Cam and Engine Build Choices
- Thread starter Eagle-Mark
- Start date
Robert Kenney
Super Moderator
I've installed and driven most of them. 345-392's the 392's with some good porting and 9-1 will like to be installed straight up (110 not 106) this helps with the upper rpm band and maintain reasonable cylinder pressures for pump gas.
A good point of reference is what you have for a cruise rpm? Larger cams will give you better hp but with a sacrifice in low end. Also should have a compression bump.
If you cruise at 2300-2700, stick with my initial recommendation. Higher and go to the next bump stick. I don't recommend it however seeing as the rig is real heavy and will have a narrower power band with the sv's asthmatic breathing potential.
I must remind you that I am quite conservative with cam choice. I don't want to risk recommending a bigger cam just to have you be unsatisfied with the low end.
Porting the exhaust will help as will some deshrouding of the valves in the combustion chambers. Let me post a picture to show you what I mean
Eagle-Mark
Member
Ok I'll wait...
they will be a good reference as I am going to teach the kid how to do his first port and polish and port match. He's got loads of spare time till collage starts in fall...
Edit: he's in the 2300 to 2700 rpm range. 3:73 manual trans and stock tires, May go to a skinny 33.
Double edit: what is recomended for compresion boost? Shave the heads?
they will be a good reference as I am going to teach the kid how to do his first port and polish and port match. He's got loads of spare time till collage starts in fall...
Edit: he's in the 2300 to 2700 rpm range. 3:73 manual trans and stock tires, May go to a skinny 33.
Double edit: what is recomended for compresion boost? Shave the heads?
Eagle-Mark
Member
How about cc measuring the combustion chamber during this?
Robert Kenney
Super Moderator
Been really busy lately so have not got around to the picture I promised. But after more thought regarding your build and application here is what I suggest.
Mark you sound like you are experienced enough to accomplish the porting but heads can also be ruined just as easily. Other then blending you won't gain much at your expected rpm range
the exhaust port ceiling where the air tube goes should be smoothed. Eg remove the hump so the roof is flat and contoured.
The valve bowls should be smoothed and blended seat to port.
The intake short side radius needs special attention. The bowl to port should be free of corners and as large a radius as reasonably possible. Posting a basic port drawing to show what I mean.
As an exercise you could cc the cc's.
could be used to dial you in on cr.
Depending on the operational altitude a compression ratio bump will help. I don't recommend head milling but do recommend "0" decking to accomplish the desired cr. You'll be very near 8.6 with a composition gasket and 0 deck. Steel hg, leave the piston in the hole .020 at tdc.
Mark you sound like you are experienced enough to accomplish the porting but heads can also be ruined just as easily. Other then blending you won't gain much at your expected rpm range
the exhaust port ceiling where the air tube goes should be smoothed. Eg remove the hump so the roof is flat and contoured.
The valve bowls should be smoothed and blended seat to port.
The intake short side radius needs special attention. The bowl to port should be free of corners and as large a radius as reasonably possible. Posting a basic port drawing to show what I mean.
As an exercise you could cc the cc's.
could be used to dial you in on cr.
Depending on the operational altitude a compression ratio bump will help. I don't recommend head milling but do recommend "0" decking to accomplish the desired cr. You'll be very near 8.6 with a composition gasket and 0 deck. Steel hg, leave the piston in the hole .020 at tdc.
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Eagle-Mark
Member
Thanks Robert! I had a port and polish thread on bp and the info there was basiclly the same. Port and polish is a waste of time. No real noticable gains in hp or tourque on these engines. This engine and it's purpose will probably never see 4000 rpm and has no purpose over that. I am using 4000 rpm as an extreme example as well.
But will take your recomendations into account and May do that mild work as we have the engine apart and it's a learning opertunity to my son. I have done about 10 sets of heads in my life. None IH and all with positive results because of my learning opertunities from others at a younger age.
So I will have to watch and see what gasket comes in iho gasket kit. I will be purchasing as much as possible there but that depends on machinist here that we are dealing with as he has hands on this engine.
Because of IH experiance he has no problems using the isky cam, lifters and springs sold and recomended here. He would like to use his bearings and pistons if we need a bore.
Again a big thanks to you. And to Jeff he's lucky to have you here!
But will take your recomendations into account and May do that mild work as we have the engine apart and it's a learning opertunity to my son. I have done about 10 sets of heads in my life. None IH and all with positive results because of my learning opertunities from others at a younger age.
So I will have to watch and see what gasket comes in iho gasket kit. I will be purchasing as much as possible there but that depends on machinist here that we are dealing with as he has hands on this engine.
Because of IH experiance he has no problems using the isky cam, lifters and springs sold and recomended here. He would like to use his bearings and pistons if we need a bore.
Again a big thanks to you. And to Jeff he's lucky to have you here!
Eagle-Mark
Member
Another question on compresion. 0 deck and composite head gasket = 8.6 to 1. Any reason to go higher? Still want the option to run readily available 87 octane fuel...
Robert Kenney
Super Moderator
Still don't know your native altitude. I don't recommend more than 0 decking and a comp hg to run 87 pump gas.
Run what ever piston you want, just make sure it is a stock compression height slug and not decompressed one. Silvolite is about the only one I know that fits the bill.
All I can do is give you what I feel is the way go. Beyond that it is your call.
Hope you and your son enjoy this project together.
Run what ever piston you want, just make sure it is a stock compression height slug and not decompressed one. Silvolite is about the only one I know that fits the bill.
All I can do is give you what I feel is the way go. Beyond that it is your call.
Hope you and your son enjoy this project together.
Eagle-Mark
Member
I'm not going to hold you to anything, you can stop the disclaimers, all is well!
we are having a good time on this, especially me! Knowing his age (18 two weeks) it;s lucky I get any time with him, so doing an engine (second one, we did his toyota engine at 14) is good times!
Altitude here is 2000 to 24000 feet and just outside town we go up! Not real high but two mountains in between us and montana are both around 6,000 feet.
What's all this talk of a decompression piston? It it just that, a piston that lowers compression. I am not looking for that at all.
we are having a good time on this, especially me! Knowing his age (18 two weeks) it;s lucky I get any time with him, so doing an engine (second one, we did his toyota engine at 14) is good times!
Altitude here is 2000 to 24000 feet and just outside town we go up! Not real high but two mountains in between us and montana are both around 6,000 feet.
What's all this talk of a decompression piston? It it just that, a piston that lowers compression. I am not looking for that at all.
Eagle-Mark
Member
I just looked at the gasket set offered by IH only and it does not say what head gasket is. Do you know if it is the composite gasket recomended?
Also I do not see pistons on his site? Does he not deal in them? You and others have recomended silovite (sp) pistons?
Also I do not see pistons on his site? Does he not deal in them? You and others have recomended silovite (sp) pistons?
Eagle-Mark
Member
Just trying to get my ducks in a row before I call and take up his time. Thanks!
Eagle-Mark
Member
One more question before I place an order and I will ask Jeff opinion when I call.
Cam springs? With the porpose built engine for towing it should never see 5000 rpm do I really need aftermarket cam springs or will stock IH be ok?
More spring presure = faster wear on cam and harder duty on valve. But is needed at high rpm, I understand engines. But for this purpose are they needed?
Cam springs? With the porpose built engine for towing it should never see 5000 rpm do I really need aftermarket cam springs or will stock IH be ok?
More spring presure = faster wear on cam and harder duty on valve. But is needed at high rpm, I understand engines. But for this purpose are they needed?
Robert Kenney
Super Moderator
If you run a stock cam run stock springs you run the comp with more lift and much higher lifting velocity you need a slightly higher spring rate.
I stated that I would set them up @ 80# on the seat. That is only a hair more than oem..
A decompressed piston had a shorter pin to piston top measurement to compensate for a block that has been whacked on before. You are not in that situation. You want to stroke the crank for more displacement use a shorter piston and stroke to 0 deck instead of machining the block. This will require re bobbing the crank and a thorough balance job. This is common engine practice not a new idea. Don't thing you are going in that direction.
I doubt ihon sells the old shim gaskets in there kit. Call Jeff.
Combining building practices from different sources will only lead to a non performer. Don't get crossed up with what we are recommending and what others are telling you.
I stated that I would set them up @ 80# on the seat. That is only a hair more than oem..
A decompressed piston had a shorter pin to piston top measurement to compensate for a block that has been whacked on before. You are not in that situation. You want to stroke the crank for more displacement use a shorter piston and stroke to 0 deck instead of machining the block. This will require re bobbing the crank and a thorough balance job. This is common engine practice not a new idea. Don't thing you are going in that direction.
I doubt ihon sells the old shim gaskets in there kit. Call Jeff.
Combining building practices from different sources will only lead to a non performer. Don't get crossed up with what we are recommending and what others are telling you.
Eagle-Mark
Member
Well I placed the order today. I told Jeff I would take a set of silovite pistons he has on the shelf. Don't know what size yet but that is what it will be bored to.
Got the comp springs to go with the duel pattern cam.
Probably only thing I May do and I don't know if it were mentioned here or on a port and polish question I had going on bp because I knew it would draw out Tom mandara. May remove hump from exhaust port if there is one. No body was sure if it was there in 72?
Other than that it will be put together tediously as outlined here. May take detailed pictures if they are not already around like the feeler gauge on both sides of rods above.
So for now thanks guys! Got's lots of cleaning to do, wait for pistons to arrive and bring to machinist for fitting. Then bring it home, more cleaning probably all oil passages, chase threads, more cleaning, then some assembly!
since I've never done mpfi on an IH it will be fired up, broken in on the carb. Mpfi will be a latter project, got a 2 barrel intake already for the machinist. But May be adding a crank sensor and going coil on plug ls1 sequential since a buddy of mine has the ring cut out already for a bb Chevy...
Got the comp springs to go with the duel pattern cam.
Probably only thing I May do and I don't know if it were mentioned here or on a port and polish question I had going on bp because I knew it would draw out Tom mandara. May remove hump from exhaust port if there is one. No body was sure if it was there in 72?
Other than that it will be put together tediously as outlined here. May take detailed pictures if they are not already around like the feeler gauge on both sides of rods above.
So for now thanks guys! Got's lots of cleaning to do, wait for pistons to arrive and bring to machinist for fitting. Then bring it home, more cleaning probably all oil passages, chase threads, more cleaning, then some assembly!
since I've never done mpfi on an IH it will be fired up, broken in on the carb. Mpfi will be a latter project, got a 2 barrel intake already for the machinist. But May be adding a crank sensor and going coil on plug ls1 sequential since a buddy of mine has the ring cut out already for a bb Chevy...
Eagle-Mark
Member
What about cam timing? Do I need a degree wheel? I read something somewhere about 4 degrees?
Robert Kenney
Super Moderator
Port hump? Thought you had the heads off? If you have air tubes then you have the hump. Either way the exhaust port is the big restriction on your heads.
Cam timing needs to be verified so plan on having a degree wheel and dial indicator handy whether you want it straight up or 4 degrees advanced.
My recommendation for you earlier in your thread was 4* advanced (106* ilca).
Do you plan on "0" decking? Bumping the compression? If so it should go in straight up. Eg 110*/110*.
Want to stay at stock compression? It should go in 106/114 with the 106* being the intake lobe centerline.
Either way the 4* is roughly equivalent to a 200 rpm shift in the torque curve. 106 shifts it down 110 shifts it up. Moving it up will always make more hp because the torque curve rolls off later.
Eagle-Mark
Member
Yes I have the heads offf but never looked closely and now they are at the machine shop. Also no air tubes in exhaust manifolds.
Going to be stock compresion. So line up the gears and still need a degree wheel?
Going to be stock compresion. So line up the gears and still need a degree wheel?
Eagle-Mark
Member
No air tube in head like the one you pictured earlier?
