7A-FE Compression Ratio, Looking at changing the CR of my 7afe when I rebuild. Options

[celica74]

But did you have the pins jumped on a hot engine when setting timing? If not, then you did not set timing.

I did do it with the engine running and at operating temp

[Bitter]

Fine, but were the pins jumped?

[celica74]

Fine, but were the pins jumped?

No. I didnt know about that when i did it. The car runs great. Honestly seems smoother now. Little more top end pull to it

[Bitter]

Fine, but were the pins jumped?

No. I didnt know about that when i did it. The car runs great. Honestly seems smoother now. Little more top end pull to it

Then you did nothing. Without the pins jumped the ECM just compensates for any rotation of the distributor, your timing is the same. Put it back to where it was and do the procedure correctly.

[celica74]

What year is yours? I never heard knock, I monitored it with a SAFC2.

95 7a with on. A 94 ecu

[PaukST]

Got my engine fully apart, I'll put up pics or start a build thread or something later, but my cylinder 3 and 4 rod bearings were obviously damaged, and the two main bearings at that end of the engine as well. The crank shows it, so it looks like I'll be having the crank cut. I was considering boring the cylinders over, but the cylinder walls look like they're in excellent shape... Haven't measured them, though. We'll see what the machine shop has to say about it, I'd enjoy not having to shell out for a new set of pistons if I don't have to. I had thought of porting and polishing the head myself (being that port/polish kits are decently cheap), but after reading into the subject I think I'll pass. It'd cost less up front, but I'm fairly confident I'd get (a lot) more for my money having it professionally done.

I did have a few open questions for anyone who cares to chime in with an opinion:
1) Assuming I do end up getting it milled, would the cam timing be adversely affected by the change in distance between the crank pulley and cam pulley?
2) Assuming that I need to have the cylinders honed, would that necessarily mean I'd need oversize pistons/rings?
3) Does anyone have a machine shop to recommend in the general Charlotte, NC / Rock Hill, SC area?

[celica74]

Got my engine fully apart, I'll put up pics or start a build thread or something later, but my cylinder 3 and 4 rod bearings were obviously damaged, and the two main bearings at that end of the engine as well. The crank shows it, so it looks like I'll be having the crank cut. I was considering boring the cylinders over, but the cylinder walls look like they're in excellent shape... Haven't measured them, though. We'll see what the machine shop has to say about it, I'd enjoy not having to shell out for a new set of pistons if I don't have to. I had thought of porting and polishing the head myself (being that port/polish kits are decently cheap), but after reading into the subject I think I'll pass. It'd cost less up front, but I'm fairly confident I'd get (a lot) more for my money having it professionally done.

I did have a few open questions for anyone who cares to chime in with an opinion:
1) Assuming I do end up getting it milled, would the cam timing be adversely affected by the change in distance between the crank pulley and cam pulley?
2) Assuming that I need to have the cylinders honed, would that necessarily mean I'd need oversize pistons/rings?
3) Does anyone have a machine shop to recommend in the general Charlotte, NC / Rock Hill, SC area?

Im assuming 1 is when your refering to having the crank cut. It shouldnt make a difference. Just make sure and spec everything to make sure you get the propper size bearings. Shouldnt have to get anything but standard unless the crank was scarred that bad. 2 you always wanna hone the bore anytime you rering. Doing this helps the rings sit and help with oil. It wouldnt take anymore then maybe a thousandth away if done propperly. No need for oversize upless you bore. 3 i live in Raleigh, NC, so im not formillar with the charlotte area.

[Special_Edy]

I think he meant having the block or heads milled. Its shouldnt adversly affect the camshaft timing. Something I learned from Chevys is that as much as 4 degrees is not noticible, and im sure you wont have anywhere near that much difference

[PaukST]

I think he meant having the block or heads milled. Its shouldnt adversly affect the camshaft timing. Something I learned from Chevys is that as much as 4 degrees is not noticible, and im sure you wont have anywhere near that much difference

Hit the nail right on the head. I was a little skeptical that a 0.3mm or 0.4mm difference would cause noticeable differences in cam timing, but my own guess wasn't really reassuring to go on. Thanks for the info!

Im assuming 1 is when your refering to having the crank cut. It shouldnt make a difference. Just make sure and spec everything to make sure you get the propper size bearings. Shouldnt have to get anything but standard unless the crank was scarred that bad. 2 you always wanna hone the bore anytime you rering. Doing this helps the rings sit and help with oil. It wouldnt take anymore then maybe a thousandth away if done propperly. No need for oversize upless you bore. 3 i live in Raleigh, NC, so im not formillar with the charlotte area.

#1 was about the block/head being milled, but I'm pretty sure my engine would eat itself alive from the inside if I had the crank cut without compensating with proper bearings. Already in the plans! Thanks for the input on honing, I want this rebuild to last a LONG time, so I don't want to leave anything undone that could increase its lifespan. Looks like a hone will be in the plans as well!

I'm planning to replace the exhaust valves, all the seals, the oil pump, and possibly valve springs. Also, aren't the rod bolts one of the stock 7A-FE's weak spots? I'm considering replacing those with ARP bolts or something, but haven't really researched into that yet. I know I need new head bolts, rod bolts, and main cap bolts anyway, so I may as well beef up the durability if I can do it without breaking the bank.

[mandrek]

there are no ARP bolts/studs that fit the 7afe stock rods.. you will have to go after-market rods or just get a fresh set of stockers.. ARP 4age head studs, and main studs do fit(ish) the 7afe but two of the head studs absolutely MUST be cut down to fit under the cam gears (far left side, 1 intake and 1 exhaust side stud closest to the timing belt) and the last pair of main studs (last cap closest to the trans) need to be cut down some to fit under the upper oil pan.. i have pix and all from when i did this on my own rebuild.. but i do not have any of this posted up just yet.. need the car finished first and get working first.. as soon as i have time to do it i will start a thread for it in the project section and have all of this covered.

and IMO if you are not planning on boosting the 7a, then a fresh stock set of rod bolts will do fine.. and even if you are, a fresh set will work well for low boost (as far as my research shows), but if you are wanting to go as far out as you are indicating, then just get your self a set of belfab rods and have them include ARP2000 units with them. (an option you can request).. the cost on the rods is not that much (compared to aftermarket rods for other applications)

[celica74]

there are no ARP bolts/studs that fit the 7afe stock rods.. you will have to go after-market rods or just get a fresh set of stockers.. ARP 4age head studs, and main studs do fit(ish) the 7afe but two of the head studs absolutely MUST be cut down to fit under the cam gears (far left side, 1 intake and 1 exhaust side stud closest to the timing belt) and the last pair of main studs (last cap closest to the trans) need to be cut down some to fit under the upper oil pan.. i have pix and all from when i did this on my own rebuild.. but i do not have any of this posted up just yet.. need the car finished first and get working first.. as soon as i have time to do it i will start a thread for it in the project section and have all of this covered.

and IMO if you are not planning on boosting the 7a, then a fresh stock set of rod bolts will do fine.. and even if you are, a fresh set will work well for low boost (as far as my research shows), but if you are wanting to go as far out as you are indicating, then just get your self a set of belfab rods and have them include ARP2000 units with them. (an option you can request).. the cost on the rods is not that much (compared to aftermarket rods for other applications)

In your thread iy will be good to show how much you had to cut off the studs. And are those rods easy to find?

[PaukST]

there are no ARP bolts/studs that fit the 7afe stock rods.. you will have to go after-market rods or just get a fresh set of stockers..

Is that definite? I'm not being rude or challenging, just trying to find out for sure... Different people say different things, you know! I've seen some posts like these that say they'll work, and heard hearsay along the lines of "they'll work but you have to work on the block a little to keep them from contacting it during the stroke"....

... But it's probably a moot point anyway, as it's most likely not going to be boosted at all... However, there are no guarantees of how high I'll be revving it, or how often during the course of just fooling around during random driving, and the state of the main bearings and rod bearings make me nervous. I just wish I knew what caused the damage, that would ease my mind a bit...

and IMO if you are not planning on boosting the 7a, then a fresh stock set of rod bolts will do fine.. and even if you are, a fresh set will work well for low boost (as far as my research shows), but if you are wanting to go as far out as you are indicating, then just get your self a set of belfab rods and have them include ARP2000 units with them. (an option you can request).. the cost on the rods is not that much (compared to aftermarket rods for other applications)

I will end up just using fresh 7a bolts, though, if there are no reasonable alternatives between that and forged rods.

[mandrek]

CAN you? yes. its is worth it? NO... sure you can get 4age/fe ARP rod bolts/studs.. but to get it to work on the stock 7a rods you would have to have the rods machined and then re tapped/cut to be able to take the new ARP hardware.. the problem is that the 7a rod is a configuration were the bolt goes through the cap, and into the rod.. the 4age (not sure about the 4afe but pretty sure ARP had no support for that motor) rods use a pass through type configuration. IIRC the 4age rods have bolts that come from the top (wrist pin side) through the bottom of the rod twords the cap. and then secured with the nuts. the top of the "bolt" is square and locked into place with the shape of the rod.. so by the time you do what you need to make the ARP hardware work, you are better off just getting the belfab rods.

link to nice write up on difrences, and lots of pix on page.

This post has been edited by mandrek: May 4, 2012 - 12:38 PM

[Special_Edy]

there are no ARP bolts/studs that fit the 7afe stock rods.. you will have to go after-market rods or just get a fresh set of stockers..

Is that definite? I'm not being rude or challenging, just trying to find out for sure... Different people say different things, you know! I've seen some posts like these that say they'll work, and heard hearsay along the lines of "they'll work but you have to work on the block a little to keep them from contacting it during the stroke"....

... But it's probably a moot point anyway, as it's most likely not going to be boosted at all... However, there are no guarantees of how high I'll be revving it, or how often during the course of just fooling around during random driving, and the state of the main bearings and rod bearings make me nervous. I just wish I knew what caused the damage, that would ease my mind a bit...

and IMO if you are not planning on boosting the 7a, then a fresh stock set of rod bolts will do fine.. and even if you are, a fresh set will work well for low boost (as far as my research shows), but if you are wanting to go as far out as you are indicating, then just get your self a set of belfab rods and have them include ARP2000 units with them. (an option you can request).. the cost on the rods is not that much (compared to aftermarket rods for other applications)

I will end up just using fresh 7a bolts, though, if there are no reasonable alternatives between that and forged rods.

Probably a PO who didnt keep up with the oil changes. At least your cylinder bores are nice and clean.

As for the rods, 4 cylinder engines are hard on the rods. Thats why you dont see big displacement I4s even though they produce superior torque to a equal sized 6 or 8 cylinder

[richee3]

^^ I love inline engines

[Special_Edy]

^^ I love inline engines

Lol you'd like the 4.1L I6 in my garage. 11 to 1 CR, full length headers(I mean 4 ft long) going into true dual 2.5in exhaust. Offenhauser 4 barrel intake, HEI ignition, high torque ministarter. Timing chain swapped for gear driven. The thing has 7 main bearings in it. Its a frickin beast and its smooth as butter to. Max torque for them stock is at 1200rpm.
But of course a 350 v8 was more bang for the buck so thats whats in my truck now. I know that 4.1L six will outpull my 5.7L v8 any day of the week though. I want to make a trike with the straight six, I6s are awesome.

[PaukST]

CAN you? yes. its is worth it? NO... sure you can get 4age/fe ARP rod bolts/studs.. but to get it to work on the stock 7a rods you would have to have the rods machined and then re tapped/cut to be able to take the new ARP hardware.. the problem is that the 7a rod is a configuration were the bolt goes through the cap, and into the rod.. the 4age (not sure about the 4afe but pretty sure ARP had no support for that motor) rods use a pass through type configuration. IIRC the 4age rods have bolts that come from the top (wrist pin side) through the bottom of the rod twords the cap. and then secured with the nuts. the top of the "bolt" is square and locked into place with the shape of the rod.. so by the time you do what you need to make the ARP hardware work, you are better off just getting the belfab rods.

link to nice write up on difrences, and lots of pix on page.

There we go, that's some info I can use. And that link has some good info, bookmarking that mess! Details > generalizations any day.

Probably a PO who didnt keep up with the oil changes. At least your cylinder bores are nice and clean.

As for the rods, 4 cylinder engines are hard on the rods. Thats why you dont see big displacement I4s even though they produce superior torque to a equal sized 6 or 8 cylinder

Thanks for the help, guys! I'm hoping to get this project moving sometime next week, I'm tired of driving around on a gimped, oil burning engine.

[Special_Edy]

Id replace the oil pump while you have it apart. So you know you arent burnin the new bearings