kit came balanced but crank to wrist pin clearance was a little tight so the shop ground a little more material off crank and rebalanced everything. Starting assembly next week.