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Opinions of guides in import heads

General engine tech -- Drag Racing to Circle Track

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cv67
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Opinions of guides in import heads

Post by cv67 » Tue Oct 08, 2019 9:19 am

For the guys who work on these a lot, are they sufficient for the avg st/strip guy?

Would you use a different one (which) and why?

Head some switch to iron, Im curious about using 8mm valves in a set.

All ears, like to hear the pros and cons. Assuming they would all need valve jobbed afterwards.

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Re: Opinions of guides in import heads

Post by Lizardracing » Tue Oct 08, 2019 10:46 am

From what I've seen over the years, the issue is the QC and not so much the materials. They are either too tight, too loose or atypical size that can be hard to find. Makes sense in the regard that the minimizing the price point means bargain bucket shopping for anything that will work.
If they are on size, and the rocker geometry is right so as not side load the stems, they will work just fine.

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Re: Opinions of guides in import heads

Post by mag2555 » Tue Oct 08, 2019 12:01 pm

Two big question here since you provided such lack of info and gave just generalities is will the motors stock red line still be used, and second will springs rates be going up over stock?

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Re: Opinions of guides in import heads

Post by Schurkey » Tue Oct 08, 2019 12:16 pm

"Import heads" = Toyota/Audi/Kia/etc.?

or

"Import heads" = low-budget Pro-Comp and generic replacements for SBC, SBF, etc.?

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Re: Opinions of guides in import heads

Post by cv67 » Tue Oct 08, 2019 12:21 pm

sbc dart knockoffs for example.
Have a set that, all sized out pretty well but many dont (or so I hear).

Pressures could range from flat tappet to say 130-140 HR stuff.

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Re: Opinions of guides in import heads

Post by ProPower engines » Tue Oct 08, 2019 3:13 pm

cv67 wrote:
Tue Oct 08, 2019 12:21 pm
sbc dart knockoffs for example.
Have a set that, all sized out pretty well but many dont (or so I hear).

Pressures could range from flat tappet to say 130-140 HR stuff.

Good FT stuff is 130-140. and HR stuff starts about 150-160 seat.

And can you Define sized out well??? What does that even mean??? What are the actual guide clearances or can you not measure to the .0001" in other words if you can wiggle the valve its too loose already.
Most all perf. guide sizes depending on valve stem run out of a quality valve being less then .0003? would be in
the range of .0008 to.0012 for int. and a max of .0015" exh.

Those aftermarket off shore heads guides are not close to round or straight in 95% of what I have seen and need work
to correct the guides. IE replacement is needed. And a side note the seats are too soft for my liking as they wear very fast
in most cases.
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Re: Opinions of guides in import heads

Post by cv67 » Tue Oct 08, 2019 3:49 pm

Sheesh, here it comes you know exactly what I meant.
They are cheap heads I wouldnt expect miracles from them, nobody doing a serious engine (I think) would use em but they got their place.

Im simply asking if your opinion is poor then what is your preferred type?

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Re: Opinions of guides in import heads

Post by ProPower engines » Tue Oct 08, 2019 4:24 pm

cv67 wrote:
Tue Oct 08, 2019 3:49 pm
Sheesh, here it comes you know exactly what I meant.
They are cheap heads I wouldnt expect miracles from them, nobody doing a serious engine (I think) would use em but they got their place.

Im simply asking if your opinion is poor then what is your preferred type?
That 3was not real clear to start with but here goes.

I have customers that want economy heads but the fact remains is they need work out of the box like every other econo
aluminum head sold.

Fact remains is they have their place but there are several others here that will say the same thing. Buy the castings bare
and rework them based on what they can do.

The heat treat is not that great and the alloy blend is marginal at beat for any serious HP engine.
But stuff up to the 450 range with no power adders and they have a place but unless you get the castings from the source then you have more time and money in them then they are really worth. At that point you may as well get dart or similar quality castings to start with but the budget for such builds this is not on everyone's mind since the internet provides lots of vague descriptions of quality and power gains.

But the guides and seats all need to be redone for the most part. CNC work is easy to get done as an option these days
to improve these heads but limited based on the port and chamber shapes.

They are a cheap lower quality version of a North American made head but like I said unless you get them in bulk
un-finished seats and guide sizing you pay too much with the extra work they need to salvage them for any HP build.
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Re: Opinions of guides in import heads

Post by cv67 » Tue Oct 08, 2019 6:52 pm

Thanks for the info; got a set from someone for a personal project..curiosity more or less to see what all the fuss on line was about.
In my mind always wondering about ways to improve wether it may be worthwhile or not.

Some say run them, other say replace asap but wont give a specific reason. Thats what reading the web gets ya =D>

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Re: Opinions of guides in import heads

Post by BillK » Tue Oct 08, 2019 8:49 pm

I have a set of Small Block Chevy ones in the shop right now. Customer says they have less than 500 miles on them and I tend to believe him as clean as they are. The guides are just plain worn out. I didn't even bother to measure them because you can lift the valve an inch off the seat and it moves a good 1/8" :( He took them off the engine because it wiped a lobe on the flat tappet cam and he is switching to a hydraulic roller and wanted to make sure the heads were set up properly.

In all fairness I don't have a clue how the geometry is or how the original valve job was. Either one can kill a guide. The guides are an oddball od size. Had to special order them and will still have to cut the length down to make them right. I guess they try to save money but now he will have at least $800 more in them to make them right. I would prefer to spend it all the first time and not have the hassles :)
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Re: Opinions of guides in import heads

Post by ProPower engines » Wed Oct 09, 2019 12:31 am

BillK wrote:
Tue Oct 08, 2019 8:49 pm
I have a set of Small Block Chevy ones in the shop right now. Customer says they have less than 500 miles on them and I tend to believe him as clean as they are. The guides are just plain worn out. I didn't even bother to measure them because you can lift the valve an inch off the seat and it moves a good 1/8" :( He took them off the engine because it wiped a lobe on the flat tappet cam and he is switching to a hydraulic roller and wanted to make sure the heads were set up properly.

In all fairness I don't have a clue how the geometry is or how the original valve job was. Either one can kill a guide. The guides are an oddball od size. Had to special order them and will still have to cut the length down to make them right. I guess they try to save money but now he will have at least $800 more in them to make them right. I would prefer to spend it all the first time and not have the hassles :)
=D> =D> =D>
Well said Bill.
Thats the point I try to tell guys when they bitch about Dart stuff or other heads made here.

They think they are getting the killer deal complete but most times end up changing springs etc. anyway.
The last set I had here the guides were .512"od. What size did you end up needing to repair then.
I just started going to .562" od on them which is commonly available from EPWI and others.
Serdi combo boring tool for 3/8" id guides with the tip ground to suit the 11/32 guide id.
They do not sell an 11/32 combo boring reamer yet.
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Re: Opinions of guides in import heads

Post by BillK » Wed Oct 09, 2019 6:48 am

ProPower engines wrote:
Wed Oct 09, 2019 12:31 am
What size did you end up needing to repair then.
The guides in this set are .507 ???? I thought about going to .562 but Pep had some in .507 but they are a little too long.
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Re: Opinions of guides in import heads

Post by Belgian1979 » Wed Oct 09, 2019 2:54 pm

How do you spot a knock of Dart sbc head from an original ?

And second question : with the valves in the head, doing a wiggle test : how much wiggle is acceptable and what is not ...

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Re: Opinions of guides in import heads

Post by BillK » Wed Oct 09, 2019 3:04 pm

Belgian1979 wrote:
Wed Oct 09, 2019 2:54 pm
How do you spot a knock of Dart sbc head from an original ?
Personally I have not seen an actual counterfeit but would not be surprised if they are out there. A dart head will say Dart on it and have a Dart part number. The others will have their own part number or no part number at all.
Belgian1979 wrote:
Wed Oct 09, 2019 2:54 pm
And second question : with the valves in the head, doing a wiggle test : how much wiggle is acceptable and what is not ...
The wiggle test is really not an accurate test. Someone who has done hundreds of heads can use it for quick check but a bore gauge is the correct way to do it. The wiggle test has too many variables. How far you pull it out of the guide and the length of the guide will both affect it considerably.

That being said . . . . VW actually specifies the wiggle test in their service manuals on several engines. But they tell you exactly how far to pull the head out of the guide to measure it.
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Re: Opinions of guides in import heads

Post by Belgian1979 » Wed Oct 09, 2019 3:26 pm

BillK wrote:
Wed Oct 09, 2019 3:04 pm
Belgian1979 wrote:
Wed Oct 09, 2019 2:54 pm
How do you spot a knock of Dart sbc head from an original ?
Personally I have not seen an actual counterfeit but would not be surprised if they are out there. A dart head will say Dart on it and have a Dart part number. The others will have their own part number or no part number at all.
Belgian1979 wrote:
Wed Oct 09, 2019 2:54 pm
And second question : with the valves in the head, doing a wiggle test : how much wiggle is acceptable and what is not ...
The wiggle test is really not an accurate test. Someone who has done hundreds of heads can use it for quick check but a bore gauge is the correct way to do it. The wiggle test has too many variables. How far you pull it out of the guide and the length of the guide will both affect it considerably.

That being said . . . . VW actually specifies the wiggle test in their service manuals on several engines. But they tell you exactly how far to pull the head out of the guide to measure it.
So if you want to check the valve guides, pulling the heads is the only option #-o

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