Like Brian said about chamber clearance that can be accomplished somewhat during the valve job. Lay out your gasket size and have them run a 15 degree cutter down the chamber wall.
SM Head Modifications on a budget
- Thread starter Earlie A
- Start date
-
Will do. My apologies to Brian. I was thinking about hand blending, not the valve job.
Like I said that would have to be discussed with your machinist before the valve job. I would suggest blueing the head and laying it out for him. The Cometic gaskets I just ordered are 4.180 as I will sacrifice some compression for better flow.
PRH
Well-Known Member
I think Post 75 demonstrates that, on these heads in particular, the as cast SSR form becomes an area that holds back the progress early on…….which is why I start tweaking it pretty early in the porting process.
That’s not to say that some of the “area” enhancements couldn’t be worth some amount of power on a stroker bracket race type combo(even if they showed next to nothing on the bench).
But if I’m doing a budget oriented porting job, I’ll spend some time on the SSR before spending much time on the PRP or head bolt bulge.
That’s not to say that some of the “area” enhancements couldn’t be worth some amount of power on a stroker bracket race type combo(even if they showed next to nothing on the bench).
But if I’m doing a budget oriented porting job, I’ll spend some time on the SSR before spending much time on the PRP or head bolt bulge.
PRH
Well-Known Member
I’ll leave you guys to it.
That my friend is what this post is all about. It’s super hard for me to flow test every single thing I do to a head but he is being gracious enough to do so. And probably learning during the process. I know how to get 290 out of a 2.02 valve, and 312-315 out of a 2.055 valve, and 330 plus out of a 2.08 valve. But during this test we are testing things guys can do at home and probably send it out for a competition type of valve job. If we could find simple things a non head porter could do at home and get 285-290 out of it I think that would be great. Probably a hard target to hit but why set your target low.
Last edited:
I love your input but the average guy is deathly afraid of the short turn. All in all for this type of head it’s not bad but to hit the 30ish target cfm gain we are going to lose 80% of the guys that are brave enough to grab a grinder. Going up is safe but that only gets you so far. It needs widening bigtime and yes lowering
I think most of us, as we get older, feel the obligation and the desire to give back some of the knowledge and wisdom that we have been blessed to obtain. I learned a long time ago not to be afraid to raise my hand and ask a question. The long term benefit of learning the answer far outweighs the temporary embarrassment of asking. You guys are an incredible blessing. I've said it before and I'll say it again - one word or one phrase that you think means nothing might just be the answer we're looking for. Thank you, and please keep posting when you see ignorance raise its hand. I for one and very grateful. I think many others are as well.
PRH
Well-Known Member
It’ll be interesting to see how it unfolds without addressing the SSR, and how the flow numbers shake out.
I wish I could give you a safe width number at the head bolt hole that you could safely go to but I can’t I can’t even give you a roof measurement as I go by eye of sight raising the roof then take my floor measurements off of that. Again metal Removal that must guys won’t feel comfortable doing
ValiantRacing
Well-Known Member
From my experience, just working the chamber and nothing else on a set of Edelbrocks that are on my daughters 340, the flow pickup is really good.
Here's the current state of the chamber with 4.070 bore line and 4.170 gasket line marked. Looks like the current 15 degree top cut is already about 0.020 away from the bore line, so I guess I'll cut out to the gasket line in the morning. Is that your preference PBR?
Last edited:
I got some free time this evening, so the deshrouding of the intake valve is complete. The 15 degree top cutter was set to just touch the 4.170 diameter gasket line. This resulted in about a 0.060"-0.070"cut on the chamber wall. As can be seen from the before picture above and the after picture below, this was quite a large cut. Flow results are shown below. Nice little gain through most of the curve. Thanks Brian.
The exhaust valve seat has not been recut and the exhaust valve sits around 0.040"-0.050" higher than the intake. I think I'll lower the exhaust valve in the morning and also give it a radius. Won't be much but both moves should help flow a little.
The exhaust valve seat has not been recut and the exhaust valve sits around 0.040"-0.050" higher than the intake. I think I'll lower the exhaust valve in the morning and also give it a radius. Won't be much but both moves should help flow a little.
mopowers
Well-Known Member
Cool thread! I like seeing the incremental gains from each step. Do you think blending the top cut into the chamber would be worth anything?
These damn parking brakes on my 3/4 ton dodge are fighting me hard. If I get a chance tomorrow I’ll try to sonic check my thickness of material left at my bolt hole and then measure across the shortside. Sooner or later your going to have to address that ugly bulge.
Do you think opening the throat to 90-91% of the valve would help ?
Good question. I have never tried that on the bench. I believe conventional wisdom would say leave it sharp on the intake for a fuel shear ridge and round it on the exhaust to give exhaust the best chance to escape. I bet leaving it sharp on the intake would help fight reversion as well. Hopefully others will address this.
That has not been my experience on this head. I have had the best luck at 88%. But throat size does not exist in a vacuum by itself. What’s going on in the bowl, what’s going on in the chamber, where are you trying to direct the air, fighting reversion on the short side all play a part. I personally think valve lift plays a part. Others do not agree.
Hey @pittsburghracer. Want to run this by you this morning. Take a look at the picture below regarding the short side. Green is the almost untouched short side. Purple stripe is the 70 degree, wide red is the 60 degree, black is the 45 degree. The transition between the green and the purple is a fairly hard line/ridge. Wouldn't take much with a cartridge roll to smooth it out and even take out some of the 60. I'm quite sure there's some gain to be made there. Is now the time to try it?
-
